Free radical ''grafting from'' hyperbranched polyesters based on polymeric azo initiators

Aromatic and aliphatic hyperbranched polyesters were prepared by AB, polycondensation process. The highly branched, functional structure of these polymers leads to excellent solubility in combination with low solution viscosities. Varied numbers of the functional groups of the hyperbranched structures were modified with azo functions which are able to initiate free radical polymerization. An increase in temperature in the presence of the vinyl monomers methyl methacrylate (MMA), butyl methacrylate (BMA), styrene (S), or acrylamide (AA) results in ''grafting from'' the hyperbranched structure. Using this method several graft products were synthesized with variations in structure, number, and size of the graft arms. Gel-permeation chromatography (GPC) with universal calibration and viscosity measurements indicate a strong influence 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 : grafted monomer. The film forming properties which are very poor for unmodified hyperbranched polyester were improved by grafting with linear polymer chains.