Highly crosslinked polymers can be readily synthesized by photoinitiated polymerization of multifunctional monomers or functionalized polymers. The reaction can be followed in situ by real‐time infrared (RT‐IR) spectroscopy, a technique that records conversion versus time curves in photosensitive resins undergoing ultrafast polymerization upon UV exposure. For acrylate‐based resins, UV‐curing proceeds with long kinetic chains (7700 mol/radical) in spite of the high initiation rate. RT‐IR spectroscopy proved very valuable in assessing the influence of various parameters, such as initiation efficiency, chemical structure of the telechelic oligomer, light intensity, inhibitory effect of oxygen, on polymerization kinetics. Interpenetrating polymer networks can be rapidly synthesized by means of UV irradiation of a mixture of difunctional acrylate and epoxy monomers in the presence of both radical and cationic‐type photoinitiators. The same UV technology can be applied to crosslink solid polymers at ambient temperature, which bear different types of reactive groups (acrylate and vinyl double bonds, epoxy ring). UV radiation curing has been successfully used to produce within seconds weathering resistant protective coatings, high‐resolution relief images, glass laminates and nanocomposites materials.Photoinitiated crosslinking polymerization.magnified imagePhotoinitiated crosslinking polymerization.

The inhibition by oxygen of the photopolymerization of multi-acrylate systems was investigated by IR spectroscopy. Both conventional and laser UV irradiations were used to initiate the reaction; the effect of the light intensity on polymerization kinetics was followed over a 4-orders-of-magnitude range. Based on a simple kinetic scheme, the equation of the steady concentration of 02 was calculated as a function of the initiation rate and of the ratio of the polymerization rates with and without oxygen; under the conditions employed, the [02]a value was found to be on the order of 5 X 10™6 mol L™1. The less-than-first-order dependence of the inhibition period on the reciprocal light intensity indicates that 02 is consumed by a chain peroxidation process with kinetic chain lengths between 1.6 and 16, depending on the light intensity.

No abstract