Photopolymerizable systems

Photopolymerizable Systems.—Patents of interest concerning photopolymerizable and photocurable systems can be found in references 303—388 and under the following British patent numbers  

Cepciansky, Coll. Czech. Chem. Comm., 1973,38, 697 U. Steiner, M. Hafner, and S. Schreiner, Photochem. and Photobiol., 1974, 19, 119 R. Bonneau and 

Gilbert and H. Guesten, Kernforschungszentrum Karlsruhe Ber.), 1974, 104 Y. Kojima, Kagaku Sochi, 1974, 16, 103 M. Hirose, T. Endoh, and K. Mima, Kagaku Kogaku, 1974,38, 479. 

488 Nippon Telegraph and Telephone Public Corp., 14 Sept. 1972, JA 49 051 355. 

R1 is an acyclic or cyclic hydrocarbon radical and each R2 independently represents a halogen or cyclic or acyclic hydrocarbon radical = 0—4 

8 Appendix Review of Patent Literature Photopolymerizable Systems.— The following patents have appeared on photo-polymerizable systems for UK, Europe, West Germany, Japan, and USA. 

R = Ph,H2C = CH,Me3Q octyl,3,5-di-t-butyI-4-hydroxyphenyl, PhCH=CH, cyclohexyl 

Institute of Physical-Organic Chemistry, Academy of Sciences, Belorussian SSR Polimir Industrial Enterprises, USSR P, 740787, 1980. American Cyanamid Corp., US P, 4192796, 1980. 

Institute of Physical-Organic Chemistry, Belorussian SSR, USSR P, 744001, 1981. 

R = alkyl, alkenyl, alkynyl, aralkyl, alkoxyalkyl, or similar group 

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In the study of the chemorheology of photopolymerizable systems, the use of a traditional rheometer is particularly difficult and the development of improved time resolution from several seconds to better than 1 ms has been noted, together with an increase in the intensity of initiating radiation that may be employed (Schmidt et al, 2005). The challenge is to gather data at the best possible SNR and then use the appropriate algorithm for recovery and analysis of the phase information and intensity to enable calculation of G and tan <5 (Schmidt et al, 2005, Chiou and Khan, 1997). These studies are often augmented by simultaneous real-time spectroscopic studies on the sample in the rheometer in order to provide conversion data as discussed in Section 3.3. 

Intermediate species such as macromolecules bearing acrylate-type residues represent a cross between photopolymerizable monomers and photocrosslinkable polymers. The gap between photopolymerizable systems and photocrosslinkable polymers is closed since the two systems are basically the same. A photocrosslinkable polymer can be considered the extreme case of a macromolecular photopolymerizable monomer. 

These results point to two processes, premature radical chain termination and film shrinkage, which compete in determining the ultimate polymerization conversion efficient of multifunctional acrylates. It is obvious that critical attention must be paid to the pulse repetition rate, photoinitiator concentration, and acrylate functionality in developing any photopolymerizable system for laser-initiated polymerization. Future publications on laser-initiated polymerization of multifunctional acrylates will deal with monomer extraction of partially polymerized films, mechanical properties of laser polymerized films, and the Idnetics of single-pulsed systems. 

Photopolymerizable monomers and oligomers can be classified under four main groups including radical monomers and oligomers, unsaturated polyester resins, thiol-ene systems, and cationic monomers. In addition to these systems, particular photopolymerizable systems are also available such as expanding monomers, liquid crystalline monomers, and some other miscellaneous monomers. 

As stated above, photopolymerizable systems have found utility in a wide range of fields, including for imaging, surface coatings and modifications, printed circuit boards and integrated circuits, and the fabrication of oriented crystalline materials for electro-optical applications. However, in recent years, photopolymerization is becoming a viable technique for... 

Photopolymerizable systems have received a lot of recent attention in biomaterial applications due to the ability to rapidly form a solid polymer (gel) from a liquid precursor solution (monomer or macromer) with spatial and temporal control under physiological conditions. The development of cytocompatible systems has provided the ability to form materials in the presence of proteins, cells, and tissues to allow for minimally invasive biomaterial-based therapies. In particular, photopolymerizable systems have been used extensively as dental restoratives, controlled microenvironments to study cellular behavior and develop tissue substitutes, and to encapsulate growth fartors and cytokines in a polymer matrix for controlled release applications. 

Okino et also demonstrated dmg permeability into tissues from in situ forming hydrogels. Photopolymerized hydrogels based on styrene-derivatized gelatin were formed on the surface of rat liver tissue and rhodamine-albumin was used as a dmg model to characterize dmg release and diffusion into the tissue. This work showed the multitude of variables inherent to photopolymerizable systems to control dmg release characteristics. 

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