FREE-RADICAL SYNTHESIS OF BLOCK-COPOLYMERS VIA DIXANTHOGEN-LINKED POLYMER SEQUENCES

Due to high chain transfer and the subsequent terminator properties of the dixanthogen moiety, (AB)(n) multiblock copolymers of poly(oxyethy lene-block-methyl methacrylate) and ABA triblock copolymers of poly(me thyl methacrylate-block-2-ethylhexyl acrylate) could be synthesized fr om dixanthogen-linked poly(oxyethylene) and poly(methyl methacrylate) pre-polymer sequences, respectively, using free-radical chemistry. A s imple and efficient method was developed for the synthesis of dixantho gen-linked polymers: Hydroxyl-functionalized pre-polymers were reduced using NaH to form alkoxide; CS2 was then added to the alkoxide to for m xanthate; and finally the xanthate was oxidized either in an aqueous or organic medium to form the dixanthogen. The synthesis techniques p rovided in this paper are general and thus, in principle, can be appli ed to many other block copolymer systems.