Surface active azogroup-containing polymers and their use in emulsion polymerization

Polymeric azoinitiators have been obtained by the acidcatalyzed polyreaction of azobisisobutyronitrile (AIBN) with tetraethylene glycol (TEG) and 1.6-hexanediol resp. The kinetics of decomposition of these polyazoesters were investigated by differential scanning calorimetry (DSC) resulting in an activation energy of E_a=124.5 KJ/mol and a frequency factor of A= 3.6 · 10¹⁴ sec^–1.The polyazoesters were used to initiate radical polymerization of acrylamide limiting the decomposition of the initiator to 37%. The resulting polyacrylamides containing azogroups had molecular weights between 50 000 and 250 000 g/mol. They are surface active polymers having a critical micell concentration of 0.1 to 0.3 g./l. By use of these polyacrylamides as an emulsifying initiator system stable emulsions of polymers were obtained without additional use of a tenside. Polymethacrylic acid containing azogroups can be used as well as an emulsifying initiator.The latex particles are stabilized by a solvated shell of a polymer. Thus it is possible to obtain stable emulsions in organic solvents by use of an azogroup-containing prepolymer which is soluble in that solvent. An emulsion of polyacrylamide in methanol ohtained by use of an azogroup-containing polyvinylacetate is an example.Dedicated to Professor F. H. Müller.Thanks are due to Dr. R. Menhold, Bayer AG, Leverkusen for performing the electronmicroscopic investigations. Financial support by Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie is gratefully acknowledged.