Free-radical polymerization naphthalene

When AT,iV-dimethylaniline (DMA) or naphthalene is added to styrene-MA systems, the incorporation of MA in the copolymers is increased and the rate of copolymerization decreases.The rate drop is attributed to increased degradative chain transfer. Dimethylaniline-MA or naphthalene-MA complexes bring about a shift of monomer ratios in the copolymer. The free radicals which contribute to the chain transfer must be predominantly of the type that have a MA unit at the end, since it is known polystyryl radicals do not react with DMA donor. These free radicals react with the DMA-MA CTC to form transfer radicals with the MA component of the CTC. Thus, a low-grade MA-MA block is formed by a reinitiation mechanism and the MA content in the copolymer increases. This supports a CTC polymerization mechanism concept, since in more polar solvents or in the presence of donor additives the amount of donor monomer-MA CTC formed would be less and the rate of copolymerization reduced accordingly. Tsuchida and coworkers, from measured rate studies of the copolymerization of styrene with MA in a variety of solvents, support this concept and conclude that copolymerization of the styrene-MA pair clearly involves propagation in part by a CTC. 

Benzofulvene derivatives are isomers of corresponding naphthalene derivatives that have been relatively less studied than their monocyclic and tricyclic counterparts. A particular mention can be made for 7-methyl-l-methylene-3-phenylindene (BF2, Fig. 2), a benzofulvene derivative described by Londergan and coworkers, that was reported to polymerize under free radical catalysis to afford a vinyl polymer containing pendant aromatic chromophores [15]. 

Naphthalene excitation by UV-light in glassy cellulose triacetate films induces formation of polymeric free radicals, polymer chain break and addition of naphthalene fractures to macromolecules. In the absence of oxygen, the naphthalene consumption rate increases in direct proportion to UV-light intensity, whereas the rate of polymeric chain breaks varies in proportion to quadratic intensity. The process is initiated by singly excited triplet naphthalene molecules localized in the structural matrix zones, where they are incapable of irradiative deactivation. The features of phototransformation are explained in the framework of the hetero-nanophase kinetic model of the process, taking into account the radiationless translation of triplet excitation energy to naphthalene molecules present in the zones, where sensitization is absent and only triplet state deactivation is performed. 

The radical-anion proceeds to propagate in the same manner as discussed above for initiation by sodium naphthalene. (Polymerizations in liquid ammonia are very different from those in organic solvents in that free ions probably constitute the major portion of propagating species.)... 

An explanation for the non-formation of aromatic products under entry 4 in Table 1 is that hydrogen atom abstraction from the corresponding dihydro derivative would lead to a /3-thio substituted radical, which would rapidly eliminate a thiyl radical, which in turn would readily polymerize. The last entry in the table is also surprising in that the cyclization takes place on the naphthalene /3-position when an a-position is free. The use of this photocyclization-oxidation sequence for the construction of heterohelicenes has been reviewed (71ACR65). 

Anionic polymerization of o-divinylbenzene was examined by Aso et al. [294]. The authors used n-BuLi, phenyllithium, and naphthalene/alkali metal in THF, ether, dioxane, and toluene at temperatures between —78 and 20 °C. Generally, it was found that as with radical and cationic initiators, a competition between cyclopolymerization and conventional 1,2-polymerization occurs, with the tendency for cyclization to be lower than with the other mechanisms. The polymerization initiated with the lithium organic compounds resulted in polymers with up to 92% double bonds per monomer unit (THF, 20 °C). Polymerization with lithium, potassium, and sodium naphthalene also showed a rather weak tendency for cyclization. In THF at 0°C and 20 °C the cyclization tendency increased with decreasing ionic radii of the counter cation, while in dioxane the reverse effect was observed, and in ether still another dependence was found (K > Li > Na). Nitadori and Tsuruta [299] used lithium diisopropyl amide in THF at 20 °C to polymerize m- and p-divinylbenzene. The authors obtained soluble products with molecular weight up to 100 000 g/mol (GPC) and showed the polymers to contain pendant double bonds by IR and NMR spectra. It seemed to be important that a rather large excess of free amine (the initiator was formed by reaction of -BuLi with excess diisopropylamine) was present in the polymerization mixture. In later studies [300,301] a closer view was taken on polymerization kinetics and the steric course of the polymerization reaction. 

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