POLY(VINYL METHYL ETHER)

Definition

ChEBI: A macromolecule composed of repeating methoxyethyl groups.

Preparation

Vinyl ethers are prepared by reaction of acetylene and alcohols in the presence of the potassium alkoxide as catalyst:

For the production of polymers, methyl, ethyl and isobutyl vinyl ethers are the most common monomers.
Vinyl ethers are susceptible only to cationic polymerization. In a typical process, methyl vinyl ether is agitated with boron trifluoride (BF 3. 2H20). The temperature is kept at about l0?? by cooling for 3-4 hours; the reactor is then sealed and the temperature allowed to rise to 100??C. Reaction is complete in about 10 hours and the polymer is obtained as a viscous mass. It is interesting to note that poly(vinyl isobuty ether) may be obtained in crystalline form by conducting polymerization at - 80?? to -60??C in liquid propane using boron trifluoride etherate as initiator. This was the first stereoregular polymerization to be achieved. Incidentally, isotactic polymer has also been prepared by the use of Ziegler-Natta type catalysts and this was the first indication that these catalysts could polymerize a suitable monomer by a cationic mechanism.
Poly(vinyl methyl ether) is water-soluble and is used in adhesive and textile sizes. The ethyl and isobutyl polymers find use in pressure-sensitive adhesives.