Structure and properties of highly stereoregular isotactic poly(methyl methacrylate) and syndiotactic poly(methyl methacrylate) blends treated with supercritical CO2

The structure and properties of highly stereoregular isotactic poly(methyl methacrylate) (it-PMMA) and syndiotactic poly(methyl methacrylate) (st-PMMA) blends with crystalline stereocomplex formed by supercritical CO2 treatment at temperatures ranging from 35 to 130°C were investigated by means of d...

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Bibliographic Details
Published in:Polymer (Guilford) 2007-08, Vol.48 (17), p.5116-5124
Main Authors: Asai, Shigeo, Kawano, Takatsugu, Hirota, Shin-ichi, Tominaga, Yoichi, Sumita, Masao, Mizumoto, Tomohiro
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Poly(methyl methacrylate)
Polymer blend
Properties and characterization
Structure, morphology and analysis
Supercritical carbon dioxide
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Summary:The structure and properties of highly stereoregular isotactic poly(methyl methacrylate) (it-PMMA) and syndiotactic poly(methyl methacrylate) (st-PMMA) blends with crystalline stereocomplex formed by supercritical CO2 treatment at temperatures ranging from 35 to 130°C were investigated by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and dynamic mechanical analysis (DMA) measurements. The melting temperature, Tm, and the heat of fusion, ΔHm, had maximum values at about 200°C and 25J/g, respectively. The degree of crystallinity evaluated by WAXD ranged in value from 32 to 38%. The fringed-micellar stereocomplex crystallites were formed in case of treatment temperatures below 90°C, and the orderliness perpendicular to the helix axis of the fringed-micellar crystallites was considered to be increased with increasing treatment temperature. In case of treatment temperature of 130°C, the fringed-micellar crystallites and the lamellar crystallites with high orderliness parallel to the helix axis coupled with the perpendicular orderliness were formed, and the respective double endothermic peaks, Tm1 and Tm3, were observed in DSC due to the melting of the two kinds of stereocomplex crystallites. The it-PMMA/st-PMMA blends containing the fringed-micellar crystallites maintained high values of storage modulus, E′, up to higher temperature compared with the amorphous blends. The E′ of the blend treated with CO2 at 130°C decreased twice at temperatures corresponding to Tm1 and Tm3.
ISSN:0032-3861
1873-2291
DOI:10.1016/j.polymer.2007.06.065