Photopolymerisation-Free Radical

J. V. Crivello and K. Dietliker, in Photoinitiators for Free Radical Cationic and Anionic Photopolymerisation, 2nd ed., G. Bradley, ed., Wiley, Chichester, Chapter 3, (1998). 

Structure on hydrogel properties of 2-hydroxyethyl acrylate determined. " Polymers bearing tertiary amino groups have been synthesised and their fluorescence spectra found to be significantly quenched while maleic anhydride " and cyclododecanones have been found to be effective initiators of the photopolymerisation of styrene. Poly(methylphenylsilane) is also an effective photoinitiator for styrenes and acrylates via a photolytic process to give silyl radicals. Iron oxalate is also an effective photo initiator for acrylate monomers while a theoretical description of the kinetics of free radical dye-initiated polymerisation via an electron transfer process has been proposed. Using the Marcus theory it has been shown that the rate of electron transfer can affect the rate of initiation. 

Triphenylsilyl ether aluminium acetylacetonate and triphenylarsonium-p-nitrophenacylide have been found to induce the photopolymerisation of acrylic monomers by a free radical mechanism while arylthiyl radicals induce the photopolymerisation of vinyl monomers (CH2=CHX) in the order X= -C(CH3)3 < -( 2)3 3 < -(CH2)Si(OCH3)3 <= -CH2Si(CH3)3 -Si(OCH3)3 -Si(CH3)3 ... 

CriveUo, J.V. and Dietliker, K. (1998) Photoinitiators for Free Radical Cationic Anionic Photopolymerisation, John WUey Sons, Ltd, Chichester. 

The cationic curing systems can impart requisite barrier and electrical properties unlike the free radical initiated polymerisation of acrylates. In the cationic photopolymerisation, the process involves the ring opening of oxiranes and/or oxetanes and is initiated by strong protonic acids. The use of photosensitisers like thioxanthone and anthracene derivatives and photoinitiators further enhances the polymerisation process. 

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