The amphiphilic block copolymer poly(ethylene
oxide)-b-poly(N,N′-dihydroxypyromellitimide-hexamethylene diisocyanate)
(PEO-b-PNH) with photocleavable N?O urethanes has
been prepared to investigate the photodegradation of the hydrophobic
main chain and therefore the disruption of copolymer
micelles. Measurements of absorption and emission spectra, optical
transmittance, DLS analysis, and TEM observations were applied. It
was shown that PEO-b-PNH could self-assemble into flower
compound micelles in water. The photodegradation of the
hydrophobic polyurethane within the micellar core upon irradiation
with 365 nm light could be conveniently controlled by changing the irradiation intensity; furthermore, complete micellar
disruption could be achieved when 42% of N?O urethanes were photocleaved. By using DOX as the hydrophobic guest, the
drug release profile showed a linear leakage of DOX out of the swelling polymer micelles in the initial stage and thereafter a much
more quick exponential decay of DOX precipitation because of the micellar disruption upon further irradiation. The diffusion
experiment of the leaked DOX into buffer solution (pH 7.4) showed that the DOX leakage could be prominently accelerated by
a very short time of 365 nm irradiation, indicating that the N?O photocleavage can serve as a “turn-on” switch for the release of
DOX in aqueous media.
