Effects of chemical variations on the mesophase behavior of new fluorinated poly(vinylcyclopropane)s

Article abstract of DOI:10.1016/j.jfluchem.2003.07.010

Several new structures of fluorinated polymers poly(1)-poly(9) were prepared by free radical ring opening polymerization of vinylcyclopropane monomers 1-9 containing different fluorinated side groups of the type -(CH₂)_n(CF₂) _pF. While in poly(1)-poly(3) p varied from 6 to 10 for a fixed n=2, in poly(4)-poly(6) n increased from 3 to 5 at the given p=8. In poly(7) and poly(8) a phenyl ring was incorporated to elongate the mesogenic side group (n=2; p=6 and 8, respectively), that was further separated from the polymer backbone by a methylene spacer (m=11) in poly(9). Therefore, the effects of various chemical variations of the polymer structure on the mesophase behavior could be assessed. The polymers were in fact co-polymers comprising both 1,5-linear and cyclobutane-ring isomer units. In any case they formed smectic mesophase(s) owing to the special character of the perfluorinated chains. The order and the isotropization temperature (T_i) of the mesophase were enhanced by increasing p, but T_i lowered with increasing n. Extension of the side group by insertion of a phenyl ring improved T_i. Wide angle X-ray diffraction studies clarified the nature of the different smectic phases, the occurrence of which was discussed in terms of the ability of the fluorinated side groups to pack antiparallel in either a partly or fully interdigitated structure. Co-polymers of 3 with a non-mesogenic, not fluorinated co-monomer 10 were also prepared with different chemical compositions. Co-polymerization was found to be another effective means of modifying the mesophase behavior of the poly(vinylcyclopropane)s.

Full text of DOI:10.1016/j.jfluchem.2003.07.010

Journal of Fluorine Chemistry 125 (2004) 283–292
Effects of chemical variations on the mesophase behavior
of new fluorinated poly(vinylcyclopropane)s
Marina Ragnolia, Elena Puccia, Massimo Bertoluccia, Bernard Gallotb, Giancarlo Gallia,*
a
`
Dipartimento di Chimica e Chimica Industriale, UdR Pisa INSTM, Universita di Pisa, via Risorgimento 35, 56126 Pisa, Italy
b
´ `
Laboratoire des Materiaux Organiques a Proprietes Specifiques, CNRS, BP 24, 69390 Vernaison, France
´
´
Received 13 February 2003; received in revised form 24 July 2003; accepted 30 July 2003
Abstract
Several new structures of fluorinated polymers poly(1)–poly(9) were prepared by free radical ring opening polymerization of
vinylcyclopropane monomers 1–9 containing different fluorinated side groups of the type –(CH2)n(CF2)pF. While in poly(1)–poly(3) p
varied from 6 to 10 for a fixed n ¼ 2, in poly(4)–poly(6) n increased from 3 to 5 at the given p ¼ 8. In poly(7) and poly(8) a phenyl ring was
incorporated to elongate the mesogenic side group (n ¼ 2; p ¼ 6 and 8, respectively), that was further separated from the polymer backbone
by a methylene spacer ðm ¼ 11Þ in poly(9). Therefore, the effects of various chemical variations of the polymer structure on the mesophase
behavior could be assessed. The polymers were in fact co-polymers comprising both 1,5-linear and cyclobutane-ring isomer units. In any case
they formed smectic mesophase(s) owing to the special character of the perfluorinated chains. The order and the isotropization temperature
(Ti) of the mesophase were enhanced by increasing p, but Ti lowered with increasing n. Extension of the side group by insertion of a phenyl
ring improved Ti. Wide angle X-ray diffraction studies clarified the nature of the different smectic phases, the occurrence of which was
discussed in terms of the ability of the fluorinated side groups to pack antiparallel in either a partly or fully interdigitated structure. Co-
polymers of 3 with a non-mesogenic, not fluorinated co-monomer 10 were also prepared with different chemical compositions. Co-
polymerization was found to be another effective means of modifying the mesophase behavior of the poly(vinylcyclopropane)s.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Fluorine substitution; Fluorinated polymer; Liquid crystalline polymer; Mesophase; Ring opening polymerization; Vinylcyclopropane
1. Introduction and brief overview
surface reconstruction, still has not been resolved and limits
their useful practical application. The reason mainly attrib-
uted for this response is the poor stability of the amorphous
fluorinated surface chains which cannot prevent movement
of polar groups to the surface. Long-term hydrophobicity
even after exposure to a polar fluid, such as water, may arise
in particular when the fluorinated side chains of a polymer
are capable of organizing into an ordered structure both in
the bulk and at the surface in such a way that leads to the
formation of a surface primarily composed of tightly packed
–CF3 groups [1,22,23]. These unique characteristics render
fluorinated polymers particularly suitable for applications
such as hydrophobic, non-adherent coatings.
From a molecular level perspective, a uniformly orga-
nized array of –CF3 groups would be a surface with the
lowest possible surface tension. Self-assembly of amphiphi-
lic perfluorocarboxylic acid salts [24] occurs at the air–water
interface of Langmuir–Blodgett (LB) films to produce
among the lowest energy surfaces known. To create such
a surface with LB film quality, –CF3 groups must be aligned
and oriented at the air–film interface. Additional functional
Fluorinated polymers represent a class of very interesting
and versatile polymeric materials that may find application
in many different fields [1] ranging from electronics and
optics to coatings, thanks to their outstanding properties
such as low dielectric constant, low refractive index and high
optical transparency, as well as chemical and thermal resis-
tance (for some examples, see [2–9]). The incorporation of
fluorine in a polymer causes the polymer to have a low
surface energy [10,11] potentially leading to low wettability,
low friction coefficient and low adhesion [12–16]. Commer-
cially available fluorinated ester side chain acrylic and
methacrylic polymers are typical low surface energy coating
materials [17].
In recent years novel low surface energy fluorinated
polymers have been described [18–21]. However, among
these reported fluorinated polymers, one critical problem,
* Corresponding author. Tel.: þ39-050-2219272; fax: þ39-050-28438.
E-mail address: gallig@dcci.unipi.it (G. Galli).
0022-1139/$ – see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2003.07.010

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M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
groups can also be exploited as anchoring sites to bind self-
assembled LB films onto solid substrates [25]. An effective
alternative approach which avoids LB techniques for pro-
duction of a uniform –CF3 surface might be to harness the
self-assembly behavior of a class of fluorinated materials,
the liquid crystalline semifluorinated alkanes. For example,
free standing films of semifluorinated side group ionenes
[26] possess a very low critical surface tension (<10 mN/m)
due to their ability to arrange fluorinated groups in a highly
ordered smectic layer structure.
The latter molecules, in fact, are typified by core structures
composed of two or more aromatic or cycloaliphatic rings,
or combinations of them, that are either directly linked
together, as e.g. in biphenyls, or interconnected by a bridging
group, as e.g. an ester group in phenyl benzoates. Alkyl tails
are also normally attached at both ends of the mesogenic
core to introduce flexibility in the molecule and help tailor
the mesophase transitions and properties of the materials
[43]. More conventional mesogenic units, e.g. biphenyls,
have also been used in combination with partly fluorinated
tails in low molar mass [44–49] and polymeric liquid
crystals [34].
