Vinyl alkyl ethers, stereoregular polymerizations

The cationic polymerization of vinyl isobutyl ether at —40°C produces stereoregular polymers (structure 5.21). The carbocations of vinyl alkyl ethers are stabilized by the delocalization of p valence electrons in the oxygen atom, and thus these monomers are readily polymerized by cationic initiators. Poly(vinyl isobutyl ether) has a low Tg because of the steric hindrance offered by the isobutyl group. It is used as an adhesive and an impregnating resin. 

Many of the stereoregular polymerizations by cationic catalysis involve coordination of catalyst with monomer. In this category one finds the vinyl alkyl ethers and closely related compounds. For... 

Since coordination of the ether oxygen is involved in the stereoregulating step, any factor which weakens this will decrease stereospecificity. This explains why the more hindered, higher alkyl vinyl ethers give less stereoregular polymerization than vinyl methyl ether. 

Neither chromyl chloride nor the mixed initiator diethyl zinc/phosphoryl chloride were found to induce stereoregularity in the polymerization of alkyl vinyl ethers. 

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