No abstract

Photoinduced ATRP was successfully performed in aqueous media. Polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) in the presence of CuBr2 catalyst and tris(2-pyridylmethyl)amine ligand when irradiated with visible light of 392 nm wavelength at 0.9 mW/cm(2) intensity was well controlled. Linear semi-logarithmic kinetic plots and molecular weights increasing with conversion were observed. Polymers of OEOMA were synthesized with low dispersity (Mw/Mn = 1.12) using only 22 ppm of copper catalyst in the presence of excess bromide anions in highly diluted (90% v/v) aqueous media. The effects of copper concentration, salt, and targeted degrees of polymerization were investigated. The polymerization could be directly regulated by external stimulation, i.e., switching the irradiation on/off, with a good retention of chain-end functionality, as proved by clean chain extension of the OEOMA polymers. This new system could enable applications for controlled aqueous radical polymerization due to its low catalyst loading in the absence of any other chemicals.

A robust mechanically controlled atom transfer radical polymerization (mechano-ATRP) was developed by enhancing the interaction between piezoelectric nanoparticles and ATRP Cu catalysts. The interactions favor a mechano-induced electron transfer from the surface of the nanoparticles to the deactivator CuII/L complex under ultrasonic agitation, promoting the formation of the activator CuI/L complex, thereby increasing the rate of the polymerization. This mechano-ATRP was carried out with a low loading of zinc oxide nanoparticles, providing a polymer with high end-group fidelity, predetermined molecular weight, and low dispersity. Propagation of the polymer chains was switched on/off in response to the ultrasound. The effects of the nature of the nanoparticle, nanoparticle loading, and targeted degrees of polymerization were investigated to evaluate the mechanism of mechano-ATRP.

Polymerization-induced self-assembly (PISA) was achieved by conducting an initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) at low ppm of copper catalyst concentration. A poly(oligo(ethylene oxide) methyl ether methacrylate) 50 (POEOMA 50 ) macroinitiator and stabilizer was synthesized by an aqueous ICAR ATRP using Cu II Cl 2 /tris(pyridin-2-ylmethyl)amine (TPMA) complex. Subsequently, the dispersion polymerization of benzyl methacrylate (BnMA) in ethanol was realized with a Cu II Br 2 /TPMA complex either at room temperature or at 65 °C using V-70 or AIBN as radical initiators, respectively. The effect of catalyst concentration, radical initiators, targeted degree of polymerization (DP) of PBnMA, solids content, and temperature on the molecular characteristics and self-assembly behavior of block copolymers POEOMA−PBnMA was evaluated by gel permeation chromatography (GPC), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Block copolymers assembled into spheres, wormlike aggregates, and vesicles with diameters ranging from 100 to 600 nm, depending on the temperature, solids content, and the DP of PBnMA. The effect of the temperature on the polymerization behavior and morphological evolution was attributed to the temperature-dependent plasticization of the core-forming PBnMA block above and below its glass transition temperature (T g = 54 °C).

A new procedure for ultrasonication-induced atom transfer radical polymerization (sono-ATRP) in aqueous media was developed. Polymerizations of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) and 2-hydroxyethyl acrylate (HEA) in water were successfully carried out in the presence of ppm amounts of CuBr 2 catalyst and tris(2pyridylmethyl)amine ligand when exposed to ultrasonication (40 kHz, 110 W) at room temperature. Aqueous sono-ATRP enabled polymerization of watersoluble monomers with excellent control over the molecular weight, dispersity, and high retention of chain-end functionality. Temporal control over the polymer chain growth was demonstrated by switching the ultrasound on/off due to the regeneration of activators by hydroxyl radicals formed by ultrasonication. The synthesis of a well-defined block copolymer and DNA− polymer biohybrid was also successful using this process.