Novel degradable polymer networks containing acetal components

Article abstract of DOI:10.1007/s11426-011-4223-0

A novel copolymer network with acetal structure was prepared using bis[4-(vinyloxy)butyl] (4-methyl-1,3-phenylene)biscarbamate (BECT) as the crosslinking agent. Firstly, a tri-copolymer of maleic anhydride (MAn), n-butyl vinyl ether (BVE) and 4-hydroxybut

Full text of DOI:10.1007/s11426-011-4223-0

SCIENCE CHINA
Chemistry
March 2011 Vol.54 No.3: 419–425
doi: 10.1007/s11426-011-4223-0
• ARTICLES •
Novel degradable polymer networks containing acetal components
SUI XinCe, SHI Yan & FU ZhiFeng*
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
Received July 2, 2010; accepted October 8, 2010
A novel copolymer network with acetal structure was prepared using bis[4-(vinyloxy)butyl] (4-methyl-1,3-phenylene)biscar-
bamate (BECT) as the crosslinking agent. Firstly, a tri-copolymer of maleic anhydride (MAn), n-butyl vinyl ether (BVE) and
4-hydroxybutyl vinyl ether (HBVE) was synthesized via free-radical polymerization with 2,2′-azobisisobutyronitrile as the ini-
tiator. The tri-copolymer consisted of two sorts of alternating units, MAn-alt-BVE and MAn-alt-HBVE. The linear copolymer
Poly((MAn-alt-BVE)-co-(MAn-alt-HBVE)) with pending hydroxyl groups was then combined with BECT in the presence of
pyridinium p-toluenesulfonate, generating a copolymer network comprising acetal components in the crosslinking segment.
This polymer network exhibited degradation in acid conditions.
alternating copolymerization, maleic anhydride, network, degradation
methacrylate) [11] or acrylic acid [12] as end blocker. These
1 Introduction
dimethacrylate polyacetal were used as crosslinkers in
free-radical polymerization to produce polymer gels that
would decompose in an acid. In another way, a copolymer
network with acetal components in the crosslinking segment
had been synthesized by the addition reaction of divinyl
ethers and linear polymer with hydroxyl side groups [13].
In the post decades, the well defined alternating copoly-
mer of maleic anhydride and n-alkyl vinyl ether via free-
radical polymerization had been widely investigated due to
the applications to photosensitive coatings and biomedical
materials [14–18]. And the divinyl ethers can also be co-
polymerized with maleic anhydride to generate networks
which are useful in membrane separations [19] and drug
delivery system [20]. Meanwhile, the hydrolyzed copoly-
mers exhibited pH-responsive behavior in aqueous media
and the hydrolyzed copolymers with various size alkyl
groups underwent a conformation transition as the pH
changed [21]. As far as we know, there is no report on the
synthesis of degradable networks based on the copolymer of
maleic anhydride and n-alkyl vinyl ether via free-radical
polymerization.
The intelligent gels, such as pH-sensitive gels, have been
widely investigated due to their special characteristics. The
general pH-sensitive polymer gels exhibited swelling or
deswelling as pH changed [1–3], but pH did not affect their
chemical compositions and molecular structures. So the
pH-sensitive polymer gels with special components that
could decompose in selective media attracted great attention
for the biomedical materials, such as controlled drug delivery
and tissue engineering [4–6], and for electronics industry
[7–9]. Polymer network containing (poly)acetal segments
[10] is one of these kinds because the acetal structure de-
graded in acid environment while kept stable in basic or
neutral conditions. A series of degradable macro-crosslinkers
consisting of polyacetal structure were synthesized to pro-
duce polymer gels that behaved degradability in acid condi-
tions. A telechelic poly(1,3-dioxolane) (polyDXL) with
methacrylate end groups was synthesized via cationic ring-
opening polymerization of DXL with methylenebis(oxyethyl
*Corresponding author (email: fuzf@mail.buct.edu.cn)
The aim of this study is to prepare a degradable copoly-
© Science China Press and Springer-Verlag Berlin Heidelberg 2011
chem.scichina.com
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Sui XC, et al. Sci China Chem March (2011) Vol.54 No.3
mer network using the alternating copolymer of maleic an-
hydride and n-alkyl vinyl ether as backbone. This kind of
degradable polymer networks might be used as reworkable
adhesives [22]. As shown in Scheme 1, the copolymer with
pending hydroxyl groups was prepared by the copolymeri-
zation of maleic anhydride (MAn), n-butyl vinyl ether
(n-BVE) and hydroxybutyl vinyl ether (HBVE) with 2,2′-
azobisisobutyronitrile (AIBN) as initiator. By the end of the
copolymerization process, the crosslinker bis[4-(vinyloxy)
butyl] (4-methyl-1,3-phenylene) biscarbamate (BECT) with
a trace amount of pyridinium p-toluenesulfonate (PTS) was
added into the system, generating a copolymer gel that con-
sisted of poly(MAn-alt-BVE) backbone and acetal crosslink-
ing components. This copolymer gel would decompose in
acid conditions.
