文献类型：期刊文献

英文题名：Interfacial Interactions and Segmental Dynamics of Poly(vinyl acetate)/Silica Nanocomposites

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

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

年份：2015

卷号：119

期号：23

起止页码：12956

外文期刊名：JOURNAL OF PHYSICAL CHEMISTRY C

收录：;EI(收录号：20152500947075);WOS:【SCI-EXPANDED(收录号:WOS:000356317500021)】；

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

语种：英文

外文关键词：Glass transition - Hydrophilicity - Calcination - Hydrogen - Nanocomposites - Fourier transform infrared spectroscopy - Hydrogen bonds - Hydrophobicity - Dynamics - Glass

摘要：We investigate the interfacial interactions and segmental dynamics of hydrophilic and hydrophobic (calcined) silica nanoparticle (NP) filled poly(vinyl acetate) (PVAc) composites via a combination of Fourier transform infrared spectroscopy (FTIR) and broadband dielectric spectroscopy measurements. For hydrophilic silica NP filled composites, an increase in the amount of bound carbonyl groups with increasing silica loading can be noted due to hydrogen bonding interactions with hydroxyls on the NP surfaces and carbonyl groups of PVAc. It is surprising that the apparent glass transition temperature (T-g) increases very slightly (similar to 1 K) compared to pure PVAc, but the glass transition process becomes much broader, indicating the existence of a slower relaxation mode. In addition to the bulklike alpha-relaxation assigned to polymer segments away from the NP surfaces, the nanocomposites also exhibit a slower interfacial alpha'-relaxation by 34 orders of magnitude compared to bulk polymers. However, in the case of hydrophobic (calcined) silica NP filled composites, T-g shifts to higher temperatures by 4-5 K even if there is the absence of strong polymer-NP interfacial interactions confirmed by the FTIR results. Consequently, the overall alpha-relaxation dynamics are suppressed in the presence of silica NPs, which is attributed to an increase of steric hindrance and decrease of free volume. More importantly, in the nanocomposites with high NP loadings, it is worth noting a weak physical adsorption interfacial layer for which the segmental mobility is on average slower by 1-2 orders of magnitude relative to that for bulk polymers. However, the dielectric strength and interfacial bound fraction is much smaller than that of hydrophilic silica NP filled composites, indicating the fact that physical adsorption is much weaker compared to hydrogen bonding