Monodisperse thermosensitive particles prepared by emulsifier-free emulsion polymerization with microwave irradiation

摘要

The emulsifier-free emulsion polymerization of styrene (St) and N-isopropylacrylamide (NIP-AAm) was successfully carried out with microwave irradiation,and the monodisperse thermoresponsive poly(styrene-co-N-isopropylacryla-mide) (poly(St-co-NIPAAm)) particles with diameters in the range 100-130 nm were prepared.The morphology,size and size distribution of the poly(St-co-NIPAAm) particles were characterized by transmission electron microscopy,scanning electron microscopy (SEM) and photon correlation spectroscopy (PCS),respectively.The results showed that poly(St-co-NIPAAm) particles had spherical morphology,and the poly(St-co-NIPAAm) particles prepared by emulsifier-free emulsion polymerization with microwave irradiation were smaller,more uniform than those obtained with conventional heating.The hydrodynamic diameters of poly(St-co-NIPAAm) particles were decreased as the temperature increased from 25degC to 40degC,and poly(St-co-NIPAAm) particles collapsed remarkably at 32degC,which is the lower critical solution temperature of the poly(N-isopropylacrylamide).The morphology of the assembled poly(St-co-NIPAAm) particles was observed by SEM,it was found that monodisperse poly(St-co-NIPAAm) particles could assemble to form the two-dimensional order structures.