中文摘要：

采用布朗动力学研究了在良溶剂中荷电平衡的接枝聚两性电解质（GPA）的单链构象转变行为,讨论了主链链长、支链数及电荷密度对GPA分子链构象转变的影响.研究发现,随着静电相互作用的增强,GPA分子链构象转变过程由线团、主链与支链间的折叠、链段塌缩和电荷配对形成偶极子与四极子等4个阶段构成.与线型聚两性电解质不同,GPA存在的额外支链间空间排斥与静电排斥作用随着分子结构的变化而改变,并影响构象转变行为.在强静电相互作用下,良溶剂中的GPA链由于溶剂化作用会再伸展,以保证偶极子完全配对成四极子.减小主链长度或电荷密度或增加支链数目都会增大体系的排斥力和主链的刚性,阻滞分子链的塌缩,并使得分子链再伸展的幅度增大.

英文摘要：

Ascribed to the coexistence of opposite charges on same chain,polyampholytes present novel conformational behavior. By means of Brownian dynamics simulations,the conformations of moderately grafted polyampholytes（ GPA）,whose backbone and branches are oppositely charged in equilibrium,were investigated in salt-free good solvents. The influences of backbone length,side chain number and charge density were analyzed. The results revealed that with enhancing the electrostatic interactions,conformational transition process of GPA was composed of four stages including coil,overlapping between backbone and side chains,segment collapsing and charge pairing. Differ from linear polyampholytes,the strength of additional steric and electrostatic repulsions between side chains in GPA varies with changing the molecular structure and affects the conformational transition. Due to solvation of good solvents,a re-extension of GPA chains occurs under strong electrostatic interactions to ensure the completion of quadrupoles paired by dipoles. Decreasing the backbone length or the charge fraction,or increasing the side chain number strengthens the repulsions and rigidifies the backbone,resulting in retardation of molecular collapse and intensification of chain re-extension.