Free-radical polymerization of phenylacetylene

The free-radical polymerization of phenylacetylene initiated by azobisisobutyronitrile at 50°C was studied in bulk and in the presence of benzene and toluene. The polymerization rate is approximately first-order with respect to the initiator concentration. The number-average molecular weight of the polymer is independent of the initiator concentration in bulk and is approximately proportional to the monomer concentration in the presence of the two diluents, but independent of their nature. The data are consistent with a mechanism based on first-order decay of active to inactive radicals. This step appears to exert the major control over kinetic and molecular chain lengths. Chain transfer to the monomer is concluded to be absent or to make only a small contribution to molecular termination.     

Free-radical polymerization of vinyl ferrocene

The results of quantitative studies of the rates of free-radical polymerization of vinyl ferrocene indicate that the latter has polymerization characteristics similar to those of styrene. The rates of homopolymerization of these two monomers in benzene at 70°C. were measured with the use of azobisisobutyronitrile as catalyst. The rate constants (k = R_p/[M][I]^1/2) are k_VF = (1.1 ? 1.8) × 10^?4, k_STY = 1.65 × 10^?4. Small amounts of vinyl ferrocene and styrene have similar effects on the rates of polymerizations of methyl methacrylate and ethyl acrylate and on the molecular weights of the resulting polymer. Polystyrene and poly(vinyl ferrocene) with similar molecular weights are isolated from polymerizations carried out under identical conditions. The rates of copolymerization of vinyl ferrocene—methyl methacrylate, vinyl ferrocene—styrene, and styrene—methyl methacrylate were determined by following the disappearance of monomers by means of gas chromatographic analyses. The relative reactivity for vinyl ferrocene is slightly lower than that for styrene.     

Trapping of thiaziridinimines with thiocarbonyl compounds

Thermolysis of 4-benzyl-5-tosylimino-1,2,3,4-thiatriazoline at 60–70° in the presence of representative C = S unsaturated compounds furnished 1,2,4-dithiazolidin-5-imines in moderate yields. The reaction is assumed to proceed via the inlermediacy of an unstable thiaziridinimine which is trapped by the C=S compound in a regiospecific manner. Among the thiocarbonyl compounds used are p,p′-dimethoxythiobenzophenone, xanthates and 3-benzylrhodanine, the latter giving rise to a spiro adduct.     

Free-radical polymerization of styrene in worm-like micelles

The solubilization of styrene in wormlike micelles of the cationic surfactant, cetyltrimethylammonium tosilate (CTAT), and its polymerization is examined here by UV spectroscopy, oscillatory rheometry, small angle X-ray scattering, polarizing light microscopy, and transmission electron microscopy. At low CTAT concentrations, the polymerization of styrene yields small and rigid rods in coexistence with wormlike micelles that form from the excess surfactant after the polymerization process. At high CTAT concentrations, polymeric rods (of large aspect ratio), spheroid polymer particles, and wormlike micelles coexist. The polymerization rate is second order, indicating that polymerization reactions end mainly by bimolecular termination.     

Electronic absorption spectra of selenocarbonyl and thiocarbonyl compounds

Electronic absorption spectra of a variety of thiocarbonyl and selenocarbonyl compounds have been compared to point out their similarities. Interesting correlations between the absorption maxima and electronegativities of substituents in both the seleno- and thio-carbonyl compounds have been reported.     

Solid-state polymerization of long-chain vinyl compounds. VI. In-source polymerization of octadecyl acrylate by γ-ray irradiation

The in-source polymerization of octadecyl acrylate in the lamellar crystal (hexagonal packing) by γ-ray irradiation has been investigated, as compared with the two-step and one-step postpolymerizations. The viscosity-average molecular weight is very high even in the initial stage and is practically saturated after 3–5 hr, although the conversion increases successively with time. The molecular weight distribution of poly(octadecyl acrylate) obtained by in-source polymerization is very wide (M _w/M _n = 13.1, at 20°C). The results of in-source polymerization of the long-chain vinyl compounds can be interpreted using the cone model for polymerization probability, similar to those of one-step and two-step postpolymerizations.     

Free-radical multicomponent polymerization reactors and chemical composition distribution

Formulae to calculate the statistically caused instantaneous copolymer composition distribution as well as the chemical distribution of accumulated macromolecules, which is due to polymerization statistics and shifts in mean polymer composition during the reaction process, are derived on the basis of a universal model for free-radical solution polymerization with any number of monomers proceeding in a batch, semi-batch or continuous, ideally mixed vessel. The influence of the reactor type on chemical composition distributions is investigated for a copolymerization of different reactive components (methyl methacrylate/styrene/maleic anhydride), a system with nearly equal reactive monomers (methyl methacrylate/styrene), and the ternary polymerization of methyl methacrylate/styrene/maleic anhydride. Though products of constant mean composition are obtainable in a semi-batch or steady-state continuous reactors, considerable statistical dispersion cannot be removed in any case.     

Free-radical polymerization in micellar media: Effect of microenvironment

A micellar polymerization process has been used to prepare polyacrylamide or poly(acrylic acid) hydrophobically modified with low amounts (1–5 mol%) of an N-alkyl- or N-alkylarylacrylamide. The effect of the initial monomer segregation on the copolymer microstructure and the copolymerization mechanism has been investigated. This method leads generally to multiblock copolymers in which the number and length of the hydrophobic blocks vary with the initial number of hydrophobes per micelle. Interestingly, the copolymerization of acrylamide with disubstituted acrylamides leads to homogeneous samples with an average copolymer composition independent of the degree of conversion, in contrast to what is observed with monosubstituted acrylamides for which a drift in composition is observed. The difference in polarity between the bulk phase and the micellar phase is responsible for this behavior. This microenvironment effect modifies the reactivity ratios of those hydrophobes capable of forming hydrogen bonds, whereas the reactivity of the other hydrophobes remains unaffected.     

Free-radical addition reactions initiated by metal oxides, VI

CuO catalyzed additions of ethyl cyanoacetate, initiated thermally and by di-tert-butyl peroxide, to 1-decene and ethyl 10-undecylenoate were investigated. The CuO catalyzed reaction proceeds already at 80°C at a high rate, produces 11 adducts in high yields and represents the first example of catalysis in radical addition reactions of non-halogenated compounds.

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1- 10-, CuO, -.-. , CuO, 80°C, 11 . .