The Distribution of Glass Transition Temperatures in Ultrathin Polymer Films Controlled by Segment Density or Interfacial Interaction

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• 作者：Yijing Nie ; Zhiping Zhou ; Tongfan Hao ; Xubo Ye and Wenming Yang
• 关键词：glass transition ; molecular simulation ; ultrathin polymer films
• 刊名：Macromolecular Theory and Simulations
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：25
• 期：2
• 页码：187-195
• 全文大小：1848K
• ISSN：1521-3919

文摘

Nowadays, the microscopic mechanism controlling the distribution of local glass transition temperatures (T_gs) across thin polymer films is still unclear and thus large-scale applications of polymer films are restricted. Dynamic Monte Carlo simulations are performed to investigate the key factors dominating the distribution of layer T_gs in two kinds of capped ultrathin films with and without attractive polymer–substrate interactions, respectively. For the film without polymer–substrate interaction, the interfacial layer T_g is lower than the middle layer T_g. Additionally, the layer T_gs and the layer segment densities below T_g are linearly correlated, indicating that polymer density determines the distribution of layer T_gs. However, for the films with polymer–substrate interactions, the interfacial layer T_g increases dramatically with the raise of interfacial interactions, while the middle layer T_g decreases slightly. The interfacial layer T_g is proportional to the strength of interfacial interaction, while the middle layer T_g is linearly correlated with the segment density of the middle layer below T_g. Namely, interfacial interaction is the main factor dominating the interfacial layer T_g, while segment density controls the middle layer T_g.