Anionic polymerizations of seven styrenes para-substituted with N-arylimino groups were carried out in THF at −78 °C with oligo(α-methylstyryl)dipotassium and -dilithium as the initiators. The N-aryl functionalities contained phenyl (1), 2-(tert-butyl)phenyl (2), 2,6-dimethylphenyl (3), 2,6-diethylphenyl (4), 2,6-diisopropylphenyl (5), 4-cyanophenyl (6), and 2,3,4,5,6-pentafluorophenyl (7) groups. The monomers 3−5 underwent anionic polymerization quantitatively to produce the polymers having predicted molecular weights based on molar ratios of monomers to initiators and narrow molecular weight distributions, the M w/M n values being around 1.1. On the other hand, no polymeric products were obtained from the polymerization mixture of 1, 2, 6, and 7 under identical conditions. The bulkiness of the two ortho alkyl substituents on the N-aryl moiety was necessary to achieve the anionic living polymerization of styrenes bearing N-arylimino groups. Well-defined new block copolymers having poly(5) segments were synthesized by the sequential addition of 5 and styrene or tert-butyl methacrylate. The resulting poly(3−5) could be quantitatively transformed into the poly(4-formylstyrene) having tailored chain structures by the acid hydrolysis of N-arylimino moieties.

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Anionic polymerizations of the three acetal-protected styrene derivatives 2-(2-vinylphenyl)-(3a), 2-(3-vinylphenyl)-(3b), and 2-(4-vinylphenyl)-1,3-dioxolanes (3c) were carried out in THE at -78 °C with a variety of initiators. The meta isomeric monomer, 3b, underwent anionic living polymerization to produce polymers of controlled molecular weights and narrow molecular weight distributions. New welldefined block copolymers of both the ABA and the BAB types were readily synthesized by the sequential polymerizations of 3b and styrene and vice versa. On the contrary, complications were observed in the polymerizations of the ortho and para isomers, 3a and 3c. Soluble polymers with very broad molecular weight distributions from 3a and insoluble polymers from 3c were obtained in low yields by these polymerizations. Thus, the anionic polymerization behavior was significantly influenced by the difference in placement of the acetal group on the aromatic ring of the monomer. To explain these results, we propose a reaction mechanism based on the base-induced l,6(or l,4)-elimination of the acetal to generate the very reactive p(or o)-xylene intermediate. This is the first clear example that shows the positional effect of this substituent in the anionic polymerization of styrene derivatives. The anionic polymerizations of some related styrene derivatives containing acetal functionalities are also described.

Poly(4vinylbenzaldehyde)s (4) of known chain lengths and of narrow molecular weight distributions (a,,, /a, = 1,l) were synthesized by means of anionic living polymerization of 1,3dimethyl-2-(4-vinylphenyl)imidazolidine (1) with oligo[a-methylstyryl]potassium (2) and subsequent acid hydrolysis to remove the imidazolidine protective group. The living polymer of 1 can initiate further polymerization of a-methylstyrene, resulting in the preparation of a triblock copolymer of the type poly[a-methylstyrene-b-(4-vinylbenzaldehyde)-b-a-methylstyrene] in quantitative yield after hydrolysis. *) Poly[l-(4-formylphenyl)ethylene].

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