was performed at 50 °C for 12 h. Then white solid BECT
powder was obtained by twice precipitation in a large
amount of hexane from THF solution, dried under vacuum
and stored at room temperature.
2.3 Copolymerization of MAn, n-BVE and HBVE
The monomer mixture of an equal molar ratio of MAn (2.45 g,
0.025 mol) and vinyl ethers (Moln-BVE/MolHBVE = 2/1; 4/1;
9/1) with the initiator AIBN (0.041 g, 0.25 mmol) was dis-
solved in THF (20 mL) in a round-bottomed flask equipped
with a magnetic stirrer. The mixture was degassed with
three freeze-evacuate-thaw cycles, and polymerized under
argon at 70 °C in an oil bath. After a certain reaction time,
trace amount of samples were taken out with dry syringes to
determine monomer conversions, molecular weights and
molecular weight distributions of the copolymer. The co-
polymer samples for 1H NMR analysis were further purified
by precipitation in hexane from THF solution to remove the
unreacted monomers and then vacuum-dried over night at
50 °C.
2 Experimental
2.1 Materials
Tetrahydrofuran (THF) was dried with CaH2 under reflux
for 24 h and distilled just before use. 4-Hydroxybutyl vinyl
ether (HBVE, Chongqing Research Institute of Chemical
Industry, 95%) was dried with CaO for 24 h and distilled
twice under reduced pressure. Diphenylmethane diisocy-
anate (MDI, Beijing Keju Chemical Material) was distilled
under reduced pressure. n-Butyl vinyl ether (n-BVE, Acros,
99%) was dried with CaH2 for 24 h and distilled before use.
Pyridinium p-toluenesulfonate (PTS, Aldrich, 98%) was
used as received. 2,2′-Azobisisobutyronitrile (AIBN) was
recrystallized from ethanol and dried under vacuum.
2.4 Preparation of degradable polymer gel
When the monomer conversion reached above 99%, the
polymerization was stopped by cooling the mixture to room
temperature. Half the molar amount of BECT relative to
HBVE with a trace amount of PTS was then added into the
mixture under the protection of nitrogen with magnetic stir-
ring. The crosslinking reaction took place at 30 °C. Before
the gel formation, a trace amount of sample was taken out
with a dry syringe for GPC measurement, and further puri-
1
fied by precipitation in hexane for H NMR analysis. A co-
2.2 Synthesis of BECT
polymer gel was generated in the flask when the stirrer
failed in running. The gel was washed by THF in a Soxhlet
extractor for 24 h to remove the sol fraction. After the ex-
traction, the swelled gel was cut into pieces and weighed.
In a well-dried round-bottom flask with magnetic stirring,
MDI and HBVE with molar ratio of 1:2 were dissolved in
purified THF under the protection of nitrogen. The reaction
Scheme 1 Synthesis and hydrolysis of degradable polymer network.

Sui XC, et al. Sci China Chem March (2011) Vol.54 No.3
421
Portions of the pieces were treated with NaOH aqueous
solution (0.1 M) for 12 h. Subsequently, each piece was
dried in a vacuum oven at room temperature for 48 h, and
reweighed. The dry samples were then placed in a large
amount of deionized water and methanol for 48 h at room
temperature, respectively. The gel samples were weighed
after the solvents were removed by syringes. The swelling
ratio of the copolymer network in THF, water and methanol
was calculated with equation (1).
been prepared by the Williamson reaction, but the conver-
sion was low [24]. Thus, it is attractive to produce divinyl
ethers under mild condition with high conversion and con-
venient separation process. In the present work, a conven-
ient method was employed to synthesize divinyl ethers us-
ing hydroxyalkyl vinyl ethers and diisocyanates.
