Cooperative Segmental Motions in Ethyl Acrylate/Triethylene Glycol Dimethacrylate Copolymer Networks Studied by Dielectric Techniques

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• 作者：Andreas T. Stathopoulos ; Apostolos Kyritsis ; Gloria Gallego Ferrer ; Jos茅 Luis G贸mez Ribelles ; Costas Christodoulides ; Polycarpos Pissis
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：October 25, 2011
• 年：2011
• 卷：44
• 期：20
• 页码：8233-8244
• 全文大小：1081K
• 年卷期：v.44,no.20(October 25, 2011)
• ISSN：1520-5835

文摘

The molecular dynamics of ethyl acrylate/triethylene glycol dimethacrylate (EA/TrEGDMA) copolymer networks on the overall composition range were investigated thoroughly by employing dielectric techniques: thermally stimulated depolarization currents (TSDC) and dielectric relaxation spectroscopy (DRS). Furthermore, differential scanning calorimetry (DSC) was performed in order to investigate the thermal glass transition of these copolymers. The results show that, for low content of the TrEGDMA component, the overall dielectric behavior of the copolymers is dictated by the dynamics of PEA component, exhibiting the 伪_cop relaxation process which is strongly affected by the TrEGDMA moieties becoming broader and shifting to higher temperatures with increasing cross-linker (TrEGDMA) content. For the copolymer networks rich in TrEGDMA (w_TE 鈮?40 wt %), the overall dielectric behavior indicates that the dynamics of the dimethacrylate component dominates, resembling that of poly(n-alkyl methacrylates) in the sense that the temperature dependence of molecular relaxation processes presents a merging region where the local relaxation process of TrEGDMA, 尾_PTE, merges with the more cooperative 伪_cop process of the copolymers into an 伪尾_cop locally cooperative relaxation process. By increasing the EA content, the strength of 伪_cop relaxation process enhances and simultaneously the merging region shifts to lower temperatures. The cooperative motions are significantly suppressed in the copolymers with TrEGDMA contents higher that 80 wt %. The copolymers present enhanced spatial heterogeneity the more TrEGDMA content, whereas no dynamic heterogeneity was detected.