Intramolecular and Intermolecular Rearrangements in Nanoconfined Polystyrene

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• 作者：Sudeshna Chattopadhyay ; Alokmay Datta ; A. Giglia ; N. Mahne ; A. Das ; S. Nannarone
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：December 11, 2007
• 年：2007
• 卷：40
• 期：25
• 页码：9190 - 9196
• 全文大小：437K
• 年卷期：v.40,no.25(December 11, 2007)
• ISSN：1520-5835

文摘

Vacuum ultraviolet spectroscopy reveals an intramolecular rearrangement involving a change in"physical dimers" of adjacent pendant benzene rings of atactic polystyrene (aPS) from "oblique" to "head-to-tail" (ht) configuration in aPS films spin coated on fused quartz, as film thickness R goes below 4R_g (R_g =unperturbed polystyrene gyration radius 20.4 nm). Simultaneously, transverse layering of molecular "gyrationspheres", for film thickness R 4R_g, causes an increase in free energy (reduction in cohesion) that follows a(R_g/R)^b dependence with b 3, a clear deviation from planar confinement. The variation of in-plane and out-of-plane cohesive energy over a film of a given thickness is explained by invoking a fixed-range, repulsive,modified Pöschl-Teller intermolecular potential, with the strength of this potential decreasing with increase in R.Possible reduction of "dimer" dipole moment due to ht configuration is consistent with reduction of cohesionbetween aPS molecular gyration spheres.