As shown in Scheme 2, the addition reaction of MDI and
HBVE was performed in THF at 50 °C for 12 h. The con-
tent of isocyanate group in the system was determined by a
reaction of the sample with an excess of di-n-butylamine in
acetone, and then the excess di-n-butylamine was deter-
mined by back-titration with standard hydrochloric acid
[25]. The final conversion of isocyanate group reached up to
99%. The purified product of BECT was obtained as white
powder by twice precipitation in a large amount of hexane
from THF solution, yield 90%.
Ws Wd
Wd
SR 
(1)
where Ws was weight of the swelled network and Wd was
weight of the dried network.
1
2.5 pH response of the copolymer network
Figure 1 depicts the H NMR spectrum of BECT. The
peaks at  3.99, 4.16, and 6.47 ppm (peak a′, a, b) belonged
to the carbon-carbon double bond protons. The singles at 
7.28 and 7.10 ppm (peak h, i) belonged to the aromatic pro-
tons of MDI units, and the peak at  3.88 ppm (peak j) cor-
responded to methylene protons (Ar-CH2-Ar). Furthermore,
the integral intensity of peak b (Ib) exactly equaled to Ij,
indicating that the divinyl ether bis[4-(vinyloxy)butyl]
(4-methyl-1,3-phenylene) biscarbamate (BECT) was ob-
tained successfully.
At room temperature, a certain amount of dried copolymer
gel (2.0 g) was swelled in THF (30 mL) for 48 h. And hy-
drochloric acid (2 mL, 0.1 M/103 M/105 M), NaOH aque-
ous solution (2 mL, 0.1 M), or deionized water (2 mL) were
then added, respectively. The hydrolysis was performed at
room temperature with magnetic stirring. At regular time
intervals, traces of solvent/solution were taken out via sy-
ringes to determine the hydrolyzing rate of the swelled gels
gravimetrically. And the time needed to form a clear solu-
tion was recorded. The clear solution obtained was then
neutralized to pH 7, followed by being poured into a large
excess of hexane, and the precipitated polymer was washed
with water and then with methanol, vacuum-dried at room
temperature over night.
2.6 Measurements
1H NMR spectra were recorded on a Bruker AV 600 MHz
NMR spectrometer with CDCl3 or acetone-d6 as solvent at
room temperature. TMS was used as internal standard.
FT-IR spectra were recorded on a Nicolet 8700 spectrome-
ter using KBr tablets. Molecular weights and molecular
weight distributions of the polymers were determined by gel
permeation chromatography (GPC) on a Tosoh HLC 8320
GPC (column: TSK-Gel Super HZM-M × 2) on the basis of
a polystyrene calibration curve, using THF as solvent with a
0.35 mL/min flow rate at 40 °C.
Scheme 2 Synthesis of BECT.
3 Results and discussion
3.1 Synthesis of BECT
In the post decades, divinyl ethers were synthesized by the
reaction of acetylene with diols in the presence of a basic
catalyst, generating both divinyl ethers and monovinyl
ethers. A complex separation process was needed to obtain
the product with good purity [23]. Divinyl ethers also had
Figure 1 1H NMR spectrum (in CDCl3) of BECT.

422
Sui XC, et al. Sci China Chem March (2011) Vol.54 No.3
3.2 Copolymerization of MAn, n-BVE and HBVE
of crosslinking sites, can be controlled accordingly.
Figure 3 shows the GPC chromatograms of copolymers
obtained at different feeding ratio of HBVE and n-BVE.
The molecular weight distribution (Mw/Mn) of copolymer
became broader with the increase of HBVE content in the
polymerization system because of the association with hy-
drogen bonds in THF solution [26]. As shown in Figure 3
(a), the Mw/Mn of copolymer obtained in the absence of
HBVE was 2.94, while it shifted to 9.75 in case (d).
The copolymerization of MAn, n-BVE and HBVE was car-
ried out in THF under argon at 70 °C. Because the process
went though a free-radical alternating copolymerization
mechanism, the reaction rate was so fast that the monomers
conversion was above 90% for 2 h in each case and reached
99% for 3 h.
