期刊
MACROMOLECULES
卷 49, 期 1, 页码 298-307出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.macromol.5b02214
关键词
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资金
- National Science Foundation (USA) [DMR-1005606]
- Oklahoma State University
- National Science Foundation [OCI-1126330]
We performed a combined calorimetric and molecular modeling investigation of poly(vinyl acetate) (PVAc) on silica to characterize the intermolecular interactions and the behavior of the adsorbed polymer. From temperature-modulated differential scanning calorimetry experiments, different regions of thermal activity suggested a gradient of mobility in the adsorbed polymer. Polymer segments in more direct contact with silica (tightly bound) showed a significantly elevated and broadened glass transition relative to the bulk polymer, while polymer further away (loosely bound) showed only a slightly elevated transition relative to the bulk polymer. A thermal transition for PVAc at the air interface (more-mobile) was also observed and was at lower temperatures than the bulk polymer. Density profiles from molecular dynamics studies suggested a structure of the adsorbed polymer similar to that experimentally observed. These studies were consistent with the presence of a motional gradient in the polymer segments, and concomitant glass transition changes from the silica to the air interfaces. These results also demonstrate that hydrogen-bonding interactions, at the PVAc/silica interface, are critical to the high-temperature shifts in the glass transition.
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