The photopolymerization behavior and reaction kinetics of ethylhexyl methacrylate (EHMA) and ethylene glycol dimethacrylate (EGDMA) monomers in styrene−butadiene−styrene block copolymer (SBS) were studied. For both monomers, di- and tetrafunctional, reaction diffusion was found to be the only mechanism of termination when the polymerization is carried out in this polymeric medium, that is, reaction diffusion controls the termination reaction from the beginning of the reaction. The polymerization of EGDMA in polystyrene and polybutadiene showed similar behavior to that in SBS. Also, the relationship between the individual rate constants k t and k p was studied, and a constant ratio of these kinetic constants was found.

The kinetics and mechanism of the photoinitiated polymerization of tetrafunctional and difunctional methacrylate monomers (di-, hexa-, and decamethylene dimethacrylates; and ethylhexyl and dodecyl methacrylates) in a styrene−butadiene−styrene (SBS) block copolymer matrix have been studied. Reaction diffusion was found to be the only termination mechanism for tetrafunctional monomers when the monomer concentration in the matrix is below 30−40%; for higher monomer concentrations, reaction diffusion controls the termination process only after approximately 10% conversion was reached. The values of both the propagation kinetic constant and the overall double bond conversion for the three tetrafunctional monomers studied showed the following order:  deca- > hexa- > dimethylene dimethacrylate. The termination process in the photoinitiated polymerization of difunctional methacrylate monomers is clearly controlled by reaction diffusion right from the beginning of the polymerization reaction only at a very low monomer concentration in the matrix (10−15%); for medium monomer concentrations (20−40%), a combination of both mechanisms, segmental diffusion-controlled (autoaccelerated kinetics) and reaction diffusion, was observed until reaching a double bond conversion of 20%, from which point reaction diffusion predominated; for higher monomer concentrations (60−90%), the termination kinetic constant values at low conversions (<30%) were close to those corresponding with standard polymerizations, observing the Trommsdorff effect (autoacceleration) at higher double bond conversions. The SBS matrix participates appreciably in the polymerization process through the direct addition of the macroradical or the primary radical to the double bond of the polybutadiene moiety and through hydrogen abstraction from the matrix with the formation of benzylic and allylic radicals.

The photopolymerization of several di‐ and tetrafunctional (meth)acrylic monomers in the presence of a styrene–butadiene–styrene polymeric matrix (SBS) has been studied. Electron spin resonance spectroscopy (ESR) and differential scanning photocalorimetry (photo‐DSC) were used as monitoring techniques to identify the photogenerated radicals and analyze photopolymerization profiles, radical environments, and radical secondary reactions. The study of the photopolymerization and/or photocrosslinking reactions of these monomers in the solid media was carried out by taking into consideration different factors, such as the influence of both monomer and photoinitiator structures on the hydrogen abstraction in the binder with formation of benzylic and allylic radicals, the polymerization of the monomers itself and the hydrogen abstraction reaction in the polymerized acrylic chains. Finally, irradiation of the system SBS/photoinitiator in the absence of monomer was also accomplished. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2775–2783, 1998

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Rate constants ( q / E values) for laser pulse initiated photopolymerization have been determined for 1200-2700-&diameter bilayer surfactant vesicles prepared from dioctadecylmethyl(2-[ (4-vinylbenzoy1)-oxylethy1)ammonium bromide (31, from mixtures of dioctadecyldimethylammonium bromide (DODAB) and vinylbenzoic acid, from mixtures of 3 and DODAB, and from mixtures of 3 and vinylbenzoic acid. q / E values were 1.35 J-' for 1650-A-diameter 3 vesicles, were 0.059 J-' for mixed vesicles prepared from vinylbenzoic acid and DODAB (0.25:l mole fraction), varied between 0.123 and 1.46 J-' for vesicles prepared from different mixtures of DODAB and 3, and varied between 0.16 and 0.314 J-l for different mixtures of vinylbenzoic acid and DODAB. Plots of polymerization rate constants against the mole fraction of 3 in vesicles prepared by cosonicating 3 + DODAB were found to increase curvilinearly to a plateau value, indicating domain formation. Subsequent to vesicle polymerizations, cumulants, weight-and number-average molecular weights of the separated poly(viny1benzoates) and, hence, the average chain lengths were determined by gel exclusion chromatography. The average chain lengths varied from 10 in laser-polymerized 3 vesicles, through 20 in laser-polymerized vesicles prepared from mixtures of DODAB and vinylbenzoic acid, to 40 in laser-polymerized vesicles prepared from mixtures of 3 and vinylbenzoic acid. These relatively small chain lengths were discussed in terms of the restricted geometries prevailing a t intravesicular surface polymerizations. Fluorescence measurements and a Monte Carlo based computer simulation of the photopolymerization were used to substantiate the proposed mechanism of vesicle polymerization.

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The reaction kinetics in the dark of photopolymerized mono‐ and dimethacrylates in a polymeric binder has been studied. Electron spin resonance spectroscopy (ESR) provided useful information regarding the nature of the radicals involved in postpolymerization reactions. Computer simulations were performed to study the decay of the propagating radicals by considering normal bimolecular termination and transfer reactions of the radicals to the binder. Differences were found in the termination reactions for mono‐ and difunctional monomers when they were photopolymerized in a solid medium. Absolute kinetic constants for H‐transfer reaction with the binder, relative kinetic rate constants for radical–radical coupling, and average lifetimes for the radicals have been calculated. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2785–2791, 1998

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