Photoinitiated free-radical polymerization

Mn2(CO)io in a simple photoinitiated free radical polymerization. The antiplatelet activity of these polymers were compared with that of poly(ether-Wrethane) carrying the hydantoin residues in side chains. 

Photoinitiated free radical polymerization proceeds via three main steps ... 

Primary, and Secondary Reactions in Photoinitiated Free-Radical Polymerization of Organic Coatings... 

Photoinitiated free radical polymerization is a typical chain reaction. Oster and Nang (8) and Ledwith (9) have described the kinetics and the mechanisms for such photopolymerization reactions. The rate of polymerization depends on the intensity of incident light (/ ), the quantum yield for production of radicals ( ), the molar extinction coefficient of the initiator at the wavelength employed ( ), the initiator concentration [5], and the path length (/) of the light through the sample. Assuming the usual radical termination processes at steady state, the rate of photopolymerization is often approximated by... 

In contrast, photoinitiated free radical polymerization of glycidyl methacrylate and trimethylolpropane trimethacrylate in the presence of porogenic solvent affords a monolithic plug within the column that serves as a frit. This procedure represents a simple approach to reproducible fabrication of frits even in capillaries with large inner diameters. 

Photocurable coatings are widely used for metal, plastics wood and paper. Photoinitiated free-radical polymerization, however, can only be applied to vinyl monomers. The studies of Crivello have broadened the scope of monomers. In addition, photoinitiated cationic polymerization is not sensitive toward oxygen (air). Photoinitiated free-radical polymerization sometimes requires working in inert atmosphere in order to avoid the inhibition through oxygen1). 

Photoinitiated Free Radical Polymerization by Using Pyridinium... 

Tasdelen, M. A., Kiskan, B., Yagci, Y., Photoinitiated Free Radical Polymerization using Benzoxazines as Hydrogen Donors, Macromol. Rapid Commun. 2006, 27, 1539 1544. 

Yu, C., Xu, M., Svec, F., and Frechet, J. M. J., Preparation of monolithic polymers with controlled porous properties for microfluidic chip applications using photoinitiated free radical polymerization,... 

Scheme 10.1 Reaction scheme illustrating the photoinitiated free radical polymerization of monomer M, commonly a compound with a C=C bond.

Beyazit, S. Aydogan, B. Osken, L Ozturk, T. Yagci, Y. (2011). Long wavelength photoinitiated free radical polymerization using conjugated thiophene derivatives in the presence of onium salts Polym. Chem., 2 pp(1185-1189). 

One useful property of cationic polymerization is that it is not air inhibited. In the absence of nucleophilic impurities, there are no inherent modes of termination. Thus, the polymerization may continue for long periods (hours to days) after the light is turned off, in contrast to photoinitiated free radical polymerization (24). This post-cure should be useful for laminating two opaque materials, in that irradiation of the adhesive followed by lamination should result in a well cured adhesive, although it may take 1-2 days to form maximum bond strength. 

Kahveci MU, Beyazkilic Z, Yagci Y (2010) Polyacrylamide cryogels by photoinitiated free radical polymerization. J Polym Sci Polym Chem 48 4989 994... 

The methods used to prepare NC gels are simple and versatile, i.e., injection of reaction solutions into closed vessels followed by polymerization at ambient temperature. Hence, NC gels can be readily formed in various shapes and sizes, such as films, sheets, rods, spheres, hollow tubes, etc. (Fig. 4a) [21,29]. NC gels can also be prepared by photoinitiated free-radical polymerization using very low concentrations (e.g., 0.1 wt% relative to the monomer) of a hydrophobic photoinitiator in aqueous systems (Fig. 4b) [48], Furthermore, the other type of NC gel, i.e., tetra-PEG-based NC gels, with good biocompatibility can be prepared by incorporating clay nanoparticles into the tetra-PEG network [30],... 

Autoacceleration, where the rate of polymerization increases with conversion in isothermal conditions, is observed in both thermal- and photoinitiated free-radical polymerizations because the termination mechanisms are the same for both. As the chains grow longer, it becomes more difficult for the active centers to diffuse and imdergo bimolecular termination thus, termination frequency decreases and active centers at the chain ends can become trapped. In cases where termination is controlled by diffusion, the pseudo-steady-state assumption is no longer valid and chain length dependent termination (CLDT) may occur (67). As is discussed for chain cross-linking photopolymerizations below, more complicated kinetic treatments must then be considered, including unsteady-state kinetics. 

TAS 06a] Tasdelen M.A., Kiskan B., Yagci Y., Photoinitiated free radical polymerization using benzoxazines as hydrogen donors , Macromolecular Rapid Communications, vol. 27, pp. 1539-1544,2006. 

TAS 06b] Tasdelen M.A., Kumbaraci V., Talinli N. et al., Photochemically masked benzophenone Photoinitiated free radical polymerization by using benzodioxinone . Polymer, vol. 47, pp. 7611-7614, 2006. 

TAS 07a] Tasdelen M.A., Demirel A.L., Yagci Y., Poly(propylene imine) dendrimers as hydrogen donor in Type II photoinitiated free radical polymerization , European Polymer Journal, vol. 43, pp. 4423-4430, 2007. 

KAB 98] Kabatc J., Pietrzak M., Paczkowski J., Cyanine borates revisited. Application of the Marcus equation for the description of the kinetics of photoinitiated free radical polymerization . Macromolecules, vol. 31, pp. 4651-4654, 1998. 

Evans, M. G., M. Santabpa, andN. Uri Photoinitiated free-radical polymerization of vinyl compounds in aqueous solution. J. Polymer Sci. 7, 243 (1951). 

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