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Novel thermo‐responsive poly(N‐isopropylacrylamide)‐block‐poly(l‐lactide)‐block‐poly(N‐isopropylacylamide) (PNIPAAm‐b‐PLLA‐b‐PNIPAAm) triblock copolymers were successfully prepared by atom transfer radical polymerization of NIPAAm with Br‐PLLA‐Br macroinitiator, using a CuCl/tris(2‐dimethylaminoethyl) amine (Me6TREN) complex as catalyst at 25 °C in a N,N‐dimethylformamide/water mixture. The molecular weight of the copolymers ranges from 18,000 to 38,000 g mol−1, and the dispersity from 1.10 to 1.28. Micelles are formed by self‐assembly of copolymers in aqueous medium at room temperature, as evidenced by 1H NMR, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The critical micelle concentration determined by fluorescence spectroscopy ranges from 0.0077 to 0.016 mg mL−1. 1H NMR analysis in selective solvents confirmed the core‐shell structure of micelles. The copolymers exhibit a lower critical solution temperature (LCST) between 32.1 and 32.8 °C. The micelles are spherical in shape with a mean diameter between 31.4 and 83.3 nm, as determined by TEM and DLS. When the temperature is raised above the LCST, micelle size increases at high copolymer concentrations due to aggregation. In contrast, at low copolymer concentrations, decrease of micelle size is observed due to collapse of PNIPAAm chains. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3274–3283

Intelligent polymeric micelles have been developed as potential nanoplatforms for efficient drug delivery and diagnosis. Herein, we successfully prepared redox-sensitive polymeric micelles combined aggregation-induced emission (AIE) imaging as an outstanding anticancer drug carrier system for simultaneous chemotherapy and bioimaging. The amphiphilic copolymer TPE-SS-PLAsp- b-PMPC could self-assemble into spherical micelles, and these biomimetic micelles exhibited great biocompatibility and remarkable ability in antiprotein adsorption, showing great potential for biomedical application. Anticancer drug doxorubicin (DOX) could be encapsulated during the self-assembly process, and these drug-loaded micelles showed intelligent drug release and improved antitumor efficacy due to the quick disassembly in response to high levels of glutathione (GSH) in the environment. Moreover, the intracellular DOX release could be traced through the fluorescent imaging of these AIE micelles. As expected, the in vivo antitumor study exhibited that these DOX-carried micelles showed better antitumor efficacy and less adverse effects than that of free DOX. These results strongly indicated that this smart biomimetic micelle system would be a prominent candidate for chemotherapy and bioimaging.

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Thermo-responsive P(NIPAAm-co-DMAAm)-b-PLLA-b-P(NIPAAm-co-DMAAm) triblock copolymers are synthesized via combination of ring-opening polymerization and atom transfer radical polymerization.

A series of copolymers have been synthesized by the ring-opening polymerization of glycolide, L-lactide, and e-caprolactone with zirconium(IV) acetylacetonate [Zr(Acac) 4 ] or stannous octoate [Sn(Oct) 2 ] as the catalyst. The resulting terpolymers have been characterized by analytical techniques such as proton nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry. Data have confirmed that Sn(Oct) 2 leads to less transesterification of polymer chains than Zr(Acac) 4 under similar conditions. The various copolymers have been compressionmolded and allowed to degrade in a pH 7.4 phosphate buffer at 378C. The results show that the degradation rate depends not only on the copolymer composition but also on the chain microstructure, the Sn(Oct) 2 -initiated copolymers degrading less rapidly than Zr(Acac) 4 -initiated ones with more random chain structures. The caproyl component appears the most resistant to degradation as its content increases in almost all cases. Moreover, caproyl units exhibit a protecting effect on neighboring lactyl or glycolyl units. The glycolyl content exhibits different features: it decreases because of faster degradation of glycolyl units, which are more hydrophilic than caproyl and lactyl ones, remains stable in the case of abundant CÀ ÀGÀ ÀC sequences, which are very resistant to degradation, or even increases because of the formation of polyglycolide crystallites. Terpolymers can crystallize during degradation if the block length of one of the components is sufficiently long, even though they are amorphous initially.

A series of biodegradable chitosan-graft-polylactide (CS-g-PLA) copolymers were prepared by grafting of poly(L-lactide) (PLLA) or poly(D-lactide) (PDLA) precursor to the backbone of chitosan using N,N -carbonyldiimidazole as coupling agent. The composition of the copolymers was varied by adjusting the chain length of PLA as well as the ratio of chitosan to PLA. The copolymers synthesized via this 'graft-onto' method present interesting properties as shown by NMR and infrared spectroscopy, gel permeation chromatography and solubility tests. Hydrogels were prepared by mixing water-soluble CS-g-PLLA and CSg-PDLA solutions. Gelation was assigned to stereocomplexation between PLLA and PDLA blocks as evidenced by differential scanning calorimetry and wide-angle X-ray diffraction measurements. Thymopentin (TP5) was taken as a model drug to evaluate the potential of these CS-g-PLA hydrogels as drug carriers. An initial burst and a final release up to 82% of TP5 were observed from high-performance liquid chromatography analysis.