Synthesis and reactivity of a fluorinated N-alkylmaleimide towards free-radical grafting and polymerization reactions

Article abstract of DOI:10.1016/j.jfluchem.2003.07.014

A new fluorinated N-alkylmaleimide, N-(2-pentadecafluoro-n-octanoyloxy)- ethyl)maleimide (FOMI), was synthesized from perfluorooctyl carboxylic acid (FOCA) by reaction of the furan adduct of maleic anhydride (MAH) with ethanolamine and esterification of the resulting alcohol-imide. The reactivity of FOMI in free-radical reactions such as copolymerization with butyl vinyl ether (BVE) and grafting onto olefin copolymers (OCP) was investigated. Copolymerization with 2/1 molar excess BVE yields a copolymer with 63 mol% FOMI in moderate conversion, indicating that homopropagation of the maleimide prevails over comonomer alternation. The thermal stability of FOMI is quite poor, with onset of the pyrolytic loss of the N-perfluoroalkylcarboxyethyl moiety just above 100 °C, similarly to that of FOCA. This restricts the possibilities for direct melt functionalization of OCP with FOMI. To bypass this limitation three distinct approaches were preliminarly investigated. These were respectively based on either direct grafting of FOMI at low temperature, or reaction of a MAH-grafted polyolefin with a low molecular weight amine or amino-terminated oligomer bearing the perfluoroheptyl group. A functionalization degree FD=2% was achieved by solution grafting of a linear very low density polyethylene (VLDPE) with FOMI and Perkadox 16 as the free-radical initiator. The relatively high grafting efficiency was attributed to the growth of some oligomeric FOMI grafts onto the OCP. The alternative routes of post-modification of VLDPE- g -MAH by imidization with an amidoamine obtained by amidation of FOCA with a diamine or an amino-terminated FOMI/BVE oligomer, respectively, were also preliminarly investigated.

Full text of DOI:10.1016/j.jfluchem.2003.07.014

Journal of Fluorine Chemistry 125 (2004) 315–328
Synthesis and reactivity of a fluorinated N-alkylmaleimide towards
free-radical grafting and polymerization reactions
*
Valter Castelvetro , Mauro Aglietto, Francesco Ciardelli, Federica Spagnoli
Dipartimento di Chimica e Chimica Industriale, University of Pisa and INSTM, Research Unit of Pisa, Via Risorgimento 35, 56126 Pisa, Italy
Received 10 February 2003; received in revised form 26 June 2003; accepted 28 July 2003
Abstract
A new fluorinated N-alkylmaleimide, N-(2-pentadecafluoro-n-octanoyloxy)-ethyl)maleimide (FOMI), was synthesized from perfluor-
ooctyl carboxylic acid (FOCA) by reaction of the furan adduct of maleic anhydride (MAH) with ethanolamine and esterification of the
resulting alcohol-imide. The reactivity of FOMI in free-radical reactions such as copolymerization with butyl vinyl ether (BVE) and grafting
onto olefin copolymers (OCP) was investigated. Copolymerization with 2/1 molar excess BVE yields a copolymer with 63 mol% FOMI in
moderate conversion, indicating that homopropagation of the maleimide prevails over comonomer alternation. The thermal stability of FOMI
is quite poor, with onset of the pyrolytic loss of the N-perfluoroalkylcarboxyethyl moiety just above 100 8C, similarly to that of FOCA. This
restricts the possibilities for direct melt functionalization of OCP with FOMI. To bypass this limitation three distinct approaches were
preliminarly investigated. These were respectively based on either direct grafting of FOMI at low temperature, or reaction of a MAH-grafted
polyolefin with a low molecular weight amine or amino-terminated oligomer bearing the perfluoroheptyl group. A functionalization degree
FD ¼ 2% was achieved by solution grafting of a linear very low density polyethylene (VLDPE) with FOMI and Perkadox 16 as the free-
radical initiator. The relatively high grafting efficiency was attributed to the growth of some oligomeric FOMI grafts onto the OCP. The
alternative routes of post-modification of VLDPE-g-MAH by imidization with an amidoamine obtained by amidation of FOCA with a
diamine or an amino-terminated FOMI/BVE oligomer, respectively, were also preliminarly investigated.
#
2003 Elsevier B.V. All rights reserved.
Keywords: Fluorinated maleimide; Free-radical grafting; Polyolefin modification; Maleated polyolefin; Alternating copolymer; Perfluorocarboxylic acid
1
. Introduction
simply selective enrichment of fluorinated groups at the
interface. While such behavior is easily obtained and under-
stood with relatively sophisticated polymeric structures, such
as block copolymers, and a number of studies have described
the self-assembling into crystal-like domains of long linear
perfluorinated molecules in monolayers or even at the poly-
mer–air interface of relatively highly fluorinated copolymers
It is well known that the replacement of hydrogen with
fluorine atoms improves the chemical, thermal and photo-
chemical stability of polymeric materials. Moreover, the
presence of even a small fraction of fluorinated groups or
co-monomers can result in dramatic reduction of surface
energy, particularly when the polymeric structure, the phy-
sico-chemical properties of the material and the type of
fabrication, contribute to magnify this effect. This is well
documented in the literature, and heterophasic multilayered
thin films, coatings with microphase-segregated or gradient
composition or, more commonly, with a macroscopically
homogeneous composition but a molecularly thin highly
fluorinated layer at the air–polymer interface can be obtained
as the result of self-assembling of highly fluorinated com-
ponents, thermodynamically driven phase segregation, or
with perfluorinated side chains (typically linear C or longer),
8
more flexible and economically viable approaches are still
needed and explored with the aim of obtaining materials with
useful additional properties for a number of applications.
Thus a high optical purity, toughness, chemical stability,
photoinduced crosslinking or cleavage behavior are needed
in optical applications such as waveguides and photolitho-
graphy; good adhesion, photochemical stability and/or soil-
release behavior are required for protective coatings or water-
repellent finishing of masonry, textile, paper, leather and other
materials; scratch and mar resistance, long-term stability of
the polymer surface against molecular reorganization leading
to unwanted increase of surface energy are required for
antifouling applications.
*
Corresponding author. Tel.: þ39-050-221-9256;
fax: þ39-050-221-9320.
E-mail address: vetro@dcci.unipi.it (V. Castelvetro).
0022-1139/$ – see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2003.07.014