The perfluorinated species are chemically stable and
possess low viscosity and can, in suitable cases, dope the
stability of the resulting mesomorphic phases. Such sub-
stitutions (fluorine for hydrogen) in the flexible extremities
of mesogens, such as partial or total fluorination of either
one of the end chains of classical rod-like molecules, lead to
asymmetric compounds [46,50–56]. It is worth noting that
the nature of the spacer connecting the perfluorinated tail to
the rigid core, can govern the potential smectogenic char-
acter of the mesogen [57–60]. However, comparatively little
attention has been devoted to incorporating fluoroalkyl tails
bridged with short methylene segments ðx < 3Þ into any
kind of fluorinated mesogens [29,34,61,62].
We have very recently developed a novel architecture of
fluorinated polymers forming liquid crystalline phases from
2-vinylcyclopropanes [63]. Among various cyclic mono-
mers [64], 2-vinylcyclopropanes [65] are of interest because
they easily polymerize by a free radical ring opening
mechanism thanks to the release of the cyclopropane ring
strain [66–68]. Furthermore, the presence of bulky substi-
tuents on the ring can limit the increase in conformational
freedom during polymerization, thereby resulting in a
reduced contraction of free volume [67]. In consequence
of these particular features, vinylcyclopropanes undergo a
little volume shrinkage upon ring opening polymerization
[64,65], and their polymers appear to be candidate materials
for coating films, fillings, curing resins in which applications
a careful control of the bulk and surface properties of the
polymer is a demanding requirement. Introduction of fluoro-
substituents can additionally impart low energy surface
properties to the polymer films through enriching the surface
of orderly assembled perfluorinated chain segments.
In this work we have prepared new families of poly-
(vinylcyclopropane)s from different monomers containing
varied fluorinated side groups (Fig. 1). The principal objec-
tive was to confirm the capability of such new polymer
structures to form thermotropic mesophases as a function of
the mesogenic character of the fluorinated groups. There-
fore, the effects of chemical variations of the fluorinated
vinylcyclopropane monomer on the mesophase structure
and transition temperatures were studied, including changes
in the length of the perfluorinated chain (p) and the alkyl
chain spacer (m and n). Co-polymerization with not fluori-
nated vinylcyclopropane was also exploited to dilute the
Precise control of the surface properties of polymeric
materials by means of self-organization is a major objective
of current science technology. Such self-organization can be
driven by several mechanisms including phase separation of
block co-polymers, liquid crystallinity, hydrogen bonding,
and surface segregation [27]. Under some circumstances,
these mechanisms may be used together to form an ordered
surface structure. As an example, block co-polymers micro-
phase-separate to preferred microstructure, but when low
surface energy blocks are incorporated, surface and interface
segregation will also take place to create further organiza-
tion in the region of the low energy surface. In particular
liquid crystallinity may provide a useful means for preparing
low surface energy polymeric materials for non-stick coat-
ing application [1,28]. The attachment of a fluorinated
mesogen pendent to a polymer backbone can bring about
improvement and temporal stabilization of the surface upon
exposure to different environments, as a consequence of the
induced mesomorphic behavior in the bulk of the material.
For example, investigations on block co-polymers contain-
ing a fluorinated polymer block showed that rigid rod-like
fluorinated groups can form a highly organized surface
structure, stable to reconstruction upon exposure to water
as a consequence of the ordering of the fluorinated groups in
a liquid crystalline, smectic mesophase [1]. In fact, the
fluorinated side groups of these polymers residing in a
smectic mesophase while covering the surface of a polymer
film should overcome a too high enthalpy barrier to rear-
range when in contact with water.
Fluorinated liquid crystalline polymers are a relatively
new class of fluoropolymers [1,23,28–34]. Initial studies on
fluorinated liquid crystals focused on partly fluorinated
alkanes, namely diblock hydrocarbon–fluorocarbon mole-
cules such as H(CH2)x(CF2)yF (x, y ꢀ 6) [35–39]. The
ability of these compounds was shown to form liquid
crystalline mesophases presumably due to the strong phase
separation of fluorocarbon from hydrocarbon chain seg-
ments [40] and also to the rigid rod-like nature of the
fluorocarbon chains which tend to adopt a helical conforma-
tion in the mesophase state [41,42]. Later synthetic efforts
resulted in the development of liquid crystalline polymers in
which the length of the fluorinated tail was varied over a
wide range of numbers x and y [28,29,31,33,34]. Thus,
appropriately fluorinated molecules may be conceived as
unconventional mesogens in that they do not possess the
usual molecular features of more traditional liquid crystals.

M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
285
1) AIBN / 80 ˚C
+
F(CF ) I
F(CF ) (CH ) OH
(CH )
OH
2 p
2 p
2 n
2 n - 2
2) LiAlH
4
C H OOC COO(CH ) (CF ) F 1, 2, 3 (n = 2; p = 6, 8, 10)
14-n,p
12-p
13-n
2
5
2 n
2 p
4, 5, 6 (n = 3, 4, 5; p = 8)
_
1) PhCOCl / OH
HO
OH
PhCOO
OH
16
C H OOC COO
O(CH ) (CF ) F
2 n 2 p
+
7, 8 (n = 2; p = 6, 8)
2
5
2) H
15
F(CF ) (CH ) OH DEAD
2 p
2 n
PPh
3
14-n,p
C H OOC COO(CH )
O
O(CH ) (CF ) F 9 (m = 11; n = 2; p = 6)
2 n 2 p
2
5
2 m
_
1) OH
PhCOO
O(CH ) (CF ) F
2 n 2 p
HO
O(CH ) (CF ) F
2 n 2 p
+
2) H
C H OOC COOC H
2 5
10
2
5
17-n,p
18-n,p (n = 2; p = 6, 8)
Fig. 1. Structures of the vinylcyclopropane monomers 1–10 synthesized
Br(CH ) OH / K CO
3
and polymerized.
2 m
2
HO(CH )
O
O(CH ) (CF ) F
2 n 2 p
2 m
fluorinated repeat unit along the macromolecular chain and
influence the mesophase behavior.
19 (m = 11; n = 2; p = 6)
The surface structure and properties of these fluorinated
poly(vinylcyclopropane)s seem to be of special interest and
will be presented elsewhere.
Fig. 3. Reaction scheme for the synthesis of the fluorinated alcohols 14-
n,p and 19 and phenols 18-n,p.
the corresponding monocarboxylic acid 11. On the other
hand, different alcohols and phenols bearing the fluorinated
chain had been prepared following a sequential reaction
scheme that is outlined in Fig. 3. Intermediate 10 is actually
a vinylcyclopropane monomer in itself and was used for the
preparation of co-polymers poly(3-co-10) with variable
contents of fluorinated units 3.
2. Results and discussion
2.1. Synthesis
Several new vinylcyclopropane monomers 1–9 were pre-
pared that contained different, regularly varied fluorinated
side groups (Fig. 1). Thus, the effects of diverse chemical
variations in the fluorinated vinylcyclopropane units could
be assessed. According to this approach, monomers 1–3
consisted of a 2-(perfluoroalkyl)ethyl chain ðn ¼ 2Þ in
which the fluorinated segment was lengthened (p ¼ 6, 8,
or 10). Monomers 4–6 comprised a same perfluorooctyl
segment ðp ¼ 8Þ that was connected to an alkylene segment
of varying length (n ¼ 3, 4, or 5). Vinylcyclopropanes 7 and
8 (n ¼ 2; p ¼ 6 and 8, respectively) possessed an elongated
side group by incorporation of a phenyl ring, that was further
spaced by an additional alkylene segment in monomer 9
ðm ¼ 11Þ.
