Incorporation of cyclic phosphazene trimers into saturated and unsaturated ethylene-like polymer backbones

Article abstract of DOI:10.1021/ma011012n

The synthesis of well-defined cyclolinear phosphazene polymers via acyclic diene metathesis (ADMET) has been demonstrated. This work extends the range of properties achievable in cyclolinear phosphazenes synthesized via ADMET and provides an assessment of

Full text of DOI:10.1021/ma011012n

40
Macromolecules 2002, 35, 40-47
Articles
Incorporation of Cyclic Phosphazene Trimers into Saturated and
Unsaturated Ethylene-like Polymer Backbones
Ha r r y R. Allcock * a n d E. Cla y Kella m , III
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
Received J une 11, 2001; Revised Manuscript Received October 1, 2001
ABSTRACT: The synthesis of well-defined cyclolinear phosphazene polymers via acyclic diene metathesis
(ADMET) has been demonstrated. This work extends the range of properties achievable in cyclolinear
phosphazenes synthesized via ADMET and provides an assessment of the synthetic limitations. A series
of tetraphenoxy and tetramethoxyethoxyethoxy functionalized phosphazene trimers have been synthesized
that bear two alkene side chains, which together form the diene structure necessary for ADMET. The
alkene chains vary in length from three carbons to 11 carbons. This has allowed the influence of the
negative neighboring group effect to be examined as well as steric factors as they apply to the metathesis
of phosphazene monomers. Moreover, the role of different catalysts is discussed together with the influence
of the nonolefinic phosphazene substituents on the reactivity of the monomers. The influence on bulk
polymer properties of the incorporation of different amounts of cyclic phosphazene per average polymer
chain, through copolymerization studies with decadiene, is also discussed.
In tr od u ction
ents on each phosphorus atom. By contrast, in this
paper we discuss the use of small-molecule cyclic trimers
as components in the main chain of hybrid organic-
inorganic polymers.8 The degree of tailorability possible
in phosphazenes is unique because the reactive phos-
phorus-chlorine bonds present in the precursors to both
the cyclic and high polymer species can be replaced by
a wide range of different side groups. For the linear high
polymers this has generated properties appropriate for
fuel cell membranes, lithium ion transport layers,
biodegradable polymers, biologically inert polymers,
noncombustible materials, and high-performance elas-
tomers.9-14 The incorporation of functionalized cyclic
phosphazene moieties into commodity organic polymer
structures could substantially alter the physical proper-
ties and resistance to combustion through careful tailor-
ing of the phosphazene component. In this work we
describe the synthesis of cyclolinear polymers in which
cyclic phosphazene trimer units are incorporated into
the polymer backbone of saturated and unsaturated
polyethylene-like systems.
The synthesis of cyclolinear phosphazene polymers
has been an important topic of research for many years
because of the high thermal stability and fire resist-
ance of polymers that contain cyclic phosphazene moi-
eties.15,16 In the late 1960s and early 1970s a great deal
of research was reported on the formation of cyclolinear
and cyclomatrix phosphazenes via condensation proc-
esses. Most of these materials were synthesized at
relatively high temperatures (∼700 °C), and the prod-
ucts were frequently poorly characterized, densely cross-
linked materials, or low molecular weight oligomers.15,16
More recently, cyclolinear phosphazene-containing poly-
mers have been developed for a range of backbone
systems including polyimides,17-19 polyamides,20 poly-
Olefin metathesis has significantly broadened the
scope of polymer chemistry in the past 10 years together
with the advent of highly specialized catalysts that
initiate the ring-opening metathesis polymerization
(ROMP) and acyclic diene metathesis (ADMET) of a
wide variety of functionalized monomers.1 Polymer
structures that were difficult, or even impossible, to
synthesize less than 20 years ago can now be produced
efficiently via ROMP techniques, and the commercial-
ization of a number of materials has been made pos-
sible.1 ADMET is a related polymerization route, in
which terminal dienes condense to form polymer chains
with the release of ethylene.1-3 The versatility of this
polymerization route has made it possible to polymerize
numerous terminal dienes, provided ethylene is re-
moved from the system to move the equilibrium toward
polymer formation. This has led to the synthesis of well-
defined macromolecules, such as perfectly linear poly-
ethylene.4,5 It has also allowed the study of regularly
spaced functional groups introduced into polymer back-
bone structures of unsaturated polyethylene and other
unsaturated systems.1,3
Cyclic phosphazene compounds have recently been
incorporated into polymer systems based on both ROMP6
and ADMET7 chemistry. In each case, the size and
functionality of the cyclic phosphazene trimer do not
significantly inhibit the performance of the catalyst.
These extensions of olefin metathesis chemistry now
make it possible to incorporate the versatile phospha-
zene platform into a wide range of organic polymers.
The most widely studied phosphazene polymers are
linear macromolecules with alternating phosphorus and
nitrogen atoms in the skeleton and with two substitu-
10.1021/ma011012n CCC: $22.00 © 2002 American Chemical Society
Published on Web 11/28/2001

Macromolecules, Vol. 35, No. 1, 2002
Ethylene-like Polymer Backbones 41
Sch em e 1. Syn th esis of P h osp h a zen e Mon om er s 3-8
a n d 10-13
oxide or sodium methoxyethoxyethoxide to yield a
mixture of cyclic phosphazenes with four or five sub-
stituents. The cyclic phosphazene trimers with phenoxy
substituents were separated via column chromatogra-
phy in a 45/55 mixture of hexanes/CH2Cl2. The oligo-
ethyleneoxy-substituted trimers were also separated via
column chromatography, but because of the higher
polarity of these side groups, a solvent mixture of 90/
10 ethyl acetate/methanol was used. The tetrasubsti-
tuted trimers thus isolated were then treated with the
various sodium alkenoxides to complete the substitution
and yield a diene structure. If complete chlorine re-
placement does not occur during treatment with the
alkenoxide, the resultant cyclic phosphazene could bear
only one olefin group and therefore end-cap a growing
polymer chain. Similarly, if displacement of one organic
side group by another occurs, the possibility exists for
three or more olefin groups to be present on a single
cyclic phosphazene trimer. This would lead to cross-
linking of the polymer chains due to the larger number
of possible propagation sites.
esters,21 polyurethanes,22,23 and polyketones24 in order
to improve the properties of the organic polymer.
