文献类型：期刊文献

英文题名：Unexpected segmental dynamics in polystyrene-grafted silica nanocomposites

作者：Lin, Yu[1];Liu, Langping[1];Zhang, Dongge[1];Liu, Yuanbiao[1];Guan, Aiguo[1];Wu, Guozhang[1]

机构：[1]East China Univ Sci & Technol, Sch Mat Sci & Engn, Shanghai Key Lab Adv Polymer Mat, Shanghai 200237, Peoples R China

年份：2016

卷号：12

期号：41

起止页码：8542

外文期刊名：SOFT MATTER

收录：;EI(收录号：20164402958173);WOS:【SCI-EXPANDED(收录号:WOS:000386247100011)】；

基金：This work was supported by the National Basic Research Program of China (2013CB035505), the National Nature Science Foundation of China (51503066, 51373053), Shanghai Sailing Program (14YF1404900), China Postdoctoral Science Foundation (2015M571502) and the Fundamental Research Funds for the Central Universities (22A201514004).

语种：英文

外文关键词：Relaxation processes - Glass transition - Dynamics - Nanocomposites - Temperature - Mechanisms - Esters - Grafting (chemical) - Polystyrenes - Polymer matrix composites

摘要：Establishing the relationship between interfacial layer chain packing and dynamics remains a continuing challenge in polymer nanocomposites (PNCs). This issue is expected to be significant in our understanding of the mechanism of the dynamic response of such materials and the manner in which these parameters affect the macroscopic properties of PNCs. In this study, we report the dynamics of free polystyrene (PS) and poly(methyl methacrylate) (PMMA) matrix chains, as well as those of polymer chains surrounding the spherical silica nanoparticles (NPs) where silica NPs are either bare or PS grafted, to discriminate the role of grafted chains and interfacial interactions between grafted NPs and the matrix. The a-relaxation dynamics of the PS matrix is unaffected by silica NP loadings, it slows down in PMMA nanocomposites because of polymer-NP interfacial interactions and steric hindrance. More interestingly, we probe the enhanced mobility of the interfacial layer (alpha'-relaxation) in PNCs filled with grafted NPs, and this phenomenon is further corroborated by the accelerated Maxwell-Wagner-Sillars polarization process in the presence of grafted silica NPs. Moreover, the alpha-relaxation time in the vicinity of glass transition temperature of the polymer matrix unexpectedly increases with increasing temperature. Such an anomalous temperature-dependent behavior can be attributed to the influence exerted by slow a-relaxation dynamics. Considering these phenomena and the mechanical properties, we propose a three-layer model to explain the observed behavior of grafted silica NP-filled nanocomposites. These findings provide new insight into the mechanisms responsible for mechanical reinforcement and therefore provide guidance in designing PNCs with tunable macroscopic properties.