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Our research activity at the University of Pisa, started
Different material properties and performances in coating
and related thin film applications were expected from con-
trolled introduction of fluorinated groups through the use of
variously fluorinated comonomers and, if required, con-
trolled polymerization processes. Both homogeneous and
dispersed phase polymerization processes were considered,
one of the goals being the development of environmentally
friendly, highly durable and performing coating materials,
possibly obtained with a moderate degree of fluorination
which makes the material less costly and thus more appeal-
ing for industrial applications.
In particular the free-radical copolymerization of two
classes of FA was investigated. The first includes acrylic
(or methacrylic) esters containing fluorine only in the alkoxy
moiety, with at least one unfluorinated carbon next to the
ester group (structure a of Scheme 1); the reactivity of type a
monomer is similar to that of their unfluorinated analogs
[1,2]. The second class includes fluorovinyl (structures b and
c) and fluoroalkyl-substituted (structure d) acrylates, includ-
ing those fluorinated both at the double bond and in the side
chain (structure e). The electronic polarization due to the
presence of F next to the double bond affects the reactivity of
monomers b–e [2,3] by increasing electrophilicity and there-
fore affinity towards electron-rich, nucleophilic monomers
such as, e.g. VE, vinyl esters and a-olefins.
about 10 years ago, was prompted by the increasing aware-
ness of the need of new products for the preservation of our
country’s rich cultural heritage. Indeed most products com-
monly employed as protective coatings or consolidants for
deteriorated objects, particularly stone and masonry surfaces
exposed to severe environmental hazard and accelerated
decay in polluted areas, are commercially available only
because they were developed for more profitable applica-
tions, and can hardly be considered the most suitable for the
specific requirements of the preservation of works of art. Our
early activity was therefore mainly focused at the synthesis
and testing of relatively simple copolymers of fluorinated
alkyl (meth)acrylates (FA), which can be polymerized by
simple free-radical process and can be applied as solutions in
common (not fluorinated) organic solvents, giving efficient
and durable water repellent protective coatings for natural
stones of different composition and morphology.
While an appreciable improvement of hydrophobic and
photodegradation behavior of acrylic-based copolymers was
usually observed as the result of the introduction of FA it was
immediately clear that better control on the structure,
amount and local distribution of fluorinated groups through-
out the macromolecule was needed in order to significantly
improve the above properties. In addition, solubility, adhe-
sion to the substrate and interfacial properties in general
were observed to be strongly dependent on the (co)polymer
composition and structure. The polymerization of both
commercial and newly synthesized FA with unfluorinated
ones and with other unsaturated comonomers, particularly
vinyl ethers VE, was therefore studied in detail.
1.2. Synthesis of acrylic-based copolymers by
free-radical polymerization
Copolymerization of type a acrylates with unfluorinated
ones proceeds smoothly and in good yields to give substan-
tially random copolymers with easily predictable properties
1
.1. Reactive characteristics of partially fluorinated
vinyl monomers
(e.g. glass transition temperature T , solubility, surface
g
energy); on the other hand, efficient incorporation of dif-
ferent nucleophilic comonomers, such as VE, can be better
achieved with the more electrophilic type b–e acrylates. In
fact, while the negatively polarized double bond of VE
precludes their homopolymerization under free-radical con-
ditions, the same feature makes them well suited to produce
alternating or quasi-alternating copolymer sequences with
FA, since the latter can form with VE charge transfer
complexes or polarized adducts. The tendency of type a
acrylates to build alternating comonomers sequences and the
efficiency of VE incorporation depend both on the nature of
the VE (the bulkier, the better [4]) and, to a larger extent, on
The presence of fluorine can dramatically affect the
chemical reactivity of vinyl derivatives, particularly when
fluorine substitution occurs at or close to the polymerizable
vinyl group.
With the main objective of developing a simple and
versatile process for the preparation of fluorinated macro-
molecular compounds for diverse applications, the main
focus being on protective coatings, the reactivity of a series
of fluorinated vinyl monomers in free-radical and ionic
polymerization was investigated.
F
F
H(Me)
O
F
F
F
F
F
R = H, CF3
x = 1, 2
O
O
O
O
O
O
O
O
O
(CH-R)x
(CH-R)x
n = 1 - 8
CnF
CnF2n+1
2n+1
(a)
(b)
(c)
(d)
(e)
Scheme 1.

V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
317
F
F
F
CF3
F
F
>
>
>
>
~
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
F3C
CF3
F3C
CF3
CF3
C6F
13
C8F17
HFIFA
EDFMA
MTFMA
HFIMA
IFA
FHEFA
TFEMA
FOEMA
MMA
Scheme 2.
the magnitude of the electronic perturbation of the acrylic
group, that is, on the structure of the fluoroalkyl moiety and
its distance from the ester group. In particular, the reactivity
is not significantly affected when the perfluoroalkyl group is
that was unexpectedly enriched in the fluorinated VE to the
expense of BVE with respect to the feed composition, as if
its nucleophilic character were enhanced rather than reduced
by the presence of the fluorinated substituent, thus promot-
ing its preferential copolymerization with DEM.
spaced apart from the ester oxygen by at least a C unfluori-
2
nated spacer; in this case an equimolar feed of FA and butyl
vinyl ether (BVE) yields copolymers with over 85 mol%
acrylic units, whereas as much as 32 mol% BVE incorpora-
tion is obtained in the same conditions with HFIMA (a,
R ¼ CF3, x ¼ 1, n ¼ 1) [2,5]. Combining the data collected
for copolymerization of primary VE with different types of
FA, the tendency to build alternating structures, including
perfectly alternating ones as in HFIFA (e, R ¼ CF3, x ¼ 1,
n ¼ 1) is in the order reported in Scheme 2.
The cationic polymerization of FOEVE under controlled/
living conditions was also investigated, since a living poly-
merization process can allow the synthesis of block copo-
lymers and other interesting macromolecular structures. Due
to the negligible solubility of FOEVE in unfluorinated
solvents, the controlled/living cationic polymerization of
BVE in 1,1,2-trichloro trifluoroethane was initially studied
and shown to occur at T ¼ 0 8C with the initiating system
based on EtAlCl , 1-butoxyethyl-acetate and 1,4-dioxane
2
Appropriate selection of comonomers and composition
allows therefore to independently modify the copolymer
structure and properties (average fluorine content, Tg,
etc.). In addition, monomers such as MTFMA, hardly
homopolymerizable by free-radical mechanism, can be con-
verted in good yields into quasi-alternating copolymers with
VE under the same conditions [3]. When the comonomer
distribution becomes increasingly alternating, the physico-
chemical properties of the copolymer can no longer be
predicted and must be experimentally determined. This
was specifically investigated, particularly in connection with
the photodegradative behavior and the surface properties of
thin films of these materials, as discussed later.
[8]. The fluorinated solvent slows down the polymerization
and lowers the blocking activity (that is, the capacity of the
living macrocation of further chain growth upon addition of
a second comonomer) at high monomer conversions. Unfor-
tunately, when the homopolymerization of FOEVE was
tested under the same conditions proved successful for
BVE, only negligible conversions were obtained, while a
conventional initiator such as BF –OEt was highly effective
3
2
in the same solvent. This was a clear indication of the
extreme sensitivity of the selected initiating system to the
nature of both solvent and monomer.
1.4. Surface properties
1.3. Ionic polymerization of fluorinated acrylates and
vinyl ethers
The surface properties and surface dynamics of thin films
of the above described acrylic-based copolymers, prepared
by solution casting, spin coating and Langmuir–Blodgett
(LB) technique have been studied by means of static and
dynamic contact angle using both the sessile drop and the
Wilhelmy balance methods [9,10]. In addition, their perme-
ability to water and the dynamics of surface restructuring,
conducive to significant variations of the surface energy of
the films, were investigated by the attenuated total reflection
(ATR) technique, revealing the strong dependence of film
swelling on its surface composition and structural order [11].
Comparing the properties of spin coated and LB films, it
was shown how the structural order, more than the average
chemical composition, can affect the wetting behavior of a
hydrophobic polymer by dictating the chemical composition
and homogeneity of the outermost molecular layer, which
ultimately determines the surface properties. In contrast to
the spin coated films, nearly isotropic and with a surface
The anionic polymerization of type a FA can be per-
formed, as expected, with similar results as of their unfluori-
nated analogs; appropriate selection of the reaction
conditions can lead to polymers with different tacticity [6].
The reactivity of perfluorooctylethyl vinyl ether (FOEVE)
was investigated under both free-radical and carbocationic
polymerization conditions. Preliminary results from our
laboratory on bulk free-radical copolymerization with elec-
trophilic monomers (diethyl maleate, DEM, and butyl
methacrylate) confirmed the negligible influence of the
perfluoroalkyl moiety when spaced apart by a dimethylene
from the polymerizable group [7]. In fact a mixture of
FOEVE, BVE and DEM gave a terpolymer with alternating
structure (that is, with a 50 mol% total content of the vinyl
ethers, alternating with the remaining 50 mol% DEM units)

