Block copolymers by combination of radical and promoted cationic polymerization routes

Abstract

A block copolymer of cyclohexene oxide and styrene was prepared by using bifunctional azobenzoin initiators via a two-step procedure. The functionality of the initiator pertains to thermally degradable azo group and thermally stable photoactive benzoin groups. In the first step, thermal polymerization of styrene using azobenzoin initiators was carried out to yield polymers with photoactive end groups. These prepolymers were used to induce polymerization of cyclohexene oxide through formation of electron donor macroradicals upon photolysis and subsequent oxidation to corresponding carbocations in the presence of 1-ethoxy-2-methylpyridinium hexafluorophosphate resulting in the formation of a block copolymer. A different sequence of the same procedure was also employed. Successful blocking has been confirmed by a strong change in the molecular weight of the prepolymer and the block copolymer as well as IR and NMR spectral measurements.

Synthesis of Block Copolymers by Transformation of Free Radical Promoted Cationic Polymerization to Atom Transfer Radical Polymerization

“…It is assumed that in the system under consideration the alkoxyalkyl radical, which was formed upon irradiation according to Scheme 4, acts as a fairly powerful reducing agent. 33 The pyridinyl radical formed in this way is very short lived. 12 Its decomposition according to following reaction occurs very rapidly.…”

Synthesis of Block Copolymers by Combination of Atom Transfer Radical Polymerization and Visible Light‐Induced Free Radical Promoted Cationic Polymerization

“…[ 10 , 11 ] Several strategies such as use of dual functional initiators [12][13][14][15][16] and propagating chain end switches [17][18][19][20][21] have been proposed and successfully applied. Previous efforts in this laboratory have focused on the development of the transformations involving combinations of free radical systems with anionic, [ 22 ] activated monomer, [ 23 ] cationic, [24][25][26] free radical promoted cationic, [27][28][29] and condensation [ 30 ] polymerizations. In some cases, the same polymerization mechanisms but different initiating systems were also employed.…”

Block Copolymer Synthesis of N-Vinylcarbazole and Cyclohexene Oxide by Radical/Cation Transformation Polymerization

“…[23 -35] Since the transformation of active propagating ends, in principle, extends the range of possible monomer combinations in block copolymer formation, several groups have tried such a transformation polymerization for block copolymer synthesis. [24,30,31] However, block copolymer synthesis from the transformation of active propagating ends has usually been performed in two steps through the preparation of telechelic polymers. Recently, block copolymer formation through the telechelic polymers has been performed as an extension of controlled/"living" radical polymerization.…”