Living cationic polymerization of cyclic unsaturated ethers

Abstract

The living cationic polymerization of 5-methyl-2, 3-dihydrofuran (MeDHF; 4) has been achieved with acetyl perchlorate (AcClO4) as an initiator in a nonpolar solvent (toluene) at −78°C to give nearly monodisperse polymers (Mw/Mn∼1.1). Under these conditions, the number-average molecular weight (Mn) of the polymer increased in proportion to conversion, and it further increased on addition of a new monomer-feed to a completely polymerized solution. The Mn values were in good agreement with the calculated values for living polymers. Similar increases in Mn with conversion were observed in the MeDHF polymerizations by AcClO4 in CH2Cl2 or by iodine in both toluene and CH2Cl2, but the product polymers showed broader molecular weight distributions. These polymerizations thus involve long-lived (though not perfectly living) propagating species. 2, 3-Dihydrofuran (3) also gave long-lived polymers, when polymerized with iodine in toluene and CH2Cl2 at −40°C. Therefore, these unsaturated cyclic ethers give living/long-lived species over a range of reaction conditions wider than that for the corresponding linear monomers (substituted vinyl ethers). © 1984 The Society of Polymer Science, Japan.