The monomers were free radically polymerized with a,a0-
azobis(isobutyronitrile) (AIBN) in bulk or in trifluoroto-
luene solution at 60 or 65 8C (polymerization yields 60–
85%). The resulting polymers were typically insoluble in
common organic solvents but soluble in Cl2FCCF2Cl or
trifluorotoluene/Cl2FCCF2Cl mixtures, and their molar
masses could not be fully characterized. Only poly(10)
and poly(3-co-10)b,c containing high proportions of not
fluorinated 10 units were soluble, for instance in chloroform
or tetrahydrofuran. The two co-polymers had Mn ¼ 38 000
and 18 000 g molꢁ1, Mw=Mn ¼ 2:02 and 1.73, respectively.
It is documented [66] that vinylcyclopropanes contain-
ing electron-withdrawing and radical-stabilizing groups
easily undergo radical ring opening polymerization yield-
ing polymers consisting predominantly, though not exclu-
sively, of 1,5-linear structures (Fig. 4, path A). Isomer
cyclobutane-ring structures have also been shown to form
[66], probably by recyclization of the propagating ring-
opened radical (Fig. 4, path C). The concomitant occur-
rence of such linear and cyclic repeat units was confirmed
by our previous investigations of the polymerization of
fluorinated vinylcylopropanes [63]. Therefore, the sup-
posed homopolymerization of monomers 1–9 (and 10)
led in effect to co-polymers (Fig. 5) comprising both
types of isomer repeat units. The relative proportions of
linear units (z) and cyclic units (1ꢁz) were evaluated
from the integrated areas of the 1H NMR signals at
5.5 ppm (–CH¼CH–), 2.3 ppm (ꢁCH2ꢁCH¼CHꢁCH2ꢁ)
and 1.6–2.2 ppm (cyclobutane ring) (Tables 1–4). It was
found that z depended considerably on the structure of the
The fluorinated vinylcyclopropane monomers 1–9 were
synthesized following one same general reaction pathway
(Fig. 2), in which a key intermediate was 1,1-diethoxycar-
bonyl-2-vinylcyclopropane (10). This was prepared by reac-
tion of trans-1,4-dibromobutene with the diethyl malonate
sodium salt and then selectively hydrolyzed [68,69] to yield
-
1) OH / EtOH
COOC H
2
Br
NaOEt
5
5
+
+
COOC H
2
2) H
Br
C H OOC COOC H
2
5
2
5
10
DCC
PPy
+
HO-Rf
C H OOC COOH
C H OOC COO-Rf
2
5
2
5
11
14-n,p
18-n,p
19
1-9
Fig. 2. Reaction scheme for the synthesis of the fluorinated vinylcyclo-
propanes 1–9.

286
M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
X
Y
X
Y
II
I
R
.
B
C
X
Y
R
.
.
X
Y
R
A
.
R
X
Y
X
Y
X, Y = Cl, phenyl, COOC H , COO(CH ) (CF ) F
2
5
2 n
2 p
Fig. 4. Mechanisms for the formation of linear and cyclic repeat units in the free radical ring opening polymerization of vinylcylopropanes (after [66]).
However, this effect was mitigated by the steric hindrance of
the fluorinated side chains which by contrast would rather
1-9
C H OOC COO-Rf
2
5
favour the formation of the cyclic e.g. z ¼ 0:48 in poly(3).
Such repeat units would in fact more easily accommodate the
bulky perfluorinated segments along the polymer backbone.
This is consistent with the results obtained in the polymer-
ization of vinylcylopropane monomers containing large ada-
mantanyl side groups [67].
AIBN
60-65 ˚C
C H OOC COO-Rf
2
5
COOC H
2
5
poly(1)-poly(9)
1-z
By assuming that in the formation of the co-polymers
poly(3-co-10) the two different co-monomer species could
follow the same propagation mechanisms as in the corre-
sponding ‘‘homopolymers’’, the repeat units from 10 would
be preferentially linear, whereas those from 3 would be
mainly cyclic, as schematically shown in Fig. 6.
z
COO-Rf
Fig. 5. Free radical ring opening polymerization scheme for the
preparation of fluorinated poly(vinylcyclopropane)s poly(1)–poly(9).
fluorinated substituents on the cyclopropane ring. While
stronger electron withdrawing side groups appeared to direct
the polymerization preferably towards the formation of the
cyclobutane repeat unit, e.g. z ¼ 0:10 in poly(1), weaker
electron withdrawing side groups led to the predominant
formation of the linear repeat unit, e.g. z ¼ 0:80 in poly(10).
2.2. Mesophase behavior
Each fluorinated poly(vinylcyclopropane) sample exhib-
ited thermotropic mesophase behavior (Tables 1–4). No
Table 1
Physico-chemical characterization of the poly(vinylcylopropane)s containing different (perfluoroalkyl)ethyl side groups ðn ¼ 2Þ
Polymera
p
zb
Mesophase behavior
c
Tg (8C)
Tic (8C)
DHic (J gꢁ1
)
Structure
dd (ꢂ0.1 A)
24.9
28.4
31.7
˚
Poly(1)
Poly(2)
Poly(3)
6
8
0.10
0.40
0.48
64
89
78
179
186
187
6.0
7.9
6.7
SmAd
SmAd
e
10
SmBd, SmAd
a Prepared in trifluorotoluene solution (AIBN, 60 8C).
b Content of linear units, by NMR.
c Glass transition temperature and isotropization temperature (and enthalpy), by DSC.
d Smectic layer periodicity, by WAXD.
e Smectic-smectic transition at 118 8C (DH ¼ 0:7 J gꢁ1).
Table 2
Physico-chemical characterization of the poly(vinylcylopropane)s containing different (perfluorooctyl)alkyl side groups ðp ¼ 8Þ
Polymera
n
zb
Mesophase behavior
c
Tg (8C)
Tic (8C)
DHic (J gꢁ1
)
Structure
dd (ꢂ0.1 A)
˚
Poly(4)
Poly(5)
Poly(6)
3
4
5
0.58
0.53
0.76
40
36
34
146
113
98
4.4
5.2
2.9
SmAd
SmAd
SmAd
29.6
30.5
31.9
a Prepared in bulk (AIBN, 65 8C).
b Content of linear units, by NMR.
c Glass transition temperature and isotropization temperature (and enthalpy), by DSC.
d Smectic layer periodicity, by WAXD.

