Polymer-Polymer and Copolymer-Copolymer Miscibility in Blends: A Morphological Study

Abstract

ABSTRACT:Curves of instantaneous copolymer composition vs. fractional conversion have been calculated for the copolymerization of N-vinyl-2-pyrrolidone (VP) with n-butyl acrylate (BA). Low conversion samples ofpoly(VP-ca-BA) possessing minimal heterogeneity in composition, were blended in appropriate proportions so as to simulate the cumulative copolymer compositions produced at various levels of conversion in an actual copolymerization. The phase behavior of these blends has been examined by electron microscopy. The results show that the miscibility between the copolymers within each blend is limited and is a consequence of the compositional heterogeneity predicted from the calculated curves. A morphological study for a series of blends of the homopolymers PVP and PBA was also effected and is discussed. KEY WORDSScanning Electron Microscopy/ Poly(N-vinyl-2-pyrrolidoneco-n-butyl acrylate) / Copolymerization / Compositional Heterogeneity / Blends / Polymer Miscibility / Morphological studies of multiphase amorphous polymers by electron microscopy and often hindered by lack of contrast between the phases. Preferential-solvent etching techniques are usually employed to remove one phase selectively, and subsequently examine the topography of the blend. The authors are at present engaged in the study of polymer miscibility in blends during copolymerization for systems in which blending of polymers occurs simultaneously with their chemical formation, viz., the copolymerization of two monomers M 1 and M 2 to various levels of conversion.In previous publications 1 · 2 curves of instantaneous copolymer composition vs. fractional conversion C, were calculated for different initial feed mixtures contammg N-vinyl-2-pyrrolidone (VP) and n-butyl acrylate (BA) as monomers M 1 and M 2 , respec-* To whom correspondence should be addressed.tively. The values of the mole fraction/1 of VP in the feed were 0.821, 1 0.956, 1 and 0. 772 2 corresponding to 80, 95, 75 wt¾ VP in the feed, respectively. The values used for reactivity ratios r 1 and r 2 were 0.02 and 0.8, respectively.1·3·4 The compatibility within the blends of these systems assessed by light transmission, 1 glass transition behavior, 1 solution viscosity measurements, 2 and solubility parameters,2 was in reasonable accord with the compositional heterogeneity predicted from the calculated curves. The objective of the research presented herein is to explore the detailed morphology by electron microscopy and to gain a deeper insight into the phase behavior of the two systems comprising 80 and 95 wt¾ VP in the feed. These compositions are far from the azeotropic composition (/1 = 0.151 ), and hence, are selected here in order to provide reasonably wide ranges in the 435

The Resistance of Polyethersulfone Membranes on the Alkaline Cleaning Solutions

“…The similarity in the size of spherical particles and pores indicates that the pores were created by removing the particles. The formation of similar spherical particles was observed due to the agglomeration of PVP blended inside another polymer [30]. Most likely, during the production of PES membranes, some of the added PVP (hydrophilic) did not mix with PES (hydrophobic) and agglomerated into the observed spherical particles that were incorporated into the surface layer.…”

Phase separation in random copolymers from high conversion free radical copolymerization, 3

“…For many reasons it is expected that remarkable changes in physical properties depend on the phase separation within heterogeneous copolymers [2][3][4][5][6][7] . As long as no phase separation occurs, the deviations of physical properties depend on changes in molecular weight or copolymer composition.…”