Low-Concentration Polymers Inhibit and Accelerate Crystal Growth in Organic Glasses in Correlation with Segmental Mobility
| Autor: | Ping Gao, C. Travis Powell, Ting Cai, Erica Gunn, Yuchuan Gong, Lian Yu, Geoff G. Z. Zhang, Mariko Hasebe |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
chemistry.chemical_classification
Calorimetry Differential Scanning Nifedipine Polymers Chemistry Hydrogen bond Doping Hydrogen Bonding Crystal growth Polymer Phase Transition Polyethylene Glycols Surfaces Coatings and Films Solvent Chemical engineering Exponential growth Polymer chemistry Materials Chemistry Transition Temperature Molecule Glass Physical and Theoretical Chemistry Crystallization Glass transition |
| Zdroj: | The Journal of Physical Chemistry B. 117:10334-10341 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/jp406418n |
| Popis: | Crystal growth in organic glasses has been studied in the presence of low-concentration polymers. Doping the organic glass nifedipine (NIF) with 1 wt % polymer has no measurable effect on the glass transition temperature Tg of host molecules, but substantially alters the rate of crystal growth, from a 10-fold reduction to a 30% increase at 12 °C below the host Tg. Among the polymers tested, all but polyethylene oxide (PEO) inhibit growth. The inhibitory effects greatly diminish in the liquid state (at Tg + 38 °C), but PEO persists to speed crystal growth. The crystal growth rate varies exponentially with polymer concentration, in analogy with the polymer effect on solvent mobility, though the effect on crystal growth can be much stronger. The ability to inhibit crystal growth is not well ordered by the strength of host-polymer hydrogen bonds, but correlates remarkably well with the neat polymer's Tg, suggesting that the mobility of polymer chains is an important factor in inhibiting crystal growth in organic glasses. The polymer dopants also affect crystal growth at the free surface of NIF glasses, but the effect is attenuated according to the power law us ∝ ub(0.35), where us and ub are the surface and bulk growth rates. |
| Databáze: | OpenAIRE |
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