纳米粒子诱导聚合物结晶行为的分子模拟研究
详细信息 查看官网全文
- 英文论文题名：Molecular simulations of nanoparticles-induced polymer crystallization
- 论文作者：聂仪晶 ; 周志平 ; 郝桐帆
- 英文论文作者：Yijing Nie ; Zhiping Zhou ; Tongfan Hao ; Institute of Polymer Materials ; School of Materials Science and Engineering ; Jiangsu University
- 年：2016
- 作者机构：江苏大学材料学院高分子材料研究所;
- 论文关键词：Monte Carlo模拟 ; 纳米粒子 ; 聚合物结晶
- 会议召开时间：2016-08-25
- 会议录名称：中国化学会2016年软物质理论计算与模拟会议论文摘要集
- 语种：中文
- 分类号：TB383.1;O631
- 学会代码：ZGHY
- 会议名称：中国化学会2016年软物质理论计算与模拟会议
- 会议地点：中国天津
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：2
- 文件大小：199k
- 原文格式：D
- 会议级别：全国
摘要
纳米粒子的加入可以大幅度提高高分子材料的物理性能,如力学性能、导热性能或者导电性能等。结晶性聚合物纳米复合材料具有良好的物理性能的原因之一是,纳米粒子的引入会引起聚合物结晶行为的改变,从而导致物理性能发生显著的变化[1]。纳米粒子的众多因素,如维度、聚合物-纳米粒子相互作用、填料网络或者接枝情况等,均会影响聚合物结晶过程。为揭示纳米粒子诱导聚合物结晶的微观机理,我们使用动态Monte Carlo模拟方法对聚合物纳米复合材料的结晶过程进行了系统的研究。我们模拟发现,在聚合物稀溶液中,一维纳米粒子会诱导聚合物形成纳米杂化串晶结构,如Fig.1所示[2]。这种纳米杂化串晶结构的形成主要受到两种因素的影响:侧向尺寸和聚合物-纳米粒子相互作用。在发生结晶之前,在聚合物-纳米粒子相互作用下,聚合物链被吸附到纳米粒子的表面;由于一维纳米粒子的各向异性,在吸附过程中,聚合物链段沿着纳米粒子的长轴方向发生局部的取向,即各向异性吸附过程。随后的结晶过程中,这些局部的取向链段在纳米粒子的表面发生异相成核,最终形成纳米杂化串晶结构。在聚合物溶液中引入一维纳米粒子组成的同向填料网络时,我们模拟发现同向填料网络诱导聚合物结晶形成了新型的多shish(一维纳米粒子)的纳米杂化串晶结构[3]。类似的结构曾在剪切诱导的聚丙烯熔体中被发现。由于填料网络的限制作用,处于填料网络内部的聚合物链受到纳米粒子的侧向挤压作用,侧向尺寸减小,其沿着纳米粒子长轴方向的取向度更高,构象熵更小。因此处于内部的聚合物链优先发生异相成核,形成多shish的纳米杂化串晶结构。不过与单个纳米粒子诱导形成纳米杂化串晶结构不一样的是,在聚合物-纳米相互作用较大时,才会形成纳米杂化串晶结构,而多shish的纳米杂化串晶结构在聚合物-纳米相互作用较小时也可以形成。我们也模拟研究了接枝在二维纳米粒子上的聚合物的结晶过程[4]。相比于非接枝聚合物,接枝聚合物的结晶成核速度更快。随着接枝密度的提高,聚合物链的伸展程度越高,界面处的聚合物链段的密度越高,导致其构象熵显著下降,熔点提高,因此结晶成核能力增强。此外,接枝密度的变化也会引起结晶成核方式的改变。当接枝密度较小时,聚合物链不"拥挤",因此其采用链内成核的方式进行结晶成核与生长。当接枝密度较大时,聚合物链较"拥挤",因此其采用链间成核的方式进行结晶成核与生长。
The addition of nanoparticles can greatly improve physical properties of polymer materials,such as mechanical properties,thermal conductivity,or electrical conductivity.The presence of the nanoparticles can lead to the changes of polymer crystallization behaviors,which further influence the corresponding physical properties.There are some factors that will affect the polymer crystallization,such as filler dimensions,polymer-filler interactions,filler networks or the grafting of filler.Thus,we performed dynamic Monte Carlo simulations to investigate the crystallization behaviors of polymer nanocomposites.By dynamic Monte Carlo simulations,we found that nanofillers with small lateral size under attractive polymer-filler interactions induce the formation of the nanohybrid shish-kebab(NHSK) structures.Prior to crystallization,segments are absorbed onto the filler surface due to the polymer-filler interactions.Simultaneously,the segments are oriented along the long axis of the filler.Subsequently,the local oriented segments nucleate in the polymer-filler interface,and eventually developed into kebabs with uniform orientation.This anisotropic absorption process of segments is codetermined by two key factors:(1) the lateral size of filler and(2) the polymer-filler interaction.Both the decrease of the lateral size of filler and the increase of the polymer-filler interactions can cause the improvement of the orientational orders of segments along the long axis of the filler,and thus are beneficial for the formation of the NHSK structures.We found that the aligned anisotropic filler networks can induce the appearance of an unexpected NHSK structure with multiple shish.The aligned fillers act as multiple shish and the polymer crystal lamellae form kebabs.The filler networks impose confinement effects on the conformations of chains inside,force the chains to orient along the long axis of the fillers,and reduce the conformational entropy,thus resulting in stronger nucleation ability of the chains inside.Thus,during crystallization,crystal nucleation firstly occurs inside the filler networks.Then,the nuclei grow up to connect the fillers to finally form the NHSK structure with multiple shish.Dynamic Monte Carlo simulations were preformed to investigate the crystallization behaviors of polymers grafted on two-dimensional filler.Compared with ungrafted polymers,grafted polymers have shorter nucleation induction period.Higher grafting density results in higher degree of chain extension and higher monomer density in the interfacial regions.Thus,the melting temperature is increased,further leading to the enhancement of polymer crystallizability.In addition,grafting density also influences nucleation mechanism.For the system with low grafting density,the crowding effect is weak and the chains can join in nucleation and growth by the intramolecular crystal nucleation mode.For the system with high grafting density,due to the strong crowding effect and stretched chain conformation,the chains choose the intermolecular crystal nucleation mode.
