Telechelic polymers by living and controlled/living polymerization methods

Telechelic polymers, defined as macromolecules that contain two reactive end groups, are used as cross-linkers, chain extenders, and important building blocks for various macromolecular structures, including block and graft copolymers, star, hyperbranched or dendritic polymers. This review article describes the general techniques for the preparation of telechelic polymers by living and controlled/living polymerization methods; namely atom transfer radical polymerization, nitroxide mediated radical polymerization, reversible addition-fragmentation chain transfer polymerization, iniferters, iodine transfer polymerization, cobalt mediated radical polymerization, organotellurium-, organostibine-, organobismuthine-mediated living radical polymerization, living anionic polymerization, living cationic polymerization, and ring opening metathesis polymerization. The efficient click reactions for the synthesis of telechelic polymers are also presented.     

Polymer vectors via controlled/living radical polymerization for gene delivery

The design of efficient gene delivery vectors is a challenging task in gene therapy. Recent progress in living/controlled radical polymerizations (LRPs), in particular atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization providing a means for the design and synthesis of new polymeric gene vectors with well-defined compositions, architectures and functionalities is reviewed here. Polymeric gene vectors with different architectures, including homopolymers, block copolymers, graft copolymers, and star-shaped polymers, are conveniently prepared via ATRP and RAFT polymerization. The corresponding synthesis strategies are described in detail. The recent research activities indicate that ATRP and RAFT polymerization have become essential tools for the design and synthesis of advanced, noble and novel gene carriers.     

Self-assembly of thermo-responsive poly(oligo(ethylene glycol) methyl ether methacrylate)-C60 in water-methanol mixtures

Well-defined statistical copolymer of poly (di(ethylene glycol) methyl ether methacrylate-stat-oligo(ethylene glycol) methyl ether methacrylate-C₆₀ ((PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀) was synthesized via atom transfer radical polymerization (ATRP) reaction and atom transfer radical addition (ATRA) processes. The lower critical solution temperature (LCST) of PMEO₂MA-stat-POEGMA₃₀₀ increased from 42 to 95 °C when the amounts of methanol was increased from 0 to 30 vol%, beyond which the LCST could not be quantified. Similarly, the LCST of (PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀ also increased with methanol content, however it was lower than PMEO₂MA-stat-POEGMA₃₀₀ for all methanol/water compositions. The CMC of (PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀ increased with increasing methanol content, suggesting that methanol is a better solvent for PMEO₂MA-stat-POEGMA₃₀₀ segment. The amphiphilic (PMEO₂MA-stat-POEGMA₃₀₀)-C₆₀ structure formed spherical micelles in water/methanol mixture, and larger micelles were formed at higher methanol content. The hydrodynamic radius (R_h) remained constant at temperature below the LCST. It increased dramatically at temperature greater than the LCST, and the (R_g/R_h) increased from ∼0.75 to ∼1.0. We believe that the (PMEO₂MA-stat-POEGMA₃₀₀) coronas dehydrate at higher temperature, and the micelles associate to form larger aggregates. In water/methanol mixtures, core-shell micelles and large compound micelles are produced below and above the LCST respectively.