Preparation of functionalized low molecular weight natural rubber latex using solid nanometric TiO₂ film as a photocatalyst

Natural rubber (NR) is a high molecular weight (MW) hydrophobic polymer, which can not be easily dissolved in several kinds of solvents, leading to the limitation of usage. NR latex containing low MW and reactive-terminal groups is another interesting form to extend the applications of NR. In this study, a photochemical degradation of NR using H₂O₂, nanometric TiO₂ film and UV irradiation was applied to prepare the hydroxylated low MW NR (LNR). A solid nanometric TiO₂ film prepared from titanium solution was applied in the present work. The photosensitivity of the selfassembled TiO₂ film was determined by the decomposition rate of methylene blue stock solution using UV/VIS spectrophotometer. The effect of type of NR latex used, H₂O₂, UV light and TiO₂ film on the molecular weight reduction was studied, based on change in intrinsic viscosity determined by Ubbelohde solution viscosity. The structural characterization of the resulting LNR was analyzed by FT-IR and NMR techniques. It was found that hydroxylated LNR with number average molecular weight of 1 × 10⁴ g/mol was obtained by UV irradiation (40 W) of deproteinized natural rubber (DPNR) latex (10% DRC) containing 30% w/w H ₂O₂, on a petri dish coated with TiO₂ film for 5 hr. The advantage of this method is that the obtained hydroxylated LNR in either latex or dry rubber form is very clean without further purification.