MECHANICAL-PROPERTIES OF ACRYLATE NETWORKS FORMED BY VISIBLE LASER-INDUCED POLYMERIZATION .1. DEPENDENCE ON PHOTOPOLYMERIZATION PARAMETERS

The mechanical properties of network molecular systems, prepared throu gh visible (Ar+) laser-induced polymerization of multifunctional acryl ates, were studied as a function of some of the photopolymerization pa rameters. The properties investigated were the Young's modulus of elas ticity and the stress-at-break, both derived from the stress versus st rain test of dogbone-shaped photopolymerized samples. The parameters s tudied included the dye and co-initiator concentrations, and the laser power. We also compared the mechanical properties of samples made usi ng different types of fluorone dyes and using two different amines as co-initiator. Better polymers are formed by the dyes with low fluoresc ence quantum yield. The three photopolymerization parameters modify th e mechanical properties in a very similar way: they initially tend to increase both the Young's modulus and the stress-at-break but have a d eleterious effect on the material strength if used in excess. N-phenyl glycine, NPG, was shown to form stronger polymers (higher Young's modu lus) than if N,N-dimethyl-2,6-diisopropylaniline, DIDMA, was used as c o-initiator. We discuss the possible molecular mechanisms for such obs ervations. (C) 1994 John Wiley & Sons, Inc.