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Poly(allyl Glycidyl Ether)-A Versatile and Functional Polyether Platform
Bongjae F. Lee,1,2 Matthew J. Kade,1,3 Jerred A. Chute,1,3 Nalini Gupta,1,2 Luis M. Campos,1
Glenn H. Fredrickson,1,2,4 Edward J. Kramer,1,2,4 Nathaniel A. Lynd,1 Craig J. Hawker1,2,3
1
Materials Research Laboratory, University of California, Santa Barbara, California 93106
Materials Department, University of California, Santa Barbara, California 93106
3
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106
4
Department of Chemical Engineering, University of California, Santa Barbara, California 93106
2
Correspondence to: C. J. Hawker (E-mail: hawker@mrl.ucsb.edu) or N. A. Lynd (E-mail: lynd@mrl.ucsb.edu)
Received 20 May 2011; accepted 8 July 2011; published online 9 August 2011
DOI: 10.1002/pola.24891
ABSTRACT: Allyl glycidyl ether, polymerized from potassium
alkoxide/naphthalenide initiators under both neat and solution
conditions was shown to be a highly controlled process. In
both cases, molar masses (10–100 kg/mol) were determined by
the reaction stoichiometry, and low polydispersity indices
(1.05–1.33) could be obtained with a full understanding of the
dominant side reaction, isomerization of the allyl side chain,
being developed. The degree of isomerization of allyl to cisprop-1-enyl ether groups (0–10% mol) was not correlated to
INTRODUCTION Polyethers, such as poly(ethylene glycol)
(PEG), are widely used materials in commercially established fields such as drug-delivery,1 and control of biocompatibility,2 and are becoming increasingly important in
emerging technologies such as dye-sensitized solar cells,3
and lithium-polymer batteries.4 A fundamental challenge
with all PEG-based systems is the lack of functional handles along the polymer backbone which limits the modification and tunability of this valuable materials platform.5
As a functional alternative to PEG in some applications,
low-Tg poly(allyl glycidyl ether) (PAGE) has been examined due to its inherent chemical flexibility stemming
from the pendant allyl groups. For example, the allylethers along the PAGE backbone are amenable to thiolene radical coupling chemistry which enables the elaboration of PAGE with a wide variety of functionalities without the need for tedious protection–deprotection chemistries.6 Such modular and facile reactivity increases the
relevance of PAGE for applications in therapeutics, bioconjugation, and polymer-supported catalysis.7,8 This combination of latent chemical functionality, and inherent physical properties (low Tg, lack of crystallinity) makes a
compelling case to systematically explore the synthesis
and reactivity of this potentially useful and inexpensive
polyether materials platform.
C 2011 Wiley Periodicals, Inc.
V
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the molar mass or polydispersity of the polymer but was dictated by the polymerization temperature. This allows the extent
of isomerization to be reduced to essentially zero under either
melt or solution conditions at polymerization temperatures of
C 2011 Wiley Periodicals, Inc. J Polym Sci Part
less than 40 C. V
A: Polym Chem 49: 4498–4504, 2011
KEYWORDS: anionic polymerization; polyethers; ring-opening
polymerization
Examples of the polymerization of AGE,9,10 and the selective
functionalization of its pendant allyl groups by thiol-ene
radical coupling can be found in the literature.11–13 Erberich
et al.10 carried out an extensive analysis of the polymerization chemistry of AGE and the functionalization, protection,
and allyl-deprotection to linear polyglycidol. However, the
authors concluded that the polymerization of allyl glycidyl
ether (AGE) was only controlled to 80% conversion with termination by abstraction of an allylic proton competing with
propagation. Hrubý et al.11 also investigated the application
of poly(ethylene oxide)-b-poly(allyl glycidyl ether) (PEOPAGE) as a micellar drug delivery vehicle with doxorubicin
units being randomly attached, via pH-sensitive hydrazone
linkages, along the PAGE block. Similarly, Persson and Jannasch synthesized a poly(allyl glycidyl ether)-b-poly(ethylene
oxide)-b-poly(allyl glycidyl ether) (PAGE-PEO-PAGE) triblock
copolymer and graft copolymers of PAGE on a poly(phydroxy styrene) backbone. In these cases, thiol-ene coupling
of benzimidazole units to the PAGE blocks creates robust
proton-exchange membrane materials for hydrogen fuel-cell
applications.12 The challenge with these studies is that the
polymerization of AGE under the reported conditions results
in significant termination and other side reactions with
impure block copolymers being obtained that required removal of PEO and PAGE homopolymer contaminants. Alternatively, Hu et al.14 have polymerized AGE to low molar
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masses (2–4 kg/mol) using a sodium ethoxide initiator and
xylene as the polymerization solvent. The molar masses
agreed well with the reaction stoichiometry; however, the resultant polydispersity indices (PDIs) were low (1.04–1.08)
only at low molecular weights. Obermeier and Frey investigated the copolymerization of ethylene oxide and AGE.13
However, their analysis was limited to low molecular weights
of less than 10 kg/mol and utilized cesium alkoxide initiators that were generated by the deprotonation of an alcohol
with cesium hydroxide, followed by removal of water. The
molar masses they reported were consistently 10% above
that defined by the reaction stoichiometry.
