Methyl methacrylate Reversible chain

Fijten MWM, Meier MAR, Hoogenboom R, Schubert US (2004) Automated parallel inves-tigations/optimizations of the reversible addition-fragmentation chain transfer polymerization of methyl methacrylate. J Polym Sci Part A Polym Chem 42 5775-5783... 

It is not possible to predict which mechanism is involved in a certain copolymerization. In the system a-methylstyrene-methyl methacrylate depolymerization of sequences of two monomer units seemed to occur as well as depolymerization of a-methylstyrene from longer sequences. In the system a-methylstyrene -acrylonitrile the sequence of two monomer units of a-methylstyrene is stable and does not depolymerize. The reversibility of the polymerizations of a-methylstyrene and methyl methacrylate can be explained by sterically induced strain in the polymer chain (13). In the copolymer a-methylstyrene-methyl methacrylate this strain involves the whole polymer chain whereas in the a-methylstyrene— acrylonitrile system the strain is broken by the acrylonitrile sequences and is built up again in the a-methylstyrene. This explains the difference in the depolymerization tendencies of sequences of two units of a-methylstyrene and longer sequences in this system. 

Linear Polymers Long chains are necessary to confer the mechanical properties of fibers, plastics, and elastomers that make polymers so valuable. Fibers such as cellulose and polyester arc semicrystalline materials in which the same chemical stmeture exists in both rigid microcrystalline and flexible amorphous phases. Plastics may be either semicrystalline, such as poly(ethylene terephthalate) (the same polyester of fibers is also the PET of beverage bottles), or completely amorphous and glassy, such as polystyrene or poly(methyl methacrylate) (PMMA, Plexiglas or Lucite ). Elastomers are completely amorphous and flexible and would flow as a viscous mbbery liquid except that the polymer chains are cross-hnked to prevent macroscopic flow but allow reversible stretching. As an example, poly(dimethylsiloxane)... 

In CCT a metalloradical reversibly abstracts H from the chain-carrying radical and starts a new chain. Early work on CCT during radical polymerizations employed cobalt porphyrins during the polymerization of methyl methacrylate, and was carried out in the USSR (Smirnov, Marchenko in 1975 Enikolopyan in 1977). Gridnev discovered in Moscow in 1979 that cobaloximes were effective CCT catalysts, then moved to the US in 1992 (Wayland laboratory. University of Pennsylvania) and joined DuPont in 1994. The basic features of CCT have been described in a series of patents (at first Russian, then largely DuPont) that appeared in the 1980s [71], and in a comprehensive review that appeared in 2001 [72]. The mechanism in Scheme 1.8 has become generally accepted, and CCT has been successfully applied to other monomers (styrene, methacrylonitrile) and comonomers. 

Segmented terpolymers of poly(alkyl methacrylate)-g-poly(D-lactide)/poly(dimethylsiloxane) (PLA/PDMS) were prepared by combination of a grafting through technique (macromonomer method) and controlled/living radical polymerization such as atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer polymerization. In a single-step approach, the low molecular weight methacrylate monomer (methyl methacrylate... 

FIGURE 10.2 MALDI TOP mass spectra obtained from the automated spotting of the synthesized poly(methyl methacrylate) polymers at different reaction times. The insert (right top) shows the peak molecular weight (M ) (obtained from MALDI TOFMS spectra) as function of the reaction time. Matrix DCTB. This material is reproduced with permission of John Wiley Sons, Inc. from Fijten MWM, Meier MAR, Hoogenboom R, Schubert US. Automated parallel investigations/optimizations of the reversible addition-fragmentation chain transfer polymerization of methyl methacrylate. J Polym Sci A Polym Chem 2004 42 5775-5783. 

Barner-Kowollik C, Quinn FJ, Nguyen TLU, Heuts JPA, Davis TP. Kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate. Macromolecules 2001 34 7849-7857. 

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