The previous syntheses of phosphazene trimers with
similar structures showed evidence of side group dis-
placement. Therefore, further purification by column
chromatography of the final monomers was necessary
before successful polymerizations could be carried out.7
The use of shorter chain alkenols avoided this problem.
The tendency for side group displacement is increased
in the presence of large excesses of the salt of the
alkenol, with long reaction times, and at elevated
temperatures. However, complete substitution by the
undecenoxide species requires high reaction tempera-
tures (refluxing dioxane), a large excess of sodium salt
(from 4 to 10 excess equivalents), and long reaction
times (up to 1 week). This is attributed to the low
solubility of long chain sodium alkenoxides in organic
solvents. As the length of the alkenol is decreased, the
solubility of the corresponding sodium salt is increased,
and therefore lower reaction temperatures, shorter
reaction times, and smaller excesses are required for
complete reaction. Problems of side group displacement
were still encountered for the introduction of the decenol
derivative. This resulted in the need to perform ad-
ditional column chromatography for monomer purifica-
tion.
Ra tion a le. Recent work in our laboratory utilized
olefin metathesis catalysts and ADMET chemistry to
synthesize a variety of cyclolinear phosphazene poly-
mers.7 These polymers are of moderate molecular
weight, with good solubility in organic solvents, and low
polydispersities. Moreover, it was found that the physi-
cal properties of these polymers could be varied through
alteration of the substituents on the phosphazene rings.
The present work extends ADMET chemistry as it
applies to cyclic phosphazene systems. New monomers
have been synthesized that bear four nonpolymerizable
phenoxy or alkyl ether cosubstituents and two reactive
terminal olefin sites. The olefins units were linked to
the phosphazene trimer by nucleophilic substitution
using alkoxides derived from a series of commercially
available alkenols that ranged from allyl alcohol to 10-
undecen-1-ol. It is well-known that the number of
carbon atoms between an active olefin group and a
potential second catalyst coordination site has a strong
influence on ADMET polymerizations. Because the
nitrogen atoms in the phosphazene ring and the oxygen
atoms between the ring and the double bond are
potential coordination sites, it was of interest to examine
monomer reactivity in terms of separation between the
olefinic sites and these electron-donating groups. In
addition, the properties of each polymer were modified
slightly by varying the spacing between the phos-
phazene units along the polymer backbone through
copolymerization of the phosphazene monomers with
1,9-decadiene. The copolymerizations yielded a series
of polymers that contained from 1 to 20 mol % phos-
phazene repeating units. Additional treatment of the
resultant copolymers with p-toluenesulfonhydrazide
(TSH) gave a fully saturated backbone with polyethylene-
like structures between the cyclic phosphazene residues
that were spaced intermittently along the polymer
backbone. These variations allowed the effect of the
phosphazene rings on a variety of polymer properties
to be studied.
The cyclic phosphazene dienes were characterized by
31P, 1H, and 13C NMR as well as by mass spectrometry.
The 31P NMR spectra indicate tetra-/di-substitution
through the characteristic A2B splitting pattern.15 This
splitting is not as clear for cyclic trimers that bear
chemically similar groups as, for example, with the
oligoethyleneoxy derivatives, and the spectra degenerate
into a singlet with several smaller surrounding peaks.25
1H and 13C NMR provided further structural confirma-
1
tion, and integration of the H NMR spectra together
with the mass spectra confirmed the identity and purity
of the monomers.
P olym er Syn th esis a n d Ch a r a cter iza tion . The
monomers were polymerized with both the bis(tricyclo-
hexylphosphine)benzylideneruthenium(IV) dichloride
(A) and the tricyclohexylphosphine[1,3-bis(2,4,6-tri-
methylphenyl)-4,5-dihydroimidazol-2-ylidene]ruthe-
nium(IV) dichloride (B) Grubbs catalysts (Figure 1). The
polymerizations were carried out initially with the
addition of 1 equiv of catalyst (A or B) to 100 equiv of
monomer. The stirred reaction mixtures were monitored
for ethylene evolution, and, after gas evolution had
Resu lts a n d Discu ssion
Mon om er Syn th esis. All the monomers for this
work were synthesized in a similar fashion (Scheme 1).
The starting material, hexachlorocyclotriphosphazene
(1), was treated with 4.7 equiv of either sodium phen-

42 Allcock and Kellam
Macromolecules, Vol. 35, No. 1, 2002
and similar results have been found for other ADMET
monomers with functional groups adjacent to the active
site.29,30 This has been termed the negative neighboring
group effect. Monomers 4 and 5, bearing butenoxy and
pentenoxy side groups, respectively, showed evidence
of oligomerization based on 1H NMR spectra and had
low molecular weights as monitored by GPC. If the
hindrance to polymerization of these monomers was
entirely a result of the negative neighboring group
effect, then slow oligomerization of the butenoxy species
(monomer 4) would be expected (based on comparisons
to the polymerization of monomers with an etheric
functionality).31 Moreover, normal polymerization of the
phosphazene trimer that bears pentenoxy groups (mono-
mer 5) might be anticipated. This does not occur.
Therefore, it is unlikely that the failure of monomers 4
and 5 to polymerize is entirely a result of the neg-
ative neighboring group effect. Steric factors can also
inhibit ADMET polymerizations if the formation of the
metallocyclobutane species is hindered, and this has
been reported when pendent methyl groups are located
too close to the reactive olefin.32-34
F igu r e 1. Grubbs catalysts used for ADMET reactions.
Ta ble 1. Ch a r a cter iza tion Da ta for P olym er iza tion of
Mon om er s 4-8 a n d 11-13
polymer Mn(cat A) PDI(cat A) Mn(cat B) PDI(cat B) Tg
4
5
6
7
8
11
12
13
1230
1350
21700
26300
33300
1470
1.2
1.1
4.4
2.1
2.6
1.1
1.6
1.9
1120
1440
16300
28400
29500
1520
1.1
1.1
3.3
2.4
2.0
1.1
1.8
1.7
-29
-34
-33
-36
-35
-72
-74
-75
8700
45400
11800
29200
ceased, another equivalent of catalyst was added. Ap-
proximately 24 h after the second catalyst addition the
reaction mixture was heated, and the temperature was
gradually increased to promote further polymerization.
