Comparison of Calorimetric and Dielectric Single Component Glass Transitions in PtBS−PI Blends

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• 作者：S. Arrese-Igor ; A. Alegra ; J. Colmenero
• 刊名：Macromolecules
• 出版年：2010
• 出版时间：August 10, 2010
• 年：2010
• 卷：43
• 期：15
• 页码：6406-6413
• 全文大小：936K
• 年卷期：v.43,no.15(August 10, 2010)
• ISSN：1520-5835

文摘

Miscible blends of polyisoprene (PI) and poly(tert-butylstyrene) (PtBS) have been studied over the entire composition range by means of differential scanning calorimetry (DSC) and dielectric spectroscopy (DS) techniques. Blends with two different molecular weight PtBS, M_n = 1300 and M_n = 2300, and a M_n = 2700 PI have been investigated. The molecular weight of all the polymers were chosen in order to be well bellow the entanglement limit for PI. Calorimetric measurements confirm the presence of two component glass transitions (T_g) as previously reported. The comparison of the component’s T_g observed by DSC and the segmental dynamics directly measured for PI by DS, evidence the equivalence between the calorimetric effective T_g and the freezing of the segmental relaxation of PI around 10²s observed by DS. Fitting of the experimental T_g values to the Lodge−McLeish model gives self-concentration values that depend on the molecular weight of the PtBS. Finally, blends with the lowest PI content exhibit unusual behavior which is discussed in the framework of nonequilibrium effects.