Photoinduced graft copolymerization of ethyl acrylate, methyl methacrylate and methyl acrylate onto ethyl cellulose in homogeneous media

The vinyl monomers ethyl acrylate (EA), methyl methacrylate (MMA) and methyl acrylate (MA) were photografted onto ethyl cellulose (EC) in the presence of azobisisobutyronitrile (AlBN) and benzil (Bz) using UV irradiation in the range 310-460 nm in homogeneous media. Variables affecting the grafting yield (GY (%)), such as the time of UV irradiation and the concentrations of monomer and initiator, were investigated. Different techniques were used, e.g. IR, UV and viscosity measurements. The UV spectra of AlBN and Bz show strong absorption in the near-UV region due to n-pi* transitions. The order of the monomers used in terms of increasing GY values and increasing intrinsic viscosities of the graft copolymers and attendant homopolymers was found to be EA > MMA > MA. The order of reactivity of the initiators used in terms of increasing GY was found to be AlBN > Bz. The highest rates of propagation of graft copolymerization of the vinyl monomers onto EC in the presence of Bz and tetrahydrofuran (THF) were found to be 0.22% min(-1), 0.11% min(-1) and 0.1% min(-1) for EA, MMA and MA respectively. The mechanism of grafting in the presence of Bz and THF is discussed. (C) 1997 Elsevier Science S.A.