Abstract

An investigation of molecular weight distributions (MWDs) resulting from initiation of free radical polymerization by an arbitrary sequence of short laser pulses has been undertaken. The analytical expressions have been derived to calculate MWDs for a polymerization scheme that contains reactions of chain initiation, propagation and termination by recombination or disproportionation. The MWDs produced by pulse‐periodic irradiation have been calculated for a wide range of initiating pulses repetition rates (f = 0.05–100 Hz). The MWD dynamics in the act of polymerization and the influence of the duration of polymerization pseudostationary regime establishment upon the MWD have also been studied. The suitability of the derived expressions for describing the MWD generated by CW radiation before and after the establishment of polymerization quasi‐stationary regime has been considered.

Highlights

  • Polymerization of vinyl monomers and oligomers photoinduced by pulsed laser radiation is an intensively studied process. 1-11 The interest in this way of polymerization initiation is due both to the possibility of exerting control over energy input to the polymerization medium and, to some extent over the polymerization process in itself, and to a principal opportunity of extracting some information on this process kinetic parameters from the experiments on pulsed polymerization

  • The present paper studies theoretically the molecular weight distributions (MWDs) resulting from polymerization initiation by an arbitrary sequence of short laser pulses

  • In the present paper the expressions have been derived that enable to study the distributions of polymer molecules along the chain length on initiation of linear polymerization by an arbitrary sequence of short pulses

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Summary

INTRODUCTION

Polymerization of vinyl monomers and oligomers photoinduced by pulsed laser radiation is an intensively studied process. 1-11 The interest in this way of polymerization initiation is due both to the possibility of exerting control over energy input to the polymerization medium and, to some extent over the polymerization process in itself, and to a principal opportunity of extracting some information on this process kinetic parameters from the experiments on pulsed polymerization. 13’14 Alternatively, the MWD features under pulsed irradiation allow in a number of cases to immediately evaluate the rate constants of polymerization (kp) and a polymer chain termination (kt) in the same experiment4-6’15-18 which is not feasible under polymerization by CW radiation. The MWDs under pseudostationary polymerization 15 with small degree of monomer-to-polymer conversion were calculated on the assumption that the Flory principle aa is satisfied and growing radicals are instantaneously generated. Consideration was given to the pulsed-laser-initiated free radical polymerization of monomers (M) having a single reactive double bond. Polymerization of such compounds produces linear macromolecules differing in the number of elementary links (i).

A Let the initiating radicals concentration
CALCULATION RESULTS AND DISCUSSION
CONCLUSIONS
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