SYNTHESIS AND AQUEOUS-SOLUTION PROPERTIES OF AMPHIPHILIC DIBLOCK COPOLYMERS BASED ON METHYL TRIETHYLENE GLYCOL VINYL ETHER AND BENZYL VINYLETHER

Water-soluble diblock copolymers of methyl triethylene glycol vinyl et her and benzyl vinyl ether were synthesized by living cationic polymer ization, giving molecular weights in the range 13 400-17 300 and narro w molecular weight distributions (M-w/M-n = 1.18-1.28). The MTEGVE blo ck length was fixed at 56 monomer units and the BzVE block length vari ed from 6 to 56 units. Aqueous solutions were studied by using dynamic light scattering and turbidimetry to determine the effect of block ra tio on micellization and precipitation. Dynamic light scattering at ro om temperature in water revealed two intensity-average populations for all the copolymers, assigned as well-defined micelles and large aggre gates. 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 MTEGV E homopolymer. The cloud points of the block copolymers decreased with increasing BzVE content and leveled off at higher BzVE contents. Sele ctive removal of the benzyl group was achieved by catalytic hydrogenol ysis, as a route to block copolymers with poly(vinyl alcohol) sequence s. The maximum extent of deprotection was only 88%. Incomplete deprote ction was attributed to the adsorption of the MTEGVE block onto the ca rbon support, thus blocking the catalyst sites.