Photoinitiation mechanism of free radical photopolymerization in the presence of cyclic acetals and related compounds

Abstract

The behavior of six cyclic acetals and related compounds in the photoinitiation step of a radical photopolymerization was investigated. As shown by the photopolymerization kinetic data obtained from FTIR spectroscopy, most of them are efficient coinitiators in the presence of benzophenone (BP) with efficiencies close to a reference amine coinitiator (ethyl dimethylaminobenzoate, EDB). Laser flash photolysis and ESR spin trapping technique were used to study the photochemical mechanisms of the production of initiating radicals and explain the differences in reactivity. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5758-5766, 2010

Visible light sensitive photoinitiating systems: Recent progress in cationic and radical photopolymerization reactions under soft conditions

“…k q values >10 9 M −1 s −1 indicate that the processes are almost diffusion-controlled; (ii) Evaluation of the 1 PI/additive electron transfer quantum yields (˚e T ): they can be calculated according to ˚e T = k q 0 [additive]/(1 + k q 0 [additive]), and the higher ˚e T values indicate the higher PI/additives reactivity; (iii) The free energy changes ( G) for the electron transfer between PI and the additive: G can be calculated from the classical Rehm-Weller equation [26] [ G = E ox − E red − E S (or E T ) + C; where E ox , E red , E S (or E T ), and C are the oxidation potentials of the electron donors, the reduction potential of the electron acceptors, the excited singlet (or triplet) state energies of PI, and the electrostatic interaction energy for the initially formed ion pair, generally considered as [25,27]: the evolution of the functional groups of the monomers -conversion C (%) -is determined by measuring the peak area A of the corresponding characteristic bands (e.g., the epoxy group content of EPOX, the double bond content of TMPTA, the double bond content of DVE-3 and the thiol (S-H) content of Trithiol at about 790 cm −1 , 1630 cm −1 , 1620 cm −1 and 2580 cm −1 , respectively) at each time: C (%) = (A 0 − A t )/A 0 × 100 where C is the conversion at t time, A 0 the initial peak area before irradiation and A t the peak area of the functional groups at t time.…”

Synthesis and application of dyes derived from benz[cd]indol‐2(1H)‐one as visible‐light‐absorbing polymerisation photoinitiators

“…Thioxanthone [19][20][21][22] and benzophenone [23][24][25][26] and, more recently, novel erythrosine B [27] and naphthoquinone [28] derivatives linked with appropriate groups have been synthesised and applied as initiators for free radical polymerisation. There are very few chromophores that can be used to design onecomponent initiator systems.…”

Keggin‐Type Polyoxometalate ([PMo12O40]3−) in Radical Initiating Systems: Application to Radical and Cationic Photopolymerization Reactions

“…ESR‐ST experiments were carried out using an X‐Band spectrometer (MS 400 Magnettech). The radicals were generated at room temperature (RT) upon exposure to a Xe–Hg lamp under N 2 and trapped by phenyl‐ N ‐ tert ‐butylnitrone (PBN) according to a procedure10 described in detail. The ESR spectra simulations were carried out with the WINSIM software.…”