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SynopsisThe mechanism of cyclopolymerization was investigated by using N-n-propyldimethacrylamide (PDMA). Completely cyclized polymers were formed on polymerization of PDMA by a radical initiator. Moreover, those copolymers of PDMA and various monomers, such as styrene, methyl methacrylate, and vinyl acetate, obtained did not contain any detectable pendent double bonds. The kinetic investigation showed that the termination reaction proceeded between the cyclized radicals. The attempted polymerization of N-n-propyl-N-isobutyrylmethacrylamide, the monofunctional counterpart of PDMA, was failed. These results appear to confirm that cyclopolymerization of PDMA proceeds through a concerted mechanism which has been proposed for the mechanism of the cyclopolymerization of various difunctional monomers. Measurement of the ESR spectra of propagating radical has, however, revealed that the rate-determining step of the cyclopolymerization of PDMA is not intermolecular propagation but intramolecular cyclization, which indicates that the cyclization reaction proceeds in a stepwise way. This apparent contradiction was explained based upon thermodynamic considerations. 897

To study the possibility of living cationic polymerization of vinyl ethers with a urethane group, 4‐vinyloxybutyl n‐butylcarbamate (1) and 4‐vinyloxybutyl phenylcarbamate (2) were polymerized with the hydrogen chloride/zinc chloride initiating system in methylene chloride solvent at −30 °C ([monomer]0 = 0.30 M, [HCl]0/[ZnCl2]0 = 5.0/2.0 mM). The polymerization of 1 was very slow and gave only low‐molecular‐weight polymers with a number‐average molecular weight (Mn) of about 2000 even at 100% monomer conversion. The structural analysis of the products showed occurrence of chain‐transfer reactions because of the urethane group of monomer 1. In contrast, the polymerization of vinyl ether 2 proceeded much faster than 1 and led to high‐molecular‐weight polymers with narrow molecular weight distributions (MWDs ≤ ∼1.2) in quantitative yield. The Mn's of the product polymers increased in direct proportion to monomer conversion and continued to increase linearly after sequential addition of a fresh monomer feed to the almost completely polymerized reaction mixture, whereas the MWDs of the polymers remained narrow. These results indicated the formation of living polymer from vinyl ether 2. The difference of living nature between monomers 1 and 2 was attributable to the difference of the electron‐withdrawing power of the carbamate substituents, namely, n‐butyl for 1 versus phenyl for 2, of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2960–2972, 2004

To establish the optimum conditions for obtaining high molecular weight polyacetals by the self‐polyaddition of vinyl ethers with a hydroxyl group, we performed the polymerization of 4‐hydroxybutyl vinyl ether (CH2CHOCH2CH2CH2CH2OH) with various acidic catalysts [p‐toluene sulfonic acid monohydrate, p‐toluene sulfonic anhydride (TSAA), pyridinium p‐toluene sulfonate, HCl, and BF3OEt2] in different solvents (tetrahydrofuran and toluene) at 0 °C. All the polymerizations proceeded exclusively via the polyaddition mechanism to give polyacetals of the structure [CH(CH3)OCH2CH2CH2CH2O]n quantitatively. The reaction with TSAA in tetrahydrofuran led to the highest molecular weight polymers (number‐average molecular weight = 110,000, weight‐average molecular weight/number‐average molecular weight = 1.59). 2‐Hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, cyclohexane dimethanol monovinyl ether, and tricyclodecane dimethanol monovinyl ether were also employed as monomers, and polyacetals with various main‐chain structures were obtained. This structural variety of the main chain changed the glass‐transition temperature of the polyacetals from approximately −70 °C to room temperature. These polyacetals were thermally stable but exhibited smooth degradation with a treatment of aqueous acid to give the corresponding diol compounds in quantitative yields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4053–4064, 2002

ABSTRACT:Anionic cyclopolymerizabilities of N-methyldiacrylamide (MDA), N-propyldimethacrylamide (POMA), and N-methyldimethacrylamide (MOMA) were studied. MDA initiated by tert-butylmagnesium chloride at -78°C yields polymers which consists almost exclusively of 5-membered ring as repeating unit, even though the nature of solvents employed are varied widely. This indicates that MDA has strong tendency toward head-to-head and tail-to-tail additions even in anionic polymerization. NMR spectroscopic studies showed that conjugation between C=C and C=O double bonds of MDA is as effective as that of acrylic esters. Favorable conformation of MDA for the 5-membered ring formation and higher electron density of propagating anion (--CH2-CH--CO-) in spite of the fact that its acryloyl groups have conjugative nature are regarded as possible reasons for the unusual addition behavior. Attempted anionic polymerizations of POMA and MOMA were unsuccessful. NMR spectroscopic studies revealed that conjugation between olefin and C = 0 double bonds in these monomers is ineffective owing to the twisted conformation between the two double bonds. This unconjugative nature of the methacryloyl groups of POMA and MOMA is considered to be responsible for their lower polymerizability in the anionic polymerization.KEY WORDS