M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
287
Table 3
Physico-chemical characterization of the poly(vinylcylopropane)s containing different (perfluoroalkyl)ethyl side groups ðn ¼ 2Þ without or with alkylene
spacer ðm ¼ 11Þ
Polymera
zb
Mesophase behavior
c
Tg (8C)
p
Tic (8C)
DHic (J gꢁ1
)
Structure
dd (ꢂ0.1 A)
˚
Poly(7)
Poly(8)
Poly(9)
6
0.81
0.81
0.36
48
46
21
200
205
81
13.0
15.1
4.5
SmAd
SmAd
SmAd
29.3
33.4
58.2
8
6e
a Prepared in bulk (AIBN, 65 8C).
b Content of linear units, by NMR.
c Glass transition temperature and isotropization temperature (and enthalpy), by DSC.
d Smectic layer periodicity, by WAXD.
e With alkylene spacer ðm ¼ 11Þ.
Table 4
Physico-chemical characterization of the co-poly(vinylcylopropane)s containing fluorinated (n ¼ 2; p ¼ 10) and not fluorinated side groups
Polymera
3b (mol%)
zc (mol%)
Mesophase behavior
d
Tg (8C)
Tid (8C)
DHid (J gꢁ1
)
Structure
d (ꢂ0.2 A)
e
˚
Poly(3-co-10)a
Poly(3-co-10)b
Poly(3-co-10)c
Poly(10)
50
40
30
0
0.50
0.60
0.80
0.80
35
35
35
33
173
168
140
–
8.2
10.8
9.6
–
SmA1
SmA1
SmA1
–
26.2
26.0
26.0
–
a Prepared in trifluorotoluene solution (AIBN, 60 8C).
b Content of fluorinated side groups in the co-polymer, by NMR.
c Content of linear repeat units, by NMR.
d Glass transition temperature and isotropization temperature (and enthalpy), by DSC.
e Smectic layer periodicity, by WAXD.
evidence of partial crystallinity was detected by differential
scanning calorimetry (DSC) or wide angle X-ray diffraction
(WAXD) analyses, and the mesophases formed directly
above the glass transition temperature of the polymer.
The glass transition temperatures were typically higher than
room temperature (30 ꢃC < Tg < 90 8C), with the only
exception of poly(9) (Tg ¼ 21 8C). In this polymer the long
alkylene spacer segment in the side groups probably acted as
an internal plasticizer. Thus, in the latter sample the meso-
phase was present at room temperature, while in all the
others it remained frozen in the glassy state at room tem-
perature. Generally speaking, the mesophase was very per-
sistent, the highest isotropization temperature (Ti ¼ 205 8C)
and the widest existence range (Ti ꢁ Tg ¼ 159 8C) being
detected for poly(8). However, the details of the mesophase
behavior of the polymers depended on their chemical struc-
ture and on the chemical composition of the co-polymers.
Polymers poly(1)–poly(3) presented a consistently high
Ti that slightly rose in passing from the sample with a
short perfluorinated tail ðp ¼ 6Þ to the sample with a long
perfluorinated tail ðp ¼ 10Þ (Table 1). Furthermore, while
there was one mesophase (SmAd) in poly(1) and poly(2),
poly(3) exhibited two mesophases (SmBd and SmAd) in a
sequence (Fig. 7). Therefore, lengthening the perfluori-
nated segment enhanced the mesogenic character of the
side groups and facilitated their in-plane correlation,
thereby permitting an efficient assembling in an ordered
mesophase. On the other hand, polymers poly(2) and
poly(4)–poly(6) presented one mesophase (SmAd), for
which Ti progressively decreased with increasing length
(n ¼ 2–5) of the alkylene segment in the (perfluoroocty-
l)alkyl side group (Table 2). This finding shows that, for a
given length of the perfluorinated tail ðp ¼ 8Þ, insertion of
longer hydrocarbon spacers depresses the tendency to form
mesophases of the semifluorinated side groups. This argu-
ment was further supported by evaluations of the isotropi-
zation enthalpy (DHi) that gradually decreased with
increasing number n from 7.9 to 2.9 J gꢁ1 (Table 2). Elon-
gation of the side groups of polymers poly(7) and poly(8)
by incorporation of a phenyl ring resulted in a significant
rise of Ti up to about 200 8C (Table 3). In fact, an increase in
the axial ratio (length over breadth) of the side groups
improved their ability to stabilize a mesophase by favoring
intermolecular interactions through the phenyl rings. By
contrast, this positive contribution was offset by the long
spacer segment ðm ¼ 11Þ in poly(9) that significantly
reduced the effective axial ratio of the more flexible side
groups with depression of Ti (down to 81 8C).
F(CF ) (CH ) OOC COOC H
2 5
2 10
2 2
COOC H
2
5
1-x
x
COOC H
2
5
Fig. 6. Simplified structure of the co-poly(vinylcyclopropane)s poly(3-co-
10).

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M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
miscibility of the aliphatic–fluoroaliphatic side groups with
the aliphatic macromolecular chain.
It is also worth noting that the present poly(vinylcyclo-
propane)s gave rise to mesophase behavior despite the fact
that the fluorinated side groups were diluted along the poly-
mer chain, even in the ‘‘homopolymer’’ samples, viz. one
fluorinated side group per five backbone carbon atoms in the
1,5-opened unit. This is at variance with most common liquid
crystalline polymers, specifically polysiloxanes and poly(-
meth)acrylates, in which normally the mesogens are much
more concentrated, a side group being present per two back-
bone atoms [72]. In one other example of liquid crystalline
poly(vinylcyclopropane)s, two typical cholesteryl or biphe-
nyl mesogens were present per repeat unit [73], which easily
accounts for the mesophase behavior of such polymers.
2.3. Mesophase structure
The structure and the structural parameters of the meso-
phase(s) of the polymers were determined by WAXD as
function of temperature. In any case the mesophase was
found to be smectic, even though the details of the packing in
the smectic layers depended on the chemical structure of the
polymers and co-polymers. The lower temperature meso-
phase of poly(3) (T < 115 8C) was a hexatic smectic phase
in which the side groups were locally ordered over a pseudo-
˚
hexagonal lattice (a ¼ 6:9 A) (Fig. 7a). The layer periodi-
˚
city d ¼ 31:7 A was much longer than the calculated length
Fig. 7. Powder WAXD patterns of poly(3): SmBd at 40 8C (a) and SmAd at
130 8C (b).
of the repeat unit in its fully extended conformation
˚
(L ¼ 25:6 A). Consistently, the average surface per side
2
˚
group (S ¼ 41 A ) was large enough to permit an antipar-
The mesogenic tendency of the long perfluorinated chain
ðp ¼ 10Þ was not disrupted in the co-polymers poly(3-co-
10) possessing significant contents of not fluorinated 10
units (Table 4). Upon dilution of the fluorinated 3 groups, Ti
was lowered with respect to poly(3) but was nevertheless as
high as 140 8C for poly(3-co-10)c containing 70 mol% non-
mesogenic 10 units.
