Preparation of Nanocapsules Formed Temperature-Responsive Block Polymers Containing PEG.

Novel graft block polymers, Poly(SMA-g-PEG)-b-PNIPAM and PEG-b-PSMA-b-PNIPAM, that possess PEG chains, and temperature and pH-sensitive segments, were synthesized by living radical polymerization for the reaction of novel functionalized nanocapsules for medical applications. PSMA and PNIPAM were used as pH-sensitive segment and temperature-sensitive segment, respectively. Light scattering, optical transmittance and NMR measurements evaluated temperature dependence of nanocapsule formation in the aqueous polymer solutions. Raising the temperature above 35°C, the intensity of light scattering abruptly increased, but no turbidity was observed even above the lower critical solution temperature (LCST) of the PNIPAM segments. These results indicate the formation of a nano-scale self-assembled structure of the polymers by phase separation of the PNIPAM segments. Furthermore, the preparation of nanocapsules by crosslinking of the PSMA segment was carried out by the addition of multivalent metal ions. It was also confirmed that tri-block polymer kept a similar diameter even after freeze-drying and showed high redispersibility in water. These nanoparticles are promising for biomedical applications such as drug delivery. [ABSTRACT FROM AUTHOR]