INFLUENCE OF THE FUNCTIONALITY OF THE QUATERNIZING AGENT AND THE POLYMER MOLECULAR-WEIGHT ON THE VISCOELASTIC BEHAVIOR OF ALPHA,OMEGA-(DIMETHYLAMINO)POLYISOPRENES

Quaternization of the end-groups of alpha,omega-(dimethylamino)polyiso prenes with monofunctional, difunctional and trifunctional halides (io dides and bromides) has been undertaken on polymers of different molec ular weights ((M) over bar(n) = 6000 and 38 000 g mol(-1)). The therma l stability of the ammonium end-groups is somewhat better when iodide counteranions are present. Quaternization increases the T-g of the mat erial. This effect is more pronounced for low molecular weight chains, especially when a short alkyl group quaternizing agent is used. Howev er, the size of the alkyl or aryl radical has a minor effect on polyme r T-g when difunctional quaternizing agents are used. Nevertheless, th e modulus of the rubber-like plateau of materials with difunctional ag ents is higher than with monofunctional quaternizing agents, owing to coupling reactions between the chain-ends. Rheological measurements in dicate that the quaternized low molecular weight polyisoprenes exhibit an Arrhenius-type temperature dependence characterized by activation energies which vary between 121 and 146 kJ mol(-1) and suggest that th e relaxations attributed to dipole-dipole interactions dominate over l ong chain entanglements.