Reactive multiacrylic copolymers prepared by suspension polymerization

A review with 46 references covering reactive copolymers prepared by suspension polymerization of multiacrylic monomers containing ester groupings, with the number of vinyl groups higher than 2, viz., trimethylolpropane tri(meth)acrylate (TMPMA and TMPA) and pentaerithritol tri- and tetra-acrylates (PENTA and TTPA) (Fig. 1). The resulting products are endowed with the porous or expanded gel structure depending on the type of crosslinker, multiacrylic comonomers, and the amount and type of inert diluents used in the copolymerization process. The former group includes TMPMA copolymers and homopolymers; they are considerably porous and rich in 2-nm pores as a result of internal cyclization. When swollen in a poor solvent, the TMPA is more porous than the TMPMA homopolymer, but the pores collapse during the modification step. TMPA copolymers with butyl acrylate (BA), and PENTA homo- and co-polymers, have exhibited a similar behavior. Semicrystalline acrylonitrile (AN)-rich TMPA/AN copolymers were macroporous and could be easily modified. Most porous were TTPA co- and home-polymers. Owing to their reactive oxirane ring, copolymers of TMPA and TMPMA with glycidyl methacrylate (GMA) are useful precursors of carriers for bioactive substances. The modification intended to introduce functional groups, involving additional vinyl acetate (VA) mers, resulted in more-porous copolymers. TMPMA-crosslinked copolymers were mechanically (compression strength) more stable than divinylbenzene-crosslinked copolymers. TMPMA homo- and co-polymers can be used as sorbents, microspheres, and fillers in chromatography, and after having been chemically modified, as bioactive substance carriers, ion immobilizers and catalysts. Selected homo- and co-polymers of multiacrylic monomers were characterized (composition, water uptake, porosity, and average pore radius, cf. Table 1). Pore size distributions are presented for selected copolymers (Figs. 2-5, 7, 9, 10). Water uptake by several solvents (Fig. 6) and partition coefficients for several alcohols in these copolymers are given. When surface-treated and aminolyzed, homo- and co-polymers of TMPA and PENTA endowed with an expanded gel structure can be used respectively as carriers and as hydrogels with high water uptake imparted to (up to 60 g water/g copolymer).