The addition of nanoparticles can greatly improve physical properties of polymer materials,such as mechanical properties,thermal conductivity,or electrical conductivity.The presence of the nanoparticles can lead to the changes of polymer crystallization behaviors,which further influence the corresponding physical properties.There are some factors that will affect the polymer crystallization,such as filler dimensions,polymer-filler interactions,filler networks or the grafting of filler.Thus,we performed dynamic Monte Carlo simulations to investigate the crystallization behaviors of polymer nanocomposites.By dynamic Monte Carlo simulations,we found that nanofillers with small lateral size under attractive polymer-filler interactions induce the formation of the nanohybrid shish-kebab(NHSK) structures.Prior to crystallization,segments are absorbed onto the filler surface due to the polymer-filler interactions.Simultaneously,the segments are oriented along the long axis of the filler.Subsequently,the local oriented segments nucleate in the polymer-filler interface,and eventually developed into kebabs with uniform orientation.This anisotropic absorption process of segments is codetermined by two key factors:(1) the lateral size of filler and(2) the polymer-filler interaction.Both the decrease of the lateral size of filler and the increase of the polymer-filler interactions can cause the improvement of the orientational orders of segments along the long axis of the filler,and thus are beneficial for the formation of the NHSK structures.We found that the aligned anisotropic filler networks can induce the appearance of an unexpected NHSK structure with multiple shish.The aligned fillers act as multiple shish and the polymer crystal lamellae form kebabs.The filler networks impose confinement effects on the conformations of chains inside,force the chains to orient along the long axis of the fillers,and reduce the conformational entropy,thus resulting in stronger nucleation ability of the chains inside.Thus,during crystallization,crystal nucleation firstly occurs inside the filler networks.Then,the nuclei grow up to connect the fillers to finally form the NHSK structure with multiple shish.Dynamic Monte Carlo simulations were preformed to investigate the crystallization behaviors of polymers grafted on two-dimensional filler.Compared with ungrafted polymers,grafted polymers have shorter nucleation induction period.Higher grafting density results in higher degree of chain extension and higher monomer density in the interfacial regions.Thus,the melting temperature is increased,further leading to the enhancement of polymer crystallizability.In addition,grafting density also influences nucleation mechanism.For the system with low grafting density,the crowding effect is weak and the chains can join in nucleation and growth by the intramolecular crystal nucleation mode.For the system with high grafting density,due to the strong crowding effect and stretched chain conformation,the chains choose the intermolecular crystal nucleation mode.
引文
[1]Li,L.Y.;Li,C.Y.;Ni,C.Y,J.Am.Chem.Soc.2006,128:1692.
[2]Nie,Y.J.;Zhang,R.J.;Zheng,K.S.;Zhou,Z.P.,Polymer 2015,76:1.
[3]Nie,Y.J.;Hao,T.F.;Wei,Y.;Zhou,Z.P.RSC Advances 2016,6:50451.
[4]Hao,T.F.;Zhou,Z.P.,Nie,Y.J.,Wei,Y.;Li,S.J.,Submitted to Polymer.
[2]Nie,Y.J.;Zhang,R.J.;Zheng,K.S.;Zhou,Z.P.,Polymer 2015,76:1.
[3]Nie,Y.J.;Hao,T.F.;Wei,Y.;Zhou,Z.P.RSC Advances 2016,6:50451.
[4]Hao,T.F.;Zhou,Z.P.,Nie,Y.J.,Wei,Y.;Li,S.J.,Submitted to Polymer.