Ximing Song

Synthesis and self-assembly of new amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) block copolymers via the combination of ring-opening polymerization and click chemistry

New amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by click reaction with alkynyl-terminated poly(N-vinylcaprolactam) (PNVCL-Cu2009≡u2009CH) and azido-terminated poly(ε-caprolactone) (N3-PCL). The structures of the polymers were determined by proton nuclear magnetic resonance spectroscopy (1H NMR) and gel permeation chromatography (GPC) measurements. The fluorescence technique was used to determine the critical micelle concentrations (CMC) of copolymer solutions. The factors affecting the lower critical solution temperature (LCST) of the copolymers were studied by UV-visible analysis. The diameters and distribution of the micelles were characterized by dynamic light scattering (DLS), and their shapes were observed by transmission electron microscopy (TEM). The results showed that these copolymers could self-assemble into nano-micelles in water. The CMC values of the copolymer solutions and the sizes of micelles reduced with increasing proportion of hydrophobic parts. TEM images demonstrated that the micelles are all spherical. On the other hand, the UV–visible measurements showed that these block copolymers exhibit a reproducible temperature-responsive behavior with a LCST that is tunable by block composition.

Synthesis and self-assembly of a new amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) block copolymer

New amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by ring-opening polymerization of ε-caprolactone with hydroxy-terminated poly(N-vinylcaprolactam) (PNVCL-OH) as a macroinitiator. The structures of the polymers were confirmed by IR, 1H NMR and GPC. The critical micelle concentrations of copolymer in aqueous solution measured by the fluorescence probe technique reduced with the increasing of the proportion of hydrophobic parts, so did the diameter and distribution of the micelles determined by dynamic light scattering. The shape observed by transmission electron microscopy (TEM) demonstrated that the micelles are spherical. On the other hand, the UV–vis measurement showed that polymers exhibit a reproducible temperature-responsive behavior with a lower critical solution temperature (LCST). The LCST of PNVCL-OH can be adjusted by controlling the molecular weights, and that of copolymers can be adjusted by controlling the compositions and the concentration. Variable temperature TEM measurements demonstrated that LCST transition was the result of transition of individual micelles to larger aggregates.

Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex

A new cyclometalated iridium(III) complex Ir(DPP)3 (DPP = 2,3-diphenylpyrazine) was prepared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, 1H NMR, and mass spectroscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respectively. The complex also shows strong photoluminescence at 573 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.

Synthesis and self-assembly of thermoresponsive amphiphilic biodegradable polypeptide/poly(ethyl ethylene phosphate) block copolymers.

We report the design and synthesis of new fully biodegradable thermoresponsive amphiphilic poly(γ-benzyl L-glutamate)/poly(ethyl ethylene phosphate) (PBLG-b-PEEP) block copolymers by ring-opening polymerization of N-carboxy-γ-benzyl L-glutamate anhydride (BLG-NCA) with amine-terminated poly(ethyl ethylene phosphate) (H2N-PEEP) as a macroinitiator. The fluorescence technique demonstrated that the block copolymers could form micelles composed of a hydrophobic core and a hydrophilic shell in aqueous solution. The morphology of the micelles as determined by transmission electron microscopy (TEM) was spherical. The size and critical micelle concentration (CMC) values of the micelles showed a decreasing trend as the PBLG segment increased. However, UV/Vis measurements showed that these block copolymers exhibited a reproducible temperature-responsive behavior with a lower critical solution temperature (LCST) that could be tuned by the block composition and the concentration.