Network formation by chain crosslinking photopolymerization and its applications in electronics

Abstract

The formation of densely crosslinked networks by chain crosslinking photopolymerization is discussed in relation to selected applications in the electronics industry. All of these applications make use of the high speed and of the latitude to meet other requirements by variation of the chemical structure of the monomers. The selection comprises: 1. The coating of optical fibers ; 2. The replication of optical discs; 3. The replication of aspherical lenses, used for laser read-out of these discs. Other important processes will only be mentioned briefly for the benefit of a discussion of more fundamental results that have been obtained during the study of the selected examples. These results relate to the crosslink density, the influence of light intensity on polymer structure, the relation between shrinkage and chemical conversion, a parallel with physical aging, kinetics during vitrification, the importance of chain transfer, the build-up of peroxides in photopolymers and computer simulation of network formation by crosslinking polymerization. This serves to illustrate the continuous interaction between development of applications and fundamental research.

Time-intensity superposition for photoinitiated polymerization of fluorinated and hyperbranched acrylate nanocomposites

“…A third stage in which polymerization continues at very low rate, attributed to vitrification [35] was not present, in agreement with the fact that the T g of the polymers used in this study is lower than the polymerization temperature. However for PFOA based materials the reaction rate versus conversion curve shows a shoulder at a conversion of about 0.8 (Fig.…”

“…the product of the time of the exposure and the light intensity [33,34]. On the other hand some researchers found that the final conversion and properties of the polymerized materials depended on the light intensity [17,21,35,36]. The contradictory results obtained brought up the debate on the applicability to the photopolymerization of acrylates of the radiant exposure reciprocity law, stating that it is only the energy dose that determines the final effect on the light sensitive material [24].…”

“…This is the so-called autoacceleration or gelation effect [35]: due to the increased viscosity the mobility of the long-chain radical species is reduced, therefore reducing the termination rate as the recombination of two radical chains is not favored, while the small initiator radicals and the monomers can still move freely and continue the polymerization.…”

Using polymeric materials to generate an amplified response to molecular recognition events

“…In photoinitiated free-radical polymerization 13 , carbon-based radicals derived from organic initiator molecules react with the carbon-carbon double bonds of acrylate monomers, and polymers are formed via a chain-growth mechanism. The concept of amplification is inherent in chain-growth polymerization reactions owing to the extremely large number of propagation steps that result from a single initiation event.…”

Thermo-mechanical behavior and specific volume of highly crosslinked networks based on glycerol dimethacrylate and its derivatives

“…Because of good thermomechanical properties, crosslinked (meth)acrylates have found use in a wide variety of applications. They are successfully employed in coatings for flooring and furniture, dental restorative materials, optical fibers, hard and soft contact lenses, and photolithography [1][2][3][4][5][6].…”