Monodisperse Styrene-Maleic Anhydride-Isoprene Terpolymer Microspheres with Tunable Crosslinking Density Prepared by Self-Stabilized Precipitation Polymerization

Synthesis and industrial production of functional monodisperse microspheres still face enormous challenges like precise size control and process simplification. Herein, a strategy to prepare monodisperse styrene-maleic anhydride-isoprene terpolymer microspheres via self-stabilized precipitation polymerization was reported. The prepared microspheres with different isoprene proportions have uniform particle sizes (623-1156 nm) and narrow size distributions. The structure analysis showed that the copolymerization proceeded in an alternating way between the electron donor (styrene and isoprene) and electron acceptor (maleic anhydride) monomer, and isoprene was incorporated into the polymer chain through 1, 4 addition. The gel fraction of microspheres varies from 0 to 99% along with an increasing isoprene feeding ratio. The Diels-Alder (D-A) reaction between maleic anhydride and isoprene can be effectively inhibited by increasing the amount of initiator or decreasing the polymerization temperature. The resultant uniform microspheres contain reactive anhydride groups and unsaturated C=C bonds derived from isoprene, which can be used to covalently attach functional moieties and have great potential in fields of adsorption and separation, drug delivery, biodetection, and enzyme immobilization.

Automated summary

This study reports a strategy to prepare monodisperse styrene-maleic anhydride-isoprene terpolymer microspheres via self-stabilized precipitation polymerization. The prepared microspheres have uniform particle sizes and narrow size distributions. The copolymerization proceeds in an alternating way between the electron donor and electron acceptor monomers, and isoprene is incorporated into the polymer chain through 1,4 addition. The gel fraction of microspheres varies with the feeding ratio of isoprene. The Diels-Alder reaction between maleic anhydride and isoprene can be effectively inhibited by adjusting the amount of initiator or polymerization temperature.