Photoinitiation, 6. Copolymerization of styrene with maleic anhydride photoinitiated by the excited charge‐transfer complex styrene‐maleic anhydride

Abstract

The kinetics of styrene (St) copolymerization with maleic anhydride (MA) initiated by light (at 1 = 365 nm) was studied in acetone, acetonitrile, chloroform, and N,N-dimethyl formamide at 30 "C. With the exception of the chloroform containing system, the copolymerizations took place in homogeneous reaction media. The copolymerization rate R , = -d([St] + [MA])/dt was found to be a function of the mole ratio of the comonomers in the reaction mixture. For a given ratio of comonomers R , and the molecular weight of the resulting copolymer were found to be a function of the donor number of the solvent used for a given rate of initiation. Due to the dependence of R , on the concentration of an equimolar mixture of both comonomers in acetone on [St] (at constant [MA]), and on [MA] (at constant [St]) the participation of the exciplex [St.. .acetone]* in the ingation reaction can bKexpected. Theraticof the overall rate constants for the propagation (k,) and termination (kJ reactions, kP/2k,, determined by a rotating sector technique, was found to depend on the composition of the comonomer mixture. The copolymerization rate is proportional to the square root of the intensity of incident light, which, together with the observed inhibition effect of oxygen points to a radical mechanism of the photoinitiated copolymerization of St with MA. In the presence of the photosensitizer benzophenone in the system St/MA/acetone an increase in R , was observed, accompanied by a decrease in molecular weight of the copolymer in comparison with the system without benzophenone.

Ultrahigh Molecular Weight Hydrophobic Acrylic and Styrenic Polymers through Organic-Phase Photoiniferter-Mediated Polymerization

“…It was therefore expected that our low-temperature photoiniferter conditions would be suitable for the synthesis of UHMW poly­(styrene- alt -maleic anhydride) (PS- alt -PMAn). However, we observed poor control over the photoiniferter-mediated copolymerization of styrene and maleic anhydride, which we attributed to background initiation of the styrene/MAn charge-transfer complex under UV irradiation . Because TTC and dithiobenzoate iniferters also undergo photolysis under visible light irradiation, , we reasoned that it may be possible to selectively initiate the photoiniferter-mediated process without also activating the styrene/MAn complex.…”

“…However, we observed poor control over the photoiniferter-mediated copolymerization of styrene and maleic anhydride, which we attributed to background initiation of the styrene/MAn charge-transfer complex under UV irradiation. 30 Because TTC and dithiobenzoate iniferters also undergo photolysis under visible light irradiation, 31,32 we reasoned that it may be possible to selectively initiate the photoiniferter-mediated process without also activating the styrene/MAn complex. Indeed, the use of a dithiobenzoate iniferter and blue light irradiation (450 nm) afforded welldefined UHMW PS-alt-PMAn with good agreement between theoretical and measured molecular weights while maintaining a narrow molecular weight distribution (Table 1, entry 13, Figures 3 and S11).…”

Microemulsion Polymerization of Butyl Acrylate. Effect of Radical Scavenger and Formation of Primary Radicals

“…A more dense surface layer is expected to be formed by MAn due to its high ability to form donor acceptor complexes with electronrich compounds. 33 However, the effect of MAn is more complex while decrease of Rp,max can also be attributed to accumulation of maleic acid (hydrolytic product of MAn). During 24 h MAn (maleic acid) was mostly transformed from the monomer to aqueous phase.…”

High conversion copolymerization, 2. Styrene/maleic anhydride copolymer composition studies

“…Purification of styrene (S), maleic anhydride (MAn), 1 ,Cdioxane and acetone (resp. ethyl methyl ketone) has been described earlier 8,9). p-Benzoquinone was a reagent grade chemical, N,N-dimethylaniline (DMA) was purified according to lo).…”