The results of these polymerizations are shown in
Table 1. One point of interest is the lack of difference
seen between the two catalyst systems. The newer
catalyst (B) shows higher reactivities in metathesis
reactions for a variety of other systems,26-28 but this
behavior was not observed consistently for any of the
monomers studied in this work. The molecular weights
obtained using these two catalysts were very similar.
However, in some cases, polymers produced using
catalyst A had higher molecular weights. The rates of
reaction were also very similar for the two catalysts,
typically requiring more than 48 h for complete reaction.
A possible explanation for this behavior is the low
concentration of olefin sites. Even at relatively high
catalyst-to-monomer ratios, the formation of a produc-
tive metallocyclobutane complex3 with an olefinic end
group is unlikely because of the large phosphazene
structure. Moreover, the phosphazene ring and its
substituents could interfere through steric interactions
with coordination of the catalyst to the olefin unit. These
factors would account for the small difference in activity
found for the two catalysts, the relatively slow reaction,
and the smaller number of repeating units detected in
these polymers compared to simpler olefin systems.
The synthesis of different phosphazene monomers
with olefinic side groups of different lengths was de-
signed to test the limits of polymerization of cyclic
phosphazenes via ADMET as well as to compare prop-
erties of cyclolinear polymers with different spacer
groups between the phosphazene rings. In the phenoxy
series (monomers 3-8) the polymerizations were largely
unsuccessful unless the alkenoxy group was at least six
carbon atoms in length or had a four-carbon spacer unit
between the olefin and the phosphazene ring (monomer
6). The phosphazene trimer with allyloxy groups (3)
underwent almost no polymerization reaction, and the
NMR spectra of the reaction mixture showed evidence
of numerous side reactions. This could be a result of
steric hindrance that prevents the formation of a
metallocyclobutane ring as well as possible complex-
ation of the catalyst with the oxygen atom of the allyloxy
group. Coordination of the catalyst to oxygen is sup-
To determine whether the lack of polymerization is a
result of the negative neighboring group effect or steric
factors, a series of monomers were prepared with
flexible methoxyethoxyethoxy side groups. Trimers co-
functionalized with methoxyethoxyethoxy and allyloxy,
butenoxy, or pentenoxy were prepared (monomers 10,
11, and 12). The polymerization of the allyl species (10)
yielded products with complex NMR spectra, similar to
those seen for the phenoxy/allyloxy monomer (3). This
suggested catalyst coordination to the oxygen atoms of
the allyloxy groups had occurred. Attempted polymer-
ization of the butenoxy derivative (11) resulted in some
oligomer formation, as in the case of the similar phenoxy
trimer (4). The pentenoxy functionalized trimer (12)
polymerized to give moderate molecular weight macro-
molecules. This suggests that, for the phenoxy-substi-
tuted counterpart (5), steric hindrance inhibits the
polymerization rather than possible catalyst coordina-
tion. The formation of the metallocyclobutane interme-
diate is crucial for ADMET polymerization to occur, and
it is likely that steric hindrance from bulky phosphazene
substituents can slow or prevent this formation.
The glass transition temperatures of the new homo-
polymers were measured using DSC analysis. Slight
changes in the polymer repeat unit had little effect on
the glass transition temperature. The increase from 10
carbon atoms between phosphazene units (polymer 6)
to 20 carbon atoms between phosphazene units (polymer
8) results in a change in Tg of only 2 °C. The Tg values
are similar for all of the cyclolinear polymers and
oligomers functionalized with phenoxy groups. If the
measured Tg for oligomers produced from monomers 4
and 5 (six and eight carbons between phosphazene
units, respectively) are compared with those for poly-
mers from monomers 6-8, then a slight lowering of
glass transition temperature from -29 to -35 °C can
be detected. This is attributed to the increased flexibility
of the polymer chain as the separation between phos-
phazene units increases. The polymers that contain
oligoethyleneoxy functionalized cyclic trimers show
similar trends. The overall difference in glass transition
temperature is rather small, but a slight decrease can
be accounted for by increased molecular motion as the
phosphazene rings become more separated along the
polymer backbone.
1
ported by the complexity of the 31P and H NMR spectra,

Macromolecules, Vol. 35, No. 1, 2002
Ethylene-like Polymer Backbones 43
Sch em e 2. Syn th esis of Cop olym er s of 1,9-Deca d ien e
a n d Mon om er
adjacent to the oxygen atoms. These signals did not
arise from monomer trapped in the polymer structure
because the polymer had been purified by precipitation
into cold CH2Cl2 in which the monomers are highly
soluble. The GPC traces showed only one polymer peak,
with no evidence of a second, cyclic phosphazene trimer,
peak. Further evidence that the phosphazene is co-
valently incorporated into the backbone structure is the
solubility of the resultant polymers. Polyethylenes and
similar polymers typically have low solubility in most
solvents at room temperature. All the homopolymers
derived from the cyclotriphosphazene monomers are
readily soluble in a variety of solvents at and below room
temperature. Only the polymer produced from the
homopolymerization of decadiene was completely in-
soluble in CH2Cl2 at room temperature. As the amount
of phosphazene monomer incorporated into the co-
polymerization was increased, the solubility of the
resultant copolymers improved until the copolymer with
20% phosphazene is fully soluble in CH2Cl2 at room
temperature.
