【作者】 刘丽莉；

【导师】 蔡伟；

【作者基本信息】 哈尔滨工业大学 ， 材料物理与化学， 2009， 博士

【摘要】 本文采用熔融共缩聚的方法合成了具有不同组成和凝胶程度的聚癸二酸丙三醇酯(PGS)及以乙二醇为第三单体的聚癸二酸乙二醇丙三醇酯(PGGS),采用红外光谱分析、X射线光电子能谱分析、示差扫描量热分析、X射线衍射分析、偏光显微分析、拉伸试验、体外降解和细胞培养试验,研究了PGS和PGGS的微观结构、力学性能、降解特性、细胞相容性以及单程和双程形状记忆效应,揭示了微观结构与性能之间的内在联系,阐明了形状记忆效应的微观机制。结构分析结果表明,单体组成和交联时间对PGS和PGGS的结构有较大影响。癸二酸含量增加,PGS的交联速度加快,交联程度增大。癸二酸含量为45mol%,交联时间为134小时,PGS的凝胶度仅为35.2%。PGS的结晶相为球晶,癸二酸含量增加,结晶度下降。乙二醇的加入增加了交联点之间的链段长度,提高了结晶度。乙二醇为30.8mol%时,交联时间短于36h,结晶相为球晶,当交联时间超过48h,结晶相大都仍为球晶,但出现少量的取向生长的片层晶;交联时间继续延长,片层晶含量增多,片间距减小。拉伸试验结果表明,癸二酸含量为50mol%和55mol%时,PGS的断裂强度随交联时间的增加而降低。第三单体的加入提高了强度,当交联时间为60和72h时,随乙二醇含量增加,PGGS断裂强度和断裂应变先略有降低后快速增加,至乙二醇含量为30.8mol%时达最大值,断裂强度为9.4MPa和11.3MPa,断裂应变为482%和417%,此时应力-应变曲线呈硬弹性特征。降解试验和细胞培养试验结果表明,癸二酸含量为50mol%的PGS为表面降解;对于PGGS和癸二酸含量高于50mol%的PGS,表面降解和本体降解同时发生。PGGS的降解速度慢于PGS。癸二酸含量为55mol%时,PGS的水接触角为57.3°,亲水性适中,有利于MSCs细胞的粘附和生长,PGGS的细胞相容性较PGS略有降低。试验发现,癸二酸含量为50-55mol%时,PGS二元共聚物呈现出单程形状记忆效应,其中化学交联的三维网络为固定相,结晶相作为可逆相。增加癸二酸含量使PGS二元共聚物的形状恢复率增大,形状保持率减小,而形状恢复温度先升高后降低。癸二酸含量为50mol%的PGS在拉伸变形量为100%时,形状回复率为100%,形状保持率为96.5%;当拉伸变形量达到300%时,形状恢复率和形状保持率均超过90%。PGGS呈现良好的单程形状记忆效应,形状保持率和形状恢复温度均高于PGS。交联时间增加,PGGS的形状恢复率增加,形状恢复温度下降。当乙二醇含量为30.8mol%,交联时间为72h,拉伸变形量为100%时,PGGS的形状恢复温度为40℃,形状恢复率和形状保持率均高于99%;当拉伸变形量为400%时,形状恢复率和形状保持率均高于95%。研究发现,乙二醇含量为30.8mol%,交联时间为60h和72h的PGGS,经过热机械训练后获得了双程形状记忆效应。交联时间为72h的PGGS,训练拉伸变形量为100%时,双程形状恢复率达20.9%。足够量片层晶的存在是PGGS呈现双程记忆效应的必要条件,以片层晶为交联点的物理交联网络作为低温形状固定相,球晶为可逆相,热机械训练时经拉伸后的高分子链加热回缩导致片层晶弯曲为低温下分子链伸长提供驱动力,形成双程形状记忆效应。更多还原

