HETERO-ARM STAR COPOLYMERS WITH POTENTIALLY IONOGENIC BRANCHES

Hetero-arm star copolymers-i.e. star polymers the cores of which carry branches of two different kinds-have been made by a three-step anionic process. The polystyrene (PS) precursor was made first, and used to initiate the polymerization of a small amount of divinylbenzene. The cores of the resulting star polymers still contain the active sites and can therefore be used to initiate the polymerization of another suitable monomer. tert.Butyl acrylate (t.BuA) was shown by Teyssie to polymerize anionically without transfer or termination, provided lithium chloride is present. An attempt was made to have poly(t.BuA) branches grow from the "living" cores of the PS star molecules. A detailed characterization of the resulting samples was performed, to establish whether these hetero-arm star copolymers exhibit the expected structure. The method can be considered quite reliable, and leads to star polymers with branches that are potentially ionogenic.