The significant promise shown by PAGE-based materials,
coupled with unresolved issues concerning the polymerization of AGE, prompted a thorough reinvestigation of the
homopolymerization of AGE. A driving force for this focus on
homopolymerization is the ease of handling AGE compared
to ethylene oxide with its associated low boiling point and
high toxicity which increases the complexity of the polymerization. The use of alternate initiating systems under a
wide variety of bulk and solution conditions resulted in optimized polymerization conditions and the development of a
fundamental understanding for controlling side reactions in
this useful materials platform.
RESULTS AND DISCUSSION
In examining the methods to synthesize PAGE, many of the
approaches have relied on the utilization of a strong, nonnucleophilic base and removal of the conjugate acid (e.g.,
water, or tert-butanol) to generate an alkoxide initiator followed by the addition of AGE and polymerization at high
temperatures (ca. 100 C).9–12 A challenge with these strategies is that protic impurities are introduced during generation of the initiating system and these impurities may be difficult to quantitatively remove, leading to subsequent
interference with the polymerization. Moreover, the use of
high polymerization temperatures can be detrimental to the
polymerization leading to unwanted side reactions.
To overcome these issues, the radical-anion potassium naphthalenide was used to generate a potassium alkoxide initiator which was employed for the polymerization of AGE.15,16
Significantly, the by-products of deprotonation of the benzyl
alcohol initiator with potassium naphthalenide are naphthalene and dihydronaphthalene13 which are innocuous to the
polymerization, and the introduction and removal of residual
FIGURE 1 Number-average molar mass (Mobs.) as measured by
1
H NMR spectroscopy versus the molar mass defined by the
reaction stoichiometry (Mstoich.). The line plotted alongside the
data has a slope of one and an intercept of zero. Polydispersity
indices as measured by size-exclusion chromatography are
shown adjacent to each data-point. In the case of several
closely space data points, the average polydispersity is shown.
Detailed polymerization results are shown in Table 1.
water or alcohol characteristic of other initiation strategies
such as sodium or cesium alkoxides is unnecessary.9–12
Scheme 1 shows the generation of potassium alkoxide initiator and subsequent polymerization of AGE.
In developing a fundamental understanding of the effect of
polymerization conditions on the resulting PAGE polymers,
polymerizations were conducted over the temperature range,
30–80 C, both neat and in solution. All polymerizations
were carried out for 20 h, which was sufficient time for
quantitative conversion of AGE except for the highest molar
masses (>50 kg/mol) for which 144 h was used to reach
completion. It should be noted that the polymerization of
AGE was controlled over an order of magnitude in molar
mass (10–100 kg/mol) and under a variety of polymerization conditions. Figure 1 details the observed number-averaged molar mass (Mobs
n ) plotted versus the molar mass as
defined by the reaction stoichiometry (Mstoich
) with numbern
SCHEME 1 Polymerization of allyl glycidyl ether from potassium benzoxide.
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TABLE 1 Polymerization Results Carried Out Under a Variety of
Polymerization Conditions
a
b
Mstoich
PDIc %Isomerd Solvente TPolym.( C)
Samples Mobs
n
n
1
9.0
10.0
1.09 0.0
Neat
2
11.8
10.0
1.08 8.8
Diglyme 80
3
14.0
10.0
1.08 0.6
Diglyme 40
4
19.2
20.0
1.11 1.3
Neat
60
5
22.5
25.0
1.12 0.0
Neat
30
6
27.5
30.0
1.07 6.3
Neat
80
7
29.1
30.0
1.10 0.0
Diglyme 40
8
30.0
30.0
1.05 2.8
Neat
80
9
42.7
40.0
1.18 0.2
Neat
40
10
50.0
50.0
1.13 5.0
Diglyme 80
11
90.2f
90.0
1.33 0.0
Neat
1.20 4.0
Diglyme 80
12
105
100
30
30
a
Mobs
measured by NMR spectroscopy.
n
b
Mstoich
was defined by the monomer to
n
c
initiator ratio.
