Preparation, Structure and Properties of PLLA-TMC/PDLA-TMC Stereocomplexes†

doi:10.7503/cjcu20160363

Abstract

Abstract:

A series of copolymers with high molecular weight(M_n>1×10⁵) based on 1, 3-trimethylene carbonate(TMC) and L-lactide(L-LA) or D-lactide(D-LA) was synthesized by ring-opening polymerization using stannous octoate as catalyst. Then the stereocomplex sc-PLA films were prepared by mixing equal amount of the corresponding PLLA-TMC and PDLA-TMC solution and followed by solution casting. The chemical structure, thermal properties and enzymatic degradation behavior of sc-PLA films were characterized respectively. The results show that crystallinity of homochiral crystals in sc-PLA-TMC samples decreases with the increase of TMC content. Only stereocomplex crystals exist in sc-PLA-TMC samples when TMC contents beyond 5%. The enzymatic degradation results show that the degradation rate of samples is accelerated when TMC unit is introduced.

Key words: Poly(lactic acid), Poly(1, 3-trimethylene carbonate), Stereocomplex, Crystallization, Enzymatic degradation

CLC Number:

O631

TrendMD:

WU Xiaomeng, CHEN Xiaoyu, Shi LI, FAN Zhongyong. Preparation, Structure and Properties of PLLA-TMC/PDLA-TMC Stereocomplexes^†[J]. Chem. J. Chinese Universities, 2016, 37(11): 2101.

Figures/Tables 10

Scheme 1 Synthetic route of PLLA-TMC and PDLA-TMC copolymers

Fig.1 FTIR spectra of sc-PLA, sc-PLA-TMC and PTMC a. sc-PLA; b. sc-PLA-TMC10; c. sc-PLA-TMC5; d. sc-PLA-TMC2.5; e. PTMC.

Fig.2 1H NMR(500 MHz) spectra of sc-PLA and sc-PLA-TMC in CDCl3 a. sc-PLA; b. sc-PLA-TMC10; c. sc-PLA-TMC5; d. sc-PLA-TMC2.5. Peaks a—d are corresprnding to the positions a—d in the structure.

Table 1 Molecular characterization of PL(D)LA homopolymer and PL(D)LA-TMC copolymers determined by GPC and 1H NMR

Sample	Feed ratio n(LLA) or n(DLA)∶n(TMC)	Composition^a n(LLA) or n(DLA)∶n(TMC)	10^-5 $M ˉ n b$	10^-5 $M ˉ w b$	PDI
PLLA			1.1	1.7	1.5
PDLA			1.2	2.0	1.7
PLT97.5/2.5	97.5∶2.5	97.7∶2.3	1.1	1.7	1.5
PDT97.5/2.5	97.5∶2.5	97.4∶2.6	1.1	1.7	1.5
PLT95/5	95∶5	95.7∶4.3	1.2	2.2	1.8
PDT95/5	95∶5	95.4∶4.6	1.2	2.2	1.8
PLT90/10	90∶10	90.3∶9.7	1.1	1.9	1.7
PDT90/10	90∶10	90.8∶9.2	1.1	2.0	1.8

Table 1 Molecular characterization of PL(D)LA homopolymer and PL(D)LA-TMC copolymers determined by GPC and 1H NMR

Sample	Feed ratio n(LLA) or n(DLA)∶n(TMC)	Composition^a n(LLA) or n(DLA)∶n(TMC)	10^-5 $M ˉ n b$	10^-5 $M ˉ w b$	PDI
PLLA			1.1	1.7	1.5
PDLA			1.2	2.0	1.7
PLT97.5/2.5	97.5∶2.5	97.7∶2.3	1.1	1.7	1.5
PDT97.5/2.5	97.5∶2.5	97.4∶2.6	1.1	1.7	1.5
PLT95/5	95∶5	95.7∶4.3	1.2	2.2	1.8
PDT95/5	95∶5	95.4∶4.6	1.2	2.2	1.8
PLT90/10	90∶10	90.3∶9.7	1.1	1.9	1.7
PDT90/10	90∶10	90.8∶9.2	1.1	2.0	1.8

Table 2 Thermal properties of sc-PLA and sc-PLA-TMC

Sample	T_g/℃	T_m/ ℃		ΔH_m/(J·g^-1)		f_c(%)
Sample	T_g/℃	hc crystal	sc crystal	hc crystal	sc crystal	hc crystal	sc crystal
sc-PLA	60.4	174.6	14.6	203.8	7.6	15.6	4.9
sc-PLA-TMC2.5	59.1	167.1	26.8	212.3	11.9	29.2	7.8
sc-PLA-TMC5	57.2			205.1	7.2		4.9
sc-PLA-TMC10	54.4			203.1	5.3		3.7

Fig.3 DSC curves of sc-PLA-TMC and sc-PLA after quenched from melting state a. sc-PLA-TMC10; b. sc-PLA-TMC5; c. sc-PLA-TMC2.5; d. sc-PLA.

Fig.4 WAXD patterns of PLLA, sc-PLA and sc-PLA-TMC a. PLLA; b. sc-PLA; c. sc-PLA-TMC10; d. sc-PLA-TMC5; e. sc-PLA-TMC2.5.

Fig.5 Mass loss of sc-PLA and sc-PLA-TMC during proteinase K-catalyzed degradation

Fig.6 SEM images of various solution cast films during proteinase K-catalyzed degradation (A) sc-PLA, t=0 h; (B) sc-PLA, t=120 h; (C) sc-PLA-TMC5, t=0 h; (D) sc-PLA-TMC5, t=120 h.

Table 3 Mechanical properties of sc-PLA and sc-PLA-TMC

Sample	$σ B a$ /MPa	E^b/GPa	$ε B c$ (%)
PLLA	53.9	2.1	4.6
sc-PLA	55.8	2.5	4.8
sc-PLA-TMC2.5	54.2	2.4	5.0
sc-PLA-TMC5	51.5	2.1	6.1
sc-PLA-TMC10	42.3	1.7	7.2

Table 3 Mechanical properties of sc-PLA and sc-PLA-TMC

Sample	$σ B a$ /MPa	E^b/GPa	$ε B c$ (%)
PLLA	53.9	2.1	4.6
sc-PLA	55.8	2.5	4.8
sc-PLA-TMC2.5	54.2	2.4	5.0
sc-PLA-TMC5	51.5	2.1	6.1
sc-PLA-TMC10	42.3	1.7	7.2

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