ABSTRACT:Polymerizations of trityl (TMA), diphenylmethyl (DMA) and benzyl (BMA) methacrylates were carried out mainly by n-butyllithium (n-BuLi) and the tacticities of the polymers were studied by NMR spectroscopy. Polymerization of TMA by n-BuLi gave a highly isotactic polymer in toluene as well as in tetrahydrofuran (THF). The polymer obtained in radical polymerization by AIBN catalyst had about 60 % isotacticity in triads.From these results the growing-chain-controlled mechanism was proposed to this polymerization. In the polymerization of DMA by n-BuLi a highly isotactic polymer was obtained in toluene at lower temperatures and a highly syndiotactic one in THF. The radical polymerization gave a predominantly syndiotactic polymer. Temperature dependence of the NMR signal-width of the isotactic polymer indicates that the conformational arrangement of the polymer chain in solution is much rigid up to a fairly higher temperature. These results suggest that the growing-chain-controlled mechanism may contribute to some extent to the stereoregulation of DMA in toluene. BMA behaved very similarly to methyl methacrylate in the polymerization by n-BuLi. Probably the same polymerization mechanisms can be applied for both monomers. Polymerization ofTMA, DMA and BMA by phenylmagnesium bromide or diethylaluminum diphenylamide was also investigated.KEY WORDS Stereospecific Polymerization / Poly (Trityl Methacrylate) / Poly (Diphenylmethyl Methacrylate) / Poly (Benzyl Methacrylate) / Poly (Methyl Methacrylate) / n-Butyllithium / Phenylmagnesium bromide / Diethylaluminum Diphenylamide / Growing-Chain-Controlled Mechanism of Stereoregulation / NMR Spectroscopy / Stereospecific polymerizations of methyl 1 -3 and other alkyl methacrylates 4 -9 by anionic initiator have been extensively studied. However there have been few systematic studies 10 concerning the effect of the ester group on the tacticity of polymer. EXPERIMENTAL MaterialsTMA was prepared from silver methacrylate and trityl chloride in diethyl ether. 12 The crude product was purified by recrystallization from petroleum ether. mp 102-103°C (lit. 12 101-1030C), Anal. Found: C, 84.00; H, 6.08%. Calcd for C23H 200 2 : C, 84.12; H, 6.14%. The NMR spectrum (10 % CC14 solution) showed peaks at 1.90 ppm (singlet, 2.95H) assigned to the methyl protons, 5.49 and 6.13 ppm (two singlets 2.00H) assigned to the p-protons of the vinyl group and about 7.20 ppm (multiplet, 15.2H) assigned to the phenyl protons.In a previous communication 11 we briefly reported the polymerization of trityl methacrylate by anionic and radical initiators and found that this monomer gave a highly isotactic polymer regardless of the polymerization medium, the temperature and the type of initiator. In the present work the polymerizations of trityl (TMA), diphenylmethyl (DMA) and benzyl (BMA) methacrylates were carried out mainly by n-butyllithium (n-BuLi) and the effect of the bulkiness of the ester group on the tacticity of the polymer was investigated. 36DMA was prepared by the reaction of 45 g of silve...

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The polymerization of methyl α‐ethylacrylate was carried out in toluene by n‐BuLi at various temperatures. The yield of the polymer decreased with increase in the polymerization temperature and at 30°C and above no polymer was obtained, indicating that the ceiling temperature of this monomer lay between 0 and 30°C. The isotacticity increased with an increase in the polymerization temperature and at 0°C a highly isotactic polymer was obtained. The fractionation of the polymer obtained at −78°C showed that the polymer was a mixture of isotactic and syndiotactic ones. Upon the addition of a small amount of methanol or water in the polymerization mixture the isotacticity of the polymer increased while the yield decreased. Syndiotactic polymer was obtained in the polymerization by n‐BuLi in tetrahydrofuran as well as by diisobutyl aluminum diphenylamide in toluene.

ABSTRACT:The polymerization of methyl a-phenylacrylate was carried out in toluene by n-BuLi at -78~30°C. The yield of the polymer was highest at -45°C and then decreased with increasing the temperature. No polymer was obtained above 0°C. The polymer obtained at -78°C was rich in isotacticity. By increasing the polymerization temperature the fraction of isotactic triads decreased in association with the increases in the fracrions of heterotactic and syndiotactic triads. Above -45°C, the proportion, I: H: S of the polymer obtained was close to I : 2: 1, suggesting the random stereoregulation in the propagating step. The random polymer was also obtained by n-BuLi in polar solvent such as THF at low temperature as well as by AIBN. The addition of a small amount of methanol to the polymerization system by n-BuLi in toluene increased the yield, isotacticity, and molecular weight of the polymer, and the maximum values were obtained at CH3OH/n-BuLi=0.83. The polymerization by (iso-Bu)2AlNPh2 in toluene at -78°C gave a syndiotactic polymer in low yield. The reactivity of methyl a-phenylacrylate in anionic polymerization is briefly discussed in comparison with those of some other methyl a-alkylacrylates.KEY WORDS Stereospecific Polymerization / Poly(methyl a-phenylacrylate) / n-Butyllithium / Diisobutylaluminum Diphenylamide / Random Polymer / 13 C NMR Spectrum / DSC Analysis / Stereospecific polymerizations of methyl and other alkyl methacrylates have been reported by many authors. However, little attention has been paid to stereoregulation in the polymerization of a-alkylacrylate other than methacrylate

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