Polydispersity indices were determined by SEC in chloroform relative
to polystyrene standards.
d
The percent cis-prop-1-enyl isomer incorporation was determined by
1
H NMR spectroscopy.
e
Solution polymerizations were carried out at 20 wt % monomer in diglyme.
f
Polymerization time of 144 h.
averaged molar masses being determined by 1H NMR spectroscopy using end group analysis based on the benzylic protons (2H) on the initiator and either allyl (1H) or backbone
ether protons (5H) to determine the number of repeat units.
In solution and melt polymerizations carried out between
30–80 C, the resultant molar masses compared well with
the monomer to initiator feed ratios as indicated by the close
agreement between Mobs
and Mstoich
. PDIs were measured by
n
n
size exclusion chromatography (SEC) relative to polystyrene
standards and were typically between 1.05 and 1.20 with
higher polydispersities only being observed for high molecular weight materials (Fig. 1). These increases in PDI are due
to chain coupling occurring after complete consumption of
AGE or radical coupling of backbone allyl substituent, rather
than any transfer or termination reactions competing with
propagation at high conversion as noted by Erberich et al.10
representative 1H NMR spectrum for AGE polymerized at 30
C (Table 1, entry 5) is shown in Figure 3 (top) along with
peak assignments. At lower polymerization temperatures, the
repeat-unit structure is derived from the AGE monomer
feedstock without isomerization as can be seen by the
defined resonances corresponding to the allyl substituent in
Figure 3, inset (a). However, at higher polymerization temperatures, the repeat-unit structure can no longer be
assigned to a single isomer. PAGE polymerized above 40 C
both neat and in solution exhibits 1H and 13C NMR spectra
consistent with isomerization of the allyl repeat unit (Fig. 3,
bottom and Fig. 4, respectively). Significantly, peak assignments for the three possible isomers (allyl; cis-prop-1-enyl,
and trans-prop-1-enyl) clearly reveal the presence of the cisisomer and the absence of the trans-isomer.18 Sunder et al.9
and Obermeier and Frey reported on the presence of prop-1enyl isomers but identified the isomer as trans, but as shown
above only the cis-isomer is present.13 Finally, Erberich
et al.10 reported the termination of AGE polymerizations
as possibly occurring through the abstraction of the allylic
proton but did not report the presence or formation of the
1-propenyl isomer.
On the basis of the work of Prosser, the isomerization of allyl
ethers along the backbone may occur according to Scheme
2.19 The living potassium alkoxide chain-end abstracts an allylic proton from an AGE repeat unit and the alkyl potassium
formed from this proton abstraction reaction coordinates
with the potassium counter-ion forming a five-membered
ring, stabilizing the cis-isomer. The alkyl potassium then
deprotonates a dormant alcohol creating a potassium alkoxide chain-end and propagation of AGE continues resulting in
a cis-propenyl repeat-unit isomer. As a result, this process
does not constitute a termination reaction with isomerization
being fast relative to propagation as no evidence of
Hans et al.17 reported a chain-transfer reaction in ethoxy ethyl
glycidyl ether (EEGE) polymerizations beginning with the
abstraction of a methylene proton adjacent to the epoxide
ring by an active alkoxide chain-end. Subsequently, the epoxide ring opened introducing a new alkoxide which reinitiated
polymerization. This chain-transfer to monomer generated
PEEGE materials with allylic-ether end-groups exhibiting characteristic resonances in the 1H NMR spectra, and molecular
weight distributions with long, low-molecular weight tails in
the size-exclusion chromatograms. No chain-transfer to monomer was detected in polymerizations of AGE either by 1H
NMR spectroscopy or size-exclusion chromatography (Fig. 2).
The controlled nature of this synthetic approach to PAGE
then allowed a detailed examination of the relationship
between polymer structure and polymerization conditions. A
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FIGURE 2 Size-exclusion chromatographs of polymers 2
(dashed line, Mn ¼ 11.8 kg/mol, PDI ¼ 1.08) and 6 (solid line
Mn ¼ 27.5 kg/mol, PDI ¼ 1.07) as detailed in Table 1.
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evidence from either 1H or 13C NMR spectroscopy that the
deprotonated allyl-ether side-chains react nucleophilically
with AGE monomer leading to branching and the conclusion
that the deprotonated allyl side chains are transient and
non-nucleophillic species.