Ta ble 2. Ch a r a cter iza tion Da ta for Cop olym er s of
1,9-Deca d ien e a n d Mon om er 8
1
A H NMR analysis of these polymers showed that
the experimental incorporation of phosphazene units
matches the theoretical values fairly well. On the basis
of these data, it is assumed that random copolymers
were formed with no preferential reactivity between
different monomers. Moreover, the long alkyl chain
separating the active double bond from the phosphazene
ring should minimize any difference that could cause
preferential polymerization. The relatively low molar
incorporation of phosphazene monomer, however, will
still result in a polymer with a blocky structure of
isolated phosphazene units surrounded by long seg-
ments of poly(decadiene).
mol % 8 wt % 8
Mn
PDI % 8 (NMR) Tm Tm(H2)
0
0
8 300
10 200
13 300
33 400
24 000
25 000
33 300
2.0
1.4
1.4
1.7
1.8
2.0
2.6
0
1.3
2.6
4.4
11.3
22.5
100
55
56
58
65
40
34
119
123
115
100
99
1
5.8
2.5
5
10
13.5
24.3
40.4
60.4
20
91
100
100
Cop olym er iza tion s. Monomer 8, substituted with
four phenoxy groups and two undecenoxy groups, was
copolymerized with 1,9-decadiene in five molar ratios
from 1% to 20% incorporation (Scheme 2). This phos-
phazene monomer was chosen because of its encourag-
ing behavior in homopolymerization. Decadiene was
selected as a comonomer because of its known ease of
polymerization by ADMET and its relatively low volatil-
ity. The data for these polymers are summarized in
Table 2. These copolymerizations were carried out in
the absence of a solvent, as with all the above reactions,
and the combined monomer-to-initiator ratio was held
constant at 500:1 for each polymerization. Initially, the
decadiene monomer covolatilized from the system along
with the ethylene under vacuum as the polymerization
progressed, and this prevented good control over the
ratio of the monomers. A modified polymerization ap-
paratus that allows control of the pressure was designed
to prevent the volatilization of monomer. Moreover, this
equipment allowed the addition of solvent in the later
stages of the polymerizations, while maintaining enough
vacuum to constantly remove ethylene. With this ar-
rangement, slightly different polymerization conditions
were used than for the homopolymerizations. When the
second aliquot of catalyst was added, a few milliliters
of o-dichlorobenzene was also added to help solubilize
the polymer and continue polymerization.
The theoretical and experimental incorporation as
1
estimated from H NMR integration is reported in Table
2. A melting transition for the pure poly(decadiene) is
detected at 55 °C. The copolymers with 1%, 2.5%, and
5% phosphazene monomer have very similar melting
transitions, but all at slightly higher temperatures than
the value for poly(decadiene). Phosphazene residues
would be expected to destabilize crystalline regions
within the polymer matrix due to their irregular size
and location relative to the decadiene monomers. Thus,
in theory they should lower the Tm. This was not
detected in these three copolymers possibly because of
the low molecular weights of the materials. The molec-
ular weight increases gradually for each of these
polymers, perhaps allowing the formation of more highly
ordered crystalline domains. However, beyond the point
at which 10% of the phosphazene monomer is incorpo-
rated, the Tm begins to decrease, and for materials with
100% phosphazene monomer, no crystalline transition
was detected, presumably because the proximity of
phosphazene rings interrupts any crystallite formation.
Hyd r ogen a tion s. Each of the copolymers was hy-
drogenated via a method developed by Hahn to saturate
polymer backbones in solution without the use of high
pressure and without significant molecular weight
decline.35 A sample of each polymer was heated with p-
toluenesulfonhydrazide and tripropylamine in o-xylene.
During reflux, the toluenesulfonhydrazide decomposes
to yield a diimide, which serves as the hydrogenating
agent, and the tripropylamine quenches side reactions
that can lead to polymer chain cleavage.35 These reac-
tions provided 100% hydrogenation as evidenced by the
In these copolymerizations initial concerns existed
that the phosphazene monomers would be excluded
from the reaction due to the relatively low concentration
of olefin sites attached to a phosphazene ring. However,
the incorporation of phosphazenes into the polymer
chains is confirmed by multinuclear NMR spectroscopy,
which revealed the presence of both the phosphorus
atoms and the aryloxy protons. In those copolymers with
relatively high loadings of phosphazene monomer it was
also possible to detect the resonances for the protons
1
complete disappearance of olefin peaks in the H NMR

44 Allcock and Kellam
Macromolecules, Vol. 35, No. 1, 2002
by hydrogenation, with a slight decrease from -35 to
-39 °C, as would be expected for a slight increase in
freedom of molecular motion due to decreased double-
bond character in the backbone.
Con clu sion s
A series of cyclic phosphazene trimers were prepared,
each with two olefinic side groups, to give a diene
structure capable of undergoing metathesis polymeriza-
tions. These monomers were polymerized using two
different ruthenium catalysts. The molecular weights
of the materials ranged from about 10 000 to 45 000 and
are comparable to molecular weights seen previously for
the ADMET polymerization of other phosphazene mono-
mers.37 The chemistry of ADMET requires the formation
of a metallocyclobutane intermediate in order for poly-
merization to occur. Previous studies have shown that
the formation of this intermediate can be retarded by
both electronic (preferential catalyst coordination to a
functional group) and steric effects. The polymerization
of phosphazene-containing dienes is affected signifi-
cantly by both of these factors, and the steric effects may
extend beyond those observed with other systems due
to the size of the phosphazene ring and the size and
steric bulk of substituents on that ring. This was
illustrated by the polymerization of a monomer func-
tionalized with flexible oligoethyleneoxy groups com-
pared with the failure to polymerize a similar monomer
with phenoxy cosubstituents.
Copolymerizations were carried out between one of
the cyclophosphazenes and 1,9-decadiene to illustrate
further the versatility of this approach. Levels of phos-
phazene incorporation from 1% to 20% had a significant
effect on polymer properties, most notably on the
melting transition temperature. Subsequent hydrogena-
tion of these polymers illustrated the stability of the
cyclolinear structure to these reaction conditions. The
hydrogenated polymers had significantly higher melting
temperatures, but this was affected directly by the
amount of phosphazene present in the polymer. The
phosphazene components serve to disrupt the crystal-
linity of the polyethylene-like structure once present in
high enough amounts. They also lower the melting
transition temperature. This is in agreement with other
studies that have incorporated functional groups into a
polyethylene backbone. The use of this chemistry to
generate polymers and polymer blends that resist
combustion is being investigated.
