Main chain scission reaction of poly(methyl methacrylate) caused by two‐photon ionization of dopant

Abstract

AbstractThe main chain scission reaction of poly(methyl methacrylate) (PMMA) doped with N,N,N,′,N′‐tetramethyl‐p‐phenylenediamine (TMPD) was examined by ESR spectroscopy and GPC measurement, and the scission mechanism was analyzed. The two‐photon ionization of TMPD with excimer laser excitation at 77 K produced an ester radical anion of PMMA (PMMA·m̌), which becomes the main chain tertiary radical CH2C˙(CH3)CH2after the detachment of the ester side group by annealing of the sample at room temperature. The main chain scission radical ˙C(CH3)(COOCH3)(PMMA˙) which was produced by the β‐scission fromCH2˙C(CH3)CH2showed the 13‐line ESR spectrum instead of the ordinary 9‐line, due to the fast quenching of the sample to 77 K. The change of the molecular weight distribution was measured by GPC after several irradiation‐and‐annealing operations. The simulation of the GPC curve confirmed that the scission re‐action occurs at random in the PMMA chain in the solid and the main chain scission yield from the ester radical anion, [PMMA˙]/[PMMA·m̌], is 0.30. © 1995 John Wiley & Sons, Inc.