Photodegradation of 1-naphthyl methacrylate-butyl methacrylate copolymers in benzene solution

Abstract

The photodegradation behavior of the copolymers of 1-naphthyl methacrylate (1NMA) with butyl methacrylate (BMA) in benzene solution has been investigated under deaerated conditions at room temperature. Irradiation in the 285-330-nm wavelength region led to main-chain cleavage in poly(lNMA) and poly(lNMA-co-BMA) accompanied by the evolution of carbon monoxide, whereas no chemical change was observed in the case of poly (BMA). The apparent rate constant for the main-chain scission of poly-(lNMA-co-BMA) in benzene solutions (1 g dm"3) increased with increasing 1NMA content up to 12.5 mol %. At this point the maximum value of 5.96 X 10"6 min'1 was obtained. Further increases in 1NMA content depressed the apparent rate for main-chain scission. The quantum yield for main-chain scission decreased monotonously with the increase in 1NMA content to attain its minimum value of 1.5 X 10"2 scissions per absorbed quantum for poly(lNMA).Homopolymers of alkyl methacrylates such as methyl methacrylate (MMA),1,2 butyl methacrylate (BMA),3 and tert-hutyl methacrylate ( -BMA)4 have been well characterized with respect to thermal and photochemical degradation in solution as well as in the solid state. Considerable attention has also been given to the degradation behavior of various copolymers containing alkyl methacrylate monomer units. The major processes involved in the degradation of alkyl methacrylate polymers have been demonstrated to be decomposition of side-chain ester groups, main-chain carbon-carbon bond scission, and depolymerization. These processes are significantly affected

Photodegradation of 1-naphthyl methacrylate-butyl methacrylate copolymers in benzene solution. 2. Effect of intramolecular excimer formation

“…Numerical results are listed in Table I together with the quantum yield for main-chain scission ( <.3) evaluated previously. 24 Following the so-called = 3 rule, which states that efficient intramolecular excimer formation occurs between two fluorescent chromophores separated by three carbon atoms along a polymer chain,3 one expects that the isolated 1-naphthyl chromophore in a monomer sequence such as BMA-1NMA-BMA ([BNB]) should make only a minor contribution to the intramolecular excimer emission from the poly(lNMA-co-BMA). In copolymer systems, triad fractions are useful as a measure of the relative content of isolated chromophores in a copolymer chain.…”

Aryl (meth)acrylates and polymers based on them

“…Excimers are not formed for the BMA ± NMA ± BMA sequences. 297,298 Upon irradiation with electrons (20 keV) and UV light, the perfluoroalkylated PPA is cross-linked in contrast to the non-perfluoroalkylated one which is destroyed under these conditions. 299 In the presence of oxygen, photooxidation of poly[aryl (meth)acrylates] occurs with the formation of carbonyl groups.…”