MOLECULAR-WEIGHT DISTRIBUTION GENERATED UNDER FREE-RADICAL POLYMERIZATION INITIATION BY SEQUENCE OF RADIATION PULSES

Molecular weight distributions (MWDs) under free radical polymerizatio n initiation by an arbitrary sequence of radiation pulses have been in vestigated. Analytical expressions have been obtained for polymerizati on scheme which contains reactions of chain initiation, propagation an d termination by combination or disproportionation and chains linear t ermination (for example, inhibition). On the basis of these expression s the MWDs generated by pulse-periodic radiation have been investigate d theoretically. Results of calculation of the MWD dynamics in the pro cess of polymerization are presented. The MWDs for polymerization of M MA for different laser pulse fluences are calculated. The influence of the inhibitor burning within the irradiation process on the MWDs char acter have been studied. It has been shown that possibility to employ the PLP method for determination of polymerization rate constant (k(p) ) in the case of retardation depends significantly on the efficiency o f chains linear termination: the PLP method can be confidently used at tau>T (where tau is the effective lifetime of growing radicals, T is the pulse irradiation period) and it is doubtful if tau<T/3.