Reversible addition-fragmentation chain transfer copolymerization

FOU Fourttier, D., Hoogenboom, R., Thijs, H.M.L., Paulus, R.M., and Schubert, U.S., Tunable pH- and temperature-sensitive copolymer libraries by reversible addition-fragmentation chain transfer copolymerizations of methacrylates. Macromolecules, 40, 915, 2007. 

The free radical polymerization of pinenes and limonene is of little interest, because of the modest yields and DPs obtained with their homopolymerizations. However, their copolymerization with a variety of conventional monomers has been shown to produce some interesting materials, particularly in the case of controlled reversible addition fragmentation chain-transfer (RAFT) systems involving P-pinene and acrylic comonomers [5]. 

The kinetics of the free radical emulsion polymerization of a-meth-ylene-y-valerolactone has been investigated (58). Stable polymer latices could be prepared. A homogeneous nucleation is the dominant path for particle formation. Also, the miniemulsion copolymerization with styrene as comonomer has been investigated. Both the reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization and the RAFT bulk polymerization are weU controlled and copolymers with a narrow polydispersity are formed. 

There have been reports in which j3-pinene was copolymerized by a radical copolymerization, reversible addition-fragmentation chain transfer (RAFT). As comonomers, methyl acrylate or n-butyl acrylate have been used (9,10). 

Wang Y., Li A.L., Liang LL., Lu J., Reversible addition-fragmentation chain transfer radical copolymerization of beta-pinene and methyl acrylate, Eur. Polym. J., 42(10), 2006, 2695-2702. 

Brouwer, H. De, Schellekens, M. A. Klumperman, B., Monteiro, M. J., and German, A. L. 2000. Controlled radical copolymerization of styrene and maleic anhydride and the synthesis of novel polyolefin-based block copolymers by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Journal of Polymer Science, Part A Polymer Chemistry 38 3596-3603. 

Quantum chemistry thus provides an invaluable tool for studying the mechanism and kinetics of free-radical polymerization, and should be seen as an important complement to experimental procedures. Already quantum chemical studies have made major contributions to our understanding of free-radical copolymerization kinetics, where they have provided direct evidence for the importance of penultimate imit effects (1,2). They have also helped in our understanding of substituent and chain-length effects on the frequency factors of propagation and transfer reactions (2-5). More recently, quantum chemical calculations have been used to provide an insight into the kinetics of the reversible addition fragmentation chain transfer (RAFT) polymerization process (6,7). For a more detailed introduction to quantum chemistry, the interested reader is referred to several excellent textbooks (8-16). 

Figure 16 Microwave-assisted reversible addition-fragmentation chain-transfer homopolymerization of DMA or NIPAM and subsequent block copolymerization with NIPAM, DMA, butyl acrylate, or methyl acrylate.

In a recent study, Tasdelen et al. synthesized a phenacyl morpholine-4-dithiocarbamate, which can act as both a photoiniferter and reversible addition fragmentation chain transfer (RAFT) agent. Polymerization of styrene was carried out in bulk under UV irradiation at above 300 nm at room temperature. The polymerization showed living characteristics up to 50% conversions and produced well-defined polymers with molecular weights close to those predicted from theory and relatively narrow poyldispersities (Mw/Mn 1.30). End group determination and block copolymerization... 

---