摘要
本文研究了Si/SiO2、Si/Si–H基底与聚苯乙烯(PS)之间的界面相互作用对PS薄膜的玻璃化转变及相关力学性能的影响.结果显示,无论何种基底,PS薄膜的玻璃化转变温度(Tg)都随其厚度降低而降低.但相同厚度(<110 nm)下,以Si/Si–H为基底时PS薄膜的Tg比以Si/SiO2为基底的PS薄膜高.Si/SiO2表面PS薄膜Tg开始下降的临界厚度为110 nm,远高于以Si/Si–H为基底时的40 nm.对PS薄膜的膨胀系数和弹性模量进行研究,也得到相似的临界厚度.另外,与Si/SiO2基底相比,在Si/Si–H上的PS薄膜具有更低的膨胀系数以及较高弹性模量.可能原因是Si/Si–H与PS具有较强的相互作用,限制了该界面分子的运动能力,导致基底/PS界面效应对薄膜分子运动的影响力增强,造成该薄膜Tg的厚度依赖性下降,并呈现出相对较硬的力学特征.
The glass transition temperature （Tg） and viscoelasticity of thin polystyrene （PS） films supported on Si/Si-H and Si/SiO2 substrates were investigated using an ellipsometry and force-distance （F-D） measurements of atom force microscopy. It was found that Tg of thin PS films deposited on either Si/Si-H or Si/SiO2 decrease with decreasing of film thickness. However, Tg of PS film on Si/SiO2 substrate depressed more dramatically than that on Si/Si-H. The threshold thickness for Tg reduction of thin PS film on Si/SiO2 （110 nm） is higher than that of film on Si/Si-H （40 nm）. Meanwhile, thin PS film supported by Si/SiO2 exhibits the higher thermal expansivity compared with that on Si/Si-H substrate. Surface F-D measurements reveal the film on Si/Si-H substrate is stiffened, showing a higher elastic modulus. In order to understand the mechanism of the substrate effect, the interfacial energy and long-range van der Waals potential （Фvdw） were investigated and a strong attractive interaction between PS and Si/Si-H substrate was found. Thus, the packing density was enhanced and the molecular mobility of PS chains at Si/Si-H/PS interface was suppressed. This strong interaction resulted in higher Tg and elastic modulus of thin PS film compared with that on Si/SiO2 substrate.
出处
《中国科学：化学》
CAS
CSCD
北大核心
2013年第10期1336-1345,共10页
SCIENTIA SINICA Chimica
基金
国家自然科学基金(21174134)
浙江省自然科学基金重点项目(Z4100463)支持
关键词
聚苯乙烯薄膜
玻璃化转变温度
基底界面效应
力学性能
分子运动
thin polystyrene film, glass transition temperature, interfacial interaction, mechanical properties, molecules motion
