Poly main-chain radical

The only radical intermediate observed for poly methacrylic acid was the propagating radical formed by main chain scission. This observation is similar to that noted for gamma radiolysis of poly methylmethacrylate, where the propagating radical is also found as the only stable radical intermediate following radiolysis at 303 K. In both cases the propagating radical is formed by -scission following the loss of the side chain, resulting in formation of the unstable tertiary radical. 

Figure 6. Relationship between yields of low molar mass nitrogen-containing products resulting from elimination of a section of the main chain and hydrogen abstraction radical from the irradiation of poly(amino acid)s at 25° C. (A) tyr, (A) phe, ( ) gly, (O) ala, ) val.

Washino K, Denk O, Schnabel W (1983) OH-radical-induced main-chain scission of poly(ribonucleic acids) under anoxic conditions. Z Naturforsch 38c 100-106 Washino K, Katsikas L, Schnabel W (1984) Radiation-induced strand breakage in poly(riboadenylic acid). A pulse radiolysis study on the protective action of cysteamine under anoxic conditions. IntJRadiat Biol 46 747-758... 

Main-chain poly(styrene rotaxane)s <1997MM337, 1999PLM1823> were obtained by free radical polymerization of styrene in the presence of crown ethers using initiators incorporating bulky blocking groups to prevent dethreading of the macrocyclic components. 

The majority of packaging plastic materials consists of polyolefins and vinyl polymers, namely polyethylene (PE), polypropylene (PP), polystyrene (PS) and poly(vinyl chloride) (PVC). Obviously, these polymers have many other applications not only as packaging materials. Chemically they are all composed of saturated hydrocarbon chains of macro-molecular size their typical thermal decomposition pathway is free radical one initiated by the homolytic scission of a backbone carbon-carbon bond. In spite of the basic similarity of the initial cleavage, the decomposition of the hydrocarbon macroradicals is strongly influenced by fhe nafure of the side groups of the main chain. 

Division of the side groups from the main chain occurs only in those vinyl polymers in which the bonding of the substituent to the chain is weaker than the backbone C-C bond. The radical of the cleaved substituent draws hydrogen from the neighbouring carbon atom and is eliminated, for example as acetic acid from poly(vinyl acetate), or as hydrogen chloride from PVC. 

A multistep reaction pathway leads to polymers 43 and 44 with phosphatidylcholine moieties in the main chain and long alkyl groups in the side chain [122]. These polymers exhibit thermotropic liquid-crystalline behavior. Polyamides 45 were obtained by interfacial polycondensation they are insoluble in any normal solvent [123]. Poly-MPC capped with cholesteryl moieties at one or both polymer ends was prepared by the radical polymerization of MFC initiated with 4,4 -azobis[(3-cholesteryl)-4-cyanopentanoate] in the presence of a chain transfer agent [124]. The self-organization of these polymers was analyzed with fluorescence and NMR measurements. 

Lemaire DGE, Bothe E, Schulte-Frohlinde D. (1984) Yields of radiation-induced main chain scission of poly U in aqueous solution Strand break formation via base radicals. Int J Radiat Biol A5 351-358. 

As reported in Table 15, the kinetic data clearly indicate that the photoinitiation activity of poly(BMOA-co-MtA) is not substantially affected by the content of BMOA co-units along the polymer chain and is of the same order of magnitude as that found for the model compound BMOAc. The absence of a polymer effect in the above photoinitiators has been interpreted [84] in terms of a photodegradation mechanism of the macromolecules involving the ftee radical species anchored to the main chain, even in the presence of acrylic monomers, analogous to what is reported in Scheme 18. Moreover, the induction period of the HDDA/BA photoinduced polymerization increases, on decreasing the content of... 

Despite their inherent electronic advantages, CT complexes and radical cation salts tend to be brittle and unprocessable. This problem might be overcome by the incorporation of oligomeric tetrathiafulvalenes in polymers, whereby the TTFs can be part of a main-chain or side-chain polymer. The key concern thereby is to achieve the suitable packing of the donor moieties, which is, of course, less perfect than in the crystalline state. Remarkably, the rigid-rod poly-TTF 164 could be made recently by a precursor route in which 164 is made by dimethyl disulfide extrusion of the precursor polymer (scheme 39). The electrical conductivity after iodine doping amounts to 0.6 S/cm [221]. Other examples of TTF-containing polymers, either in the backbone [222] or in the side-chain [223], are summarized in chart 25. 

Furthermore, a polycarboxybetaine with a peptide main chain was synthesized from poly(methyl L-glutamate) [57]. Several zwitterionic monomers based on isobutylene with long alkyl spacers between the polymerizable group and the zwitterionic moiety exhibit surfactant properties. They do not undergo free radical homopolymerization, but are copolymerizable with other monomers [58]. 

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