Non‐stationary state kinetic determination of polymer radical lifetimes

Lifetimes of polymer radicals were determined by a direct flow technique. The variation of yield of polymer with the period between initiation by an ultraviolet source and destruction in an inhibitor solution was determined by spectrophotometric analysis. A swiftly falling stream of monomer was irradiated by a sharply focussed beam of intense ultraviolet radiation, and the time of radical growth was controlled by varying the distance of fall at a constant flow rate. The variation of yield of polymer with the time interval between photochemical initiation an destruction in an inhibitor solution was determined by spectrophotometric analysis of the polymer formed. A polished elliptical reflector was used, instead of the customary quartz lenses, with the source and stream at the foci of the ellipse. A water‐jacketed capillary was employed to eliminate spurious thermal initiation. Radical lifetimes of 0.24 seconds for styrene and 1.80 seconds for butyl acrylate were obtained. The data were compared with values calculated on the basis of non‐stationary state kinetics in a flow system.