Macromolecules
Article
benzophenone as the indicator under a nitrogen atmosphere and then
stored in a glovebox. LA was purchased from Sigma-Aldrich and
dried under vacuum at 40 °C to a constant weight, a certain amount
of polymer was dissolved in CDCl to acquire the NMR spectral data.
3
recrystallized from dry toluene 3 times. Benzhydrol (Ph CHOH) was
The Procedure of Pd/C Catalytic Hydrogenation. In a 50 mL
high pressure autoclave, the polymer poly(LA-co-MBC) was dissolved
in a 4:1 (v/v) mixed solvent of ethyl acetate/methanol (∼40 mg/
mL), and the Pd/C catalyst in the amount of 5 mol % of the benzyl
groups was then added to the solution. The autoclave was charged
2
obtained from commercial sources and dried with MgSO in THF
4
solution prior to use. Deuterated NMR solvents were purchased from
Cambridge Isotopes and dried over sodium (for C D ) or a molecular
6
6
n
sieve (for CDCl and DMSO-d ). Mg Bu (1.0 M in heptane) was
3
6
2
purchased from Sigma-Aldrich. Complex 1 was prepared according to
with hydrogen gas (H ) to 3.0 MPa. After 10 h at room temperature
2
45
the established method. Pd/C (5%) (wetted with ca. 66.7% water)
was used as received. Glassware and flasks using in the polymerization
were dried in an oven at 120 °C and exposed to a vacuum-nitrogen
cycle 3 times. All other reagents and solvents are commercially
available and used without further purification.
with stirring, the Pd/C solid was filtered and then washed with the
ethyl acetate/methanol mixture. The combined filtrate was evapo-
rated to ca. 1 mL, and then, a large amount of diethyl ether was added
to obtain solid poly(LA-co-MCC). These carboxyl-containing
copolymers were dried at 40 °C for 24 h in vacuo till constant
weight, and their NMR spectra were measured in DMSO-d6.
Instruments and Measurements. NMR spectra were recorded
1
in deuterated solvents at 298 K on a Bruker AV 500 MHz (for H
The Procedure of Hydrolysis Kinetic Study. The hydrolysis
NMR) spectrometer. The number−molecular weight (M ) and
experiments of (co)polymers were carried out in Na CO (0.53 M)
n
2
3
weight distributions (M /M ) of related polymers were characterized
and NaHCO (0.25 M) deuterium aqueous buffer solution (pH =
w
n
3
by size exclusion chromatography (SEC) on a TOSOH HLC-8220
9
.97). A certain amount of poly(LA-co-MCC) in 0.5 mL of buffer
SEC instrument (Column: Super HZM-Hx3) at 40 °C using THF as
solution was put in a NMR tube, and then, accurate 4 μL of N,N-
−
1
an eluent (the flow rate was 0.35 mL min ) against polystyrene
dimethyformamide (DMF) was added as the inert internal standard.
1
standards. Glass transition temperatures (T ) and melting points (T )
g
m
H NMR spectroscopy at certain intervals of time was performed to
of related polymers were measured by differential scanning
calorimetry (DSC) using a METTLER TOPEM DSC instrument
under a nitrogen flow. Any thermal history difference in the polymers
was eliminated by first heating the specimen to 200 °C and then
monitor the hydrolytic process. According to the peak integrals of
degradation products and the internal standard (DMF), the
conversions of the corresponding products were calculated.
−
1
recording the second DSC scan from −10 to 200 °C at 10 °C min
ASSOCIATED CONTENT
for 5−10 mg of samples.
■
Synthesis of 2-Methyl-2-Benzyloxycarbonyl-1,3-Trimethy-
lene Carbonate (MBC). The MBC monomer was synthesized in two
*
sı Supporting Information
46
steps according to modified procedures. 20 g (149.1 mmol) of 2,2-
bis(hydroxymethyl) propionic acid and 9.2 g (164.0 mmol) of KOH
were dissolved in 80 mL of DMF in a 250 mL flask equipped with a
condenser. The potassium salt was allowed to form at 100 °C for 1 h,
and then 18.0 mL (156.4 mmol) of benzyl chloride was added slowly.
