Pore Memory of Macroporous Styrene–Divinylbenzene Copolymers EROL ERBAY, 1,2 OG ˘ UZ OKAY 1,3 1 Kocaeli University, Department of Chemistry, 41300 Izmit, Kocaeli, Turkey 2 PETKIM Petrochemicals Holding Inc., Research Center, P.O. Box 9, 41740 Korfez, Kocaeli, Turkey 3 TUBITAK Marmara Research Center, Department of Chemistry, P.O. Box 21, 41470 Gebze, Kocaeli, Turkey Received 20 January 1998; accepted 18 April 1998 ABSTRACT: The variation of the pore structure of styrene– divinylbenzene (S–DVB) copolymer beads with the drying conditions was investigated. Macroporous S–DVB copolymer beads with various DVB contents were prepared in the presence of toluene- cyclohexanol mixtures as a diluent. It was found that the pores of 10 1 -nm radius, corresponding to the interstices between the microspheres, collapse upon drying of the copolymers from toluene. The collapsed pores reexpand if the copolymers were dried from methanol. The collapse–reexpansion process of the pores was found to be revers- ible, indicating that the actual pore structure formed during the crosslinking copoly- merization is memorized by the copolymer network. The magnitude of the pore struc- ture variation increased on worsening the polymer– diluent interactions during the gel formation process due to the simultaneous increase in crosslink density distribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1055–1062, 1999 Key words: macroporous styrene– divinylbenzene copolymers; pore structure; pore memory; pore structure variation; crosslink density distribution INTRODUCTION Macroporous (heterogeneous) styrene– divinyl- benzene (S–DVB) copolymer networks are widely used as starting materials for ion exchangers and as specific sorbents; therefore, they have been the subject of a large number of studies. 1–5 These materials are mainly prepared by free-radical crosslinking copolymerization of S and DVB monomers in the presence of an inert diluent. The diluent (a solvent, a nonsolvent, or a linear poly- mer) is included in the reaction system as a pore forming agent and plays an important role in the design of the pore structure of these crosslinked materials. 2 If the diluent remains in the gel throughout the copolymerization, an expanded network structure is obtained. The expanded networks thus formed shrink during the removal of the diluent after their synthesis and therefore they are nonporous in the glassy state. Heterogeneities in the net- work structure appear if the diluent separates out of the gel phase during the polymerization reac- tions. 2,6 –10 The incipient phase separation during the crosslinking copolymerization may occur be- fore the onset of macrogelation; this results in the formation of a polymer dispersion in the liquid Correspondence to: O. Okay, Istanbul Technical Univer- sity, Department of Chemistry, 80626 Maslak, Istanbul, Tur- key. (oguz@mam.gov.tr). Contract grant sponsor: TUBITAK; contract grant number: TBAG-1561. Journal of Applied Polymer Science, Vol. 71, 1055–1062 (1999) © 1999 John Wiley & Sons, Inc. CCC 0021-8995/99/071055-08 1055