KINETICS AND MECHANISM OF THE CRAFTING OF 2-(DIMETHYLAMINO)ETHYL METHACRYLATE ONTO HYDROCARBON SUBSTRATES

The kinetics of grafting a basic monomer, 2-(dimethylamino)-ethyl meth acrylate (DMAEMA) to hydrocarbon substrates have been investigated. Th ese systems were chosen as models for the grafting of a homopolymeriza ble monomer to polyolefins such as polyethylene. The reactions with sq ualane and n-eicosane were initiated by an organic peroxide, 2,5-dimet hyl-2,5-di(t-butylperoxy)-3-hexyne; grafting yields become significant at high reaction temperatures and low monomer concentrations. In squa lane, the order of reaction with respect to monomer increased from abo ut 1.1 for 0.22-0.44M DMAEMA to almost 2 at 0.69M DMAEMA; the order wi th respect to initiator was 0.56. The overall activation energy in the 130-160 degrees C temperature range was, however, surprisingly low, 4 2 +/- 5 kJ mol(-1) When analytical data were used to separate the over all rate into those for grafting and homopolymerization, different kin etic paths were observed for the competing reactions. These results ar e interpreted in terms of two different mechanisms; intramolecular cha in transfer plays an important role in grafting, while depropagation b ecomes a major factor in homopolymerization at temperatures above 150 degrees C. (C) 1995 John Wiley & Sons, Inc.