FREE-RADICAL GRAFTING FROM HYPERBRANCHED POLYESTERS BASED ON POLYMERIC AZO INITIATORS

Aromatic and aliphatic hyperbranched polyesters were prepared by AB, p olycondensation process. The highly branched, functional structure of these polymers leads to excellent solubility in combination with low s olution viscosities. Varied numbers of the functional groups of the hy perbranched structures were modified with azo functions which are able to initiate free radical polymerization. An increase in temperature i n the presence of the vinyl monomers methyl methacrylate (MMA), butyl methacrylate (BMA), styrene (S), or acrylamide (AA) results in ''graft ing from'' the hyperbranched structure. Using this method several graf t products were synthesized with variations in structure, number, and size of the graft arms. Gel-permeation chromatography (GPC) with unive rsal calibration and viscosity measurements indicate a strong influenc e of the hyperbranched core oh the properties of the graft product. It was possible to control the phase behavior of the graft products from two phases to homogeneous by the ratio hyperbranched polyester : graf ted monomer. The film forming properties which are very poor for unmod ified hyperbranched polyester were improved by grafting with linear po lymer chains.