New polymer synthesis by nitroxide mediated living radical polymerizations.

Metal-catalyzed living radical polymerization.

Controlled/living radical polymerization: Features, developments, and perspectives

Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates.

Current status and future perspectives in atom transfer radical polymerization (ATRP) are presented. Special emphasis is placed on mechanistic understanding of ATRP, recent synthetic and process development, and new controlled polymer architectures enabled by ATRP. New hybrid materials based on organic/inorganic systems and natural/synthetic polymers are presented. Some current and forthcoming applications are described.

Atom Transfer Radical Polymerization (ATRP): Current Status and Future Perspectives

Polystyrene and poly(styrene-co-butadiene) with narrow polydispersity (1.19-1.36) could be obtained by free radical polymerization in solution, bulk or suspension in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy using benzoyl peroxide as initiator

Narrow molecular weight resins by a free-radical polymerization process

Isodimorphism in bacterial poly(β-hydroxybutyrate-co-β-hydroxyvalerate)

ESR was used to follow the time-dependent concentration of stable TEMPO nitroxide radical in situ to understand the formation of narrow polydispersity, high molecular weight resins by a modified free radical polymerization process. This process involves the reversible termination of growing free radical chains by the TEMPO radicals. The first step is shown to involve a bimolecular reaction of nitroxide radical and benzoyl peroxide (BPO) initiator. This bimolecular reaction, which leads to peroxide radicals, is a rate-promoted decomposition having an activation energy of 40±5 KJ/mol in toluene, compared to 125 kJ/mol for the thermal decomposition of BPO to its radicals. Computer simulations were used to numerically solve the reaction kinetics

Free radical polymerizations for narrow polydispersity resins: electron spin resonance studies of the kinetics and mechanism

It is shown that the rate of polymerization of nitrixide-mediated stable free radical polymerization processes for styrene-based polymers and copolymers can be dramatically increased by the addition of camphorsulphonic acid (CSA). Very narrow polydispersity resins are obtained with CSA concentrations of 0.02 M or less, while larger amounts of CSA result in slight increases in polydispersity

Narrow Polydispersity Polystyrene by a Free-Radical Polymerization Process-Rate Enhancement

This work focuses on the mechanism of the pseudoliving free radical bulk polymerization of styrene, which produces narrow polydispersity resin, using nitroxide radicals to reversibly terminate the growing polymer chain. The polymerization kinetics and the rate of breaking of the nitroxide to polymer NO-C bond were studied. The polymerization gives an increase in molecular weight that is linear with conversion to high conversion, gives polydispersities that are narrow (<1.3) and relatively insensitive to conversion, and shows first-order kinetics in monomer concentration. Calculations demonstrate that the kinetics of polymerization greatly reduce the termination of the polymerization by the reaction of two growing chains, which is the predominant mechanism in conventional free radical polymerization. It is concluded that this nitroxide-mediated free radical polymerization is a living polymerization. To study the stability of the NO-C bond, model compounds, comprising a styrene unit terminated at either end with a benzoyloxy moiety and a nitroxide moiety, were prepared and characterized. These compounds were heated in situ in the ESR cavity to generate nitroxide radicals. Radical concentrations were followed as a function of time and temperature, and an activation energy for cleavage of the NO-C bond was calculated. A proposed mechanism fits the available kinetic data well, and measured activation energies for nitroxide compounds correlate with rates of polymerization.

Richard P. N. Veregin

Papers

Narrow molecular weight resins by a free-radical polymerization process

Isodimorphism in bacterial poly(β-hydroxybutyrate-co-β-hydroxyvalerate)

Free radical polymerizations for narrow polydispersity resins: electron spin resonance studies of the kinetics and mechanism

Narrow Polydispersity Polystyrene by a Free-Radical Polymerization Process-Rate Enhancement

Mechanism of Living Free Radical Polymerizations with Narrow Polydispersity: Electron Spin Resonance and Kinetic Studies