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V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
fluorine content only slightly higher than in the bulk, the LB
films are intrinsically anisotropic, with alternation of layers
of hydrophilic unfluorinated main chains and hydrophobic
fluorinated side chains. This anisotropy can produce appar-
ently contradictory results, such as a higher water swelling
of the more highly fluorinated copolymers when the
construction of the LB film causes the perfluorinated side
chains to be oriented inward and thus effectively buried
inside the film.
Those having long or branched side alkyl chains follow a
common degradation pathway which mainly produces
extensive cross linking, promoted by radicals generated
on the flexible side groups; gel formation is the most
apparent consequence of the photooxidative processes for
this class of copolymers. On the contrary, in the presence of
methyl acrylate (MA) units the oxidation occurs primarily
starting from the main chain tertiary carbon position, indu-
cing scission reactions in the macromolecules.
A more extensive study on a series of copolymers of
FOEMA, FHEFA, HFIFA, HFIMA and IFA highlighted the
strong contribution of the terminal CF groups in increasing
The most effective T -lowering vinyl comonomers that
g
is those providing a macromolecular main chain with
enhanced conformational flexibility, are characterized by
either long plasticizing side chains or by less sterically
hindered vinyl groups as in acrylates [7]. Incidentally, these
comonomers are also particularly sensitive to photooxida-
tive conditions. As in the case of MA copolymers, also for
those with VE crosslinking is no longer the main degradation
pathway [17]. Both TFEMA/BVE and MTFMA/BVE
undergo extensive photooxidation, with development of
new carbonyl containing functional groups and onset of
chain scission processes controlled by the reactivity of
the VE units [16]. Fluorine atoms are in such structures
too far from the weak tertiary C–H of the VE to provide
long-term stabilization of the polymer, although the kinetics
of the overall photodegradation process is usually slowed
down. Aside from the different effects on molecular weight
distribution and gel formation, the structural changes caused
by photooxidation of these copolymers are quite similar,
consisting in the formation of hydroxyl-bearing groups
through the typical mechanism of hydrocarbon oxidation,
and of lactone groups.
3
both static (y) and advancing (y ) contact angle with water
a
[9], well beyond their weighed contribution to the average
fluorine content in the copolymer (%F). On the contrary,
a better correlation was observed between %F and the
receding contact angle, y , as expected from its sensitivity
r
to the low-surface energy microdomains. An increase of Tg
and a moderate crosslinking (obtained by introducing the
reactive comonomer 3-trimethoxysilylpropyl methacrylate,
TSPMA), both affecting the segmental mobility of the
macromolecular chain, improve the film stability against
surface restructuring on wetting. As a general rule y , rather
r
than y , is related to the protection efficiency of the film,
a
since it reflects the swelling behavior of the wet film surface.
In fact y was shown to be more strictly connected to the true
r
equilibrium contact angle as measured by a modified Wil-
helmy plate method, where an applied vibration allows
relaxation of kinetic instabilities during the contact angle
measurement under static conditions [12].
1
.5. Photodegradation behavior
Two representative cases of the evolution of molecular
weight distribution as the consequence of chain scission and
crosslinking processes, respectively, are shown in Fig. 1.
One can see from Fig. 1a that at the beginning of the
degradation the molecular weight distribution of FOEMA/
BA (BA: butyl acrylate) broadens on the higher molecular
weight (lower retention volume) side, indicating chain
extension. At longer degradation times, when gel formation
is no longer negligible, the normalized curves are only
representative of the soluble fractions remaining in the
samples. In the case of TFEMA/BVE negligible gel forma-
tion and fast reduction of molecular weight clearly indicate
that chain scission is the prevailing photodegradation pro-
cess.
The introduction of fluorine atoms in a-position of the
acrylic monomer effectively reduces the oxidation reactions
taking place on adjacent VE units. However, a detailed study
carried out on HFIFA/BVE and EDFMA/BVE copolymers
showed that their degradation is not suppressed, although the
structural changes revealed by FT-IR analysis are quite
different in comparison with the previous cases [18]. As
an alternative approach, an alkyl isopropenyl ether was used
in place of the VE, thus suppressing the reactivity associated
with the main chain tertiary carbon. In any case the structural
regularity achievable by copolymerization of VE with a- or
The photodegradation processes taking place on repre-
sentative fluorinated copolymers and on selected unfluori-
nated analogs were studied by Chiantore and coworkers at
the University of Turin, by means of accelerated photoaging
under strictly controlled conditions, using a fluorescent
xenon lamp to mimic solar irradiation. Chromatographic
and spectroscopic techniques were used to monitor the
chemical evolution during up to 2000 h of irradiation
[
13–16].
The first results regarding homo- and copolymers of type
a fluoroalkyl acrylates and methacrylates with unfluorinated
ones confirmed the expected high stability of fluoro-contain-
ing homopolymers and of the fluorinated co-units of the
copolymers [13–15]. Unfortunately, while a methacrylic
polymer with solely fluorinated side chains would grant
excellent stability, its application possibilities are quite
limited and copolymerization with simply unfluorinated
or otherwise functional comonomers is usually necessary
to improve adhesion, solubility, etc. The overall stability of
type a FA copolymers was observed to be generally con-
trolled by the reactivity of the unfluorinated co-units, which
may be schematically divided in two classes on the basis of
their main effect on the mechanism of photooxidation.

V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
319
0h
0h
1
000h
1
500h
250h
500h
500h
250h
1750h
1000h
1500h
15
20
25
30
35
40
20
25
30
35
40
Time (min)
Time (min)
Fig. 1. Normalized SEC analyses of fluorinated copolymers subjected to up to 1500 h accelerated photoaging: (a) FOEMA/BA; (b) TFEMA/BVE.
b-fluorinated acrylates is a useful tool to improve the
chemical and photochemical stability of these materials.
were screened in order to single out those affecting most the
relevant application properties of the coating.
As an example, copolymers of TFEMA and FOEMAwith
dodecyl methacrylate (DMA), methyl acrylate (MA) and
BVE, with comparable average F content, were tested to
assess the role of side chains of various length and of the
unfluorinated comonomer [20]. A FOEMA/DMA copoly-
mer with 28 wt.% F (about 30 mol% FOEMA units) was the
most effective in lowering capillary water absorption at
shorter wetting times (<24 h), whereas TFEMA/MA and,
particularly, TFEMA/BVE perform better than FOEMA/
DMA at times exceeding 48 h. This behavior can be under-
stood in terms of local reorganization of the coating material
at the polymer–water interface. In the case of the TFEMA
copolymers, containing a much higher (about 70%) mole
1
.6. Fluorinated acrylic-based copolymers as protective
coating materials for stone
The performances of a series of copolymers of type a–e
fluorinated acrylates, containing up to four different fluori-
nated and unfluorinated comonomers to adapt their proper-
ties to the specific application, have been tested over the
years by various laboratories in Florence, Venice and Milan,
aiming at developing new protective coating materials for
the safeguard of cultural heritage [1,2,5,19–24]. The funda-
mental requirements for a protective coating when the
substrate is a porous one, such as a natural stone, are water
repellence, preservation of the substrate permeability to
water vapor, good optical properties (i.e. negligible short-
and long-term modification of color and gloss upon applica-
tion), chemical and photochemical stability and inertness
towards the stone substrate, also related to the required
reversibility of the treatment [25]. The protective properties
of the selected fluorinated copolymers were compared with
fraction of fluorinated units, the CF groups are more likely
3
to be homogeneously distributed in the bulk of the polymer
with little enrichment at the polymer–air interface; there-
fore, the good but not outstanding performance of the
coating at short contact times is balanced by a fair and
long-lasting water repellency. The very high initial hydro-
phobicity of the FOEMA copolymer is due to self-segrega-
tion and organization of the perfluorooctyl side chains in
semicrystalline domains at the polymer–air interface; such
structure is quickly destroyed when air is replaced by water
and the interfacial energy is raised, favoring a thermodyna-
mically driven surface restructuring where the fluorinated
groups are replaced by less hydrophobic ones. Any water
repellent efficacy is quickly lost also by the unfluorinated
materials, even those performing well at shorter times such
as EMA/BVE.
TM
those of representative acrylic (Paraloid B72) and silox-
ane-based commercial products widely employed in this
field. Techniques such as static and dynamic contact angle
measurement, determination of capillary water absorption
and permeability, colorimetry and monitoring of the above
parameters upon accelerated photoaging were routinely
carried out on treated stones of different composition and
porosity (from 1 to 40%), and particularly on carbonatic
ones. Special attention was devoted to the comparative
evaluation of fluorinated and unfluorinated copolymer ana-
logs. Systematic variations of structural features such as the
length of fluorinated side chain (FOEMA and TFEMA),
mole fraction of fluorinated co-units, side chain branching
The most durable hydrophobic protection was provided
by TFEMA/BVE; this was ascribed to the combined effects
of T , lower than that of TFEMA/MA and possibly allowing
g
the deposition of a more uniform coating, and to the lower
polarity of the VE unit, resulting in a reduced water sensi-
tivity of the coating. However, TFEMA/BVE loses its
(HFIMA and HFIFA), replacement of acrylate with VE
comonomers, main chain fluorination (FHEFA and HFIFA),

