Photosynthetic membranes II: Kinetic studies of photoinitiated grafting of some acrylic monomers onto cellulose

Photochemical grafting of 1,6-hexanediol diacrylate, diethylene glycol diacrylate and tetraethylene glycol diacrylate onto cellulose in the form of filter paper was investigated kinetically at 30 ± 2 °C with 1,2-diphenyl-2,2-dimethoxyethanone as a photoinitiator, under experimental conditions suitable for the preparation of membrane systems. Irradiations were carried out polychromatically, with incident radiation of flux (2.5 × 10-8)-(22.6 × 10-8) einsteins s-1 cm-2. The ratio R between the molar concentrations of photoinitiator and monomer were varied between 0.005 and 0.095, while the n/S value (n, moles of diacrylate monomer deposited per unit apparent surface S) was varied between 7.61 and 75.0 μmol cm-2. Two consecutive constant-rate processes were indicated by the kinetic curves. The quantum yields Φ1 and Φ2 for the first and second constant-rate periods were calculated. They are almost insensitive to the difference in diacrylate monomer structure; the Φ1 show a linear dependence on R, while the Φ2 show an inverse dependence on n/S. The relevance of photochemical parameters in the proposed reaction mechanism is discussed.