Control of Particle Dispersion with Autophobic Dewetting in Polymer Nanocomposites
Control of Particle Dispersion with Autophobic Dewetting in Polymer Nanocomposites
复制标题
DOI：
10.1021/acs.macromol.0c00190
复制
发表时间：
2020-06-23
期刊：
影响因子：
5.5
通讯作者：
Kim, So Youn
中科院分区：
文献类型：
--
作者：
Kwon, Na Kyung;Kim, Hyunhong;Kim, So Youn
聚合物纳米复合材料（PNC）中良好的颗粒分散常常受到自疏反润湿的阻碍，其中基体聚合物从接枝聚合物中排出，通常认为这会导致稀释颗粒状态下颗粒聚集的增加和机械性能的增强。然而，我们发现高度延伸的短链聚合物的自疏去湿可以改善/破坏颗粒分散性，这在很大程度上取决于颗粒体积分数。在强自疏条件下，基体 P 与接枝聚合物 N 之间的高分子量比（P/N >> 1），接枝多巴胺改性聚乙二醇（DOPA-mPEG）刷状聚合物的二氧化硅纳米粒子通过改变表面接枝率分散在 PEG 基体中。在稀释颗粒状态下，我们发现提高接枝率反而会改善颗粒分散性并降低剪切模量，因为去湿聚合物无法桥接颗粒。相反，在集中颗粒状态下，颗粒变得更加聚集，并且由于耗尽吸引力形成了更致密的颗粒网络，因此相应的机械强度随着接枝率的增加而增加。本研究分别通过小角 X 射线散射、时域质子核磁共振和振荡流变实验研究 PNC 的微观结构、动力学和流变特性，为控制 PNC 的详细结构和性能提供了额外的设计指南。
Good particle dispersion in polymer nanocomposites (PNCs) is often hampered by autophobic dewetting where the matrix polymers are expelled from the grafted polymer, generally believed to result in increased particle aggregation and enhanced mechanical properties in dilute particle regime. However, we found that autophobic dewetting with highly extended short-chain polymers improves/disrupts particle dispersity, strongly dependent on particle volume fraction. Under strong autophobic condition given with the highmolecular-weight ratio between the matrix, P, and grafted polymer, N, (P/N >> 1), silica nanoparticles grafted with dopamine-modified poly(ethylene glycol) (DOPA-mPEG) brush polymer are dispersed in the PEG matrix by varying the surface grafting rate. In the dilute particle regime, we found that increasing grafting rate ironically improves particle dispersion and reduces the shear modulus as dewetted polymers cannot bridge the particles. In the concentrated particle regime, on the contrary, particles become more aggregated and the corresponding mechanical strength increases with grafting rate as a denser particle network is formed by depletion attractions. Investigating the microstructures, dynamics, and rheological properties of PNCs with small-angle X-ray scattering, time-domain proton NMR, and oscillatory rheometry experiments, respectively, this study provides additional design guidelines for controlling the detailed structure and properties of PNCs.