1
Figure 2 (A) depicts the H NMR spectrum of a well-
purified copolymer. The single at  2.1–2.5 ppm (peak a) be-
longed to the MAn units; meanwhile the absorptions corre-
sponding to the vinyl ethers units were present at  4.0–4.5
ppm (peak b and b′) and  0.88 ppm (peak c). In order to
clarify the structure and composition of the tri-copolymer, a
copolymerization of MAn with n-BVE was also carried out
FnBVE
FHBVE
Ic
3

(2)
Ib+b  Ic
3.3 Preparation of degradable polymer gel
1
under the same conditions. The H NMR spectrum of the
The addition reaction of hydroxyl and vinyloxyl groups was
employed for the crosslinking process according to litera-
ture [27]. As the BECT and PTS were added into the THF
solution of P((MAn-alt-BVE)-co-(MAn-alt-HBVE)) under
the protection of nitrogen at 30 °C, the addition reaction of
hydroxyl group on the copolymer backbone and vinyloxyl
group of BECT took place immediately, generating a graft
copolymer at the first stage and then the network. Before
the gel formation, a trace amount of sample was taken out
di-copolymer is shown in Figure 2(B). By comparing (A)
with (B), most peaks were present as almost the same ex-
cept one at  4.65 ppm. The molar ratio of MAn and BVE
units calculated from their intensity ratio in (B) was 1:1
(Ia/Ib = 2/1) coinciding as employed, indicting that the po-
lymerization of MAn and vinyl ethers initiated by AIBN
underwent through an alternating mechanism. Accordingly,
the molar ratio of MAn units and vinyl ethers units calcu-
lated from intensity ratio of Ia/Ib+b′, in (A) was also about 1:1,
illuminating that the copolymer consisted of MAn, n-BVE,
and HBVE units. The molar ratio of n-BVE and HBVE in
the copolymer P((MAn-alt-BVE)-co-(MAn-alt-HBVE)) was
calculated with equation (2), giving 3.7/1 close to the feed-
ing ratio ([n-BVE]0/[HBVE]0 = 4/1). It was considered that
the molar ratio of n-BVE and HBVE in the copolymer can
be regulated by the feeding ratio of the two components.
Thus, the content of hydroxyl side groups, i.e. the number
1
for GPC measurement and H NMR analysis. After the
magnetic stirrer failed in working, a copolymer network
was obtained. Then the copolymer gels were washed by
THF in a Soxhlet extractor for 24 h. No sol fraction was
detected in the extracting solvent, confirming that a com-
plete gel formation occurred via the addition reaction of
linear copolymers with BECT. As shown in Table 1, the
crosslinking time was determined by the feeding ratio of
Figure 3 GPC traces of copolymers obtained at various molar ratios of
n-BVE and HBVE with MAn in THF at 70 °C for 3 h. Peak (a), [MAn]0:
[n-BVE]0:[HBVE]0 = 1:1:0; peak (b), [MAn]0:[n-BVE]0:[HBVE]0 = 10:9:1;
peak (c), [MAn]0:[n-BVE]0:[HBVE]0 = 5:4:1; peak (d), [MAn]0:[n-BVE]0:
[HBVE]0 = 3:2:1.
Figure 2 1H NMR spectra (in acetone-d6) of (A) P((MAn-alt-BVE)-co-
(MAn-alt-HBVE)) (Moln-BVE/MolHBVE = 4/1) obtained for 3 h and (B)
P(MAn-alt-BVE) prepared under the same reaction condition as (A).

Sui XC, et al. Sci China Chem March (2011) Vol.54 No.3
423
Table 1 Synthesis and hydrolysis of copolymer gels
PMBH a)
PMBH-1
PMBH-2
PMBH-3
f b)
1:2
1:4
1:9
TC c) (h)
1.5
TH1d) (h)
TH2 e) (h)
13.0
8.5
2.0
1.5
–
2.5
–
–
a) P((MAn-alt-BVE)-co-(MAn-alt-HBVE)) as the precursor. b) Feeding
ratio of HBVE and n-BVE. c) Time needed for complete gelation. d) Time
needed for complete hydrolyzation when treated with HCl (0.1 M). e) Time
needed for complete hydrolyzation when treated with HCl (10-3 M).
n-BVE and HBVE. By decreasing the content of HBVE
units in the copolymer chains, the crosslinking process was
delayed, or even absent if the content of HBVE was less
than 5 wt% ([MAn]0:[n-BVE]0:[HBVE]0 = 10:9:1).
