Polymer synthesis by cationic polymerization: Living and functionalized polymers

Nearly perfect living polymers have been obtained by the polymerization of vinyl ethers (VE) initiated with a mixture of hydrogen iodide and iodine (HI/I2 initiator) at low temperature in nonpolar solvents. The polymers had molecular weights directly proportional to monomer conversion and a nearly monodisperse molecular weight distribution (M̄w/M̄n < 1.1). A very similar living polymerization took place by the use of a 1:1 adduct between VE and HI (CH3CHI (OR)) (1) as an initiator in conjunction with iodine. From these facts, a new mechanism has been proposed for the living polymerization in which the CHI bond of the initially formed adduct 1 is activated by an electrophilic interaction of iodine and VE monomer inserts into the activated CHI linkage. The resultant polymer again has a CHI terminal that is in turn activated by iodine to allow further insertion of the monomer. Similarly, bifunctional living poly(VE) was obtained with a diiodo compound (CH3CHIO(CH2)-4OCHICH3), prepared from HI and 1,4-vinyloxybutane, as an initiator. These mono- and bifunctional living polymers were applied to synthesize AB and ABA block copolymers and function-alized poly(VE) having terminal and in-chain amino groups.