ABSTRACT

The tacticity of vinyl polymer chains strongly affects the physical properties of polymeric materials, as example the chain conformations and stiffness. In the present work we tested how the hybrid Particle-Field Molecular Dynamics (PF-MD) technique is capable to describe conformational differences of polymer chains as function of the tacticity. In particular, we focus on tacticity effect of atactic, isotactic, and syndiotactic polypropylene (PP) homopolymer melts. We found that PF-MD simulations exhibit dependence of Flory’s Characteristic Ratio from the fraction of racemo diads along the PP chains in qualitative agreement with Small Angle Neutron Scattering (SANS) experiments and theoretical previsions. Finally, we calculated and compared the packing length parameter on very high stereoregular syndiotactic PP systems with rheological measurements. A qualitative agreement between the calculated and experimental packing length is found.

摘要

乙烯基聚合物链的立构规整度强烈影响聚合物材料的物理性能，例如链构象和刚度。在本工作中，我们测试了混合粒子场分子动力学（PF-MD）技术如何能够描述聚合物链构象差异与立构规整度的关系。特别是，我们关注无规，等规和间规聚丙烯（PP）均聚物熔体的规整效果。我们发现，PF-MD模拟在小角度中子散射（SANS）实验和理论假设的定性吻合中，显示出沿PP链沿消旋二单元体的分数具有Flory特征比的依赖性。最后，我们计算并比较了非常高的立体规则间规PP系统的填充长度参数和流变学测量值。找到了计算的和实验的包装长度之间的定性协议。