On Alternative Thermal Methods for Discerning the Miscibility in Blends of Isotactic Polystyrene and Poly(cyclohexyl methacrylate) with Closely-Spaced Glass Transitions
✍ Scribed by Li-Ling Chang; Ea-Mor Woo; Chih-Pei Chiang
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 214 KB
- Volume
- 205
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Summary: Thermal characterizations were performed to further discern the miscibility and qualitative interactions in blends of isotactic polystyrene (iPS) and poly(cyclohexyl methacrylate) (PCHMA). A method based on the enthalpy relaxation of the blends was used to overcome the difficulty or ambiguity in resolving closely‐spaced glass transitions of these two constituent polymers. Interactions between the blend components were further estimated by two additional methods: the blend's glass transition temperature (T~g~) and the melting point depression. The blend's T~g~ method yielded a χ~12~ value ranging from −0.0016 (i.e., almost 0) to −1.98 (with the values depending on the amorphous PCHMA contents in the blends) in the temperature range of 95–110 °C, whereas the melting point depression led to χ~12~ = −0.039 at 240 °C. The interaction parameters obtained from these two methods are negative, confirming the miscibility with weak interactions. The results of these alternative thermal characterizations further clarified that the iPS/PCHMA blends, whose T~g~'s are too close to allow the use of conventional T~g~ criteria, are indeed completely miscible.
Specific heat increment (Δ__C~P~__) at T~g~ for the iPS/PCHMA blends.
magnified imageSpecific heat increment (Δ__C~P~__) at T~g~ for the iPS/PCHMA blends.