F igu r e 2. 1H NMR of monomer 8 (a), a copolymer of 80% 1,9-
decadiene and 20% monomer 8 (b), and the same polymer after
hydrogenation (c).
spectra. The resultant materials were significantly more
brittle than the original unsaturated copolymers. More-
over, the solubility was decreased dramatically, so much
so that the NMR analyses had to be carried out in d5-
chlorobenzene at 100 °C. Figure 2 shows 1H NMR
spectra of the phosphazene monomer, the resultant co-
polymer, and the hydrogenated copolymer for 20% cyclic
phosphazene monomer incorporation. During polymer-
ization, the olefin peaks initially shift to indicate the
formation of internal olefins and the loss of all terminal
double bonds. After hydrogenation, the internal olefin
peaks disappear completely, and the remaining spec-
trum shows only the aryloxy protons from the phos-
phazene and the protons on the carbon atom closest to
the phosphazene ring.
The marked decrease in solubility of the hydrogenated
species is a direct result of the increased stability of the
crystalline regions of these materials. In each case, the
Tm is increased by approximately 50 °C. The Tm is
similar for the first three polymers in the series (1%,
2.5%, and 5% phosphazene monomer) and then de-
creases significantly for higher percentages. Again this
can be linked to the increasing molecular weight of the
materials, which initially offsets the crystallinity-
decreasing influence of the phosphazene units. However,
eventually enough phosphazene exists in the system to
disrupt the crystallinity and decrease the Tm. This
behavior has been reported in the past by Wagener for
other pendent groups, and larger, bulkier groups lead
to a larger decrease in Tm.36 Glass transitions were not
detected for any of the hydrogenated polymers over the
temperature range scanned under any conditions and
is attributed to the generally weak and poorly defined
transition of polyethylene.
Exp er im en ta l Section
Ma ter ia ls. All chemicals and reagents were obtained from
Aldrich and used as received unless described otherwise.
Hexachlorocyclotriphosphazene, 1 (Ethyl Corp./Nippon Fine
Chemical Co.), was recrystallized from heptane and sublimed
at 40 °C (0.05 mmHg). Tetrahydrofuran was obtained from
EM Science and distilled from sodium benzophenone ketyl
prior to use.
Equ ip m en t. High-field 1H (360 MHz), 13C (90 MHz), and
31P (146 MHz) NMR spectra were obtained using a Bruker
AMX-360 spectrometer. The 31P and 13C spectra were proton-
decoupled. 31P NMR spectra were referenced to external 85%
H3PO4 with positive shifts recorded downfield from the refer-
ence. 1H and 13C were referenced to external tetramethylsilane.
Elevated temperature 1H NMR spectroscopy was performed
at 100 °C using a Bruker DPX-300 spectrometer for hydro-
genated polymer samples. Gel permeation chromatograms
were obtained using a Hewlett-Packard HP 1090 gel perme-
ation chromatograph equipped with two Phenomenex Phenogel
linear 10 columns and a Hewlett-Packard 1047A refractive
The homopolymer from monomer 8 was also hydro-
genated. However, complete reduction did not occur
under the same conditions. The double bonds may be
sterically protected by the bulky phosphazene substit-
uents. This product did remain soluble at room tem-
perature, and GPC analyses suggested that there had
been no significant molecular weight decline. Moreover,
the Tg of the homopolymer was affected only moderately

Macromolecules, Vol. 35, No. 1, 2002
Ethylene-like Polymer Backbones 45
index detector. Data collection and calculations were ac-
complished with use of a Hewlett-Packard Chemstation
equipped with Hewlett-Packard and Polymer Laboratories
software. The samples were eluted with a 0.1 wt % solution of
tetra-n-butylammonium nitrate in THF. The GPC column was
calibrated with polystyrene standards. Thermal transition
temperatures were determined by DSC using a Perkin-Elmer-7
thermal analysis system. Polymer samples were heated from
-150 to +150 °C under an atmosphere of dry nitrogen at a
heating rate of 20 °C/min.
13C NMR (CDCl3): δ (ppm) 24.5, 29.1, 32.9, 66.0, 114.5, 120.9,
124.6, 129.0, 138.0, 150.6. 31P NMR (CDCl3): δ (ppm) 13.4 (d,
2P), 10.1 (t, 1P). APCI, MH+ ) 706.2.
Syn th esis of N3P 3(OC6H5)4(O(CH2)8CHdCH2)2 (7). This
compound was synthesized as described for 3. The following
reagents and quantities were used: 9-decen-1-ol (2.40 g, 15.33
mmol), 95% NaH (0.37 g, 15.33 mmol), 2 (4.22 g, 7.30 mmol),
freshly distilled THF (200 mL). Column chromatography was
performed in an 80%/20% mixture of hexanes and CH2Cl2 (4.21
1
g, 70.6% yield). H NMR (CDCl3): δ (ppm) 1.0-1.6 (24H), 1.9
Syn th esis of N3P 3(OC6H5)4Cl2 (2). Hexachlorocyclotriphos-
phazene, 1 (100.0 g, 0.287 mol), was dissolved in 2000 mL of
THF. Phenol (124 g, 1.32 mol) was dissolved in 150 mL of THF
and added dropwise to a suspension of sodium metal (30.73 g,
1.33 mol) in 500 mL of THF. This reaction mixture was stirred
at room temperature for 24 h to allow all the sodium to react.
The resultant sodium phenoxide solution was added dropwise
to the stirred solution of 1 at -78 °C. The reaction mixture
was allowed to warm to room temperature overnight and was
monitored by 31P NMR spectroscopy to show 57% tetra-
substitution and 43% penta-substitution. Solvent was removed
by reduced pressure rotary evaporation, and the resultant oil
was dissolved in 250 mL of diethyl ether. This solution was
washed three times with 250 mL of water, dried over MgSO4,
and concentrated by rotary evaporation. Column chromatog-
raphy was carried out in a 55% CH2Cl2/45% hexanes mixture
to separate the tetra- and pentasubstituted products. The
desired product was recrystallized at -55 °C from hexanes to
yield an off-white oil (36.2 g, 25.8%). 31P NMR (CDCl3): δ (ppm)
5.2 (t, 1P) and 20.4 (d, 2P).