Having noted that the extent of cis-prop-1-enyl isomer formation was related to reaction temperature, several neat polymerizations were carried out at fixed polymerization times
(20 h) between 40 and 140 C in 20 C increments with the
degree of isomerization being characterized by 1H NMR
spectroscopy (Fig. 5). For neat polymerizations carried out
at lower temperatures (40 C), very low levels of isomerization are observed (1.5% mol) which increases on progressing to 80 C (3.7% mol) followed by a significant increase in
the level of isomerization for neat polymerizations carried
out above 100 C (8.3–16.6% mol). The mole percent of cisprop-1-enyl isomers that resulted from neat polymerizations
carried out at 40–140 C are shown in Table 2.
Heatley et al.20 investigated the isomerization of allyl ethers
to propenyl ethers that occurs during the oxyanionic polymerization of propylene oxide as a side reaction. Through a
detailed analysis by 1H NMR spectroscopy, the authors came
to the conclusion that the activation energy for the allyl to
cis-prop-1-enyl isomerization was 116 kJ/mol. For a bimolecular reaction between a living chain end and an allyl group,
the rate of isomerization is given by –d[Allyl]/dt ¼ k [Allyl]
[ROK], with the temperature dependent rate constant given
by:
ln k ¼ 26:31
13; 960=TðL mol
1
s 1Þ
(1)
FIGURE 3 (Top spectrum) 1H NMR spectrum of poly(allyl glycidyl ether) polymerized neat at 30 C (Table 1, entry 5). Peak
assignments are shown in the inset. The resonance near 4.5
ppm marked with an asterisk is due to the benzyl (2H) end
group protons used for determination of molar mass. (Bottom
spectrum) 1H NMR spectrum of PAGE polymerized neat at
120 C (see Table 2) with inset peak assignments showing the
presence of extra resonances due to the presence of cis-propenyl isomers. Three possible isomers exist: (a) allyl, (b) cis-prop1-enyl, (c) trans-prop-1-enyl. Resonances are observed for the
monomer-derived allyl, and cis-prop-1-enyl isomers only. No
evidence of trans isomerization is present.
premature termination or chain-transfer to monomer is seen
in the SEC traces (see Fig. 2). In addition, the amount of cisisomer is not correlated with the molar mass or polydispersity; instead, there is a strong correlation with reaction temperature (see Table 1 and Fig. 1). No significant isomerization occurs below a polymerization temperature of 40 C
and the mole fraction of isomerized cis-prop-1-enyl gradually
increases as the reaction temperature increases. Interestingly, at the same temperature, the nature of the reaction
conditions did not significantly affect the extent of isomerization with similar values being obtained for polymerizations
in solution, and under melt conditions. Finally, there was no
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FIGURE 4 13C NMR spectrum of PAGE polymerized neat at
120 C (see Table 2). Repeat unit isomers are shown with
assignments in (a) and (b). Resonances due to carbon atoms in
the benzyl end group are indicated with an asterisk.
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SCHEME 2 Proposed isomerization of allyl-substituents to cis-prop-1-enyl units.
Using the integrated rate law and assuming the density of
PAGE is 1.0 g/mL, for a fixed reaction time of 20 h, the
incorporation of isomers would be expected to increase precipitously above 100 C based on the rate constant determined by Heatley et al. Although the concentration of allyl
groups Heatley et al. used in their analysis was significantly
lower than that for PAGE, their kinetics for allyl to cis-prop1-enyl isomerization agree qualitatively with the temperature
dependence of allyl to cis-prop-1-enyl isomerization occurring in AGE during neat polymerization.
Obermeier and Frey briefly addressed the issue of allyl-ether
isomerization in copolymerizations of AGE and ethylene
oxide.13 A very broad range of isomerization values (0–10
mol %) was reported for polymerizations carried out even at
40 C. This is in contrast to our results where a polymerization temperature of 100 C resulted in 8 mol % cis-prop-1enyl isomers, and 30 C results in undetectable levels of
isomerization along the PAGE backbone. It is difficult to
speculate on the origins of this difference. However, the potassium naphthalenide system that we employ for the polymerization of AGE yields reproducibly undetectable levels of
isomerization for melt polymerization carried out below
40 C up to molar masses as high as 90 kg/mol explored in
this study which suggests another advantage for this polymerization system when compared to other alkoxide (cesium) systems.
