Poly , living termination with acetic

In a reversed way, cationically prepared end-functional polymers are used to quench other living polymers. For example, living anionic polystyrene may be terminated by polyisobutenes with silylchloride terminals [119,120] or epoxide ends [121,122] and by poly(vinyl ethers) with acetal terminals [123], The former case is reported to give H-shaped, tetraarmed block copolymers. 

The simplest examples of this class are the quenching living cationic polymers with living anionic or nucleophilic polymers. Namely, living poly(vi-nyl ethers) derived from the HI/ZnI2 system are allowed to react with living anionic polystyrene with the lithium counterion [115], poly(methyl methacrylate) with a silyl ketene acetal terminal by group transfer po-... 

Well-controlled polymerization of substituted acetylenes was also reported. A tetracoordinate organorhodium complex induces the stereospecific living polymerization of phenylacetylene.600 The polymerization proceeds via a 2-1 -insertion mechanism to provide stereoregular poly(phenylacetylene) with m-transoidal backbone structure. Rh complexes were also used in the same process in supercritical C02601 and in the polymerization of terminal alkyl- and arylacetylenes.602 Single-component transition-metal catalysts based on Ni acetylides603 and Pd acet-ylides604 were used in the polymerization of p-diethynylbenzene. 

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