In this study, we synthesized thermo-responsive and photo-cleavable amphiphilic block copolymers containing photodegradable linkers as junction points between hydrophilic and hydrophobic chains. We synthesized PNiPAAm-ONB-PXCL block copolymers by using a combination of ring-opening polymerization and nucleophilic substitution reactions using 5-hydroxy-2-nitrobenzyl alcohol as a difunctional photo-responsive initiator. These PNiPAAm-ONB-PXCL copolymers consisting of soft domains of amorphous PNiPAAm and PXCL exhibited amorphous T g . The polymer micelles exhibited dual responsiveness to heat and light. The lower critical solution temperature of PNiPAAm 20 -ONB-PMCL 49 was 39.3 C, which is approximately the temperature of tumor tissue. When we exposed the polymer solutions to ultraviolet (UV) irradiation, we observed major changes in the structure and morphology of the particles. Fluorescence emission measurements indicated the release of Nile red (NR), a hydrophobic dye, encapsulated by the PNiPAAm-ONB-PXCL micelles, in response to irradiation because of disruption of the micelles. Release of indomethacin (IMC) was rapid under UV irradiation at 42 C and approximately 90% of the encapsulate IMC was released in a sustained manner during the first 7 h. The nanoparticles were associated with nonsignificant toxicity at concentrations <100 mg mL À1 . Doxorubicin (DOX)-loaded micelles facilitated the uptake of DOX by HeLa cells within 30 min of treatment, and were predominantly retained in the cytoplasm. The DOX-loaded micelles were associated with low cytotoxicity against HeLa cells. Scheme 1 Synthesis of the thermo-and photo-responsive PNiPAAm-ONB-PXCL. 500 | RSC Adv., 2015, 5, 497-512 This journal is View Article Online process, (B) the plot of maximum fluorescence intensity vs. temperature, from which the critical micellization temperature (CMT) was determined, and (C) various of size as a function of solution temperature for PNiPAAm 20 -ONB-PMCL 49 micelles.This journal is

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Amphiphilic diblock copolymers with various block compositions were synthesized on poly(2‐ethyl‐2‐oxazoline) (PEtOz) as a hydrophilic block and poly(4‐methyl‐ε‐caprolactone) (PMCL) or poly(4‐phenyl‐ε‐caprolactone) (PBCL) as a hydrophobic block. These PEtOz‐b‐PMCL and PEtOz‐b‐PBCL copolymers consisting of soft domains of amorphous PEtOz and PM(B)CL had no melting endothermal peaks but displayed Tg. The lower critical solution temperature (LCST) values for the PEtOz‐b‐PMCL, and the PEtOz‐b‐PBCL aqueous solution were observed to shift to lower temperature than PEtOz homopolymers. Their aqueous solutions were characterized using fluorescence techniques and dynamic light scattering (DLS). The block copolymers formed micelles with critical micelle concentrations (CMCs) in the range 0.6–11.1 mg L−1 in an aqueous phase. As the length of the hydrophobic PMCL or PBCL blocks elongated, lower CMC values were generated. The mean diameters of the micelles were between 127 and 318 nm, with PDI in the range of 0.06–0.21, suggesting nearly monodisperse size distributions. The drug entrapment efficiency and drug‐loading content of micelles depend on block polymer compositions. In vitro cell viability assay showed that PEtOz‐b‐PMCL has low cytotoxicity. Doxorubicin hydrochloride (DOX)‐loaded micelles facilitated human cervical cancer (HeLa) cell uptake of DOX; uptake was completed within 2 h, and DOX was able to reach intracellular compartments and enter the nuclei by endocytosis. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2769–2781

Triple stimuli-responsive polymers PNiPAAm-S-S-PXCL containing a disulfide (–S–S–) bond as a junction point between hydrophilic and hydrophobic chains were synthesized and characterized.