320
V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
efficacy after photoaging, as the consequence of the very
poor photochemical stability of this latter copolymer [16].
Less systematic data are available for copolymers of type
b–e FA. Among them, copolymers of EDFMA and HFIFA
A fluorinated acrylic latex based on the general structure
reported in Fig. 2, prepared by simple batch emulsion
polymerization, was comparatively evaluated with two
other commercial fluorinated acrylic-based latexes as
water- and oil-repellent finish for textiles [27,28]. As a
further development of this research activity, better con-
trolled procedures based on starved-feed semi-continuous
emulsion polymerization process are being developed, aim-
ing at the preparation of hybrid nanostructured polymer
particles with selective fluorination (e.g. in the shell of a
core-shell structure) and controlled conversion of the silane
groups [29].
TM
with BVE were compared with Lumiflon LF200 (Asahi),
an alternating CTFE/VE copolymer (CTFE: chlorotrifluor-
oethylene). Preliminary results [19] have confirmed the
expected superior photooxidative stability of the CTFE/
VE copolymer, which undergoes fast crosslinking due to
the presence of reactive groups in the side chain, but remains
structurally unaltered as opposed to most FA/VE copoly-
mers. This coating material performs well also in terms of
protective behavior, which is comparable at short times with
that of the highly water repellent TFEMA/BVE and slightly
better than HFIFA/BVE at longer contact times. The per-
formance and surface properties (contact angle with water)
of Lumiflon was almost unaffected by 1500 h of photoaging.
A similar behavior was also observed on some substrates
when using self-crosslinkable fluorinated acrylic terpoly-
mers containing the reactive trialkoxysilyl group in the side
chain, with the general structure [26]:
1.8. Nanotechnology applications
Fluorinated polymers are increasingly considered as
materials in electronic and optoelectronic applications, such
as data storage, microlithography and other techniques
requiring high optical purity, control of refractive index,
selective sensitivity to ultra-low wavelength irradiation.
Uniform Langmuir–Blodgett (LB) films of poly(2,2,3,
3
,3-pentafluoropropyl methacrylate) (PPFPMA), that is
the same material previously tested as protective coating
1], were deposited at low surface pressure using the Lang-
[
muir–Schaefer (LS, a variation of LB) technique, yielding
from ultra-thin to relatively thick uniform layers [30]. The
quality of monolayer was good enough to allow its use for
the development of nanostructured materials. The LB films
were found to be sensitive to electron beams, allowing
nanowriting by positive patterning produced on low-dose
irradiation. At higher irradiation doses, negative pattern
associated with film crosslinking could also be produced.
The main advantage provided by PPFPMA with respect to
unfluorinated acrylic homopolymers is the improved deposi-
tion quality, and thus better quality of the nanoscripture.
1.7. Water-borne multifunctional polymers for
improved coating adhesion and self-crosslinking
1.9. Polyolefin fluorination through free-radical
grafting of fluorinated molecules
Prompted by the interesting results obtained by our
reactive terpolymers as protective coatings on stone, a
research project aimed at the development of new water-
borne fluorinated polymer dispersions bearing reactive
groups was commenced. Reactive or otherwise functional
groups are generally required in order to stabilize the
colloidal dispersion prepared by emulsion polymerization
processes, or when controlled particle size and particle
size distribution (affecting penetration into porous net-
works), high performances in terms of film formation
behavior, film mechanical strength and adhesivity, are
needed for the final application. However, control of the
polymerization can be critical when a high degree of
fluorination (which makes the polymer hydro- and oleo-
phobic) or the introduction of hydrolytically unstable
alkoxysilane groups, conducive to condensation products
through sol–gel type reactions, depress the colloidal sta-
bility of the latex.
In the present report is described the synthesis of a new
fluorinated N-alkylmaleimide from a perfluoroalkyl car-
boxylic acid readily available as industrial electrofluorina-
tion product, and its reactivity towards free-radical reactions
such as copolymerization with vinyl ethers (VE) and graft-
ing onto polyolefins. The alternative two-step grafting and
functional modification of polyolefins by means of low
molecular weight or oligomeric fluorinated compounds
based on the perfluorocarboxylic acid precursor will also
be briefly discussed.
Maleimide and bis-maleimide derivatives are useful
building blocks and crosslinking agents for highly thermo-
stable polymers and networks. Differently from maleic
anhydride (MAH), maleimide homopolymerization in the
presence of free-radical initiators can be a significant path-
way for monomer consumption [31,32]. High molecular
weight products are easily obtained by copolymerization

