PREPARATION OF TRIBLOCK STYRENE-TERT-BUTYLSTYRENE-STYRENE COPOLYMERS BY LIVING RADICAL POLYMERIZATION WITH A HETEROGENEOUS POLYMERIC INITIATOR

In the reported experiments, triblock copolymers containing the sequence styrene, p-tert-butylstyrene, styrene were prepared in an emulsion system by using isotactic polypropylene hydroperoxide as the initiator together with triethylenetetramine as an activator, according to the method of Mikulasova and co-workers. Polymerization of styrene continued after removal of the initiator from the emulsion by filtration and eventually reached 100% conversion after 4 hr at 35 degree C. tert-Butylstyrene at 80 degree C and styrene at 35 degree C were added successively to the system, with each polymerization reaction carried to 100% conversion before the next monomer was added. Thin-layer chromatography was used to separate the homopolymers and block copolymers in order to determine the purity of the product. Monomer compositions of the block copolymers was verified by infrared analysis. The existence of two separate phases in the extracted block copolymer was indicated by the observation of two distinct glass transition temperatures.