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Mixed arm star copolymers of poly(N,N-dimethylacrylamide) (PDMA) and poly(N-isopropylacrylamide) (PNIPAm) were synthesized by a sequential reversible addition−fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) from a multi-initiator-functionalized hyperbranched polyglycerol (MI-HPG) core. The MI-HPG core was synthesized from an amine-functionalized polyglycerol, modified successively with 2-chloropropionamide groups (ATRP initiator) and 4,4′-azobis(4-cyanovaleric acid) (azo initiator). N,N-Dimethylacrylamide was polymerized from MI-HPG core by the RAFT method using S,S′-bis(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate as a chain transfer agent (CTA) in acetic acid/sodium acetate aqueous buffer solutions. The ratio of [CTA]/[azo initiator] was critical in controlling the molecular weight of the PDMA grafts from MI-HPG core (HPG-g-PDMA). Controlled synthesis of mixed arm star copolymers was achieved by cografting PNIPAm on to the HPG-g-PDMA macroinitiator by ATRP. The temperature-induced phase transition of aqueous solutions of hybrid HPG-g-PDMA/PNIPAm star copolymers was studied by 1H NMR, UV−vis spectroscopy, and laser light scattering. Results show that the mixed arm star copolymers exist as either single molecules or small aggregates below the phase transition temperature (LCST) of PNIPAm in aqueous solutions. All the star copolymers formed intermolecular aggregates above the LCST of PNIPAm possibly due to the hydrophobic interaction between collapsed PNIPAM chains. These aggregates have micelle-like structure with PNIPAm core and PDMA corona. The formation of intermolecular aggregates and the stabilization of aggregates depend on the molecular weight of arms and composition of the star copolymer.

The homogeneous controlled/"living" free radical polymerization of glycidyl methacrylate (GMA) by atom transfer radical polymerization (ATRP) using Cu(I)X/N-alkyl-2-pyridylmethanimine complexes with various initiators R-X (X ) Cl, Br) and solvents was investigated. Most of these systems display characteristics of a living radical polymerization as indicated by (a) linear first-order kinetic plots of ln[M] 0/[M] vs time, (b) an increase in the number-average molecular weight (Mn) vs conversion, and (c) relatively narrow polydispersities indicating a constant number of propagating species throughout the polymerization with negligible contribution of termination or transfer reactions. The dependence of the rate of polymerization on the concentrations of initiator, ligand, and temperature is presented. We observed comparable rates of polymerization linear increase of molecular weight with conversion and low polydispersities in polar solvents. No polymerization was observed in nonpolar solvents such as toluene and xylene at room temperature. The order of controlled polymerization with different initiator system is CuBr/BPN > CuCl/BPN > CuBr/ClPN, and the polymerization did not proceed with CuCl/ClPN initiator system at room temperature. The high functionality of bromine end groups present in the polymer chains was confirmed by ESI MS analysis. The thermal stability of PGMA prepared by the CuBr/PPMI/BPN initiation system is higher than by the other three systems, indicating the high regioselectivity and the virtual absence of termination reactions in the former case. The ligand alkyl chain length from R ) propyl to octyl did not affect the rate of polymerization. The molecular weight (M n) increases linearly with conversion, and these polymers showed narrow polydispersities.

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Electrospinning of polymer scaffolds is mostly carried out using organic solvents, but the drawbacks are: solvent costs, environmental hazards, and presence of traces of solvent impurities. The use of water‐soluble polymers (WSPs), water or aqueous solutions as an electrospinning medium (green processing) is a very attractive method to avoid such issues. However, a few WSP such as polyelectrolytes are not spinnable as such, but have been electrospun by addition of WSPs, additives, and salts. This paper covers solution properties, polyelectrolyte nanofibrous scaffolds (polysaccharides, biopolymers, etc.), fabrication through green processing, and their regenerative medical applications such as wound dressing, drug delivery, and tissue engineering. This is the first review to cover the above issues, the drawbacks of current methods, and future challenges.

Cover: The fabrication of polyelectrolyte nanofibrous scaffolds from aqueous polymer solutions through a simple and versatile green electrospinning process is presented. The generation of different architectures under various spinning conditions and the application of polyelectrolyte scaffolds from polysaccharides and biopolymers for skin, cartilage, heart, and bone applications are reviewed. Further details can be found in the article by R. Krishnan, S. Sundarrajan,* and S. Ramakrishna* http://doi.wiley.com/10.1002/mame.201200323.