Segmental orientations of trains versus loops and tails: the adsorbed polymethylmethacrylate system when the surface coverage is incomplete

详细信息    查看全文

• 作者：Soga ; Iwao ; Granick ; Steve
• 关键词：Trains ; Polymer ; Anisotropy
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：2000
• 出版时间：September, 2000
• 年：2000
• 卷：170
• 期：2-3
• 页码：113-117
• 全文大小：89.7 K

文摘

We measure, for the first time, the separate surface coverage-dependent orientations of trains and of loops/tails in the structure of an adsorbed polymer, and show that these have different average orientations. The system was PMMA (atactic polymethylmethacrylate) adsorbed onto oxidized silicon from dilute solution in carbon tetrachloride at 25.0°C. The method was FTIR-ATR (infrared spectroscopy in attenuated total reflection). With increasing surface coverage, train segments were observed to maintain constant average anisotropy with respect to the solid surface. Free segments were preferentially flattened when the surface coverage was low, but with increasing surface coverage became progressively more random in orientation. Free and bound segments were separated according to shifts of the vibrational frequencies of carbonyl segments upon hydrogen-bonding to the surface silanol groups. The dependence of segmental orientation on molecular weight of the chain is also discussed.