126 research outputs found
Polymerization induced self-assembly : tuning of morphology using ionic strength and pH
Investigations of RAFT dispersion polymerization-induced self-assembly (PISA) of 2-hydroxypropyl methacrylate (HPMA) in water/methanol at 60 °C using a cationically charged macroRAFT agent as the stabilizer block, namely P(N,N-diethylaminoethyl methacrylate)-stat-poly((ethylene glycol) methyl ether methacrylate) (PDEAEMA-stat-PEGMA), have been conducted with a view to tune particle morphologies by manipulation of the pH and the ionic strength. Above the LCST (45 °C) of (PDEAEMA-stat-PEGMA), the system can only be conducted as a dispersion polymerization at sufficiently low pH such that the stabilizer block is sufficiently protonated to ensure solubility in the continuous phase. It is demonstrated (reported in the form of an extensive morphology diagram) that a range of morphologies including spherical particles, rods and vesicles can be accessed by adjustment of the pH (via addition of HCl) and the ionic strength (via the concentration of NaCl). A decrease in the charge density of the coronal stabilizer layer via an increase in the pH (less protonation) shifts the system towards higher order morphologies. At a given pH, an increase in ionic strength leads to more extensive charge screening, thus allowing formation of higher order morphologies
Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems
Polymerization induced self-assembly: tuning of morphology using ionic strength and pH
Sequence-controlled methacrylic multiblock copolymers via sulfur-free RAFT emulsion polymerization
Rate constants of substantial initiation in free-radical polymerization: A new method for determination of conversion dependences
Compartmentalization in Atom Transfer Radical Polymerization to High Conversion in Dispersed Systems: Effects of Diffusion-Controlled Reactions
Retardation in RAFT Polymerization: Does Cross-Termination Occur with Short Radicals Only?
The recently proposed model by Perrier and co-workers [J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 3455] to account for retardation effects in dithiobenzoate-mediated reversible addition fragmentation chain transfer (RAFT) polymerization of styrene has been tested experimentally. According to this model, retardation is caused by cross-termination of very short radicals only. Polymerizations were conducted employing a macroazoinitiator and a polymeric RAFT agent based on cumyl dithiobenzoate, thereby effectively eliminating all short radicals from the system. The results show, in basic agreement with the model, that there is very little, if any, retardation in dithiobenzoate-mediated RAFT polymerization of styrene in the absence of short radicals
Nitroxide-Mediated Radical Polymerization of Styrene in Aqueous Microemulsion: Initiator Efficiency, Compartmentalization, and Nitroxide Phase Transfer
Polymerization-induced self-assembly under compressed CO2 : control of morphology using a CO2 -responsive MacroRAFT agent
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