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.
