聚乙烯醇相变过程中的结构和物理性质的分子动力学模拟

Molecular dynamics simulations on structure and physical properties of polyvinyl alcohol during phase transition

基于分子动力学模拟研究聚乙烯醇(PVA)在加热和冷却过程中的结构特征和物理性质,获得了聚乙烯醇的一些重要的热力学和动力学数据。通过分析体系的键长分布、键角分布、二面角分布及全局取向有序参数考察聚乙烯醇的结构特征。结果表明:聚乙烯醇的聚合度与玻璃化转变温度(Tg)的关系与Ellis关系式吻合较好。在给定温度下,体系链越长,分子迁移率越小,黏度越大。另外,温度在Tg以上黏度值基本保持常数,而温度在Tg以下,无定形体系的黏度值是随着温度的升高而降低的,该结果与预测结果一致。

The structural features and physical properties of polyvinyl alcohol （PVA） during heating and cooling were investigated in terms of molecular dynamics simulations.Some important thermodynamics and kinetics data were obtained.The structure features of polymers were examined from the bond length,bond angle,dihedral distribution,and global orientational order parameter.Results demonstrated that the relationship between the glass transition temperature （Tg） and polymerization degree for PVA satisfied with Ellis＇ relation.At the given temperature,the molecular mobility values decreased and the viscosity values increased as the polymerization degree of PVA increased.In addition,the viscosity values substantially kept constant above Tg,and the viscosity values of the amorphous phase decreased with increasing temperature below Tg as expected.