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Liquid crystallinity: Medium effects on photopolymerization rates
Author(s) -
Hoyle C. E.,
Kang D.,
Chawla C. P.,
Griffin A. C.
Publication year - 1992
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760322008
Subject(s) - polymerization , crystallinity , materials science , kinetics , photopolymer , degree of polymerization , radical polymerization , laser , chemical physics , thermodynamics , chemical engineering , optics , polymer , composite material , chemistry , physics , quantum mechanics , engineering
Ordering of the medium in which free radical polymerization is conducted can, under appropriate circumstances, alter the kinetics of the chain‐growth process, resulting in enhanced rates. Since in many systems medium changes occur at higher conversion, it is important to take into account any alterations in the polymerization rate induced by such phenomena. We have found that exotherms initiated by individual laser pulses can be useful in identifying and providing detailed information concerning rate acceleration in liquid crystalline systems. From measurements of the pulse intensities in the sample cell, estimates of the quantum efficiency and kinetic chain length have been made directly from the integrated areas of the exotherm curves. Recent refinements in our sample geometry have allowed us to generate reproducible efficient data as a function of the degree of conversion and order in the polymerization medium.