Figure 5 1H NMR spectrum (in acetone-d6) of the graft copolymer ob-
tained by addition reaction of P((MAn-alt-BVE)-co-(MAn-alt-HBVE)) and
BECT.
As shown in Figure 4, curve (a) is the GPC chroma-
togram of copolymer PMBH-2 (see Table 1), and curve (b)
is the GPC trace of graft polymer obtained by the reaction
of PMBH-2 with BECT at the early stage. Double peaks
appeared in the polymer fraction (I) of curve (b), and the
peak molecular weight (Mp) of b1 was 152500 while Mp of
b2 was 12700 which was close to (a). Obviously, peak b1
corresponded to the graft copolymer formed by the reaction
of the linear copolymer with BECT at low degree of reac-
tion and b2 might correspond to the original linear copoly-
mer. The peaks in fraction (II) belonged to the unreacted
BECT.
PMBH-2 (B) reacted with BECT for 2.5 h. The characteris-
tic absorption of hydroxyl group in PMBH-2 appeared at
3440 cm1 (peak B-c), and was sharply weakened in the gel
sample (peak A-b), indicating that the addition reaction of
hydroxyl and vinyloxyl groups was effective for the
crosslinking process. Furthermore, two signals attributed to
amino and carbonyl groups in the urethane structure (NH-
CO-O) emerged at 3550 cm1 (peak A-a) and 1720 cm1
(peak A-d), respectively. All the information demonstrated
that the acetal group was generated in the formation of co-
polymer network.
1
Figure 5 depicts the H NMR spectrum of the graft co-
polymer. The absorptions of protons on PMBH backbone
chains were present as in Figure 3(a). Moreover, the char-
acteristic peak of the acetal methine proton was present at 
4.68 ppm (peak d). In addition, the peaks of protons origi-
nated from BECT (7.48, 7.15 ppm, ArH; 8.55 ppm, ArNH)
were all present but a bit different (see Figure 1). Figure 6
(A) presents the FT-IR spectrum of polymer gel obtained by
3.4 The pH response of the copolymer network
The copolymer network exhibited pH response because of
the acetal molecular structure as one of its components [28].
Treated with a strong acid (HCl, 0.1 M/103 M) in THF for
a certain time (see Table 1), the network disappeared and a
Figure 4 GPC chromatograms of the copolymers. Curve (a), PMBH-2
for 3 h, Mn = 6200, Mp = 12700, Mw/Mn = 5.41; curve (b), graft copolymer
obtained by addition reaction of (a) and BECT, MP = 152500/12500; curve
(c), product of copolymer gel after treatment with hydrochloric acid, Mp =
7800.
Figure 6 FT-IR spectra of polymer gel (A) and PMBH-2 (B).

424
Sui XC, et al. Sci China Chem March (2011) Vol.54 No.3
clear solution formed. The relationship between hydrolyzing
time (TH) and the feeding ratio of HBVE and n-BVE (f) was
positive correlated, but opposite to the crosslinking time
(TC). Furthermore, when the gel was treated in a stronger
acid environment, the less time was needed for the hydro-
lyzing process. The kinetics of hydrolyzation was deter-
mined by detecting the concentration of the recovered
polymer/THF solution gravimetrically. As the hydrolyzation
proceeded, more recovered polymer was dissolved in THF,
as shown in Figure 7.
