Poly(vinyl laurate) (PVL) and poly(vinyl stearate) (PVS) were synthesized by means of cobalt‐mediated radical polymerization (CMRP). Cobalt(II) diacetylacetonate (Co(acac)2) was demonstrated to control the radical polymerization of these monomers in solution. Molecular weights up to 15,000 g·mol−1 were obtained with reasonably low polydispersity indices (PDI < 1.3). The efficiency of the redox initiator [lauroyle peroxide (LPO)/citric acid (CA)] was found to be low (around 10%) as already reported for vinyl acetate. The solvent and temperature were found to have a very weak influence on the initiator efficiency. It appeared that CA played no role in the initiation process that only involved a redox reaction between LPO and Co(acac)2. PVL‐b‐PVS diblock copolymers could be synthesized using two strategies: (1) Sequential addition, that is, addition of the second monomer (VS) at high conversion of the first one (VL). (2) Macroinitiator technique, that is, isolation of a PVL macroinitiator then polymerization of VS from this cobalt functionalized macroinitiator. Both techniques allowed the synthesis of diblock copolymers with molar masses around 25,000 g·mol−1 and PDI lower than 1.4. The resulting materials were characterized by DSC, revealing that both blocks exhibit side‐chain crystallinity and phase segregate in the bulk. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Triple hydrophilic asymmetric poly(2-hydroxyethyl acrylate)-b-poly(ethylene oxide)-b-poly(2-hydroxyethyl acrylate) (PHEA-b-PEO-b-PHEA) triblock copolymers are obtained by copper(0) catalyzed reversible deactivation radical polymerization (RDRP). Copper wire catalyzed polymerization of HEA from large PEO ( M n = 35 000 g mol −1 ) macroinitiator in dimethylsulfoxide or in water fails to reach high monomer conversion in a controlled manner contrary to what is previously published with a shorter PEO macroinitiator. Catalysis by nascent Cu(0) particles generated by disproportionating CuBr in water allows rapid polymerization and high monomer conversion with a rather good control of both dispersity and HEA block length. Model disproportionation experiment shows that HEA infl uences the disproportionation/ comproportionation equilibrium. Larger quantities of HEA lead to higher apparent rate constants and less disproportionation of CuBr which is in agreement with the supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) mechanism and not with the single electron transfer-living radical polymerization (SET-LRP) mechanism.to synthesize amphiphilic diblock [ 2 ] (AB) or triblock [ 3 ] (BAB) copolymers bearing cross-linkable moieties on the hydrophobic B-blocks. These block copolymers self-assembled in aqueous solution and formed star-like [ 2,4,5 ] or fl owerlike [ 3,6 ] polymeric micelles that could be rendered permanent by in situ photo-cross-linking.Reversible deactivation radical polymerization (RDRP) techniques have been shown to allow synthesis of PHEA in a controlled manner, both in the bulk and in solution. PHEA homopolymers are readily synthesized by nitroxide mediated polymerization (NMP), [ 7 ] reversible addition fragmentation chain transfer (RAFT), [ 8,9 ] atom transfer radical polymerization (ATRP), [ 10 ] and RDRP catalyzed by copper(0) associated to copper halides [ 11,12 ] (usually called
Aqueous solutions of multiarm flower-like poly(ethylene oxide) (PEO) were formed and connected to various degrees by self-assembly. The structure was rendered permanent by in situ UV-irradiation. Dense suspensions of these single and connected soft colloids were studied by static and dynamic light scattering and viscosity measurements. The concentration dependence of the osmotic compressibility, the dynamic correlation length, and the viscosity of single flowers was shown to be close to that of equivalent PEO star-like polymers demonstrating that the effect of forming loops on the interaction is small. It was found that the osmotic compressibility and the dynamic correlation length of dense suspensions are not influenced by the bridging. However, when flower polymers are connected into clusters, motion in dense suspensions needs to be collective over larger length scales. This causes a much stronger increase of the viscosity for dense suspensions of interpenetrated clusters compared to single-flower polymers.
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