allel arrangement of the side groups orthogonal to the layer
planes in a partly interdigitated bilayer structure, such as the
SmBd phase (d/L ¼ 1:24). In the high temperature range, the
˚
mesophase (d ¼ 31:7 A) exhibited no in-plane correlation
of the side groups, according to the onset of a lower order
˚
SmAd phase (average intermolecular distance D ¼ 5:9 A)
(Fig. 7b). The same kind of low order smectic mesophase
was detected in poly(1) and poly(2) (d/L ¼ 1:21 and 1.23,
We have previously noted [63,70] that the formation of
thermotropic mesophase(s) in polymers simply incorporat-
ing perfluoroalkylethyl chains is somewhat surprising, in
that it has been previously reported in a structurally related
polyacrylate only [29]. As mentioned, the mesogenic cap-
ability of fluorocarbon chains is attributed to the rigid-rod-
like character of their helical conformation in combination
with their immiscibility with other molecular constituents
[71]. As a net effect, distinct molecular sub-layers are
formed that would result in an ordered assembly in a
mesophase, normally smectic. We also explain the onset
of liquid crystallinity in poly(vinylcylopropane)s poly(1)–
poly(3) by the strong intramolecular phase separation of the
fluorocarbon side groups from the hydrocarbon polymer
backbone. While this phenomenon seems to be amplified
in poly(7) and poly(8) comprising mutually immiscible
aliphatic–aromatic–fluoroaliphatic constituents, it would
be less effective in poly(4)–poly(6) owing to the improved
˚
respectively; D ¼ 6:0 A), which confirms that the short
perfluorinated chain segments had a weaker mesogenic
character than the longer analogue. Poly(vinylcyclopro-
pane)s poly(4)–poly(9) also formed one SmAd phase
over the entire mesophase range. While the side groups
were more strongly interdigitated in poly(4)–poly(8)
˚
(d/L ¼ 1:17–1.21; D ¼ 5:9–6.0 A), they were little over-
˚
lapped in poly(9) (d/L ¼ 1:46; D ¼ 5:9 A). Accordingly,
the occurrence of such mesophase structure appears to be
a common feature for the present fluorinated polymers.
However, the co-polymers poly(3-co-10) gave rise to a fully
interdigitated (SmA1) smectic phase (d/L ¼ 1:01; D ¼
˚
5:8 A. Therefore, by co-polymerization not only was the
transition temperature of the mesophase changed but its
detailed structure was also modified with respect to poly(3).
The terminal CF3 group of rod-like fluorocarbon chains is
rather bulky with a Van der Waals volume of the equivalent

M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
289
32
31
30
29
Fig. 8. Schematic arrangements of the polymer side groups in different
28
27
26
25
24
smectic phases: double layer (left), interdigitated (center), and monolayer
(right). The mesogenic groups are shown with a spacer and rigid-rod-like
unit.
3
hemisphere of 42.6 A (compare with 16.8 A for the CH3
3
˚
˚
2
group) [74,75] and a cross-section surface of 23 A as
˚
estimated by molecular models. Therefore, there would exist
significant steric hindrance for two fluorinated tails to over-
lap and to order within the layers of an interdigitated smectic
phase, particularly in densely crowded polymers such as
poly(siloxane)s or poly(acrylate)s. Conversely, in these lat-
ter systems an efficient space filling could be achieved by
tilting the fluorinated side groups in an end-to-end arrange-
ment of a double layer smectic structure [70]. By contrast,
the much wider spread of the fluorinated side groups 1–9
along the polymer backbone of the present poly(vinylcy-
clopropane)s facilitated their ordering in a partly overlapped
arrangement with a greater intermolecular distance D. In the
co-polymers the mesogenic fluorinated side groups 3 were
even more spaced apart from each other by non-mesogenic
side groups 10 along the macromolecular chain and could
fully interdigitate in an antiparallel structure (Fig. 8).
Within any smectic phase the layer periodicity d remained
completely unaffected by varying temperature throughout
the whole mesophase range, as is illustrated in Fig. 9 for
poly(1)–poly(3). Moreover, it increased according to an
essentially linear trend with increasing number p of CF2
moieties in the perfluorinated chain segment (Fig. 10) or
5
6
7
8
9
10
11
p
Fig. 10. Variation of the smectic layer periodicity d for poly(vinylcyclo-
propane)s poly(1)–poly(3) with number p of CF2 groups.
number n of CH2 moieties in the alkylene chain spacer
(Fig. 11). These findings suggest that the side groups were
indeed ordered orthogonal to the smectic planes and adopted
one overall same conformation independent of temperature.
The successive increments of either n or p simply resulted in
lengthening the smectic layer spacing. A helical conforma-
˚
tion (span 2.59 A) was assumed for the perfluorinated chain
segments, analogous to other such systems [76].
3. Experimental
3.1. Intermediates
2-(Perfluoroalkyl)ethanols 14-n,p (n ¼ 2; p ¼ 6, 8, or
10) were commercially available (Fluorochem, 97%).
26
25
24
23
22
21
20
32
31
30
29
28
0
50
100
150
200
Temperature (˚C)
1
2
3
4
5
6
n
Fig. 9. Temperature dependence of the smectic layer periodicity d for
poly(vinylcyclopropane)s on heating: poly(1) (*), poly(2) (&), and
poly(3) (~) (open symbols refer to the cooling cycles).
Fig. 11. Variation of the smectic layer periodicity d for poly(vinylcyclo-
propane)s poly(2) and poly(4)–poly(6) with number n of CH2 groups.

290
M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
2-(Perfluorooctyl)alkanols 14-n,p (n ¼ 3, 4, or 5; p ¼ 8)
were synthesized according to a general procedure that is
described here in detail for 14-4,8 (Fig. 3).
and 50 ml of ethanol. The solution was then heated to reflux
for 7 h, cooled down and acidified with 10% HCl to pH ꢄ 2.
The precipitate formed was filtered off and dried under
vacuum giving 2.62 g (yield 97%) of pure 18-2,6: mp
77–80 8C.
4-(Perfluorooctyl)-butan-1-ol (14-4,8): A mixture of
37.17 g (68.0 mmol) of 7.48 g (128.9 mmol) of 2-buten-1-
ol (13-4) and perfluorooctyl iodide (12-8) was heated to
80 8C under nitrogen. An amount of 0.16 g (0.97 mmol) of
AIBN was then added in small portions over 45 min, and the
reaction mixture was kept at 80 8C for an additional 5 h.
After cooling to 40 8C, the mixture was evaporated to
dryness under nitrogen. The solid residue was dissolved
in 350 ml of anhydrous Et2O and added dropwise to a
suspension of 136 ml (136 mmol) of LiAlH4 1 M in Et2O
at room temperature under nitrogen. The mixture was kept
under vigorous stirring for 16 h and then slowly hydrolyzed
with 14 ml of water, 18 ml of 10% NaOH and finally water.
The precipitate was filtered off and the solvent was evapo-
rated under vacuum. The solid residue was purified by
repeated sublimations under vacuum at 40 8C leading to
19.10 g of pure 14-4,8 (yield 57%); mp 42–45 8C.
1H NMR (CDCl3) d ðppmÞ ¼ 2:6 (2H, CH2CF2), 4.2 (2H,
CH2OPh), 4.6 (1H, OH), 6.8 (4H, aromatic).
FT-IR (KBr): ꢀnðcmꢁ1Þ ¼ 3580–3400 (n O–H), 3100–
3050 (n C–H aromatic), 2930–2850 (n C–H aliphatic),
1290–1200 (n Ar–OR), 1360–1100 (n CF2 and n CF2–
CF3), 650 (o CF2).
