Functionalization of terminal double bonds in polypropylene

A terminally anhydride-functionalized polypropylene was synthesized via the Alder Ene reaction from a low molecular weight amorphous polypropylene. A Lewis acid, SnCl2·2H2O, was found to catalyze the reaction thereby improving anhydride content in the polymer for reaction conditions comparable to an extrusion environment, i.e. elevated temperature and short residence time. The reaction was carried out at 230 °C for 5 minutes in the presence of TEMPO which acted as a free radical trap, preventing maleic anhydride from being grafted onto the backbone of the polypropylene. The product was characterized by FTIR and NMR to provide evidence of the anhydride location on the chain. A series of runs varying the catalyst concentration in the reaction has shown that an optimum in anhydride incorporation into the polypropylene exists. Examining the kinetics of the system has shown that the overall order of the reaction remains second-order despite the presence of a catalyst.