Figure 4 (c) presents the GPC chromatogram of the co-
polymer precipitated in hexane from THF solution of the
hydrolyzed network. In polymer fraction (I), single peak
appeared and the Mp reduced to 7800, indicating that a
complete degradation of the acetal component occurred in
the presence of a strong acid. However, the Mp of curve (c)
was smaller than that of (a). It was considered that portions
of the MAn units on the backbone had been hydrolyzed in
the presence of HCl, and the resulting poly(maleic acid) was
not suitable for the GPC analysis when using a HZM-M
column. The peaks in fraction (II) belonged to the low
molecules generated from the crosslinking segments in the
de-crosslinking process, and the MP’s were close to those of
BECT as in curve (b). However, when treated with a strong
alkali (i.e. NaOH, 0.1 M), deionized water or diluted acid
(i.e. HCl, 105 M) in THF, no visible degradation occurred
to the copolymer networks.
with NaOH had changed greatly comparing to those un-
treated, as shown in Table 2. The swelling ratio of the co-
polymer networks in water (SRW) and methanol (SRM) was
determined gravimetrically. For both PMBH-1 and PMBH-2
systems, the SRW and SRM of the networks treated with
NaOH were larger than those of the untreated networks,
respectively. It was considered that the maleic anhydride
unit in the backbone chains of the copolymer networks had
been hydrolyzed by treated with the strong alkali, generat-
ing hydrophilic groups that enhanced the absorption of wa-
ter and lower alcohols for the networks.
4 Conclusions
Hydroxyalkyl vinyl ether and diisocyanates could undergo
an addition reaction to prepare divinyl ether monomers with
high yield and convenient purification process. The co-
polymer of MAn, n-BVE and HBVE was prepared in THF
solution by an alternating polymerization mechanism with
AIBN as initiator. The copolymer with hydroxyl group as
crosslinking site underwent addition reaction with a divinyl
ether in the presence of PTS, generating a copolymer net-
work with acetal structure in the crosslinking segment. This
network was degradable in acid conditions, and stable in
alkali and neutral environment. The swelling ratio of the
network in water and methanol increased after the network
was treated with a strong alkali.
The swelling property of the copolymer networks treated
Figure 7 Concentration of the recovered polymer/THF solution versus hydrolyzing time for the swelled gels under different concentrations of HCl. (a) 0.1 M;
(b) 103 M. (---): The theoretic concentration.
Table 2 Swelling ratio (SR) of copolymer gels
Gel
G-1
G-2
G-3
G-4
Precursor
PMBH-1
SR (THF)
10.39
Treatment
none
SR (water)
0.63
SR (methanol)
2.62
NaOH
none
8.65
17.25
0.34
2.14
PMBH-2
7.85
NaOH
2.11
6.87

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The authors express great thanks for the support from Innovative Research
Team in Universities (IRT0706) and the Polymer Chemistry and Physics,
Beijing Municipal Education Commission (XK100100640).
sions of poly(vinyl methyl ether)-maleic anhydride half amide. J
Chem Eng Data, 1959, 4: 83–85
15 Ko WG, Park JW, Choi DG, Lee UJ, Kim DN, Lee Y. Microfluidic
system for bioassay based on nonspherical hydrogel microparticles.
Korean Pentent 083784, 2009-08-04
1
2
3
4
Peddada LY, Harris NK, Devore DI, Roth CM. Novel graft copoly-
mers enhance in vitro delivery of antisense oligonucleotides in the
presence of serum. J Controll Release, 2009, 140: 134–140
Qian B, Li J, Wei Q, Bai P, Fang B, Zhao C. Preparation and charac-
terization of pH-sensitive polyethersulfone hollow fiber membrane
for flux control. J Memb Scie, 2009, 344: 297–303
Hayashi H, Iijima M, Kataoka K, Nagasaki Y. pH-Sensitive nanogel
possessing reactive PEG tethered chains on the surface. Macromole-
cules, 2004, 37: 5389–5396
Timmer MD, Shin H, Horch RA, Ambrose CG, Mikos AG. In vitro
cytotoxicity of injectable and biodegradable poly(propylene fumarate)-
based networks: unreacted macromers, cross-linked networks, and