Syn th esis of N3P 3(OC6H5)4(OCH2CHdCH2)2 (3). Allyl
alcohol (1.69 g, 29.06 mmol) was added to 95% sodium hydride
(0.77 g, 30.45 mmol) in 100 mL of freshly distilled THF, and
the mixture was refluxed for 24 h. The solution was cooled to
room temperature and added dropwise to a solution of 2 (8.00
g, 13.84 mmol) in 75 mL of THF. After 24 h at room
temperature the reaction mixture was heated to reflux. After
48 h at reflux the reaction was complete on the basis of the
31P NMR spectra. The solvent was removed from the reaction
mixture by rotary evaporation, the residue was dissolved in
CH2Cl2, and the solution was washed with water to remove
NaCl. The organic layer was dried over MgSO4, and the solvent
was removed by rotary evaporation to yield a yellow oil (7.25
g, 84.4% yield). 1H NMR (CDCl3): δ (ppm) 3.9 (m, 2H), 4.2
(m, 2H), 5.0-5.2 (m, 4H), 5.5-5.7 (m, 2H), 6.8 (t, 4H), 7.0-
7.2 (m, 16H). 13C NMR (CDCl3): δ (ppm) 66.3, 116.8, 120.9,
124.5, 129.1, 132.4, 150.5. 31P NMR (CDCl3): δ (ppm) 13.2 (d,
2P) and 9.8 (t, 1P). APCI, MH+ ) 622.2.
(4H), 3.5 and 3.7 (4H), 4.9 (m, 4H), 5.7 (m, 2H), 6.8 (4H), 7.0-
7.2 (m, 16H). 13C NMR (CDCl3): δ (ppm) 25.3, 25.4, 25.8, 28.9,
29.4, 29.9, 33.8, 62.3, 114.1, 121.2, 124.6, 129.2, 138.9, 150.9.
31P NMR (CDCl3): δ (ppm) 13.2 (d, 2P), 10.0 (t, 1P). ESI, MH+
) 818.3.
Syn th esis of N3P 3(OC6H5)4(O(CH2)9CHdCH2)2 (8). The
synthesis of this compound has been described previously.7
Syn th esis of N3P 3(OCH2CH2OCH2CH2OCH3)4Cl2 (9).
Hexachlorocyclotriphosphazene, 1 (20 g, 57.47 mmol), was
dissolved in 200 mL of THF. Methoxyethoxyethanol (32.41 g,
270.1 mmol) was distilled from CaH2 and then added via
syringe to a suspension of sodium hydride (10.92 g, 273.0
mmol) in 200 mL of THF. The resultant sodium alkoxide
solution was added dropwise to the stirred solution of 1 at -78
°C. The reaction mixture was allowed to warm to room
temperature overnight and was analyzed by 31P NMR spec-
troscopy to show 61% tetra-substitution, 38% penta-substitu-
tion, and 1% tris-substitution. The solvent was removed by
rotary evaporation, and the resultant oil was dissolved in 250
mL of diethyl ether. This solution was cooled to -55 °C and
filtered cold to remove most of the NaCl generated during the
reaction. The solvent was then removed by rotary evaporation.
Column chromatography was performed using a 90% ethyl
acetate/10% methanol elution mixture to separate the tetra-
and penta-substituted products. Similar fractions were com-
bined to yield a pale yellow oil. (6.4 g, 16.3%) 31P NMR (CDCl3),
δ (ppm) 13.1 (tr, 2P), 16.0 (d, 1P), 25.3 (d, 2P), 28.0 (tr, 1P).
Syn th esis of N3P 3(OCH2CH2OCH2CH2OCH3)4(OCH2CHd
CH2)2 (10). Allyl alcohol (0.25 g, 4.46 mmol) was added to 95%
sodium hydride (0.11 g, 4.46 mmol) in 100 mL of THF and
refluxed for 24 h. The resultant sodium salt solution was cooled
to room temperature and added dropwise to a solution of 9
(1.0 g, 1.46 mmol) in 200 mL of THF. This reaction mixture
was monitored over 2 days by 31P NMR and then heated to
reflux for 24 h to complete the reaction. The product was
purified first by the removal of THF by rotary evaporation and
then by dissolution in diethyl ether. The ethereal solution was
then cooled to -55 °C for 24 h and filtered cold to remove NaCl.
This was repeated to ensure removal of all NaCl. The product
was then recovered as a pale yellow oil (0.83 g, 78.3% yield).
1H NMR (CDCl3): δ (ppm) 3.2 (s, 12H), 3.4 (t, 8H), 3.5 (t, 8H)
3.6 (t, 8H), 4.0 (s, 8H), 4.3 (s, 4H), 5.0 and 5.2 (dblts, 4H), 5.8
(m, 2H). 13C NMR (CDCl3): δ (ppm) 57.9, 64.2, 64.5, 69.1, 69.6,
71.0, 116.0, 132.6. 31P NMR (CDCl3): δ (ppm) 17.9 (s, 3P). ESI,
MH+ ) 726.3.
Syn th esis of N3P 3(OCH2CH2OCH2CH2OCH3)4(O(CH2)2-
CHdCH2)2 (11). This compound was synthesized as described
for 10. The following reagents and quantities were used:
butenol (0.27 g, 3.69 mmol), 95% NaH (0.09 g, 3.69 mmol), 9
(1.5 g, 2.20 mmol), freshly distilled THF (200 mL) (1.23 g,
78.8% yield). 1H NMR (CDCl3): δ (ppm) 2.3 (quad, 4H), 3.3 (s,
12H), 3.4 (quad, 8H), 3.5 (quad, 8H), 3.6 (quad, 8H), 3.9 (m,
4H), 4.0 (s, 8H), 5.0 (m, 4H), 5.7 (m, 2H). 13C NMR (CDCl3):
δ (ppm) 34.2, 58.6, 64.0, 64.6, 69.7, 70.1, 71.6, 116.8, 133.7.
31P NMR (CD2Cl2): δ (ppm) 17.9 (m, 3P). ESI, MH+ ) 754.3.