V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
321
Fig. 2. General structure of multicomponent fluorinated latex polymers.
with electron-rich monomers (e.g. VE). These latter are
usually characterized by close to alternating comonomer
sequences, although with a less regular structure if compared
with MAH copolymers due to the not negligible maleimide
homopropagation. The alternating copolymerization of mal-
eimides has long been the subject of mechanistic studies
solution, although no examples are reported with a malei-
mide derivative as the monomer. A procedure frequently
found involves the post-modification of maleated polyole-
fins with an amine or amine-terminated macromolecule
[45,46]. However, such approach is likely to lead to lower
grafting yields, and therefore to less efficient use of the
aminofunctional derivative.
[
33,34] and even recently new features related to the extre-
mely high reactivity of such system have been devised, e.g.
in photoinitiated copolymerization [35].
This can be a major concern when the functional reagent
is a costly one, such as a highly fluorinated molecule, which
is also expected to be poorly miscible with a hydrocarbon
matrix. On the other hand, fluorination of polyolefins can
result in new materials with novel surface properties, such as
ultra-low friction coefficient and oil repellence, as well as
improved compatibility with fluorinated thermoplastic and
elastomeric polymers.
We have therefore synthesized N-(2-pentadecafluoro-n-
octanoyloxy)-ethyl)maleimide (FOMI) in order to study its
behavior in free-radical copolymerization and grafting reac-
tions.
Most maleimides studied as monomers in free-radical
grafting or copolymerization reactions are N-aryl deriva-
tives, seemingly due to the relatively easy synthesis and
excellent thermal stability of the resulting succinimide
repeat units. N-arylmaleimides show a stronger tendency
towards formation of alternating copolymer structures with
respect to the N-alkyl derivatives [36,37], although strictly
alternating copolymers are hardly obtained even in the
presence of fluorinated substituents [38,39] and are best
achieved by functional conversion of alternating precursors
such as poly(maleic anhydride-alt-ethylene), e.g. with an
amine [40,41]. The presence of the aromatic groups imparts
a higher conformational rigidity, that is higher T , and
g
2. Results and discussion
increased photochemical sensitivity with respect to the
aliphatic analog. These can be undesired features if the
monomer has to be employed in the formulation of a coating
for outdoor applications where colorlessness and, more
generally, interaction with UV-Vis light can be critical
parameters. As opposed to the aromatic maleimides, only
a limited number of papers report on the synthesis and use of
N-alkylmaleimide as monomers or reagents in free-radical
processes, and only one, to our knowledge, deals with a
fluorinated N-alkylmaleimide [42]. These latter are poten-
tially interesting building blocks for new polymeric materi-
als with applications as protective coatings for valuable
surfaces, such as in the preservation of works of art and
waterproofing of historic buildings, or in optics and electro-
nic applications [43]. In addition they can be used as
fluorinating agents for polyolefins through free-radical graft-
ing, which was shown to be an efficient method of direct
melt functionalization of high density polyethylene (HDPE)
with a fluoroalkyl substituted N-arylmaleimide [44]. Free-
radical grafting should be a viable route also for reactions in
The fluorinated N-alkylmaleimide derivative N-(2-penta-
decafluoro-n-octanoyloxy)-ethyl) maleimide (FOMI) was
synthesized by way of the intermediate 3,6-oxy-(1,2,3,6-
tetrahydro)phtalic anhydride (1), the adduct of maleic anhy-
dride (MAH) and furan that is easily obtained by simple
Diels Alder addition reaction. The adduct is stable at the
relatively high temperatures generally required to carry out
the cyclization of a N-alkylmaleamic acid to the respective
imide (see Scheme 3), thus allowing to substantially increase
the yield of imidation of maleic anhydride with an aliphatic
amine. Indeed the latter is usually very low in the direct
imidation of MAH, due to the moderate but not negligible
reactivity of the MAH C¼C and the consequent formation of
polymerization products. In fact, previous attempts to pre-
pare the imide by direct condensation of the maleamic acid
obtained from MAH and ethanolamine under relatively mild
conditions were unsuccessful. A first attempt carried out in
the presence of catalytic H
several days gave negligible yields, in poor agreement with a
SO at room temperature for
4
2

322
V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
O
O
O
O
OH
H N
OH
2
NH
OH
OH
O
N
O
O
O
EtOH, 25 ˚C
EtOH, ∆
O
O
1
3
2
3
O
O
O
O
C7F15 COOH
NaHSO4
O
C7F15
O
C7F15
O
N
N
O
O
∆
, C H
6 6
4
Scheme 3.
previous report maintaining a 51% conversion [47]; a second
attempt run in heterophase with aqueous phosphoric acid in
refluxing xylene solution, according to the method adopted
by Kita et al. [48] for isopropylamine, led to the formation of
insoluble polymerization products.
The synthesis through the intermediate 1 proceeds
smoothly, although in moderate yields due to the selective
reactivity of the endo-isomer of the adduct 1. Indeed the
latter was obtained as a 2/1 exo/endo mixture (Scheme 4),
the main product being the thermodynamically favored exo
isomer due to steric compression that promotes fast isomer-
ization of the kinetically favored endo isomer. Aminolysis of
water removal, yielding the N-(2-(pentadecafluoro-n-octa-
noyloxy)-ethyl)maleimide (4) (FOMI). Unexpectedly, the
fluorinated N-alkylmaleimide thermal stability is quite poor,
and similar to that of the perfluorocarboxylic acid precursor,
as shown by the thermal degradation curve of Fig. 3 where the
onset of the first pyrolytic step is observed just above 100 8C.
This initial degradation, associated with loss of the N-per-
fluoroalkylcarboxyethyl moiety, is followed by complete
volatilization of the residue at temperatures above 400 8C.
The reactivity of the fluorinated maleimide as a monomer
in free-radical graft- and copolymerization reactions was
then investigated.
1
with stoichiometric ethanolamine, carried out in the pre-
sence of an initial excess of ethanolamine in order to prevent
competitive alcoholysis of the anhydride, gave the maleamic
acid (2), which underwent dehydration–cyclization by mild
thermal treatment in refluxing ethanol. The same reaction
led to unidentified polymerization products when carried out
at higher temperature using 2-methoxyethanol as the sol-
vent, due to retro-Diels Alder cleavage of the protecting
2.1. Copolymerization with butyl vinyl ether (BVE)
The reactivity of FOMI was firstly tested in copolymeriza-
tion reactions with VE. A single experiment was carried out,
using a large molar excess of BVE (FOMI/BVE ¼ 32/68) in
order to favor its incorporation in the copolymer structure,
that is through growth of alternating comonomer sequences.
The resulting FOMI/BVE ¼ 63/37 copolymer composition,
0
group on the maleic C¼C bond. Isolation of pure N-(2 -
1
hydroxyethyl)-(3,6-endoxy-1,2,3,6-tetrahydro)phtalimide
(
as determined from the H NMR resonances at 4.7–4.3 and
3) from the crude product was achieved with best results by
1.0–0.7 ppm, respectively, indicates that homopropagation
of the maleimide prevails over comonomer alternation,
although the low conversion (overall ¼ 39%; FOMI ¼
49%) and low molecular weight of the resulting copolymer
(Mn ¼ 11,000 g/mol, Mw=Mn ¼ 1:45 by SEC) suggest also a
low homopropagation efficiency in these conditions.
way of chromatographic separation (about 23% yield, in
addition to some 10% uncondensed amic acid precursor).
Simple reprecipitation from ethanol at T ¼ ꢀ25 8C afforded
the same product but in lower yield (about 15%). Both
products corresponded to the pure exo isomer. The moderate
overall yield was at least partially due to some unavoidable
retro-Diels Alder and polymerization side reactions.
2.2. Graft reactions on olefin copolymers (OCP)
The imide-alcohol (3) then underwent concurrent retro-
Diels Alder [49] and esterification reaction with pentadeca-
fluoro-n-octanoic acid [50] under mild conditions with an
inorganic catalyst (sodium bisulfate) and upon azeotropic
The poor thermal stability of the fluorinated compound
suggested to avoid using it for direct polyolefin grafting in
the melt, since the method usually requires temperatures that
exceed the melting temperature of polyethylene (and thus of
most olefin copolymers), that is well above the stability
range of pure FOMI. However, solution grafting of poly-
olefins in the presence of free-radical initiators can be
successfully achieved with MAH and other poorly homo-
propagating disubstituted olefins [51]. In order to generate
a sufficiently high concentration of free radicals at a tem-
perature well within the stability range of FOMI, grafting
Scheme 4.

