Miscibility of the crystalline and amorphous polymer blends

Abstract

First, the influence of tacticity of poly(methyl methacrylate) (PMMA) on the morphology and crystallization of poly(ethylene oxide) (PEO) in the binary polymer blends was reported. The main objective of this research is to obtain more information for the influence of tacticity of amorphous PMMA on the miscibility with crystalline PEO. To observe the morphology and the spherulite growth-rates (G) of PEO blends with isotactic, or atactic, or syndiotactic PMMA (i-, or a-, or s-PMMA), an optical polarizing microscopy was used. The overall morphology of the blends strongly depends on the composition and tacticity of PMMA. PEO morphology is most perturbed by s-PMMA. Under isothermal conditions, growth of the spherulite of the blends containing low contents of PMMA``s follows a characteristic pattern regardless of the tacticity of PMMA. It appears that the G values decrease by increasing the proportion of PMMA``s in all cases. However, the influence of tacticity on the growth rates of spherulite is remarkable. It is clear that the smallest G values of PEO is always found in the blends with s-PMMA at the same composition and crystallization temperature. This indicates that PEO is most miscible with s-PMMA, thus the crystallization of PEO is most hindered by sPMMA. Next, kinetics of the crystallization of PEO from the PEO blends with i, or a-, or s-PMMA was investigated. The isothermal spherulite growth rates were measured at different crystallization temperatures. The growth rates of spherulites are markedly reduced by a-PMMA and s-PMMA. However the growth rates of PEO are hardly influenced by i-PMMA. such observations are qualitatively analyzed by the modified Turnbell-Fisher equation. From the above experimental results and theoretical analysis, it was concluded that PEO forms miscible blends with a- and s-PMMA in molten states, whereas it does not form with i-PMMA. Later, the miscibility enhancements of polymer blends through the introduction of hydrogen bonding int...