Poly backbiting

RAFT end groups are known to be unstable at very high temperatures (>200 °C). Thermal elimination has been used as a means of trithiocarbonate end group removal. For ps430,4W direct elimination is observed (Scheme 9.54). For poly(butyl acrylate)464 the major product suggests a hoinolysis/backbiting/ i-scission reaction is involved (Scheme 9.55). 

Short branching has also been verified in poly(vinyl acetate), poly(vinyl chloride), and various polyacrylates. Branching in poly(vinyl acetate) and polyacrylates involve the intramolecular backbiting mechanism as in polyethylene [Adelman and Ferguson, 1975 Heatley... 

Poly(bisphenol-A-carbonate) under pseudoideal reaction conditions was investigated, and the cyclic polycarbonate was obtained as the main product. In the system, the interface of the water/toluene mixture might have favored the cyclization reaction between the polar end groups [88]. Cyclic carbonates during the (Salen)CrCl catalyzed CCh/cyclohexene oxide copolymerization process in the presence of ionic initiators was also obtained [89]. The cyclic carbonate is produced via the backbiting mechanism, and the process is assumed to take place via a metal alkoxide (polymer chain) intermediate. Subsequent ring-opening of the cyclic carbonate with concomitant formation of polyether and CO2 was fast at the reaction temperatures from 80 to 100 °C). 

From the analyses of NMR and electron-spray ionization mass (ESI-MS) spectroscopy, the polymers obtained from the polymerization of cyclic disulfides were found to be a cyclic structure [202], The cyclic structure consisting of poly(DT) is assumed to be formed by a backbiting reaction of propagating species [203]. Thermal and mechanical properties of the polymers, and decomposition behaviors of the polymers demonstrate that the polymers obtained from thermal polymerization of cyclic disulfides include a polycatenane structure. From polymerization of cyclic disulfides in the presence of cyclic polyethylene oxide), a polycatenane consisting of two different cyclic polymers was obtained [199]. Thus, poly(DT) contains spatial entanglements of cyclic polymers with each other (a polycatenane structure was presumed) (Fig. 61). 

Poly(M-allyl-alkylenimine)s (PAAIs) can be obtained by direct CROP of A/ -allylaziridines and AT-allylazetidines, but these monomers lack sufficient stabilization for polymerization by anionic polymerization. The CROP of such monomers can give rise to linear PAAIs with tertiary amines in their backbone, albeit often suffering from backbiting reactions leading to quaternary ammonium branching points, as first reported by Jones et al. (Scheme 2.11). °... 

The thermal degradation mechanisms of poly(styrene-co-methacrylonitrile) (P(S-co-MAN)) is reported in terms of the competition between the depolymerisation and backbiting reaction on the basis of the bond dissociation energies of the C-C and C-H bonds in the polymer chains [a.l88j. The activation energy of pyrolysis obtained by Ozawa s plot increased with the content of methacrylonitrile units in the copolymer chain, although the onset temperatures of loss of sample mass in the TG curves shifted to the lower temperature region. Yields of each monomer, dimer and trimer, and also those of hybrid dimers and... 

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