Improved Temperature Behavior of PNIPAM in Water with a Modified OPLS Model

被引：30

作者：

Dalgicdir, Cahit ^{[1
]}

van der Vegt, Nico F. A. ^{[1
]}

机构：

[1] Tech Univ Darmstadt, Eduard Zintl Inst Anorgan & Phys Chem, D-64287 Darmstadt, Germany

来源：

JOURNAL OF PHYSICAL CHEMISTRY B | 2019年 / 123卷 / 17期

关键词：

LINEAR CONSTRAINT SOLVER; MOLECULAR-DYNAMICS; POLY(N-ISOPROPYLACRYLAMIDE) HYDROGELS; CONFORMATION CHANGE; CONONSOLVENCY; METHANOL; SIMULATIONS; TRANSITION; OLIGOMERS; COLLAPSE;

D O I：

10.1021/acs.jpcb.9b01644

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

We test the OPLS/AA force field for a single PNIPAM 40-mer in aqueous solution using replica exchange molecular dynamics simulations and find that the force field fails to reproduce the experimental temperature behavior. To resolve this issue, we apply a modification on the partial charges previously suggested to reproduce the liquid-liquid phase separation of NIPAM aqueous solutions. The modified force field features stronger amide-water electrostatic interactions than the original OPLS model, predicts a weaker water-mediated monomer-monomer attraction, and reproduces the experimental coil-globule collapse enthalpy of PNIPAM in water. We revisit the cononsolvency problem of PNIPAM in methanol/water mixtures with the modified model and show that the dependence of the coil-globule collapse enthalpy on methanol concentration follows the experimental trend of the lower critical solution temperature. The calculations with the modified force field confirm that polymer dehydration is the determining factor for chain collapse in the cononsolvency regime.

引用

页码：3875 / 3883

页数：9