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Synergetic Kinetics of Free Radical and Cationic Photopolymerization in Three Co-Initiators and Two-Monomers System

This version is not peer-reviewed.

Submitted:

11 October 2020

Posted:

12 October 2020

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Abstract
The synergetic features of a three-component photoinitiating systems (A/B/C) based on the measured data and proposed mechanism of Liu et al (Polymers, 2020, 12(6), 1394) are analyzed. The co-initiators/additives B and C have dual functions of : (i) regeneration of photoinitiator A and (ii) generation of extra radicals. The synergic effects lead to higher conversion of free radical polymerization (FRP) and cationic polymerization (CP). The key factors and rate constants influencing the conversion efficacy are explored by analytic formulas. Enhancing strategies for various photopolymerization systems are summarized including one component (or monomer) and one-wavelength, two-component and one, two and three-wavelength, and three-component, one-wavelength system. The synergetic effects for higher monomer conversion can be achieved by co-initiators for extra radicals and multiple wavelengths for reduced oxygen-inhibition. Co-initiator B, however, might also reduces the CP radical produced by initiator C. The conversion rate of FRP is proportional to the square root of the light intensity (I), absorption (b) and the initiator initial concentratios (A0, B0, C0), whereas CP is proportional to the linear power of a parameter defined as P=bIA0C0, a stronger dependence than FRP. The CP conversion is governed by a steady-state value proportional to P, and a rate fucntion defining the depletion rate of [A][C], or the increasing rate of the conversion profile. The measured results of Liu et al (Polymers, 2020, 12(6), 1394) are well analyzed and matching the predicted features of our modeling. The specific systems analyzed are: benzophenone derivatives (A) ethyl 4-(dimethylamino)benzoate (B), and (4-tert-butylphenyl)iodonium hexafluorophosphate (C) under a UV (365 nm) LED irradiation; and monomers of trimethylolpropane triacrylate (TMPTA, for FRP) and (3,4- epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate (EPOX, for CP).
Keywords: 
polymerization kinetics; photoinitiator; monomer conversion profile; synergetic effects
Subject: 
Chemistry and Materials Science  -   Analytical Chemistry
Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse.

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