11-[4-(2-Perfluorohexylethoxy)phenyl-1-oxy]-undecan-
1-ol (19): A suspension of 2.49 g (5.46 mmol) of 18-2,6,
1.14 g (8.25 mmol) of dry K2CO3 and 50 ml of anhydrous 2-
butanone was stirred at room temperature. An amount of
1.55 g (6.17 mmol) of 11-bromoundecan-1-ol in 50 ml of
anhydrous 2-butanone was then added dropwise over 2 h and
the mixture was heated to reflux for 30 h. The solid was
filtered off and the solution was evaporated to dryness under
vacuum. The solid residue was crystallized twice from
methanol giving 2.59 g (yield 76%) of pure 19: mp 86–
89 8C.
1H NMR (CDCl3): d (ppmÞ¼1:6ꢁ1:8 (5H, ðCH2Þ2þ
CH2OH), 2.1 (2H, CHꢁ2C1 F2), 3.7 (2H,CH2OH).
FT-IR (KBr): n ðcm Þ ¼ 3320 (n O–H), 2950–2882 (n
1H NMR (CDCl3): d ðppmÞ ¼ 1:5 (18H, 9CH2), 2.6 (2H,
CH2CF2), 3.6 (2H, CH2OPh), 3.9 (2H, CH2OH), 4.2 (2H,
CH2OPh), 6.8 (4H, aꢁro1matic).
ꢀ
C–H aliphatic), 1440 (d C–H), 1206 (d O–H), 1150 (n C–F),
660 (o CF2).
ꢀ
Phenols 18-n,p (n ¼ 2; p ¼ 6 or 8) and alcohol 19
(m ¼ 11; n ¼ 2; p ¼ 6) were synthesized following a gen-
eral procedure that is described here in detail for 19 (Fig. 3).
4-Hydroxyphenyl benzoate (16): 19.00 g (0.13 mol) of
benzoyl chloride was added in small portions over 1 h to a
solution of 20.08 g (0.18 mol) of hydroquinone in 300 ml of
deaerated water and 7.69 g (0.14 mol) of KOH under nitro-
gen at 0 8C. The reaction mixture was then stirred at 0 8C for
an additional 3 h and then poured into 400 ml of NaHCO3
saturated water. The precipitate formed was filtered off,
washed with water to neutrality, dried under vacuum and
finally twice crystallized from ethanol/water (70:30 v/v)
giving 14.2 g of pure 16 (yield 34%): mp 163–165 8C.
1H NMR (DMSO-d6): d ðppmÞ ¼ 6:9 (2H, aromatic 30
and 50), 7.1 (2H, aromatic 20 and 60), 7.6 and 7.7 (3H,
aromatic 3–5), 8.2 (2Hꢁ, 1aromatic 2 and 6), 9.5 (1H, OH).
FT-IR (KBr): n ðcm Þ ¼ 3580–3400 (n O–H), 3200–3050
(n C–H aromatic), 2930–2850 (n C–H aliphatic), 1290–1200
(n Ar–OR), 1360–1100 (n CF2 and n CF2–CF3), 650 (o CF2).
3.2. Monomers
1,1-Diethoxycarbonyl-2-vinylcyclopropane (10) (bp 69–
72 8C/0.5 mm) was prepared and then selectively hydro-
lyzed to the monocarboxylic acid, 1-carboxy-1-ethoxycar-
bonyl-2-vinylcyclopropane (11), according to literature
[66,69] (Fig. 2).
The fluorinated monomers 1–9 were synthesized follow-
ing the same general procedure that is here described for 3 as
a typical example (Fig. 2).
1-Ethoxycarbonyl-1-(2-perfluorodecyl)ethoxycarbonyl-
2-vinylcyclopropane (3): 3.85 g (0.07 mol) of KOH was
added in small portions to a solution of 15.05 g
ꢀ
FT-IR (KBr): n ðcm Þ ¼ 3450 (n O–H), 3100–3050 (n
C–H aromatic), 1714 (n C¼O), 1280–1210 (n Ar–OC¼O).
4-[2-(Perfluorohexyl)ethoxy]phenol (18-2,6): A solution
of 9.00 g (0.042 mol) of 16, 11.01 g (0.042 mol) of triphe-
nylphosphine (PPh3) and 15.12 g (0.042 mol) di-2-(perfluor-
ohexyl)ethan-1-ol (14-2,6) in 250 ml of anhydrous Et2O was
stirred at room temperature for 1 h. An amount of 8.00 g
(0.046 mol) of diethyl azodicarboxylate (DEAD) was then
added and the reaction mixture was kept under vigorous
stirring for an additional 96 h. The precipitate formed was
then filtered off and the solution was evaporated to dryness
under vacuum. The crude residue was crystallized twice from
methanolgiving3.41 g (yield 15%) of(17-2,6):mp89–91 8C.
Afterwards, 3.34 g (5.97 mmol) of 17-2,6 and 0.95 g
(0.016 mol) of KOH were dissolved in 20 ml of water
(0.07 mol) of 10 in 25 ml of ethanol at ꢁ5 8C. The reaction
was then let to proceed at room temperature for 12 h. The
solution was concentrated to small volume and acidified
with 10% HCl to pH ꢄ 2:5. The organic phase separated
was dried over Na2SO4 and then evaporated to dryness,
giving 11.50 g (90% yield) of pure 11 as viscous oil.
Afterwards, 5.02 g (25.0 mmol) of N,N0-dicyclohexylcar-
bodiimide (DCC) in 15 ml of anhydrous dichloromethane
was added dropwise to a solution of 4.62 g (25.0 mmol) of
11, 0.02 g (1.1 mmol) of 4-pyrrolidinopyridine (PPy) and
12.86 g (23.0 mmol) of 14-2,10 in 16 ml of anhydrous
dichloromethane under dry nitrogen atmosphere at 0 8C.
The reaction was let to proceed for an additional 2 h at 0 8C
and then for 2 days at room temperature. The precipitate was

M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
291
filtered off and the organic phase was washed with 5% HCl,
5% NaHCO3, water, dried over Na2SO4 and finally evapo-
rated to dryness. The crude residue was purified by liquid
chromatography on silica gel with ethyl acetate/hexane (2/3
v/v) as eluent leading to 5.97 g (yield 36%) of pure 3 as a
colorless viscous liquid.
Wide-angle X-ray diffraction experiments were performed
on powder samples with an especially designed pinhole
˚
camera using Ni-filtered Cu Ka beam (l ¼ 1:54 A), under
vacuum at various temperatures with an accuracy of 1 8C.
1H NMR (CDCl3): d ¼ 1:2 ppm (3H, CH3), 1.6–1.8 (2H,
CH2 cyclopropane), 2.3–2.7 (3H, CHcyclopropaneþ
CH2CF2), 4.2 (2H, COOCH2), 4.4 (2H, COOCH2CH2CF2),
4. Conclusions
Chemical variations, including variations of the molecular
framework of the repeat unit in the homopolymers and
chemical composition in the co-polymers, can effectively
modify the mesophase characteristics of fluorinated poly(-
vinylcyclopropane)s. These systems may in fact represent a
novel architecture of liquid crystalline polymers that form
smectic mesophases, the number and nature of which
depend on the molecular parameters (m, n, or p). Any
anticipated influence of the fine structure of the polymer
backbone on the mesophase behavior and properties remains
to be ascertained, especially when devising such polymers
for practical application. The mesophase order of the bulk
might be retained at the surface of polymer films therefrom,
which in turn can produce low surface energy coatings.
