Effects of molecular structure of modifiers on the thermodynamics of phenolic blends: An entropic factor complementing PCAM

Hew Der Wu, Peter P. Chu, Chen Chi M. Ma, Feng Chih Chang

研究成果: 雜誌貢獻期刊論文同行評審

50 引文 斯高帕斯(Scopus)

摘要

Different thermodynamics in phenolic blends with different polymeric modifiers, i.e., phenoxy, poly(decamethylene adipate), poly(ethylene oxide), and poly(vinyl alcohol), calculated by the Painter and Coleman association model (PCAM) are examined. The thermodynamics is calculated based upon the equilibrium constants derived experimentally from infrared spectroscopies of low molecular weight analogues with similar hydrogen-bonding formation. The discrepancies between the PCAM predictions and the experimentally observed Tg and free volume variation with blending composition are attributed to the additional entropic effects introduced by the long repeated units of modifiers. The structural characteristics and hydrogen-bonding heterogeneity as derived from solid-state NMR and IR spectra support the notion that the length and size of the modifier repeated unit are responsible for such discrepancies. These observed nonidealities can be interpreted as competition between inter- and intraassociations (ΔHm favored), which depend on the entropy rise associated with the amount of increase of the breaking off of the self-association in phenolic and modifiers within blends. While PCAM is based on `true' miscibility, however, minor modification is required to better describe the thermodynamics for `real' blends where microdomain heterogeneity with size greater than that defined by thermodynamic criteria may be present.

原文???core.languages.en_GB???
頁(從 - 到)3097-3105
頁數9
期刊Macromolecules
32
發行號9
DOIs
出版狀態已出版 - 4 5月 1999

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