Chem. J. Chinese Universities ›› 2021, Vol. 42 ›› Issue (9): 2982.doi: 10.7503/cjcu20210241

• Polymer Chemistry • Previous Articles     Next Articles

Single-molecule Mechanics of Polyacrylamide Under Different Liquid Environments

CAO Meiqi, LIU Xia(), CUI Shuxun()   

  1. School of Life Science and Engineering,Southwest Jiaotong University,Chengdu 610031,China
  • Received:2021-04-08 Online:2021-09-10 Published:2021-09-08
  • Contact: LIU Xia,CUI Shuxun E-mail:xliu@swjtu.edu.cn;cuishuxun@swjtu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21774102)

Abstract:

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(K0). The experimental results show that K0 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 K0 has a positive correlation with the net charge of the polymer chain, the increased K0 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.

Key words: Polyacrylamide, Hydrolysis, Conformational transition, Single molecule force spectroscopy

CLC Number: 

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