The structure of “living” poly(n-butyl acrylate) homopolymers prepared via nitroxide-mediated controlled radical polymerization in bulk and in miniemulsion at 112 °C was examined by SEC, NMR, and MALDI−TOF mass spectrometry in order to study the influence of chain transfer to polymer. The absence of detectable terminal unsaturation was confirmed by proton NMR. The branched structure was observed by 13C NMR. MALDI−TOF MS demonstrated that the majority of chains, even at high conversion, had the ideal structure with one initiator fragment and one nitroxide end group. From these results, we concluded that intramolecular chain transfer occurred (presumably by backbiting) and was the predominant mechanism throughout the polymerization at 112 °C.

Controlled free-radical polymerization of styrene was performed in aqueous dispersed medium using a degenerative transfer process with iodine atom exchange. The transfer agent was the commercially available perfluorohexyl iodide. Its efficiency was shown to be low in conventional batch emulsion polymerization since polymer had molar mass higher than expected. This was explained by a slow rate of diffusion of the perfluorinated transfer agent through the water phase, from the monomer droplets to the active latex particles. This problem was overcome by using a batch miniemulsion process. In that case, 100% efficiency of the chain transfer agent was reached, and the experimental molar masses fit well with the theoretical ones. With that technique, the transfer agent could be directly located in the polymer particles without transportation. Moreover, when using a continuous addition of monomer, a linear increase of the number-average molar mass with conversion was observed.

Nitroxide-mediated controlled free-radical polymerization of styrene was studied in a miniemulsion system. The use of an acyclic β-phosphonylated nitroxide enabled polymerization to be performed at a temperature below 100 °C, typically 90 °C. A bicomponent initiating system was chosen, i.e., a radical initiator in conjunction with added free nitroxide. This work focused on the mechanistic understanding of the polymerization. The parameters that affect both the kinetics of polymerization and the control of the molar mass and molar mass distribution have been examined and discussed, such as the nature and concentration of the pH buffer, the initiator concentration, the monomer/water ratio, and the process for chain extension.

Controlled free‐radical homopolymerization of n‐butyl acrylate and its copolymerization with styrene have been studied in aqueous miniemulsion, using an acyclic β‐phosphonylated nitroxide as a mediator, the N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, also called SG1. Polymerization kinetics have been studied and characterization of the (co)polymers has been performed, demonstrating the successful synthesis of well‐defined poly(n‐butyl acrylate) homopolymers and poly(n‐butyl acrylate‐co‐styrene) gradient copolymers.

The performance of different redox initiator couples to initiate the emulsion polymerization of butyl acrylate at low temperature (40–50 °C) was investigated in both batch and seeded semibatch polymerizations. Polymerizations were carried out mimicking industrial conditions, that is, technical grade monomer and no N2 purging was used during the polymerizations. The redox systems used contained as oxidants persulfates or hydroperoxides and as reducing agents ascorbic acid, formaldehyde sulfoxilate (SFS), tetramethyl ethylene diamine (TMEDA), Bruggolit 6 and 7 (FF6 and FF7), and sodium metabisulfites. Batch experiments showed that for systems using persulfates, the ammonium persulfate (APS)/TMEDA system provided the lower induction period and higher conversion, whereas for the systems with hydroperoxide oxidants, tert‐butyl hydroperoxide (TBHP)/FF7, TBHP/SFS, and H2O2/FF7 were the best alternatives. When these selected systems were used in seeded semibatch experiments of BA with allyl methacrylate, it was found that to obtain similar kinetics and microstructure (gel content and crosslinking density) than in case of using a thermal initiator at 80 °C, the polymerization could be run at 40 °C if the reactor was purged with N2. Alternatively, in absence of N2 polymerization, temperature should be increased to 50 °C and initiator concentration increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2917–2927, 2009