A detailed understanding of the isomerization of AGE during
polymerization at elevated temperatures opens the opportunity to exploit the reactivity of the resulting cis-prop-1-enyl
groups which are hydrolytically unstable and can give rise to
hydroxyl groups. Indeed, the examination of the 1H and 13C
NMR spectra of PAGE materials containing cis-prop-1-enyl
isomers revealed an apparent loss in the number of prop-1enyl groups relative to backbone ether protons on exposure
to hydrolytic conditions. This discrepancy was correlated to
the degree of isomerization of each sample and in most
cases surpassed the amount of remaining cis-prop-1-enyl
TABLE 2 Isomerization of Allyl Groups During Neat
Polymerization of AGE at 40–140 8C
FIGURE 5 1H NMR spectra resulting from polymerizations carried out at various temperatures (40–140 C). All spectra are
normalized to the intensity of the benzyl resonance near 4.5
ppm (2H), and peak-assignments are shown in Figure 3. The
mole percent incorporation of cis-prop-1-enyl isomers
increases with polymerization temperature for polymerizations
of equivalent duration as evidenced by the increase in intensity
of the peaks due to the d0 (1H), e0 (1H), and f0 (3H) protons.
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Tpolym.a
Mnb
M nc
PDId
40
17.2
17.4
1.09
1.5
60
18.7
19.2
1.11
3.9
80
16.8
17.2
1.11
3.7
100
14.0
14.4
1.14
8.3
120
15.7
17.5
1.19
16.3
140
14.8
16.4
1.20
16.6
a
%Isomere
Polymerization temperature in C.
Molar mass in kg/mol, determined by the allyl protons using 1H NMR
spectroscopy.
c
Molar mass in kg/mol determined by the backbone-ether protons
using 1H NMR spectroscopy.
d
Determined by RI-SEC in chloroform relative to polystyrene standards.
e
Mole percent of cis-prop-1-enyl ether units determined by 1H NMR
spectroscopy.
b
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isomer. Ishizaki et al.21 reported that allyl ethers can be
deprotected to alcohols via catalytically generating in situ the
labile cis- and trans-prop-1-enyl isomers in a protic solvent
(e.g., methanol) under mildly basic conditions.22 These conditions are similar to those present during termination of the
polymerization reaction with protic solvents.
The flexibility of PAGE as a molecular platform is enhanced
by this controlled formation of cis-prop-1-enyl groups and
can be specifically exploited.19 For example, reaction of PAGE
containing 13% (mol.) cis-1-Propenyl isomer in methanol
over a polymer-supported sulfonic acid resin (DOWEX)
results in quantitative cleavage of the cis-1-propenyl groups
to hydroxy functionalities. This affords a linear random copolymer of glycidol and AGE and provides a mechanism for
orthogonal modification of the PAGE backbone via the
hydroxy- and allyl-functionalities. Significantly, the amount of
cis-1-propenyl isomerization may be tuned by the reaction
conditions; lower temperatures generally result in lower levels of isomerization (see Tables 1 and 2 and Fig. 5) for the
same polymerization time.
EXPERIMENTAL
Materials
All chemicals were used as received from Sigma-Aldrich
unless otherwise specified. THF was collected from a dry solvent system and used immediately thereafter. Benzyl alcohol
was dried over calcium hydride and distilled before titration
with potassium naphthalenide in THF. AGE (TCI-America)
was degassed through several freeze-pump-thaw cycles and
distilled from butyl magnesium chloride to a preweighed
and flame-dried buret immediately before use. Potassium
naphthalenide was prepared from potassium metal and
recrystallized naphthalene in dry THF and allowed to stir
with a glass-coated stir-bar for 24 h at room temperature
before use.
Characterization
H NMR spectroscopy was carried out on a Bruker AC 500
spectrometer in deuterated chloroform. 13C NMR spectroscopy was carried out on neat PAGE containing a sealed D2O
capillary containing for locking and shimming the spectrometer. Size exclusion chromatography (SEC) was performed on
a Waters chromatograph with four Viscotek colums (two IMBHMW-3078, I-series mixed bed high molecular weight columns and two I-MBLMW-3078, I-series mixed bed low-molecular weight columns) for fractionation, a Waters 2414 differential refractometer and a 2996 photodiode array
detector for detection of eluent, and chloroform with 0.1%
tetraethylamine at room temperature was used as the mobile
phase. Gas chromatography was carried out on a Shimadzu
GC-2014 using a flame ionization detector and a Restek column (SHRXI-5MS) for separation.