Syn th esis of N3P 3(OCH2CH2OCH2CH2OCH3)4(O(CH2)3-
CHdCH2)2 (12). This compound was synthesized as described
for 10. The following reagents and quantities were used:
pentenol (0.38 g, 4.47 mmol), 95% NaH (0.11 g, 4.47 mmol), 9
(1.0 g, 1.11 mmol), freshly distilled THF (200 mL). After 48 h
at reflux two more equivalents of pentenol sodium salt was
prepared and added, and the mixture was heated to reflux for
an additional 24 h in order to complete the reaction (0.88 g,
76.5% yield). 1H NMR (CDCl3): δ (ppm) 1.7 (quint, 4H), 2.1
(quad, 4H), 3.3 (s 12H), 3.5 (t, 8H), 3.6 (t, 8H), 3.7 (s, 8H), 3.9
Syn th esis of N3P 3(OC6H5)4(O(CH2)2CHdCH2)2 (4). This
compound was synthesized as described for 3. The following
reagents and quantities were used: 3-buten-1-ol (2.09 g, 29.07
mmol), 95% NaH (0.77 g, 30.45 mmol), 2 (8.00 g, 13.84 mmol),
1
freshly distilled THF (200 mL) (7.43 g, 82.7% yield). H NMR
(CDCl3): δ (ppm) 2.1 (quad, 2H), 2.2 (quad, 2H), 3.5 and 3.8
(4H), 4.9 (quint, 4H), 5.6 (m, 2H), 6.9(tr, 4H), 7.0-7.2 (m 16H).
13C NMR (CDCl3): δ (ppm) 34.1, 65.3, 117.0, 120.9, 124.6,
129.2, 133.4, 150.7. 31P NMR (CDCl3): δ (ppm) 13.2 (d, 2P),
9.9 (t, 1P). APCI, MH+ ) 650.2
Syn th esis of N3P 3(OC6H5)4(O(CH2)3CHdCH2)2 (5). This
compound was synthesized as described for 3. The following
reagents and quantities were used: 4-penten-1-ol (2.62 g, 30.45
mmol), 95% NaH (0.76 g, 33.22 mmol), 2 (8.00 g, 13.84 mmol),
1
freshly distilled THF (200 mL) (7.16 g, 76.4% yield). H NMR
(CDCl3): δ (ppm) 1.3 and 1.5 (quints, 4H), 1.8 and 1.9 (quads,
4H), 3.4 and 3.7 (4H), 4.8 (quint, 4H), 5.6 (m, 2H), 6.8 (tr, 4H),
6.9-7.1 (m, 16H). 13C NMR (CDCl3): δ (ppm) 28.9, 29.1, 65.6,
115.1, 121.1, 124.7, 129.2, 137.3, 150.8. 31P NMR (CDCl3): δ
(ppm) 13.3 (d, 2P), 10.0 (t, 1P). APCI, MH+ ) 678.3.
Syn th esis of N3P 3(OC6H5)4(O(CH2)4CHdCH2)2 (6). This
compound was synthesized as described for 3. The following
reagents and quantities were used: 5-hexen-1-ol (1.96 g, 19.60
mmol), 95% NaH (0.49 g, 20.49 mmol), 2 (5.15 g, 8.91 mmol),
1
freshly distilled THF (200 mL) (5.75 g, 91.5% yield). H NMR
(CDCl3): δ (ppm) 1.0-1.4 (m, 8H), 1.7-1.8 (quad, 4H), 3.3 and
3.6 (4H), 4.8 (m, 4H), 5.5 (m, 2H), 6.8(tr, 4H), 6.9-7.1 (m 16H).

46 Allcock and Kellam
Macromolecules, Vol. 35, No. 1, 2002
(s, 4H), 4.1 (s, 8H), 4.9 (m, 4H), 5.8 (m, 2H). 13C NMR
(CDCl3): δ (ppm) 29.2, 29.6, 58.8, 64.8, 65.3, 69.9, 70.4, 71.8,
115.0, 137.5. 31P NMR (CDCl3): δ (ppm) 18.1 (m, 3P). ESI,
MH+ ) 782.4.
Syn th esis of N3P 3(OCH2CH2OCH2CH2OCH3)4(O(CH2)9-
CHdCH2)2 (13). The synthesis of this compound has been
described previously.7
(distilled from CaH2) were weighed out separately in an inert
atmosphere drybox and then added to a 25 mL Schlenk flask.
The reaction mixture was stirred in the drybox until all the
catalyst was dissolved, and the flask was then removed from
the drybox and attached to a Schlenk line that was modified
to apply variable pressures through the use of a screw valve
that allowed an argon leak into the system. This mixture was
then stirred at room temperature and ∼10 mmHg pressure
until evolution of ethylene had ceased or until the viscosity
had risen to the point that stirring was no longer possible. At
this point the reaction mixture was reintroduced into the
drybox where another equivalent of catalyst was added
together with 1-3 mL of o-dichlorobenzene to solubilize the
polymer and facilitate stirring. The reaction proceeded for
another 24 h and was gradually heated to 60 °C. The polymer
was then isolated by precipitation first into methanol and then
into cold CH2Cl2 to remove any residual monomer. The
reaction was terminated by exposure to air and precipitation
into hexanes. Yields were typically very high, ranging from
85 to 95% with the lost yield attributed to polymer not
recovered from the precipitation. This was verified by the lack
of monomer peaks present in NMR spectrum of the reaction
mixture prior to workup. Because of the similar structure of
each of the copolymers, and therefore identical shifts in 1H,
31P, and 13C NMR spectra, only a representative 1H NMR
spectrum is shown in Figure 2. The relative concentrations of
phosphazene monomer as calculated from the integration of
Gen er a l P olym er iza tion P r oced u r e for Mon om er s 3-8
a n d 10-13. Each of the monomers was polymerized by placing
0.5 g of the monomer into a 25 mL Schlenk flask and drying
under vacuum for 24 h. The dry monomer was then taken into
an inert atmosphere drybox where the Grubbs catalyst was
added (typically 100:1 monomer:catalyst ratio). This mixture
was stirred in the drybox until the catalyst was completely
dissolved in the monomer, and a pale purple solution resulted.
The Schlenk flask was then removed from the drybox, and the
contents were stirred under vacuum until the evolution of
ethylene was no longer visible (typically 24-48 h). At this time
the reaction mixture was reintroduced into the drybox, and
an additional aliquot of catalyst was added (typically half the
amount added initially). This reaction mixture was again
stirred to dissolve the catalyst before removal from the drybox.
