Studies have been made of the photolysis of copolymers of methyl methacrylate (MMA) and methyl vinyl ketone (MVK) containing minor amounts of MVK. It is shown that under conditions where there is sufficient molecular mobility (in solution or in the solid phase above Te), the quantum yield for the process which leads to main-chain scission is 0.20 ± 0.02, nearly an order of magnitude higher than for poly-MVK itself. This is unexpected, because most of the ketone groups are surrounded by MMA units and consequently no hydrogens are available to form the cyclic six-membered ring postulated as the transition state for the Norrish type II process. It is suggested that in this case the scission might occur through a seven-membered intermediate, and the hydrogen is abstracted. The higher quantum yield for scission of the copolymer indicates that the isolated carbonyl group may be precluded from energy exchange along the polymer chain. CH CH3 CH CH CH CH I group absorbs a quantum of light, hydrogen is available on the -carbon atoms in the chain provided from the (1) J.

The influence of water on the polymerization of thiirane and 2-methylthiirane with CdCO, was studied. The polymerization process takes place only when a large interface monomerwater is formed. This is achieved by the presence of an amount of water in the reaction mixture which is comparable with that of the monomer. The polarity of the solvent does not influence the rate of formation of poly(2-methylthiirane). The polymerization is carried out in the mass of monomer or in the presence of an alcohol and a solvent not miscible with water.

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The polymerization of methyl methacrylate has been studied in toluene and tetrahydrofuran solution at −78°C using butyllithium as catalyst. The structure of the polymer produced was determined by analysis of the α‐methyl groups using 100 MHz NMR. It is shown that in a noncomplexing solvent such as toluene, the number of isotactic triads increases from 70% to 93% as the monomer concentration during polymerization is reduced from 5 mole/l. to approximately zero. The value of Pss/Pis depends strongly on monomer concentration, and hence any calculations regarding penultimate effects in such systems should be made at close to zero monomer concentration. In the THF solution the penultimate effect is nearly independent of monomer concentration, and both Pii/Psi and Pss/Pis are close to unity. The results may be explained in terms of a mechanism of the polymerization process in which toluene does not complex with the active site, while monomer and THF are weak and strong complexing agents, respectively.

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