The reaction kept stirring at 100 °C for 12 h. After removal of DMF
under vacuum, the residue was dissolved in a mixture of ethyl acetate
Polymerization data of supplement experiments, NMR,
ESI-MS characterization data, and SEC, DSC, WCA,
and DLS characterization (PDF)
(
80 mL) with hexane (80 mL) and water (80 mL). After extraction,
the water layer was washed with 100 mL of ethyl acetate, and then,
■
the combined organic phase was dried with MgSO . After the solvent
evaporated, the crude product was recrystallized from toluene to
4
Corresponding Authors
produce pure benzyl 2,2-bis(hydroxylmethyl) propionate (24.8 g,
Xinli Liu − State Key Laboratory of Polymer Physics and
Chemistry, Changchun Institute of Applied Chemistry, Chinese
Dongmei Cui − State Key Laboratory of Polymer Physics and
Chemistry, Changchun Institute of Applied Chemistry, Chinese
1
7
2
4.2%). H NMR (400 MHz, CDCl ) δ 7.30−7.40 (m, 5H), 5.21 (s,
3
H), 3.93 (d, J = 11.2, 2H), 3.73 (d, J = 11.2, 2H), 2.92 (br, 2H), 1.08
(
s, 3H).
Carbonate was subsequently synthesized. To a solution of 15 g
66.9 mmol) of synthesized benzyl 2,2-bis(hydroxymethyl) prop-
(
anoate in 400 mL of THF, 19.1 mL (200.7 mmol) of ethyl
chloroformate was added, and the mixture was stirred in an ice bath
for 30 min. Triethylamine (TEA, 27.9 mL, 200.7 mmol) diluted in 50
mL of THF was added dropwise over a period of 60 min. The
reaction mixture was stirred at 0 °C for another 2 h and then stirred at
room temperature overnight. The formed TEA-HCl salt was filtered
off, and the filtrate was concentrated in a vacuum to obtain a white
solid (13.0 g, 77.7%). The crude product was purified by
recrystallization 3 times from THF/diethyl ether (1:5, v/v) to give
Author
Xiufang Hua − State Key Laboratory of Polymer Physics and
Chemistry, Changchun Institute of Applied Chemistry, Chinese
Academy of Sciences, Changchun 130022, P. R. China;
University of Chinese Academy of Sciences, Beijing 100049, P.
R. China
1
MBC as acicular crystals, then dried, and reserved in a glovebox. H
NMR (400 MHz, CDCl ) δ 7.30−7.40 (m, 5H), 5.22 (s, 2H), 4.70
3
(
d, J = 10.7, 2H), 4.20 (d, J = 10.8, 2H), 1.33 (s, 3H).
A Typical Procedure of Copolymerization of LA and MBC. A
typical copolymerization of LA and MBC (Table 1, entry 1) was
carried out in a 25 mL flask under a nitrogen atmosphere. A THF
solution (1 mL) of complex 1 (7.7 mg, 10 μmol) and Ph CHOH (9.2
2
Notes
mg, 50 μmol) was added into a stirred solution (4 mL of THF) of
LLA (0.720 g, 5 mmol) and MBC (1.25 g, 5 mmol) at room
temperature. For the diblock PLLA-b-PMBC, 5.0 mmol L-LA in 5 mL
of THF was polymerized for 2 h till completely converted (catalyst,
the amount used). Then, MBC (5.0 mmol) was added for another 3
h. The polymerization was terminated using several drops of acidified
ethanol (1.0 M HCl solution in EtOH), and the viscous solution was
poured into abundant ethanol to give a white polymer. After being
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors thank financial support from the National Natural
Science Foundation of China for project No. 21774119 and
21574125.
F
Macromolecules XXXX, XXX, XXX−XXX