Relationship between Segmental Relaxation of Polystyrene Films and Stick鈥揝lip Behavior during Dynamic Wetting of Liquid Droplets on Their Surfaces

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• 作者：Biao Zuo ; Xumiao He ; Yuping Wang ; Jianquan Xu ; Juping Yang ; Xinping Wang
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：September 17, 2015
• 年：2015
• 卷：119
• 期：37
• 页码：12325-12335
• 全文大小：628K
• ISSN：1520-5207

文摘

A novel method was previously reported for detecting the glass transition of thin polystyrene (PS) films by correlating the relationships between the temperature-dependent viscoelasticity of the PS films and stick鈥搒lip behavior on their surfaces during dynamic wetting of liquid droplets. In the present study, the frequency dependence of the stick鈥搒lip behavior is investigated. The results show that the stick鈥搒lip behavior of liquid dynamic wetting on PS films is dependent on the contact line velocity, which is related to the deformation frequency of the PS surface during the moving liquid front. The stick鈥搒lip behavior was revealed to be determined by a dimensionless parameter (尉), which is the ratio of the PS segmental relaxation time (蟿_伪) and the characteristic time (蟿_c) for PS surface deformation near the droplet contact line. When 尉 is close to 1 (蟿_伪 鈮?蟿_c), the 螖胃 (jumping angle), a scale of the stick鈥搒lip behavior, reaches a maximum. This correlation between 螖胃 and 尉 demonstrates that the stick鈥搒lip behavior is related to the energy dissipation caused by the PS 伪-relaxation process, and the peak temperature (or frequency) in 螖胃 corresponds to the 伪-relaxation temperature (time) of the polymer. These results strongly demonstrate that the utilization of the stick鈥搒lip behavior is a creditable method, similar to dynamic viscoelastic measurement, for probing the glass transition and segmental relaxation of thin polymer films.