V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
323
Table 1
Free-radical grafting of maleic derivatives onto olefin copolymers (OCP)
a
b
c
FD (%)
Sample
OCP/monomer
mole ratio)
Monomer/initiator
(mole ratio)
(
VLDPE-g-MAH
EPM-g-MAH
10.3
14.7
11.4
10
10
5
0.51
0.35
2.00
VLDPE-g-FOMI
a
Grafting reaction of maleic monomer (MAH or FOMI) in benzene
solution; initiator Perkadox 16, T ¼ 70 8C, 3 h.
b
Average MW of OCP repeat units is used, based on copolymer
composition.
c
Functionalization degree (moles of grafted succinic derivative per 100
1
olefin repeat units) as determined by titration (MAH) or H NMR (FOMI).
Fig. 3. Pyrolytic weight loss curve of FOMI. Extrapolated onset of first
stage: 157 8C; residue at 300 8C: 15.9%.
exclude the possibility of thermal decomposition of the
maleimide derivative in hot toluene.
reactions were performed in benzene at T ¼ 70 8C with
In the grafting reactions with MAH, the VLDPE solution
was comparatively less viscous than that of EPM, the latter
becoming increasingly more viscous during the reaction due
to the larger fraction of crosslinked material formed. In
addition to favor gel formation, with less than 50% extrac-
table polymer, the soluble fraction of EPM-g-MAH had a
FD ¼ 0:35%, lower than that of VLDPE-g-MAH (0.51%)
and corresponding to a scant 2.5% conversion of the olefin
(see Table 2). The following grafting experiment with FOMI
was carried out only on VLDPE, since the EPM sample was
shown to be more prone to crosslinking in the reaction
conditions adopted.
The grafting reaction with FOMI, leading to the succini-
midyl derivative VLDPE-g-FOMI (Scheme 5), proceeded
with apparently lower overall conversion due to the larger
olefin/OCP weight ratio, but actually gave about the same
fraction of soluble graft copolymer (82 against 87% with
MAH, see % gel in Table 2). The significantly higher FD can
not be ascribed to the amount of initiator and thus of grafting
sites, but rather to the probable growth of some oligomeric
FOMI grafts, as expected when using a homopropagating
maleimide instead of MAH. A moderate decrease of mole-
cular weight in VLDPE-g-FOMI (see Table 3) is indicative
of free-radical induced chain scission reactions competing
with radical coupling and crosslinking processes leading to
gel formation. However, no detailed analysis was made in
order to further elucidate the actual mechanisms involved.
As an alternative approach to the above described poly-
olefin fluorination through free-radical grafting of FOMI,
TM
Perkadox 16 as the initiator (half life t1=2 ¼ 20 min at
T ¼ 70 8C). The reactivity of two different olefin copoly-
mers (OCP), a linear very low density polyethylene
(
VLDPE, a copolymer of ethylene and 1-octene) and an
ethylene–propylene copolymer (EPM), were preliminarly
tested with MAH as the grafting monomer.
Similar polyolefin/monomer molar ratios were fed to the
reaction solutions in both MAH and FOMI grafting experi-
ments, corresponding to a 1/1 polyolefin/FOMI weight
ratio (see Table 1). Such a high concentration of grafting
monomer was employed with the aim of maximizing the
functionalization degree (FD), according to previous unpub-
lished results from our laboratory, and thus allow a quanti-
tative determination of the grafting efficiency by means of
spectroscopic techniques (IR, NMR); in fact, differently
from the products of grafting with MAH, the titration
method could not be used for the polyolefin–FOMI adduct.
A relatively high monomer-to-initiator molar ratio and
minimum amount of solvent were used in order to minimize
cross linking and radical transfer side reactions, leading to
gel formation and increased fraction of ungrafted material,
respectively. The polymers grafted with MAH were
exctracted with acetone to remove low molecular weight
by-products and unreacted monomer, then with toluene to
separate the soluble fraction from any gel-like material
deriving from crosslinking reactions competitive with
the grafting process. VLDPE-g-FOMI was redissolved in
n-hexane and chloroform after the acetone extraction, to
Table 2
Free-radical grafting of activated olefins (MAH and FOMI) onto olefin copolymers (unless stated, values are given in mg)
a
Conversion (%)
Run
Soluble
fraction
OCP
Feed
Olefin
Feed
olefin
OCP
Conversion (%)
% as gel
Soluble fraction
Soluble fraction
VLDPE-g-MAH
EPM-g-MAH
73
37
40
367
184
88
420
412
110
363
182
72
83
85
4
4.5
2.5
15
13
56
18
2
VLDPE-g-FOMI
110
16
a
Soluble polymer fraction with respect to the total amount of OCP and grafting olefin.

324
V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
The amidoamine (5) was synthesized by treatment of the
O
O
fluorinated acid with oxalyl chloride in dry toluene at RT,
followed by reaction of the resulting acyl chloride with a
large excess of hexamethylenediamine. Unfortunately, the
resulting fluorinated amidoamine was insoluble in all com-
mon unfluorinated organic solvents, making unpractical its
use as a fluorinated modifier of OCP-g-MAH through reac-
tion in solution at moderately high temperature. Melt func-
tionalization was deemed unsuitable due to the expected
thermal instability of the fluorinated amide.
R
R
FOMI
O
C7F15
N
O
R
OCP
OCP-g-FOMI
Scheme 5.
Table 3
SEC analyses of VLDPE and graft-VLDPE
A preliminary test of co-oligomerization with aminofunc-
tional initiator was carried out to explore the feasibility of
the route based on grafting of an amino-terminated FOMI
oligomer (6) onto OCP-g-MAH. BVE was copolymerized
with diethyl maleate (DEM), a disubstituted olefin expected
to display a reactivity similar to that of a maleimide in free-
radical copolymerization, using an aminofunctional diazo-
Sample
M
n
(g/mol)
M
w
(g/mol)
w n
M /M
VLDPE
VLDPE-g-FOMI
91000
69000
228000
180000
2.5
2.6
0
two synthetic pathways to chemical modification of
functional MAH-grafted polyolefins (OCP-g-MAH) by
means of aminolysis of the succinyl anhydride groups with
formation of fluorinated maleimide grafts were considered,
as shown in Scheme 6. These are: (i) reaction with an
amidoamine derivative (5) of the perfluorinated carboxylic
acid precursor; (ii) reaction with an amino-terminated FOMI
copolymer (6).
compound (2,2 -azobisisobutirroamidine hydrochloride,
AIBA) as the initiator and thiol (aminoethanthiol hydro-
chloride, AET) as a chain transfer agent, in order to max-
imize the amount of NH -terminated oligomeric products.
2
The results, summarized in Table 4, indicate a quite poor
control of the polymerization process, giving oligomeric
products in low yield and with a less than quantitative degree
of chain end functionalization (EFD). The addition of AET
O
O
C7F
15
O
C7F15
H N (CH ) NH
2
2 6
(CH2)6 NH
N
5
O
O
OCP-g-FOMI
O
O
O
X
CH2 CH
OCP-g-MAH
NH2
N
O
R
x
O
O
y
N
X
CH2 CH
O
(CH2)2
O
O
R
x
O
O
y
N
O
(
CH2)2
C7F
15
6
O
OCP-g-FOMI/BVE
O
C7F
15
Scheme 6.
Table 4
Copolymerization of DEM and BVE in the presence of aminofunctional initiator and transfer agent
a
b
Run
AET
mol%)
Conversion
(%)
Composition
M
n
(g/mol)
M /M
w n
Amidine end groups
c
(% of chains)
(
(DEM/BVE/AIBA)
DEM/BVE1
DEM/BVE2
DEM/BVE3
–
39
24
15
15/7/1
2100
700
1.7
2.8
2.1
66
36
56
2.5
5.1
3/0.5/1
4.5/1.5/1
900
a
Overall comonomer conversion (the contribution of chain end moieties from AIBA or AET is here neglected, thus the conversion can be slightly
overestimated).
b
Molar composition as determined by 1H NMR; the fraction of aminoethylsulfide end groups from AET could not be evaluated.
c
From the Mncalc/Mnexp ratio, where Mncalc is calculated from the copolymer molar composition, in the hypothesis that each macromolecule carries an
2
amidine chain end from the initiator, and Mnexp is the experimental SEC value. Here the –NH end groups from AET are not included.

