Interfacial and Annealing Effects on Primary 伪-Relaxation of Ultrathin Polymer Films Investigated at Nanoscale

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• 作者：Hung K. Nguyen ; Massimiliano Labardi ; Simone Capaccioli ; Mauro Lucchesi ; Pierangelo Rolla ; Daniele Prevosto
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：February 28, 2012
• 年：2012
• 卷：45
• 期：4
• 页码：2138-2144
• 全文大小：421K
• 年卷期：v.45,no.4(February 28, 2012)
• ISSN：1520-5835

文摘

The influence of interfacial interactions and annealing time on dynamics of the 伪-relaxation in ultrathin poly(vinyl acetate) films deposited on different substrates has been studied using local dielectric spectroscopy at ambient pressure and controlled humidity. After annealing at 323 K for about 3 days, for polymer films supported on gold and aluminum substrates, an increase of the relaxation rate with decreasing film thickness below 30鈥?5 nm was observed, whereas for films deposited on silicon substrates a thickness-independent dynamics was found for films as thin as 12 nm. The difference in size effect on dynamics of the films could reasonably be related to the difference in interfacial energy between polymer films and substrates, even though a criterion simply based on interfacial energy cannot be used to explain all the results. In fact, further annealing at a higher temperature evidenced an annealing-dependent dynamics in films prepared on aluminum substrates consistent with the presence of long-living metastable states at the polymer/substrate interface. The lifetime of such metastable states seems related to the nature of the substrate as well as to the molecular weight of the polymer.