不同液体环境下聚丙烯酰胺的单分子力学  

Single-molecule Mechanics of Polyacrylamide Under Different Liquid Environments

作　　者：曹美琦 刘霞 崔树勋 CAO Meiqi;LIU Xia;CUI Shuxun(School of Life Science and Engineering,Southwest Jiaotong University,Chengdu 610031,China)

机构地区：[1]西南交通大学生命科学与工程学院,成都610031

出　　处：《高等学校化学学报》2021年第9期2982-2988,共7页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:21774102,21903065)资助.

摘　　要：利用单分子力谱研究了非离子型聚丙烯酰胺(NPAM)及其水解产物阴离子型聚丙烯酰胺(APAM)在不同液体环境下的单链弹性.利用改进的自由连接链(M-FJC)模型中的单链弹性模量参数(K_(0))描述NPAM在不同pH值水溶液中的单链弹性.实验结果表明,K_(0)随着溶液pH值增加而增大,表明NPAM在碱性溶液中的水解度具有pH依赖性.由于K_(0)和高分子链的净电荷正相关,K_(0)增大表明NPAM链净电荷增多,结构单元之间的静电排斥作用增强使高分子链呈现高度伸展的构象.在此基础上研究了APAM在不同pH值溶液中的构象,单分子力谱数据表明,APAM在酸性水溶液中为柔性链,在碱性水溶液中呈现较伸展的构象,从而在分子水平上阐明APAM链构建的水凝胶网络的溶胀机理.单分子层面的深入研究有望阐明这类高分子的减阻机理.The single-chain elasticity of nonionic polyacrylamide(NPAM)and its hydrolysate(anion polyacrylamide,APAM)in different liquid environments was investigated by single molecule force spectroscopy(SMFS).The modified freely jointed chain(M-FJC)model was used to describe the single-chain elasticity of NPAM in aqueous solution at different pH values with a parameter of single-chain modulus(K_(0)).The experimental results show that K_(0)is increased with increasing the pH value of the aqueous solution.It is demonstra-ted that the hydrolysis degrees of NPAM in the alkaline solution are pH-dependent.Because K_(0)has a positive correlation with the net charge of the polymer chain,the increased K_(0)in high-pH solution indicates that the net charge of NPAM chain is increased,and the high electrostatic repulsion between structural units makes polymers present extended conformations.On this basis,the conformations of APAM in aqueous solution at diffe-rent pH values were studied.We find that APAM is flexible in acid solution and is more rigid in basic solution.The findings can be used to illustrate the swelling mechanism of the hydrogel network constructed by APAM chains at the molecular level.

关 键 词：聚丙烯酰胺 水解 构象转变 单分子力谱 

分 类 号：O631[理学—高分子化学]