Inhomogeneities Induced by Crosslinking in the Course of Crosslinking Copolymerization
Heterogeneous gels are formed as a result of phase separation during copolymerization of 2-hydroxyethyl methacrylate with ethylene dimethacrylate and styrene with divinylbenzene in the presence of various diluents. Phase separation is induced by an increase of the degree of crosslinking and possible change of the polymer-diluent interaction and takes the form of macrosyneresis (deswelling) or microsyneresis (formation of a dispersion). Microsyneresis, if not followed by crosslinking, is a non-equilibrium form of phase separation, occurs in gels of low degrees of crosslinking, and is determined by slow relaxation of such gels. If crosslinking continues, the dispersion becomes fixed and permanent and phase equilibrium is approached again. In the course of crosslinking copolymerization, usually dispersions are formed and phase separation occurs at low polymerization conversions: the theory of equilibrium macrosyneresis can satisfactorily describe the onset of phase separation as well as the phase volume ratio and volume degree of swelling of heterogeneous gels after copolymerization. In homogeneous gels, dilution leads to an increase of the volume degree of swelling, but beyond the separation limit, it decreases with increasing concentration of the diluent.
KeywordsNetwork Chain Primary Chain Phase Volume Ratio Initial Volume Fraction Crosslinking Copolymerization
Unable to display preview. Download preview PDF.
- 3.K. A. Kun and R. Kunin, J. Polymer Sci., 6, 2689 (1968).Google Scholar
- 4.K. Duek, J. Polymer Sci., Pt.C, 16, 1289 (1967).Google Scholar
- 8.R. Chasset and P. Thirion, Proc. Internat. Conf. Non Cryst. Solids, North-Holland Publ. Co, Amsterdam 1965, p. 345.Google Scholar
- 9.M. Ilayskÿ and W. Prins, Macromolecules, in press.Google Scholar