Poly(divinylbenzene-alt-maleic anhydride) Microgels:  Intermediates to Microspheres and Macrogels in Cross-Linking Copolymerization

Abstract

Three distinct copolymer morphologies were observed during the cross-linking copolymerization of divinylbenzene-55 and maleic anhydride at low monomer concentrations in methyl ethyl ketone/heptane mixtures: microspheres, microgels, and macrogels. These morphologies depended primarily upon solvent composition and changed from microspheres and microgels to macrogels with increasing methyl ethyl ketone volume fractions. The effects of solvent composition and cross-linker concentration on the observed morphologies were investigated using electron microscopy, viscosity, and light scattering experiments. Microgels were found to be precursors to both macrogels and microspheres, and mechanisms for the formation of each morphology are proposed.

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“…Therefore, the particle growth mechanism in ILRPP should be considerably different from that of the traditional precipitation polymerization. Although the particle growth in the traditional precipitation polymerization system occurs mainly by an entropic precipitation mechanism where soluble oligomer radical species are continuously captured from the solution by their reacting with the pendant vinyl groups on the surfaces of the existing particles,9, 11, 12, 17 the polymer particles in the ILRPP system mainly grow by directly capturing monomers (including both divinyl crosslinkers and monovinyl functional monomers) from the reaction solution through the surface‐initiated controlled polymerization process. Therefore, if we use the grafting concept described in the introduction part and define the particle growth mechanism in the traditional precipitation polymerization as a “grafting to” mechanism, a “grafting from” growth mechanism should mainly work in ILRPP, just as reported for the ATRPP system 47.…”

“…Among various methods presently available for obtaining such polymer microspheres, precipitation polymerization has received particular attention because of its easy operation and no need for any surfactant or stabilizer 7–24. Several different kinds of precipitation polymerization approaches based on the conventional free radical polymerization mechanism have been developed for the preparation of uniform highly crosslinked spherical polymer particles, such as thermo‐induced precipitation polymerization,7–12, 14–17, 21, 22, 24 photo‐induced precipitation polymerization,19, 20, 23 and distillation precipitation polymerization 13, 18. Many narrow or monodisperse highly crosslinked polymer microspheres based on different monovinyl monomers and divinyl crosslinkers have been prepared by these approaches, where functional polymer microspheres are particularly interesting because they are highly promising in many advanced application areas 5…”

Synthesis of well‐defined hairy polymer microspheres by precipitation polymerization and surface‐initiated atom transfer radical polymerization

“…These polymer particles are generally synthesized by some traditional polymerization techniques such as emulsion polymerization, precipitation polymerization, dispersion polymerization, and suspension polymerization . Among these techniques, precipitation polymerization has been paid great attention because of its easy experimental setup and no need for any surfactants or stabilizers . Even though the combination of monomer and solvent is quite limited and the yield of resulting polymer particle is moderate, precipitation polymerization can afford narrowly dispersed spherical polymer microspheres.…”

“…Stöver and coworkers have established precipitation polymerization of divinylbenzene (DVB) as a precise synthetic method for preparing narrowly disperse poly(DVB) microspheres using DVB loading below 5 vol % in acetonitrile, or mixtures of acetonitrile and toluene, by free radical polymerization using AIBN as an initiator. They found that the particles increase in size by a reactive growth mechanism in which oligomeric radicals are captured from solution by reaction with surface double bonds on existing particles.…”

Structured poly(divinylbenzene-co -chloromethylstyrene) microspheres by thermal imprinting precipitation polymerization

“…Originally developed for homopolymerization of divinylbenzene‐55 (DVB55), and subsequently for copolymerization of chloromethylstyrene, maleic anhydride, or methacrylic monomers with DVB55 or ethylenedimethacrylate (EDMA) in acetonitrile and methylethylketone (MEK)/Heptane mixtures, the method has since been expanded to include, i.e., photoinitiation, distillation‐precipitation polymerization, and controlled radical polymerization . Bai et al showed that covalent crosslinking can be replaced by hydrogen‐bonding between acrylic acid units, allowing the formation of polyacrylic acid microspheres, and acetic acid can be used as solvent instead of acetonitrile .…”