Laser spectroscopic studies polymerization

Phonon spectroscopy has been found to be a powerful method to Investigate the reaction dynamics In solid state. Also, non-llnear laser spectroscopic study has been used to probe the dynamics of photochemical reactions. Future directions are clearly a more quantitative and theoretical formulation of the Importance of energy state dynamics In determining reactivity In the condensed phase. Non-llnear spectroscopy as well as time-resolved X-ray crystallography using synchrotron radiation can be expected to provide valuable approaches for future development of a dynamic model of solid state polymerization. 

Early laser Raman spectroscopic studies concluded that dilute, 0.3 M sodium siHcate solutions of varying ratios (m = 0.33-3.3) contain an equiHbrium mixture of monomeric siHcate, SiO(OH) 2 and Si02(0H) 2> polymeric anions, regardless of their histories and methods of preparation. Subsequent... 

This paper presents studies of solid state polymerization aimed towards formulating a dynamic model of reactivity in the condensed phase. Phonon spectroscopy is successfully used to elucidate the mechanism of lattice control of the reaction. Novel concepts of phonon-assisted thermal and photochemical reactions are introduced, supported by experimental data. Non-linear laser spectroscopy is used to find the importance of biexcitonic processes in photopolymerization. Also, spectroscopic studies of reactions in Langmuir-Blodgett films and at gas-solid interface which produce ordered polymers are presented. 

Quantitative in-line spectroscopic analysis of polymerization processes depends on the aTOUahUity of autoclaves ecjuipped with windows that are transparent to the probing light and, for pulsed laser-induced studies, also to excimer laser light. A survey of such optical cells for vibrational spertroscopic online measurements up to kilobar pressures is given elsewhere. ... 

Termination kinetics were studied using the SP-PLP technique, which combines single-pulse initiation of polymerization with in-line NIR-spectroscopic detection of monomer concentration, CmIO- Time-resolution of the measurement of monomer concentration may be as low as a few microseconds, and the time interval for analysis may be extended up to a few seconds after firing the laser pulse at t=0. 

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