The mixture was then stirred until the evolution of ethylene
was no longer visible (typically less than 24 h) and was then
heated to 60 °C. Some polymerizations reached very high
viscosities, and when this was the case, 1 mL of o-dichloroben-
zene was added to solubilize the reaction mixture and facilitate
stirring and reaction. The reaction was terminated by exposure
to air and precipitation into hexanes. The resultant polymer
was dissolved in THF and precipitated into hexanes a second
time before drying under reduced pressure to yield off-white
polymer. Yields were typically very high ranging from 85 to
95% with most of the lost yield attributed to polymer lost in
the precipitation. This was verified by the lack of monomer
present in NMR traces of the reaction mixture prior to workup.
P olym er 4. 1H NMR (CDCl3): δ (ppm) 1.9-2.3 (m), 3.5 (m),
3.8 (m), 4.9 (m), 5.1-5.4 (m), 5.5-5.9 (m), 6.9 (tr), and 7.0-
7.3 (m). 31P NMR (CDCl3): δ (ppm) 13.2 (d, 2P), 9.9 (t, 1P).
P olym er 5. 1H NMR (CDCl3): δ (ppm) 1.1-2.2 (m), 3.4 (m),
3.7 (m), 4.9 (m), 5.0-5.5 (m), 5.6-5.9 (m), 6.8 (tr), and 6.9-
7.3 (m). 13C NMR (CDCl3): δ (ppm) 28.8, 28.9, 65.8, 121.0,
125.2, 128.6, 129.0, 151.1. 31P NMR (CDCl3): δ (ppm) 13.0 (d,
2P), 9.9 (t, 1P).
1
peaks in the H NMR spectra are reported in Table 2 for each
copolymer.
Gen er a l P r oced u r e for Hyd r ogen a tion . The general
procedure of Hahn35 was followed as reported in several
publications by Wagener. A sample of polymer (typically 0.2
g) was placed in a 25 mL flask equipped with a condenser. To
this flask was added tripropylamine, TPA (2 equiv per mole
of olefin present), p-toluenesulfonhydrazide, TSH (2 equiv per
mole of olefin present), and 15 mL of o-xylene. This mixture
was refluxed for 3 h and then allowed to cool to room
temperature. An additional equivalent of TPA and TSH was
then added to the mixture, and the temperature was increased
to reflux for an additional 3 h. After cooling, the entire reaction
mixture was added to methanol, and the product was recovered
by filtration. Yields for the hydrogenation reactions were all
above 80% with some loss in yield attributed to polymer lost
in the workup.
P olym er 6. 1H NMR (CDCl3): δ (ppm) 1.0-1.6 (m, 8H),
1.7-2.0 (quad, 4H), 3.4 and 3.7 (4H), 5.2 (m, 2H), 6.8 (tr, 4H),
and 7.0-7.3 (m 16H). 13C NMR (CDCl3): δ (ppm) 25.6, 29.7,
32.2, 66.6, 121.3, 124.9, 129.5, 130.3, 151.0. 31P NMR
(CDCl3): δ (ppm) 13.2 (d, 2P), 9.9 (t, 1P).
Ack n ow led gm en t. This work was funded by the
Federal Aviation Administration.
1
P olym er 7. H NMR (CDCl3): δ (ppm) 0.9-1.6 (24H), 1.9
Refer en ces a n d Notes
(4H), 3.4 and 3.7 (4H), 5.3 (m, 2H), 6.8 (4H), 6.9-7.3 (m, 16H).
13C NMR (CDCl3): δ (ppm) 25.6, 25.7, 25.9, 29.7, 30.0, 34.3,
65.1, 119.6, 123.9, 127.9, 129.6, 150.8. 31P NMR (CDCl3): δ
(ppm) 13.2 (d, 2P), 9.9 (t, 1P).
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1
P olym er 8. H NMR (CD2Cl2): δ (ppm) 0.9-1.7 (m, 28H),
2.1 (4H), 3.5 and 3.8 (4H), 5.4 (2H), and 6.7-7.3 (m, 20H). 13
C
NMR (CDCl3): δ (ppm) 26.1 (d), 27.8, 29.8-30.6 (m), 33.2, 67.2
(d), 121.5 (d), 121.6, 121.7, 122.0 (d) 125.1-125.8 (m) 130.0
(d), 131.0, 151.5 (d). 31P NMR (CDCl3): δ (ppm) 13.3 (d, 2P)
and 10.0 (t, 1P).
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P olym er 11. 1H NMR (CDCl3): δ (ppm) 2.3-2.4 (m), 3.3
(s), 3.4-3.7 (m), 3.9 (m), 4.0 (m), 4.9-5.1 (m), 5.2-5.4 (m), 5.7-
5.9 (m). 13C NMR (CDCl3): δ (ppm) 34.5, 58.9, 64.3, 65.0, 70.1,
70.3, 71.7, 126.7. 31P NMR (CD2Cl2): δ (ppm) 18.0 (m, 3P).
P olym er 12. 1H NMR (CDCl3): δ (ppm) 1.6 (m, 4H), 2.0
(m, 4H), 3.3 (s, 12H), 3.5 (m, 8H), 3.6-3.7 (m, 16H), 3.9 (s,
4H), 4.0 (s, 8H), 5.4 (m, 2H). 13C NMR (CDCl3): δ (ppm) 27.7,
29.1, 58.0, 63.9, 64.5, 69.0, 69.5, 70.9, 128.8. 31P NMR
(CDCl3): δ (ppm) 18.1 (m, 3P).
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P olym er 13. 1H NMR (CDCl3): δ (ppm) 1.2 (24H), 1.6 (4H),
1.9 (4H), 3.3 (12H), 3.5 (8H), 3.6-3.7 (m, 16H), 3.9 (4H), 4.0
(8H), 5.3-5.4 (2H). 13C NMR (CDCl3): δ (ppm) 25.6, 29.0-
29.6, 30.2, 32.6, 58.9, 64.9, 66.1, 70.0, 70.5, 71.9, 129.7, 130.2.
31P NMR (CDCl3): δ (ppm) 18.1 (3P).
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Ethylene-like Polymer Backbones 47
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MA011012N