Synthesis and aqueous solution properties of amphiphilic diblock copolymers based on methyl triethylene glycol vinyl ether and benzyl vinyl ether

Water-soluble diblock copolymers of methyl triethylene glycol vinyl ether and benzyl vinyl ether were synthesized by living cationic polymerization, giving molecular weights in the range 13 400-17 300 and narrow molecular weight distributions (M-w/M-n = 1.18-1.28). The MTEGVE block length was fixed at 56 monomer units and the BzVE block length varied from 6 to 56 units. Aqueous solutions were studied by using dynamic light scattering and turbidimetry to determine the effect of block ratio on micellization and precipitation. Dynamic light scattering at room temperature in water revealed two intensity-average populations for all the copolymers, assigned as well-defined micelles and large aggregates. The hydrodynamic radii of the micelles ranged from 10.2 to 26.2 mo. Turbidimetry showed a cloud point of 83.5 degrees C for the MTEGVE homopolymer. The cloud points of the block copolymers decreased with increasing BzVE content and leveled off at higher BzVE contents. Selective removal of the benzyl group was achieved by catalytic hydrogenolysis, as a route to block copolymers with poly(vinyl alcohol) sequences. The maximum extent of deprotection was only 88%. Incomplete deprotection was attributed to the adsorption of the MTEGVE block onto the carbon support, thus blocking the catalyst sites.