¼CH).
ꢁ1
ꢀ
FT-IR (liquid film): n ðcm Þ ¼ 3092 and 2964 (n C–H
vinyl and aliphatic), 1730 (n C¼O), 1640 (n C¼C vinyl),
1372 (d C–H cyclopropane), 652 (o CF2).
19F NMR (CDCl3/CF3COOH): d ¼ ꢁ5 (3F, CF3), ꢁ37
(2F, CH2CF2), ꢁ46 to ꢁ49 (14F, 7CF2), ꢁ51 (2F, CF2).
Anal. calcd. for C21H15F21O4: C, 34.52; H, 2.05; F, 54.66.
Found: C, 34.96; H, 2.15; F, 54.5.
3.3. Polymerization
The polymers were prepared following the same proce-
dure that is here described for poly(3) as a typical example.
Poly(vinylcyclopropane) poly(3): 0.58 g (0.68 mmol) of 3
and 5 mg (0.02 mmol) of AIBN were introduced into a
Pyrex vial. After three freeze–thaw pump cycles, the vial
was sealed under vacuum and the polymerization was let to
proceed for 29 h at 65 8C. The polymer was then precipi-
tated in methanol and purified by repeated precipitations
from Cl2FCCF2Cl in methanol. An amount of 0.41 g (yield
71%) of poly(3) was obtained as white powder.
Acknowledgements
The authors thank Prof. E. Chiellini, University of Pisa,
for helpful discussions. Financial support from the EU
(Contract G5RD-2001-00554 ‘‘Dentalopt’’) and the Italian
MIUR (PRIN 2001-03-4479) is gratefully acknowledged.
1H NMR (Cl2FCCF2Cl þ CDCl3): d¼ 1:2–1.4 (3H,
CH3), 1.5–3.0 (7.1H, CH2CH¼CHCH2þcyclobutane þ
CH2CF2), 4.2–5.0 (4H, COOCH2), 5.5 (0.9H, CH¼CH).
FT-IR (polymer film): ꢀn ðcmꢁ1Þ ¼ 2984 (n CH aliphatic),
1730 (n C¼O), 652 (o CF2).
References
[1] J. Wang, G. Mao, C.K. Ober, E.J. Kramer, Macromolecules 30
(1997) 1906;
19F NMR (Cl2FCCF2Cl=CF3COOH þ CDCl3): d ¼ ꢁ5
(3F, CF3), ꢁ38 (2F, CH2CF2), ꢁ45 to ꢁ50 (14F, 7CF2), ꢁ52
(2F, CF2).
For more comprehensive texts see: J. Scheirs (Ed.), Modern
Fluoropolymers, Wiley, Chichester, 1997;
G. Hougham (Ed.), Fluoropolymers, Kluwer Academic, New York,
1999;
3.4. Characterization
D.W. Smith (Ed.), Fluoropolymer 2000, EPS Publication, Hatties-
burg, 2000; in: Proceedings of the Fluorine in Coatings
Conference, Paint Research Association, Teddington, 2003.
V
NMR (1H, 13C, 19F) spectra were recorded with a Varian
Gemini VXR 300 spectrometer (operating at 299.9, 75.4,
and 282.2 MHz, respectively).
[2] M. Yamabe, Makromol. Chem. Macromol. Symp. 64 (1992) 11.
[3] C. Pitois, S. Vukmirovic, A. Hult, D. Wiesmann, M. Robertsson,
Macromolecules 32 (1999) 2903.
Size exclusion chromatography (SEC) was carried out
with a Jasco PU-1580 liquid chromatograph equipped with
four PL gel 5 mm Mixed-C columns, a Jasco 830-RI refrac-
tive index detector and a Perkin–Elmer LC75 UV detector.
Monodisperse poly(styrene) standard samples were used for
calibration.
Differential scanning calorimetry measurements were per-
formed with a Mettler DSC-30 instrument (10 8C minꢁ1).
The phase transition temperatures were taken at the max-
imum temperature in the DSC enthalpic peaks of the heating
cycles. The glass transition temperature was taken as the
half-devitrification temperature.
[4] R.F. Brady, Prog. Org. Coat. 35 (1999) 31.
[5] B.C. Auman, D.P. Higley, K.V. Schere, E.F. McCord, W.H. Shaw,
Polymer 36 (1995) 651.
[6] I. McCulloch, H. Yoon, J. Polym. Sci. Part A: Polym. Chem. 33
(1995) 1177.
[7] J. Gaynor, G. Scheueneman, N. Murata, J. Polym. Sci. 31 (1993) 1645.
[8] T. Maruno, K. Nakamura, N. Murata, Macromolecules 29 (1996)
2006.
[9] G. Ajroldi, Chim. Ind. (Milan) 79 (1997) 484.
[10] R.F. Brady Jr., J.R. Griffith, K.S. Love, D.E. Field, J. Coat. Technol.
59 (1987) 755.
[11] R.F. Brady Jr., J. Coat. Technol. 72 (2000) 45.
[12] E. Passaglia, M. Aglietto, F. Ciardelli, B. Mendez, Polym. J. 26
(1994) 1118.

292
M. Ragnoli et al. / Journal of Fluorine Chemistry 125 (2004) 283–292
¨
¨
[13] J. Hopken, M. Moller, Macromolecules 25 (1992) 1461.
[14] L.M. Wilson, A.C. Griffin, Macromolecules 27 (1994) 1928.
[15] R.V. Honeychuck, T. Ho, K.J. Wynne, R.A. Nissan, Chem. Mater. 5
(1993) 1299.
[44] H.T. Nguyen, G. Sigaud, M.F. Achard, F. Hardouin, K. Twieg, R.J.
Betterton, Liq. Cryst. 10 (1991) 389.
[45] H. Liu, H. Nohira, Liq. Cryst. 22 (1997) 217.
[46] B.Q. Chen, Y.G. Yang, J.X. Wen, Liq. Cryst. 24 (1998) 539.
[47] B.Q. Chen, Y.G. Yang, J.X. Wen, Liq. Cryst. 26 (1999) 1135.
[48] E. Taffin de Givenchy, F. Guittard, F. Bracon, A. Cambon, Liq. Cryst.
26 (1999) 1163.
[16] B. Boutevin, G. Caporiccio, F. Guida-Pietrasanta, A. Ratsimihety,
Macromol. Chem. Phys. 199 (1998) 61.
[17] A.G. Pittman, in: L.A. Wall (Ed.), Fluoropolymers, vol. 25, Wiley,
New York, 1972, p. 419. for more recent examples see;
(a) J. Tsibouklis, P. Graham, P.J. Eaton, J.R. Smith, T.G. Nevell, J.D.
Smart, R.J. Ewen, Macromolecules 33 (2000) 8460;
[49] F. Bracon, F. Guittard, E. Taffin de Givenchy, A. Cambon, Liq. Cryst.
26 (1999) 1371.
[50] F. Guittard, P. Sixou, A. Cambon, Liq. Cryst. 19 (1995) 667.
[51] F. Guittard, S. Diele, H. Kruth, G. Pelz, A. Cambon, Liq. Cryst. 21
(1996) 603.