1
Polymerizations and Modifications
All polymerizations were carried out on a Schlenk line in
custom thick-walled glass reactors fitted with threaded ACEthreads under an argon atmosphere. The reactors were dried
under vacuum then refilled with argon five times. Under an
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argon atmosphere, benzyl alcohol initiator was added by
gas-tight syringe through a 6-mm puresep septum. Potassium alkoxide initiators were formed by titration of benzyl
alcohol with potassium naphthalenide under argon until a
green color persisted in solution indicating the deprotonation of all alcohols. Two polymerization procedures were followed: (A) Bulk polymerizations were carried out between
30 and 140 C for 20 h and terminated with methanol. (B)
Solution polymerizations were carried out in diglyme
between 30 and 140 C for 20 h and terminated with methanol. Polymerizations carried out at higher temperatures
(>100 C) were carried out on small scales (ca. 1 g). Deprotection of the cis-prop-1-enyl ether isomers was carried out
in methanol using five equivalents of DOWEX resin by mass.
Complete conversion of the cis-prop-1-enyl ethers to hydroxyls was observed by complete disappearance of all 1H NMR
signals consistent with the cis-prop-1-enyl ethers. For the
synthesis of PAGE with undetectable levels of isomerization,
controlled molar masses, and low PDIs, polymerization in
the melt at 30 C was carried out for 20–144 h depending
on the target molecular weight.
1
H NMR of PAGE (500 MHz, CDCl3): d 1.55 (d,
AOACH¼
¼CHACH3), 3.47–3.72 (broad m, AOACH2ACH
(CH2AOACH2ACH¼
¼CH2) AOA and ACH2ACH(CH2AOA
CH¼
¼CHACH3)AOA), 3.79/3.87 (two broad peaks, ACH2A
CH(CH2AOACH¼
¼CHACH3)AOA), 4.01 (d, AOACH2ACH¼
¼
CH2), 4.38 (m, AOACH¼
¼CHACH3), 4.56 (s, Ph-CH2AOA),
5.18/5.28 (doublet of doublets, AOACH2ACH¼
¼CH2), 5.91
(m, AOACH2ACH¼
¼CH2), 5.97 (d, AOACH¼
¼CHACH3), 7.30
(overlap with residual CHCl3, 1H on PhACH2AOA), 7.36 (s,
4H on PhACH2AOA). 13C NMR of PAGE (500 MHz, neat
PAGE, D2O capillary for shimming): d 70.9 (AOACH2A
CH(CH2AOACH2ACH¼
¼CH2)AOA), 72.0 (AOACH2ACH¼
¼
CH2), 79.4 (AOACH2ACH(CH2AOACH2ACH¼
¼CH2)AOA),
100.3 (AOACH¼
¼CHACH3), 116.3 (AOACH2ACH(CH2A
OACH2ACH¼
¼CH2)AOA), 127.5/128.6 (5C, PhACH2AOA),
135.6 (AOACH2ACH(CH2AOACH2ACH¼
¼CH2)AOA), 138.8
¼CHA
(1C, PhACH2AOA), 146.8 (AOACH2ACH(CH2AOACH¼
CH3) AOA).
CONCLUSIONS
The polymerization of AGE using potassium alkoxide initiators has been shown to result in low polydispersity, controlled molecular weight materials under both solution and
melt conditions. Depending on the specific polymerization
temperature, either no isomerization of the allyl groups was
observed (30 C) or the fraction of allyl groups along the
backbone isomerized into labile cis-prop-1-enyl groups was
found to increase with increasing reaction temperature. Significantly, hydrolysis of the isomerized cis-prop-1-enyl groups
to hydroxyl groups could be achieved by a postpolymerization treatment giving orthogonally reactive hydroxy and allyl
groups along the backbone. The properties and inherent
chemical functionality of the resultant PAGE material makes
it amenable as a polymeric platform with potential applications in a wide range of technological areas.
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This project has been funded in part with Federal funds from
the National Heart, Lung, and Blood Institute, National Institutes of Health, Department of Health and Human Services,
under Contract No. HHSN268201000046C. This work was also
supported by the Los Alamos National Laboratory Institute for
Multiscale Materials Studies, and the National Science Foundation (MRSEC Program DMR-05204156 (MRL-UCSB)). Materials
Research Laboratory Central Facilities are supported by the
MRSEC Program of the NSF under Award No. DMR11-21053; a
member of the NSF-funded Materials Research Facilities Network (www.mrfn.org).
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