接枝型聚两性电解质 CS-g-PLGA 的合成及溶液性质

摘要

The graft polyampholytes containing a chitosan backbone and poly( L-glutamic acid) branches, i. e. CS-g-PLGA(CGA), with different compositions were synthesized. The molecular architecture and the composition of CGA were characterized. The influences of environmental conditions, such as pH value, ionic strength and ionic types, on the aqueous solution properties of CGAs were investigated. The results show that the isoelectric point(IEP) of CGA shifts to higher pH values with increasing the ionic strength. The larger the ion hydration radius is, the less it influences the IEP. The CGA with approximative amino and carboxyl con-tents is more sensitive to the variation of ionic strength. Moreover, CGAs exhibit notable pH responsibility to form reversible aggregates in acidic and alkaline solutions, respectively. The stability of the aggregates is found to be improved by increasing the length of PLGA branches for CGAs with similar amino content. The hydrody-namic radii of the aggregates depend on the charge density on CS backbone in acidic solutions and increase with increasing PLGA length in alkaline solutions.%合成了以壳聚糖( CS)为主链、聚( L-谷氨酸)( PLGA)为侧链的接枝型聚两性电解质 CS-g-PLGA (CGA)，表征了其结构与组成，探讨了 pH 值、离子强度和离子种类等对 CGA 水溶液性质的影响。研究发现，随着溶液离子强度的增大， CGA 的等电点(IEP)移向高 pH 值；离子水化半径越大，对 CGA 分子中相反电荷的屏蔽作用越弱，对 IEP 的影响越小； CGA 中氨基和羧基相对含量越接近，对溶液离子强度的变化越敏感。此外， CGA 具有显著的 pH 响应性，在酸性及碱性溶液中分别形成结构相反的聚集体。在 CS 主链氨基含量相近的条件下，聚集体的稳定性随 PLGA 链长的增加而提高。酸性溶液中聚集体粒径取决于 CS 主链的电荷数；碱性溶液中 PLGA 侧链越长则平均粒径越大。