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46962-SE
Advances in Photo-Initiated Polymer Processes and Materials, at the Materials Research Society Meeting, April 2007, San Francisco, CA

C. Allan Guymon, University of Iowa

Photopolymerization is a field of technological endeavor that involves the interaction of light with resin systems and the subsequent curing to form films and materials for a wide range of areas including protective coatings and network structures for encapsulation of reactive components. Photopolymerization has applications or potential applications for flat panel displays, coatings of optical fibers, medical implants and devices, coatings for wood/metal/vinyl substrates, and fabrication of protective energy absorbing devices, just to name a few. From its outset, progress in photopolymerization has been fundamentally linked to an understanding of how materials absorb high energy ultraviolet and visible electromagnetic radiation and what properties are required to achieve useful technological goals.

The development and dissemination of new scientific and materials is of great importance and continues to play an integral role in the development of a new generation of coatings and thermoset plastics. Over the last three decades, government agencies, academic laboratories, government labs, and private industry have made extensive investments in the development of photocurable materials for applications in the expanding information technology and electro-optical fields in addition to other traditional coatings areas. These investments have realized commercial potential in a variety of areas including the following which were topics in the symposium:

• Stress reduction during photocuring of crosslinked networks;

• Kinetics of photopolymerization and the relationship between molecular structures and rates in free-radical and cationic photocuring systems;

• Nanocomposite photocurable coatings and the relationship between composite structure and performance parameters

• Control of photocurable liquid crystalline containing networks and reactive structures and the development of holographic liquid crystalline display matrices;

• Phoimprintable nanolithography for advance electronic applications and patternable imaging systems;

• Thiol-ene networks and their implications for advanced materials;

• Multiphoton photoinitiated polymerization systems;

• Photocurable systems with modified silane containing systems;

• Photocurable hybrids

The continued progress of these crucial photocurable technologies depends on the ongoing development and understanding of new materials. Many of the important issues in next generation applications, such as improved materials performance, reduced device cost, and improved reliability and performance can be achieved by a disciplined materials development process. The success of this development relies on the interdisciplinary cooperation of chemists, materials scientists, physicists and all engineering disciplines to create materials technologies that meet all of these criteria, ultimately helping to drive the growth of this critical technology.

It is important to keep members of the MRS at the forefront of the rapidly growing photopolymerization field. The meeting was organized by a team from academics and industry, representing scientists from the United States and Japan. The invited speakers represented a broad spectrum of interests, and experience levels. Additionally, contributed presentations were placed into topical sessions centered around the invited speakers. The symposium was held in San Francisco from April 18-20 of 2007 and was from all reports a great success. Comments were very positive about the quality and topical range of the presentations. The attendance was high for all sessions, with as many as 225 attendees, and about 120 attendees on average.

This international symposium had a program with 37 oral presentations (nine foreign) and 13 poster contributions. Examples of the foreign presentations are briefly summarized in the following text which highlights several invited presentations. Professor Tadatomi Nishikubo gave a presentation on the synthesis and photopolymerization behavior of a novel series of oxetane monomers. These monomers photocure under appropriate conditions and exhibit unique properties. Further derivatization of the oxetane polymers allows development of hyperbranched and dendrimer systems. Professor Marco Sangermano presented on a dual-curing process to form nanostructured photocurable materials. This novel parallel, dual-curing process involves cationic photopolymerization along with condensation reaction of alkoxysilane groups. These materials alone, and in combination with block copolymers, show significant enhancements in mechanical properties and in thermal stability of the cured networks. Professor Kimihiro Matsukawa gave a paper on photopolymerization through the use of photoluminescent properties of organically modified polysilanes. Organic-inorganic hybrids were produced first by photopolymerization of metal hydroxide modified acrylates, followed by sol-gel reaction to form the inorganic phase. These materials show intriguing behavior including controllable refractive index, as well as temperature controlled configuration and absorbance. Profesor Robert Liska gave a paper on recent work that demonstrates the use of two photon absorption in photocurable systems. The synthesis and development of highly reactive monomers based on acrylamide and necessary for this process will also be discussed. The combination of monomer system with two-photon absorption has allowed spatial resolution down to 300 nm. Other papers of similar quality were also given by other foreign speakers contributing to an excellent overall symposium.

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