Instantaneous initiation of pulsed laser polymerization (PLP) by an intense single pulse (SP) in conjunction with subsequent highly time-resolved EPR detection of radical concentration provides a detailed picture of polymerization kinetics and mechanism. This SP-PLP-EPR technique may also be applied to systems where, e.g., by intramolecular chain transfer, more than one type of radicals is occurring, as with acrylic monomers. Moreover, SP�PLP�EPR investigations into systems containing two types of radicals allow for analysis of reversible-deactivation radical polymerizations, such as RAFT and ATRP, and for elucidation of kinetic and mechanistic aspects of these controlled polymerizations. The potential of the new method will be illustrated by investigations into chain-length-dependent termination (CLDT) for bulk homopolymerizations of styrene, for which an SP�PLP�EPR trace is shown the figure, of vinyl acetate and of other monomers, including investigations into radical polymerization in solution. The SP�PLP�EPR studies demonstrate that CLDT is adequately represented by the composite model which encompasses the power-law exponents as and al for termination of short-chain and long-chain radicals, respectively, a crossover chain-length, ic, which separates these two regions, and the rate coefficient for termination of two radicals of chain length unity, kt1,1. Moreover, determination of deactivation rate coefficients in ATRP and of addition and fragmentation rate coefficients in RAFT polymerization will be illustrated. The potential of the new technique is far from being fully exploited.

Kinetics of reversible deactivated radical polymerization studied via SP-PLP-EPR experiments

248th National Meeting (2014)

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