摘要
分子量是聚电解质的重要参数,然而目前测量聚电解质分子量的方法均存在一定的局限性.本文提出了一种利用基于原子力显微镜的单分子力谱(SMFS)技术测量聚电解质分子量(链长)的新方法.以窄分布的聚苯乙烯磺酸钠(PSSNa)为研究对象,利用SMFS技术测量了其在高真空和水环境中的分子链长度.实验结果表明PSSNa在水中的链长统计结果明显大于在高真空中的统计结果.PSSNa是强聚电解质,在水环境中将会电离,使其在水中的构象比在高真空中更为舒展.分子链上对应于针尖抓取点与基底吸附点的位置之间的距离相对较远.因此PSSNa在水中得到的力-距离(F-E)曲线有更长的表观轮廓长度.在水环境中获得的平均链长与蒙特卡洛(Monte Carlo)模拟结果接近.研究结果表明对于较为刚性的聚电解质,当其构象较为伸展时(如PSSNa在稀溶液中),通过SMFS方法可估算其分子链平均长度.
Molecular weight is an important parameter of polyelectrolytes.However,there are certain limitations in each of the current methods for measuring the molecular weight of polyelectrolytes.In this work,we propose a novel method to measure the molecular weight(chain length)of polyelectrolytes by using atomic force microscopy(AFM)-based single-molecule force spectroscopy(SMFS).The chain lengths of poly(sodium styrenesulfonate)(PSSNa)with narrow molecular weight distribution in high vacuum and water are measured.The SMFS experimental results show that the statistical result of the chain length of PSSNa in water is significantly larger than that obtained in high vacuum.PSSNa is a strong polyelectrolyte and will ionize when dissolved in water,which will lead to a more extended conformation in water than that in high vacuum.In this case,the distance between the two positions on the PSSNa chain corresponding to the gripping point of the AFM tip and the anchor point of the substrate adsorption is relatively far.Therefore,the force-extension(F-E)curves of PSSNa obtained in water have longer apparent contour lengths than those obtained in high vacuum.The average chain length of PSSNa obtained in water is close to the Monte Carlo simulation results.This work shows that for a rigid polyelectrolyte,when it adopts an extended conformation(such as the dissolution of PSSNa in the water environment),SMFS can be used to roughly estimate the average length of the polymer chain.
作者
王海龙
单驿轩
鲍雨
崔树勋
Hai-long Wang;Yi-xuan Shan;Yu Bao;Shu-xun Cui(Key Laboratory of Advanced Technologies of Materials,Ministry of Education,Southwest Jiaotong University,Chengdu 610031)
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2022年第11期1358-1364,共7页
Acta Polymerica Sinica
基金
国家自然科学基金(基金号21774102)
中央高校基本科研业务费专项资金(项目号2682020ZT105)资助项目.
关键词
聚电解质
分子链长度
单分子力谱
聚苯乙烯磺酸钠
Polyelectrolyte
Chain length
Single-molecule force spectroscopy
Poly(sodium styrenesulfonate)
