Dependence of the glass transition temperature of poly (methyl methacrylates) on their tacticity |
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Authors: | J. Biroš T. Larina J. Trekoval J. Pouchlý |
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Affiliation: | (1) Present address: Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences, Prague, Czechoslovakia;(2) Present address: Institute of Elementoorganic Compounds, Academy of Sciences of USSR, Moscow, USSR |
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Abstract: | The specific isobaric heat capacities of poly (methylmethacrylates) (PMMA) having various tacticities were measured by the DSC method within a broad range of temperatures including the glass transition. Glasses with uniform thermal history were used in the measurements and the data were treated by employing a procedure which provided the thermodynamic Tg independent of the experimental conditions. The semiquantitative validity of Boyer's empirical relationTg×cp=const. was confirmed; also it was found that within the limits of experimental accuracy the cp,g values at 298 K andCp,l values at 400 K are independent of the tacticity of the sample.Using the data thus measured and linearized equations representing the dependence ofTg on the content of iso-, syndio- and heterotriads, the Tg values of pure isotactic PMMA and pure syndiotactic PMMA were found to be respectively 315 K and 397 K.Dedicated to Professor Dr. F. H. Müller. |
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Keywords: | Glass transition temperature stereoregular poly (methyl methacrylates) heat capacity measurements |
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