天然生物高分子材料聚乳酸

聚乳酸的合成与降解研究

摘要

本文以D，L一乳酸为原料，采用丙交醋开环聚合和直接熔融聚合制备出聚D，L-

乳酸(PDLLA)，并对PDLLA降解性能进行了研究。

丙交酷开环聚合制备PDLLA的关键在于中间体D，L一丙交酷(DLLA)的

制备，研究了催化剂、反应温度、反应时间等因素对DLLA产率的影响，通过

在反应体系中加入稀释剂乙二醇，DLLA的馏出温度明显降低，避免了DLL八

在蒸馏过程中产生碳化现象，并使DLLA的平均产率由36.8%提高至513%，

制备的PDLLA分子量最大值达18.4万。利用DSC、XRD、IR等分析测试技术

对

一

DLLA和PDLLA的性能和结构进行相关的测试和表征。

直接熔融聚合制备PDLLA的关键在于小分子水的脱除，制备出的PDLLA

分子量明显低于丙交酷开环聚合制备的PDLLA。通过研究催化剂、反应温度、反

应时间等因素对PDLLA分子量的影响，优化了工艺参数。

通过研究PDLLA的生理盐水降解性能和热降解性能，发现PDLLA在生理

盐水中首先发生分子量降解，然后产生重量损失，且降解过程中生成具有晶体

结构特征降解产物;PDLLA的热降解是一个无规的断裂过程，在1000C一25。

℃范围内，PDLLA的分子量迅速发生降解，在250OC以上，低聚物相继发生裂

解，产生重量损失。

合成方法

聚乳酸直接聚合研究

摘要

合成方法；

New synthetic absorbable polymers as BMP carriers:

Plastic properties of poly-D,L-lactic acid-polyethylene

glycol block copolymers

Abstract: Bone morphogenetic proteins (BMPs) are bio-

logically active molecules capable of eliciting new bone for-

mation. In combination with biomaterials, these proteins can

be used in a clinical setting as bone-graft substitutes to pro-

mote bone repair. To find new synthetic absorbable poly-

mers with plastic nature that can be used as BMP-carrier

materials, six types of poly-D,L-lactic acid-polyethylene gly-

col block copolymer (PLA-PEG) with various molecular

weights of PLA and PEG were synthesized. These were

PLA6,500-PEG3,000 (P-1), PLA11,500-PEG3,000 (P-2),

PLA17,500-PEG3,000 (P-3), PLA6,500-PEG1,000 (P-4),

PLA15,000-PEG8,000 (P-5), and PLA8,500-PEG1,000 (P-6).

Fifty milligrams of these polymers was mixed with 0 mg

(control) or 5, 10, or 20 mg of recombinant human BMP-2

(rhBMP-2). These pellets were implanted into the dorsal

muscle pouches of 144 mice (six pellets consisting of thesame polymer and dose of rhBMP-2 for a specific group).

Three weeks after surgery, the pellets were harvested and

examined by radiographic and histological methods. All P-1

pellets with 10 or 20 mg of rhBMP-2 showed bone formation

with hematopoietic marrow and bony trabeculae, as did one

third of those with 5 mg of rhBMP-2. The incidence of new

bone formation with P-2 pellets or that of P-5 pellets was

lower than that of P-1 pellets. No bone was formed in any

other type of pellet. These results indicated that the

PLA6,500-PEG3,000 polymer with plastic properties was

found to work well as a BMP carrier. © 1999 John Wiley &

Sons, Inc. J Biomed Mater Res, 47, 104–110, 1999.

2

Clean and Green Bioplastic Composites: Comparison of Calcium Sulfate and Carbon Nanospheres in Polylactide Composites

ABSTRACT

Two environmentally friendly fillers, carbon nanospheres (CNS)

derived from cellulose and calcium sulfate anhydrite (CaSO4), a

by-product of the polylactide (PLA) production process, are

compared as nucleating agents in commercial-grade PLA. CNS

and CaSO4 are compounded with PLA using solution blending.

Additionally, CaSO4 is melt mixed with PLA. Crystallization kinetics

are explored using differential scanning calorimetry (DSC) and

polarized optical microscopy. Mechanical properties are examined

using dynamic mechanical thermal analysis (DMTA) and

morphology is determined using field-emission scanning electron

microscopy (FE-SEM). It is found that the filler does not increase

the PLA crystallization rates significantly at loadings up to 15 wt%

(CNS) or 20 wt% (CaSO4). The lack of effect on crystallization

kinetics is attributed to the high D-lactic acid content of

commercial-grade PLA, and also to poor dispersion of the fillers in

the PLA matrix. The glassy shear storage modulus of the

composites is found to increase by 50% in the highest weight

loadings tested. These clean and green bioplastic composites may