V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
325
TM
as a chain transfer agent, while not granting a higher EFD,
causes a further reduction of monomer conversion and an
unexpected increase in polydispersity, in addition to lower
the MW as expected. Due to these discouraging results, the
analogous copolymerization with DEM replaced by more
precious FOMI was not performed.
(VLDPE Engage
8150 from Du Pont Dow Elastomers,
24 mol% of C8 co-units) were purified by 8 h soxhlet
extraction with acetone. Etanolamine (Aldrich) was distilled
from KOH under inert atmosphere. Furan (Fluka) was
distilled from Na. Tetrahydrofuran (Fluka) was twice dis-
tilled from Na and LiAlH , respectively.
4
1H NMR and 13C NMR spectra were recorded from
CDCl or DMSO-d solutions with a Varian Gemini 200
3
6
3
. Concluding remarks
spectrometer operating at 200 and 50.29 MHz, respectively,
using the solvent as an internal reference. 19F NMR spectra
were recorded on a Varian VxR-300 spectrometer operating
Following the main line of the research project aimed at
producing fluorinated polymeric materials with different
content and structural distribution of fluorine in the macro-
molecules, the grafting of long perfluoroalkyl chain (C F )
at 282.2 MHz, using CFCl as an external reference. FT-IR
3
spectra were recorded either from KBr pellets or from films
cast from CHCl solutions of the polymers on KBr disks,
7
15
3
onto polyolefins was attempted. Maleic derivatives are sui-
table to give this grafting reaction initiated by free radicals
produced in situ. For this reason a N-substituted maleimide
was selected, as this molecule combines the grafting capa-
city of the maleic double bond with the versatility offered by
the substituent on the N atom. In the present case three
distinct approaches were preliminarly investigated for the
grafting of the perfluoroalkyl chain onto ethylene/1-alkene
copolymers. These were respectively based on either direct
grafting of a N-substituted fluorinated maleimide (FOMI), or
reaction of a MAH-grafted polyolefin with a low molecular
weight amine or amino-terminated oligomer bearing the
perfluoroheptyl group. The former approach was limited
by the low thermal stability of FOMI, and could be success-
fully performed only in solution. The latter approaches offer
on the other hand much higher versatility, and even if further
optimization is needed, they can be considered as feasible
procedures for the modification of polyolefins by free-radical
addition of fluorinated molecules.
using a Perkin Elmer 1330 instrument. A Reichert Polyvar
polarizing microscope with Mettler FP52 hot plate was used
for melting points determination. Thermogravimetric ana-
lysis (TGA) was performed with a Mettler TG50 thermo-
balance and Mettler TC11 processor, using dry nitrogen
purge and a scan rate of 10 8C/min. Molecular weights were
determined by size exclusion chromatography (SEC) from
5 g/l chloroform solutions, using a Perkin Elmer Mod. 2/2
pump with Rheodyne 7161 injector, two PL GEL Mixed C
columns, a Jasco 830 RI differential refractometer and a
Perkin Elmer LC-75 spectrophotometric detector, operating
at 1 ml/min. A set of polystyrene standards (M 2.1, 9.0, 19,
w
83 and 233 kDa) was used for calibration.
4.2. Determination of the functionalization degree
(FD) of MAH-grafted polyolefins
The degree of functionalization (FD), defined as the moles
of grafted MAH per 100 polyolefin monomer units, was
determined by titration as previously described [52]. The
procedure followed for VLDPE-g-MAH is reported here as a
representative example.
4
. Experimental
A 500 ml flask fitted with reflux condenser and oil bath
was loaded with VLDPE-g-MAH (0.229 g), 150 ml toluene
and 100 ml of a 85/15 v/v n-butanol/water solution). The
mixture was stirred 1 h at 77 8C until complete dissolution of
the polymer, then purged 15 min with nitrogen. The solution
was titrated with 1.20 ml of 0.0388N KOH in butanol
(previously standardized against 0.0510N p-toluensulfonic
acid) using thymol blue as an indicator; after adding an
additional 2 ml KOH solution the mixture was back-titrated
with 1.25 ml of 0.0597N aqueous HCl (standardized against
the KOH titration solution). FD is calculated as the mean of
direct and back titration (0.50 and 0.53%, respectively).
4
.1. General experimental procedures
Pentadecafluoro-n-octanoic acid (98%, trade name RM-
58, a gift from Miteni S.p.A.), absolute ethanol (Carlo
2
Erba, 99.8%), oxalyl chloride (Aldrich), aminoethanthiol
0
hydrochloride (AET, Fluka) and 4,4 -tert-butylcyclohexyl
TM
peroxydicarbonate (Perkadox
received. Azobis-1,1-dimethyl-2-propionitrile (a,a -azobis-
isobutirronitrile, AIBN, Akzo) and 2,2 -azobisisobutirroa-
16, Akzo) were used as
0
0
midine hydrochloride (AIBA, Akzo) were recrystallized
from ethanol; maleic anhydride (Carlo Erba) was recrys-
tallized from anhydrous benzene. 1,6-Diaminohexane
(
(
Fluka) and diethyl maleate (Aldrich) were vacuum distilled
0.2 mmHg) and stored under nitrogen. Benzene (Carlo
4.3. Synthesis of N-(2-(pentadecafluoro-n-octanoyloxy)-
ethyl) maleimide (FOMI) (4)
Erba) and butyl vinyl ether (BVE, Fluka) were distilled
after refluxing over Na/K alloy. Dimethylformamide was
fractionally distilled after refluxing over KOH. Poly(ethene-
co-propene) rubber (EPR CO-038 from Enichem Elasto-
4.3.1. 3,6-Oxy-(1,2,3,6-tetrahydro)phtalic anhydride (1)
In a 250 ml three-necked flask with magnetic stirrer and
reflux condenser containing 9.80 g (0.100 mol) of maleic
anhydride dissolved in 100 ml of anhydrous benzene, were
mers, 30 mol% of C co-units) and low density polyethylene
3

