HOMOGENEOUS CATALYTIC HYDROFORMYLATION OF STYRENE-BUTADIENE COPOLYMERS IN THE PRESENCE OF HRH(CO)(PPH3)3

Homogeneous catalytic hydroformylation of unsaturated polymers offers a useful method of producing reactive polymers. Such reactive polymers may serve as substrates for grafting, cross-linking, or further modification reactions. A study of the homogeneous hydroformylation of a styrene-butadiene AB block copolymer (SBR) using the catalyst HRh(CO)(PPh3)3 is presented. The product polymer, which has been characterized using IR and H-1 and C-13 NMR, is shown to contain an internal aldehyde product as well as an anti-Markovnikov aldehyde product. No hydrogenation of the polymer was observed under hydroformylation conditions. Although the product has limited stability, gel permeation chromatography showed that no unwanted side reactions occurred during the hydroformylation process. Differential scanning calorimetry suggests a cross-linked product results upon precipitation of the product polymer from the reaction solution. Kinetic and spectral studies of the hydroformylation of SBR suggest that the active catalytic species is probably HRh(CO)2(PPh3)2. Although no attempt was made at deriving a stringent rate law in this investigation, the kinetic data were found to be useful for optimization of the reaction rate and product distribution. An increased selectivity of the catalyst toward the anti-Markovnikov product is also possible. The nature of the reaction solvent was found to have an effect on the reaction rate and degree of conversion.