Photopolymerization Of Vinyl Acetate Research Articles

Investigation into the Direct Photolysis Process of Photo-Induced RAFT Polymerization by ESR Spin Trapping.

The direct photolysis of reversible addition fragmentation chain transfer (RAFT) agents under visible light was demonstrated by electron spin resonance (ESR) using 5,5-dimethyl-1-pyrroline N-oxide as a typical spin trap. The hyperfine coupling lines obtained by ESR spectroscopy showed the successful capture of the carbon-centered and the sulfur-centered radical. Photo-polymerization of vinyl acetate under different wavelengths was performed to verify the effects of wavelength on the process. The effect of the R group of RAFT agents on the photolysis was investigated by spin-trapping experiments using poly (butyl acrylate) and poly (vinyl acetate) as macroRAFT agents. The quantitative experiment showed the yield of photolysis of a xanthate to be only 0.023% under λ > 440 nm.

Photochemical synthesis and formation mechanisms of polyvinyl acetate–CoIII(salen) “dormant” chains during “living” radical polymerization

The formation of “dormant” chains due to the acceptance of the photodissociation products of vinyl acetate by stable CoII(salen) radicals was studied. The rate of formation of “dormant” chains was found experimentally to be considerably higher than that of initiating radicals upon the initiator-free photopolymerization of vinyl acetate. A high rate of formation of “dormant” chains is caused by supression of the cell effect in the presence of a strong inhibitor. A kinetic scheme was proposed which allowed drawing up a mechanism of formation of “dormant” chains as a mathematical model suitable for the quantitative description of the process. The comparison between the absorption spectra of the reaction system at different reaction steps and the quantum chemically calculated spectra of forming “dormant” chains showed the polymer chain initiation to afford the acyl radical. The constants for the growing radicals–CoII(salen) interaction, the quantum yield of the Co–C bond dissociation in “dormant” chains, and the quantum yield of the initiator-free vinyl acetate photopolymerization were determined.

Photochemical reactions in polymeric matrices: The photopolymerization of vinylacetate in a polytetrafluorethylene matrix

Photochemical reactions in polymeric matrices: The photopolymerization of vinylacetate in a polytetrafluorethylene matrix

POLYVINYL ALCOHOL FIBERS PREPARED FROM POLYVINYL ACETATE POLYMERIZED AT LOW TEMPERATURE

Photo-polymerization of vinyl acetate was carried at 0°C and -30°C using uranyl acetate as sensitizer.Polyvinyl acetate thus obtained was saponified to polyvinyl alcohol (PVA), and the properties of this PVA and fibers prepared from it were compared with those of commercial PVA.The contents of 1, 2 glycol structure of PVA decreased and the gelation of aqueous solution was accelerated with lowering polymerization temperature of polyvinyl acetate from which the PVA was produced.Heat treated and not formalized fibers prepared from this PVA had good resistance to hot water up to 110°C, and its tenacity, elongation and elastic recovery were not inferior to the fibers from commercial PVA.

Preparation and properties of styrene‐vinyl alcohol block copolymers. Vinyl polymerization XLII

AbstractThe preparation of the styrene‐vinyl alcohol block copolymer by saponifying the styrene‐vinyl acetate block copolymer was studied. Styrene‐vinyl acetate block copolymers were synthesized by photopolymerization of vinyl acetate in presence of polystyrene containing diethyldithiocarbamate groups. These copolymers were soluble in benzene, acetone, methyl ethyl ketone or pyridine. The intrinsic viscosities of these copolymers in benzene [η] could be expressed approximately by the equation [η] = [η]PSt + [η]PVAc where [η]PSt and [η]PVAc are intrinsic viscosities of the initiator polystyrene and free polyvinyl acetate, respectively. However, the styrene‐vinyl alcohol block copolymers prepared by saponification of these vinyl acetate block copolymers were insoluble in almost solvents.

Determination of the velocity coefficients for polymerization processes II. The photosensitized polymerization of vinyl acetate by benzoyl peroxide

The photopolymerization of vinyl acetate has been found to be very much accelerated by the presence of small quantities of benzoyl peroxide. This is considered to be the result of a photochemical decomposition of the peroxide, to give free radicals such as phenyl and benzoate. The dependence of the rate of polymerization on the peroxide concentration suggests that there is a considerable inhibition of the reaction due to the presence of the peroxide. The value of the intensity exponent approaches unity as the concentration of the peroxide is increased, and the formal analysis of the reaction suggests that the inhibition is due to the peroxide molecules themselves. The analysis of the induction period and the dark period shows that these are identical and therefore real, so that it can be concluded that they depend essentially on the nature of the initiation step. The value of the initiation velocity coefficient is calculated, and the energy of activation for this step is found to be 8.4 kcal./g.mol.