326
V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
added under dry nitrogen with a dropping funnel 6.81 g
0.100 mol) of freshly distilled furan. After 2 h stirring at
(nas C¼O), 1710 (n
C¼O), 1448, 1410, 1328, 1260,
ꢀ
1
sym
1
1204, 1142, 1090, 1024, 928, 804, 696 cm . H NMR
(
room temperature a precipitate had formed; stirring was
maintained for another 24 h, the solid filtered off under dry
nitrogen and washed with anhydrous benzene. The resulting
white crystals were a 2/1 exo/endo mixture of the title
compound (15.65 g, 94% yield); mp 124–125 8C (lit.
(CDCl ): d 6.73 (2H, s, ¼CH), 4.52 (2H, t, J ¼ 5:5 Hz,
3
1
3
CH –O–C¼O), 3.90 (2H, t, J ¼ 5:5 Hz, N–CH ) ppm.
C
2
2
NMR (CDCl ): d 170 (C¼O), 134.4 (¼CH), 130–105 (m,
3
1
9
–(CF ) –CF ), 64.9 (O–CH ), 36.0 (N–CH ) ppm. F NMR
2
6
3
2
2
(CDCl ) [54]: ꢀ81.3 (3F, t, CF ), ꢀ118.8 (2F, d, –CF –
3
3
2
1
25 8C) [53]. IR (KBr pellet): n 3098, 3067, 3035, 2995
C¼O), ꢀ122.2, ꢀ122.5, ꢀ123.1, ꢀ123.2 (8F, s, –(CF ) –
2 3 2 3
2
4
(
cm
C–H); 1860 (broad, n C¼O); 1795 (broad, n
C¼O)
CF –CF ), ꢀ126.6 (2F, s, –CF –CF ) ppm.
as
sym
ꢀ
1
1
.
H NMR (CDCl , T ¼ 50 8C): d 7.45 (2H, dd,
3
J1 ¼ J2 ¼ 1; 5 Hz, O–CH endo), 7.00 (2H, s, ¼CH endo),
.55 (2H, dd, J ¼ 1; 5 Hz, ¼CH exo), 6.40 (2H, dd,
J ¼ 1; 5 Hz, –CH–C–O endo), 5.45 (2H, dd, J ¼ 1; 5 Hz,
4.4. Polyolefin grafting reactions
6
4.4.1. Solution grafting of MAH onto VLDPE
(VLDPE-g-MAH)
13
–
O–CH exo), 3.15 (2H, s, –CH–C–O exo) ppm. C NMR
(
1
4
CDCl , T ¼ 50 8C): d 169.8 (C¼O), 136.9 (¼CH exo),
VLDPE (0.420 g, approximately 8.7 mmol of olefin
co-units) was introduced under inert atmosphere in a
100 ml schlenk containing MAH (0.083 g, 0.84 mmol) in
3
36.4 (¼CH endo), 109.4 (O–CH endo), 82.2 (O–CH exo),
¯
8.7 (CH–C–O) ppm.
1
0 ml dry benzene. The mixture was stirred at 50 8C until
0
4
.3.2. N-(2 -hydroxyethyl)-3,6-endoxy-1,2,3,6-
tetrahydrophtalimide (3)
complete dissolution of the polymer, then cooled down at
room temperature before adding with a syringe a solution of
Perkadox 16 (0.032 g, 0.084 mmol) in 6 ml of benzene. The
clear and fluid solution was then stirred 3 h at 70 8C, becom-
ing viscous and cloudy after the first 20 min. The polymer
was recovered by precipitation in acetone, then extracted in
soxhlet first with acetone to remove unreacted low MW
compounds, then with toluene. The toluenic solution was
evaporated to give 0.37 g of VLDPE-g-MAH (73% yield). IR
(film on KBr): n 2922, 2856 (C–H), 1776 (n as C¼O), 1724
To a 100 ml two-necked flask with magnetic stirrer and
reflux condenser containing 1.84 g (0.030 mol) ethanolamine
and 50 ml absolute ethanol, was added 1 (4.98 g, 0.030 mol)
under nitrogen in little portions during 1 h. The suspension
was stirred 18 h at room temperature, then refluxed 5 h in
ethanol. Theresulting limpid colorlesssolutionwasdividedin
two fractions: the first was reduced to about 20 vol.% at the
rotary evaporator, left overnight at ꢀ25 8C and the obtained
precipitate filtered off, washed with absolute ethanol and
vacuum-dried (yield 15%); the second evaporated under
reduced pressure and purified by silica gel chromatography
with 5/4 methanol/ethyl acetate as the eluent (yield 23%).
Both procedures gave the same white crystalline product as
pure exo-isomer. mp 124–125 8C (decomposition). IR (KBr
pellet): n 3480 (O–H); 3098, 3035, 3000, 2970, 2936, 2892
ꢀ
1
1
(n
C¼O), 1460, 1364, 1260, 1090, 1028 cm . H NMR
3 2
sym
(CDCl ): d 3.7–3.6 (broad, CH–C¼O), 3.3–2.6 (broad, CH –
C¼O), 2.2–1.9 (broad, CH VLDPE), 1.25 (broad, CH
2
1
3
VLDPE), 0.9–0.8 (t, CH VLDPE) ppm. C NMR (CDCl )
3
3
[55]: d 170.5 (C¼O, graft-MAH), 38.8 (CH g-MAH), 37.2
(main chain –CH–), 34.6 (CH , g-MAH), 33.8 (main chain –
2
CH –CH–), 33.5 (side chain n-pentyl-CH ), 31.7 (side chain
2
2
(
1
C–H); 1766 (n C¼O); 1692 (n C¼O), 1436, 1402, 1332,
CH –Bu), 29.9 (CH –Pr), 29.5 (main chain –CH –CH –),
2 2 2 2
as
sym
ꢀ
1
1
166, 1056, 1014, 876 cm . H NMR (CDCl ): d 6.5 (2H, d,
26.5 (CH –Et), 22.5 (CH –Me), 13.9 (CH ) ppm.
2 2 3
3
J ¼ 1; 5 Hz, ¼CH), 5.25 (2H, d, J ¼ 1; 5 Hz, –O–CH), 3.75–
3
.60 (4H, m, N–CH –CH ), 2.9 (2H, s, CH–C¼O), 2.7–2.1
4.4.2. Solution grafting of FOMI onto VLDPE
(VLDPE-g-FOMI)
2
2
(
1
(
1H, broad, –OH) ppm. 13C NMR (CDCl ): d 176.7 (C¼O),
3
36.4 (¼CH), 80.9 (O–CH), 60.0 (CH –OH), 47.4
Following the same procedure described for VLDPE-g-
MAH, FOMI (0.110 g, 0.20 mmol) and VLDPE (0.110 g)
were dissolved in 3 ml dry benzene; the reaction was carried
out upon addition of Perkadox 16 (0.015 g, 0.04 mmol) in
2 ml benzene; after approximately an hour the solution,
initially fluid and limpid, had become viscous and whitish.
The polymer was precipitated and extracted with acetone,
then separated from the insoluble fraction by soxhlet extrac-
tion first with n-hexane then with chloroform. The unified
extracts gave 0.088 g (40%) of succinimide-graft copoly-
mer. IR (film on KBr): n 2960, 2922, 2854 (C–H), 1786,
1710 (C¼O), 1462, 1402, 1336, 1256, 1210, 1146, 1092,
2
¯
CH–C¼O), 41.6 (N–CH ) ppm.
2
4.3.3. N-(2-(pentadecafluoro-n-octanoyloxy)-
ethyl)maleimide (FOMI) (4)
A 250 ml three-necked flask equipped with magnetic
stirrer and Dean Stark apparatus was loaded with pentade-
cafluoro-n-octanoic acid (2.07 g, 0.005 mol), 3 (0.81 g,
3
0
.8 mmol), sodium bisulfate monohydrate (0.058 g,
.42 mmol) and 100 ml of dry benzene. The mixture was
refluxed 24 h while removing the azeotropic water and
monitoring the conversion by NMR. After roto-evaporation
of the remaining solvent, purification of the raw solid
by flash chromatography with 3/2 ethyl acetate/n-hexane
elution gave 0.73 g of a white crystalline product (yield
ꢀ
1
1
1024, 802 cm . H NMR (CDCl ): d 4.6–4.4 (2H, CH –O),
3
2
4.1 (H, CH–C¼O), 3.95–3.75 (2H, N–CH ), 2.3 (2H, CH –
2
2
C¼O), 2.1–1.5 (main chain CH), 1.4–1.1 (16H, CH
2
3
5%): mp 80–81 8C. IR (KBr): n 3110, 2960, 1776
VLDPE), 1.0–0.7 (3H, CH ) ppm.
3

V. Castelvetro et al. / Journal of Fluorine Chemistry 125 (2004) 315–328
327
4
.4.3. Poly(FOMI-co-BVE)
A 10 ml test tube with magnetic stirrer was charged with
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.4.4. Poly(DEM-co-BVE)
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1
calculated from the H NMR resonances centered at 6.8
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2
1
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874 (C–H), 1728 (C¼O), 1466, 1448, 1370, 1298, 1260,
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226, 1176, 1156, 1096, 1034, 980, 860, 798 cm . H
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