degradation products. Biomacromolecules, 2003, 4: 1026–1033
Stubbe BG, Horkay F, Amsden B, Hennink WE, De Smedt SC, De-
meester J. Tailoring the swelling pressure of degrading dextran hy-
droxyethyl methacrylate hydrogels. Biomacromolecules, 2003, 4:
691–695
Ulbrich K, Subr V, Podprová P, Bureová M. Synthesis of novel hy-
drolytically degradable hydrogels for controlled drug release. J Con-
troll Release, 1995, 34: 155–165
Ogino K, Chen J-S, Ober CK. Synthesis and characterization of
thermally degradable polymer networks. Chem Mater, 1998, 10:
3833–3838
Ober CK, Koerner H. Compounds with substituted cyclic hydrocar-
bon moieties linked by secondary or tertiary oxycarbonyl-containing
moiety for reworkable cured thermosets. US Patent 5948922,
1999-09-07
Crane LN, Ober CK, Bae YC, Yu S, Park J-W. Reworkable thermo-
setting resin compositions for electronic devices. US Patent 6657031,
2003-12-02
16 Hattori D, Hani T. Optical retardation films of imidized maleic anhy-
dride-vinyl ether polymers and polarizing plates having their protec-
tive films. JP 2009162996, 2009-07-23
17 Guo X, Deng F, Li L, Prud’homme RK. Synthesis of biocompatible
polymeric hydrogels with tunable adhesion to both hydrophobic and
hydrophilic surfaces. Biomacromolecules, 2008, 9: 1637–1642
18 Giles MR, O’Connor SJO, Hay JN, Winder RJ, Howdle SM. Novel
graft stabilizer for the free radical polymerization of methyl
methacrylate in supercritical carbon dioxide. Macromolecules, 2000,
33: 1996–1999
19 Tenhaeff WE, Gleason KK. Surface-tethered pH-responsive hydrogel
thin films as size-selective layers on nanoporous asymmetric mem-
branes. Chem Mater, 2009, 21: 4323–4331
20 Sousa-Herves A, Fernandez-Megia E, Riguera Vega R. The pH-sensitive
dendritic polymeric micelles as drug delivery systems. WO 2010018286,
2010-02-18
21 Hsu J-L, Strauss UP. Intramolecular micelles in a copolymer of
maleic anhydride and hexyl vinyl ether: determination of aggregation
number by luminescence quenching. J Phys Chem, 1987, 91:
6238–6241
22 Zhang X, Chen G-C, Collins A, Jacobson S, Morganelli P, Dar YL,
Musa OM. Thermally degradable maleimides for reworkable adhe-
sives. J Polym Sci Part A Polym Chem, 2009, 47: 1073–1084
23 Zimmerman RL, Jones GD, Nummy WR. Vinyl ethers of diethylene
glycol. I & EC Prod Res Develop, 1963, 2: 296–303
24 Hashimoto T, Nakamura T, Tanahashi S, Kodaira T. Gel formation in
cationic polymerization of divinyl ethers. III. Effect of oli-
gooxyethylene chain versus oligomethylene chain as central spacer
units. J Polym Sci Part A Polym Chem, 2004, 42: 3729–3738
25 Gisselfalt K, Edberg B, Flodin P. Synthesis and properties of de-
gradable poly(urethane urea)s to be used for ligament reconstructions.
Biomacromolecules, 2002, 3: 951–958
26 Adelmann R, Mela P, Gallyamov MO, Keul H, Möller M. Synthesis
of high-molecular-weight linear methacrylate copolymers with spi-
ropyran side groups: conformational changes of single molecules in
solution and on surfaces. J Polym Sci Part A Polym Chem, 2009, 47:
1274–1283
5
6
7
8
9
10 Themistou E, Patrickios CS. Synthesis and characterization of polymer
networks and star polymers containing a novel, hydrolyzable acetal-based
dimethacrylate cross-linker. Macromolecules, 2006, 39: 73–80
11 De Clercq RR, Goethals EJ. Polymer networks containing degradable
polyacetal segments. Macromolecules, 1992, 25: 1109–1113
12 Du J, Ding X, Zheng Z, Peng Y. Synthesis and degradation of intel-
ligent hydrogels containing polyacetal segments. Eur Polym J, 2002,
38: 1033–1037
27 Ruckenstein E, Zhang HM. Self-polyaddition of hydroxyalkyl vinyl
ethers. J Polym Sci Part A Polym Chem, 2000, 38: 3751–3760
28 Carlise JR, Kriegel RM, Rees Jr WS, Weck M. Synthesis and hy-
drolysis behavior of side-chain functionalized norbornenes. J Org
Chem, 2005, 70: 5550–5560
13 Ruckenstein E, Zhang H. Novel copolymer networks via the combi-
nation of polyaddition and anionic polymerization. J Polym Sci Part
A Polym Chem, 2001, 39: 117–126
14 Harrison AP. Effect of temperature on properties of aqueous disper-