PULSED-LASER POLYMERIZATION MEASUREMENTS OF THE PROPAGATION RATE COEFFICIENT FOR BUTYL ACRYLATE

The results are reported for a series of measurements of the propagati on rate coefficient (k(p)) of butyl acrylate obtained from pulsed-lase r polymerization (PLP). Previous attempts reported in the literature t o use PLP for this monomer have failed because the data did not satisf y the internal consistency tests afforded by PLP. The problem was obvi ated by carrying out measurements at very low temperatures and with ve ry short times between laser pulses. Data for k(p) were obtained over the range -65 to -7 degrees C which satisfy PLP consistency tests (inv ariance of the apparent It, value to laser pulse frequency, etc.). The results fit k(p) (dm(3) mol(-1) s(-1)) = 10(7.2) exp(-17.3 kJ mol(-1) )/RT); the confidence ellipse for these parameters is provided. These data extrapolate to a value of k(p) = 2.7 x 10(4) dm(3) mol(-1) s(-1) at 50 degrees C. The higher value of the frequency factor of butyl acr ylate compared to that of butyl methacrylate can be rationalized in te rms of hindered rotations in the transition states.