Graft copolymers having hydrophobic backbone and hydrophilic branches. XVI. Polystyrene microspheres with poly(N-isopropylacrylamide) branches on their surfaces: Size control factors and thermosensitive behavior

Thermosensitive monodisperse particles were prepared with diameters of 0.3- 1.8 mu m, and which consisted of polystyrene core and poly(N-isopropylacryl amide) branches on their surfaces by the free radical copolymerization of p olyNIPAAm macromonomers and styrene in ethanol or ethanol/water mixtures. T he styrene monomer concentration [St], steric stabilizer (polyNIPAAm macrom onomer) concentration [S], initiator concentration [I], polymerization temp erature and the percentage of water in the reaction medium affected the fin al microsphere size. The microsphere size in diameter (D-n) follows the rel ationship Dn proportional to[St](0.75) [S](-0.76) [I](-0.13). The dynamic s ize of microspheres decreased with increasing temperature in the dispersion solution. The effects of Lyophilization and external temperature on the mo rphology of microspheres were analysed by means of transmission electron mi crograph (TEM). The exterior environment did not seem to affect their morph ology. (C) 1999 John Wiley & Sons, Ltd.