Poly(N,N-diethylacrylamide) microspheres by dispersion polymerization

Graphical Abstract

SEM of poly(N,N-diethylacrylamide) microspheres crosslinked with 10 wt % of N,N′-methylenebisacrylamide. The microspheres were obtained by aqueous dispersion polymerization. Their size was controlled in the range 30–300 nm. Depending on the degree of crosslinking, a lower critical solution temperature behavior has been observed between 25 and 30 °C with a phase transition changing over a broader temperature range.

Abstract

Poly(N,N-diethylacrylamide)-based microspheres were prepared by ammonium persulfate (APS)-initiated and poly(vinylpyrrolidone) (PVP)-stabilized dispersion polymerization. The effects of various polymerization parameters, including concentration of N,N′-methylenebisacrylamide (MBAAm) crosslinker, monomer, initiator, stabilizer and polymerization temperature on their properties were elucidated. The hydrogel microspheres were described in terms of their size and size distribution and morphological and temperature-induced swelling properties. While scanning electron microscopy was used to characterize the morphology of the microspheres, the temperature sensitivity of the microspheres was demonstrated by dynamic light scattering. The hydrodynamic particle diameter decreased sharply as the temperature reached a critical temperature ∼ 30 °C. A decrease in the particle size was observed with increasing concentration of both the APS initiator and the PVP stabilizer. The microspheres crosslinked with 2–15 wt % of MBAAm had a fairly narrow size distribution. It was found that the higher the content of the crosslinking agent, the lower the swelling ratio. High concentration of the crosslinker gave unstable dispersions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6263–6271, 2008