【Abstract】 Poly (glycerol-sebacate) (PGS) copolymers and poly (glycol-glycerol- sebacate) (PGGS) terpolymers with different compositions and gel content were polymerized by melting copolycondensation, respectively. The microstructure, mechanical properties, degradable properties, cytocompatibilities and one-way and two way shape memory effect of PGS and PGGS were investigated by FTIR, XPS, DSC, XRD, POM, tensile test, degradation test in vitro and cell culture test in vitro. The relationship between the microstructure and the properties were revealed. The mechanism of shape memory effect was illuminated.The results of structure analysis show that molar ratio of monomers and crosslink times obviously effect on structure of PGS and PGGS. The crosslink degree of PGS increases with increasing sebacic acid (SA) content. When the crosslink time is 134h, the gel degree of PGS with SA contents of 45 mol% is only 35.2%. PGS crystal is spherulite, and the crystallinity degree decrease with increasing SA contents. Crystalline phase of PGGS crosslinked for 36h with glycol contents of 30.8mol% is spherulite. When the crosslink time is 48h, crystalline phase of PGGS is spherulite and a small amount of lamellar crystal. As the crosslinking time continued to increase, lamellar crystal content increased, and interlamellar spacing of lamellar crystal decrease.Based on tensile test, it is found that stress and strain at break of PGS with SA contents of 50mol% and 55mol% decreases with increase of crosslink time. The stress at break of PGGS is higher than that of PGS. When crosskink time is 60h and 72h,the stress and strain at break of PGGS increase after a modest decline with the glycol content growing. When the glycol content is 30.8mol%, stresses of PGGS crosslinked for 60h and 72h are 9.4MPa and 11.3MPa, strains of that are 482% and 417%, respectively. At that time, the stress-strain curve has the hard-elastic characteristic.The results of degradation test and cell culture test indicate that degradation of PGS with SA content of below 50 mol% is surface degradation, and that of PGGS and PGS with SA content of above 50 mol% is bulk degradation. The degradation rate of PGGS is slower than that of PGS. PGS with SA contents of 55mol% is beneficial to MSCs adhesion and growth, because its water contact angle is 55°and its hydrophilicity is good. Cell compatibility of PGS is better than that of PGGS.The experimental results indicate that PGS copolymers with SA contents of 50-55mol% show one-way shape memory effect. The three-dimension chemical crosslink network serves as fixed phase, the PGS crystal serves as reversible phase. With the SA contents increasing, the shape recovery rate of PGS increases, the shape retention rate of PGS decreases, and the shape recovery temperature of PGS increase initially and then decrease. PGS with SA contents of 50mol% in the specimen deformed to 100% exhibits shape recovery rate of 100% and shape retention rate of 96.5%. When the deformation is 300%, the shape recovery rate and shape retention rate of that are more than 90%. PGGS terpolymers show good one-way shape memory effect. Shape retention rate and shape recovery temperature of PGGS are higher than those of PGS. With crosslink time increasing, the shape recovery rate of PGGS increases, and the shape recovery temperature decreases. PGGS crosslinked for 72h with glycol content of 30.8mol% in the specimen deformed to 100% exhibits shape recovery rate and shape retention rate of above 90% and shape recovery temperature of 40℃. When the deformation is 300%, the shape recovery rate and shape retention rate are more than 95%.The research show that PGGS crosslinked for 60h and 72h with glycol content of 30.8mol% show two-way shape memory effect after thermomechanical training,. When the training deformation is 100%, two-way shape recovery rate of PGGS cosslinked for 72h is 20.9%. It is a necessary condition for two-way shape memory effect of PGGS that lamellae content should be enough. The physical crosslinked network with lamellar crystal as the cross-linking serves as fixed phase, the PGGS spherulite serves as reversible phase. The bend of lamellae resulting from the shrinkage of molecular chains stretched in thermomechanical training provide the driving force of molecular chain elongation during the cooling process.更多还原