3.10 - Nitroxide-Mediated Polymerization

Controlled/Living Radical Polymerization

The nitroxide-mediated copolymerization of 2-hydroxypropyl acrylate (HPA) with N-acryloylmorpholine (Amor) or N,N-dimethylacrylamide (DMA) was investigated using N-tert-butyl-N-(1′-diethylphosphono-2,2′-dimethylpropyl)-O-(2-carboxyl-prop-2-yl) (BlocBuilder) alkoxyamine initiator and additional free nitroxide (SG-1). Different reaction conditions, such as the concentration of additional SG-1, were tested to optimize the homopolymerizations using a Chemspeed ASW2000 automated parallel synthesizer. Best control for the homopolymerizations (polydispersity indices of 1.2−1.3) of all three monomers was achieved using 20% additional SG-1 (relative to the initiator) at a reaction temperature of 110 °C for 2 M solutions in N,N-dimethylformamide and a monomer/initiator ratio of 100/1. Libraries of P(Amor-stat-HPA) and P(DMA-stat-HPA) were synthesized with 0−100 mol % HPA with 10 mol % increments using the optimized conditions obtained for the homopolymerizations. The resulting polymers had narrow molecular weight d...

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Libraries of Statistical Hydroxypropyl Acrylate Containing Copolymers with LCST Properties Prepared by NMP

Controlled nitroxide‐mediated and reversible addition–fragmentation chain transfer polymerization of N‐vinylpyrrolidone: Synthesis of block copolymers with styrene and 2‐vinylpyridine

Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of an epoxide-containing monomer, glycidyl methacrylate (GMA), was successfully carried out using low concentration of catalyst (ca. 105 ppm) at 60 °C in anisole. The copper complex of tris(2-pyridylmethyl)amine was used as the catalyst, diethyl 2-bromo-2-methylmalonate as the initiator, and 2,2′-azobisisobutyronitrile as the reducing agent. When moderate degrees of polymerization were targeted (up to 200), special purification of the monomer, other than removal of the polymerization inhibitor, was not required to achieve good control. To synthesize well-defined polymers with higher degrees of polymerization (600), it was essential to use very pure monomer, and polymers of molecular weights exceeding 50,000 g mol−1 and Mw/Mn = 1.10 were prepared. The developed procedures were used to chain-extend bromine-terminated poly(methyl methacrylate) macroinitiator prepared by activators regenerated by electron transfer (ARGET) ATRP. The SnII-mediated ARGET ATRP technique was not suitable for the polymerization of GMA and resulted in polymers with multimodal molecular weight distributions. This was due to the occurrence of epoxide ring-opening reactions, catalyzed by SnII and SnIV. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Atom transfer radical polymerization of functional monomers employing Cu‐based catalysts at low concentration: Polymerization of glycidyl methacrylate

Persistent nitroxides and their corresponding alkoxyamines are important regulators of living radical polymerization. Here we describe the synthesis of β-phosphorus nitroxides bearing a β-hydrogen, that present very interesting properties for the control of the radical polymerization of styrenes, acrylates and other monomers. A large series of alkoxyamines derived from these nitroxides was prepared, and Electron Spin Resonance (ESR) was used to determine both the temperature (Tc) and the rate constant (kd) for their homolysis. For the whole series of alkoxyamines (27 compounds), a very good linear correlation was found between Tc and logkd. Satisfactory linear correlations were found between Tc and calculated (PM3 method) Bond Dissociation Energy (BDE) of the NO-C bond, for series of alkoxyamines with the same type of leaving radical. The characteristics of free radical polymerization of styrene carried out in the presence of these new nitroxides and alkoxyamines will be discussed.

Florence Chauvin

Papers

Design and use ofβ-phosphorus nitroxides and alkoxyamines in controlled/“living” free radical polymerizations