Fabrication, formation mechanism, and thermal degradation process of AM/AMPS/NVP terpolymeric microspheres with different microstructures

Terpolymeric AM/AMPS/NVP microspheres were fabricated using inverse suspension polymerization. Microstructure modulation of the microspheres was controlled by the initial amount of crosslinker. To further reveal the formation mechanism and optimize the design of terpolymeric microspheres, the formation and thermal degradation processes of the terpolymeric microspheres with different microstructures were systematically investigated. The crosslink ratios had no effect on the morphology of microsphere precursors at 22 °C but assumed an enormous effect on the microstructure of the microspheres when the temperature was increased from 22 to 70 °C. The primary nanoparticles (approximately 60−100 nm) transformed into larger ones (approximately 200 nm-2 μm) by capturing monomers in the monomer droplet and then formed many spheres composed of amoeba-like particles assembled by the minimization of interfacial energy. Finally, the spheres gelatinized to form the microspheres, which developed different microstructures as the crosslink ratios increased. Study of the degradation process of terpolymeric microspheres with different crosslink ratios provides evidence for the formation mechanism of terpolymeric microspheres.