Grafting density dominant glass transition of dry polystyrene brushes.
The effects of the grafting densities (σp), molecular weights (Mn) and thicknesses of dry polystyrene (PS) brushes on their glass transition temperature (T) were investigated by ellipsometry. The results show that T strongly depends on the grafting density of the PS brushes. The T of the PS brushes with σp> 0.30 increases with decreasing Mn(or brush thickness) and is mainly dominated by entropic effects, in which the grafted chains are highly extended along the film thickness direction resulting in a sharp reduction in configurational entropy. The T of PS brushes with σp< 0.30 decreases with decreasing Mn(or brush thickness) which is mainly dominated by surface effects. For intermediate-density brushes (σp= 0.30), T becomes independent of Mnor brush thickness. The reason for this grafting density dependence of T is attributed to the transition of the PS brush conformation from mushroom-to-brush.
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, China. wxinping@zstu.edu.cn wxinping@zstu.edu.cn.
Biao
B
Zuo
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, China. wxinping@zstu.edu.cn wxinping@zstu.edu.cn.
Shasha
S
Zhang
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, China. wxinping@zstu.edu.cn wxinping@zstu.edu.cn.
Chen
C
Niu
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, China. wxinping@zstu.edu.cn wxinping@zstu.edu.cn.
Hao
H
Zhou
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, China. wxinping@zstu.edu.cn wxinping@zstu.edu.cn.
Shuzheng
S
Sun
Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University, Hangzhou 310018, China. wxinping@zstu.edu.cn wxinping@zstu.edu.cn.
Xinping
http://orcid.org/0000-0002-2261-1625
X
Wang