In Situ Formation and Gelation Mechanism of Thermoresponsive Stereocomplexed Hydrogels upon Mixing Diblock and Triblock Poly(Lactic Acid)/Poly(Ethylene Glycol) Copolymers
In Situ Formation and Gelation Mechanism of Thermoresponsive Stereocomplexed Hydrogels upon Mixing Diblock and Triblock Poly(Lactic Acid)/Poly(Ethylene Glycol) Copolymers
复制标题
二嵌段和三嵌段聚乳酸/聚乙二醇共聚物混合的热响应性立体复合水凝胶的原位形成和凝胶化机制
DOI：
10.1021/acs.jpcb.5b03610
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发表时间：
2015-05-28
影响因子：
3.3
通讯作者：
Bao, Yongzhong
中科院分区：
文献类型：
--
作者：
Mao, Hailiang;Pan, Pengju;Bao, Yongzhong
通过将聚乳酸（PLA）嵌段构型相反的二嵌段和三嵌段聚乳酸/聚乙二醇（PLA/PEG）共聚物混合，制备了一种具有潜在生物降解性和生物相容性的新型原位凝胶体系。这种体系的原位凝胶化非常快，在混合后10 s内发生。三嵌段共聚物（DPPEG，tri）和二嵌段共聚物（DPPEG，di）中PEG嵌段的混合比例、聚合度对PLA-PEG/PLA-PEG-PLA对映体混合凝胶的原位凝胶化、凝胶-溶胶转变、结晶结构、微观结构和力学性能有显著影响。发现PLA-PEG/PLA-PEG-PLA对映体混合物的原位凝胶化只发生在相对较小的PLA-PEG/PLA-PEG-PLA质量比和较大的DPPEG，tri. PLA-PEG和PLA-PEG-PLA共聚物在稀溶液中的流体动力学直径在混合时显著增加，表明形成桥接网络。PLA-PEG/PLA-PEG-PLA对映体混合物中PLA疏水结构域形成立体复合微晶。同步辐射SAXS分析表明，随着DPPEG、tri、DPPEG、di或PLA-PEG-PLA组分的增加，对映体混合物的结构由紧密的变为松散的聚集结构，胶束间距增大。提出了PLA-PEG/PLA-PEG-PLA对映体混合物的凝胶化机理，其中部分PLA-PEG-PLA链充当星星状和花状胶束之间的连接桥梁，胶束核心中的立体复合微晶充当物理交联点。
A novel in situ formed gel system with potential biodegradability and biocompatibility is developed by mixing the diblock and triblock poly(lactic acid)/poly(ethylene glycol) (PLA/PEG) copolymers with opposite configurations of PLA blocks. In situ gelation of such system is extremely fast, which happens within 10 s after mixing. In situ gelation, gel-to-sol transition, crystalline structure, microstructures, and mechanical properties of PLA-PEG/PLA-PEG-PLA enantiomerically mixed gels are significantly influenced by the mixing ratio, degree of polymerization for PEG block in triblock (DPPEG,tri) and diblock copolymers (DPPEG,di). It is found that in situ gelation of PLA-PEG/PLA-PEG-PLA enantiomeric mixture just happen at relatively smaller PLA-PEG/PLA-PEG-PLA mass ratio and larger DPPEG,tri. Hydrodynamic diameters of PLA-PEG and PLA-PEG-PLA copolymers in dilute solution increase remarkably upon mixing, indicating the formation of bridging networks. Stereocomplexed crystallites are formed for the PLA hydrophobic domains in PLA-PEG/PLA-PEG-PLA enantiomeric mixtures. As indicated by synchrotron-radiation SAXS analysis, the enantiomeric mixture changes from a compactly to loosely aggregated structure and the intermicellar distance enhances with increasing DPPEG,tri, DPPEG,di, or PLA-PEG-PLA fraction. Gelation mechanism of PLA-PEG/PLA-PEG-PLA enantiomeric mixture is proposed, in which part of PLA-PEG-PLA chains act as the connecting bridges between star and flower-like micelles and the stereocomplexed crystallites in micelle cores act as physically cross-linked points.