(b) E. Casazza, A. Mariani, L. Ricco, S. Russo, Polymer 43 (2002)
1207.
[18] T.M. Chapman, R. Benrashid, K.G. Marra, J.P. Keener, Macro-
molecules 28 (1995) 331.
[52] H. Liu, H. Nohira, Mol. Cryst. Liq. Cryst. 302 (1997) 247.
[53] E. Dietzmann, W. Weissflog, Mol. Cryst. Liq. Cryst. 299 (1997) 419.
[54] S. Pensec, F.G. Tournilhac, P. Bassoul, C.J. Durliat, Phys. Chem. B
102 (1998) 52.
[19] T.M. Chapman, K.G. Marra, Macromolecules 28 (1995) 2081.
[20] T. Ho, K.J. Wynne, A. Vu, X. Chen, A.J. Gardella Jr., Polym.
Preprints (Am. Chem. Soc., Div. Polym. Chem.) 36 (1) (1995) 67.
[21] J.K. Pike, T. Ho, K.J. Wynne, Chem. Mater. 8 (1996) 856.
[22] G. Mao, J. Wang, S.R. Clingman, C.K. Ober, J.T. Chen, E.L.
Thomas, Macromolecules 30 (1997) 2556.
[55] D. Lose, S. Diele, G. Pelzl, E. Dietzmann, W. Weissflog, Liq. Cryst.
24 (1998) 707.
[56] J. Ebutt, R.M. Richardson, J. Blackmore, G. Macdonnel, M. Verral,
Mol. Cryst. Liq. Cryst. 261 (1995) 549.
[23] X. Li, L. Andruzzi, E. Chiellini, G. Galli, C.K. Ober, A. Hexemer,
E.J. Kramer, D.A. Fischer, Macromolecules 35 (2002) 8078.
[24] M.K. Bernett, W.A. Zisman, J. Phys. Chem. 64 (1960) 1292.
[25] F. Sun, D.G. Castner, G. Mao, W. Wang, P. McKeown, D.W.
Grainger, J. Am. Chem. Soc. 118 (1996) 1856.
[57] F. Guittard, P. Sixou, A. Cambon, Mol. Cryst. Liq. Cryst. 308 (1997)
83.
[58] F. Guittard, E. Taffin de Givenchy, S. Geribaldi, A. Cambon, J.
Fluorine Chem. 100 (1999) 85.
[59] F. Guittard, S. Geribaldi, in: R. Glaser, P. Kaszynski, (Eds.),
Anisotropic Organic Materials—Approaches to Polar Order, ACS
Symposium Series, vol. 798, American Chemical Society, Washing-
ton, 2001, p. 180.
[26] J.G. Wang, C.K. Ober, E.J. Kramer, Polym. Prepr. (Am. Chem. Soc.,
Div. Polym. Chem.) 37 (2) (1996) 815.
[27] M. Muthukumar, C.K. Ober, E.L. Thomas, Science 277 (1997) 1225.
[28] J. Wang, C. K Ober, Macromolecules 30 (1997) 7560.
´
[29] V.V. Volkov, N.A. Plate, A. Takahara, T. Kajiyama, M. Amaya, Y.
[60] F. Geribaldi, F. Guittard, E. Taffin de Givenchy, A. Cambon, Mol.
Cryst. Liq. Cryst. 332 (1999) 1.
Murata, Polymer 33 (1992) 1316.
[61] H. Okamoto, N. Yamada, S. Takenaka, J. Fluorine Chem. 91 (1998)
125.
[30] V. Percec, M. Lee, J. Macromol. Sci., Pure Appl. Chem. A29 (1992)
723.
[62] H. Okamoto, V.F. Petrov, S. Takenaka, Bull. Chem. Soc. Jpn. 72
(1999) 1637.
[31] E. Beyou, P. Babin, B. Bennetau, J. Dunogues, D. Teyssie, S.
Boileau, J. Polym. Sci., Part A: Chem. Ed. 32 (1994) 1673.
¨
[32] M. Krupers, M. Moller, Macromol. Chem. Phys. 198 (1997) 2163.
[63] G. Galli, S. Gasperetti, M. Bertolucci, B. Gallot, F. Chiellini,
Macromol. Rapid Commun. 23 (2002) 814.
[33] F. Bracon, F. Guittard, E. Taffin de Givenchy, A. Cambon, J. Polym.
Sci., Part A: Polym. Chem. 37 (1999) 4487.
[64] F. Sanda, T. Endo, J. Polym. Sci. Part A: Polym. Chem. 39 (2001) 265.
[65] N. Moszner, F. Zeuner, T. Volkel, V. Rheinberger, Macromol. Chem.
Phys. 200 (1999) 2173.
[34] L. Andruzzi, E. Chiellini, G. Galli, X. Li, S.H. Kang, C.K. Ober, J.
Mater. Chem. 12 (2002) 1684.
[66] F. Sanda, T. Takata, T. Endo, Macromolecules 26 (1993) 1818.
[67] J. Sugiyama, N. Kayamori, S. Shimada, Macromolecules 29 (1996)
1943.
[35] W. Mahler, D. Guillon, A. Skoulios, Mol. Cryst. Liq. Cryst. Lett. 2
(1985) 111.
[36] C. Viney, R.J. Twieg, T.P. Russel, L.E. Depero, Liq. Cryst. 5 (1989)
1783.
[68] V. Alupei, H. Ritter, Macromol. Rapid Commun. 22 (2001) 1349.
[69] N. Moszner, F. Zeuner, V. Rheinberger, Macromol. Rapid Commun.
18 (1997) 775.
[37] C. Viney, R.J. Twieg, B.R. Gordon, J.F. Rabolt, Mol. Cryst. Liq.
Cryst. 198 (1991) 285.
[70] L. Andruzzi, F. D’Apollo, G. Galli, B. Gallot, Macromolecules 34
(2001) 7707.
[38] L.M. Wilson, Macromolecules 28 (1995) 325.
[39] M. Napoli, J. Fluorine Chem. 79 (1996) 59.
[40] A.M. Semenov, S.V. Vasilenko, Serv. Phys. JEPT 63 (1985) 70.
[41] C.W. Bunn, E.R. Howells, Nature (London) 174 (1954) 549.
[42] T.P. Russell, J.F. Rabolt, R.J. Twieg, R.L. Siemens, B.L. Farner,
Macromolecules 19 (1986) 1135.
[71] C. Tschierske, J. Mater. Chem. 11 (2001) 2647.
[72] G. Galli, in: H.S. Nalwa (Ed.), Advanced Functional Molecules and
Polymers, vol. I, Overseas Publishers Association, Singapore, 2001,
p. 271.
[73] I. Cho, K. Chang, Macromol. Rapid Commun. 18 (1997) 45.
[74] D. Seebach, Angew. Chem. Int. Ed. Engl. 29 (1990) 1320.
[75] A. Bondi, J. Phys. Chem. 68 (1964) 44.
[43] D. Demus, J. Goodby, G.W. Gray, H.-W. Spiess, V. Vill (Eds.),
Handbook of Liquid Crystals, vols. 2A and 2B, Wiley–VCH,
Weinheim, 1998.
[76] J. Wang, C.K. Ober, Liq. Cryst. 26 (1999) 637.