AMPHIPHILIC BLOCK COPOLYMERS OF VINYL ETHERS BY LIVING CATIONIC POLYMERIZATION .4. MACROMOLECULAR AMPHIPHILES WITH MULTIPLE HYDROXYL-GROUPS AND A CYLINDRICAL TOPOLOGY

Amphiphilic block polymers (3) of vinyl ethers, [-CH2CH(OCH2CH2R')-]m[-CH2CH(OR)-]n (R'= CH(CONHC(CH2OH)3)2; R = n-C16H33, i-C8H17; M = 5-100, n = 10 or 50), with narrow molecular weight distributions were prepared, in which the hydrophilic segment had a unique cylindrical shape that originates from the highly branched, bulky pendant substituent (R') with six hydroxyl groups. The precursor block polymers (2), [-CH2CH(OCH2CH2R")-]m[-CH2CH(OR)-]n (R" = CH(COOEt)2), were obtained by the HI/I2-initiated sequential living cationic polymerization of vinyl ethers, CH2=CH(OCH2CH2R") and CH2=CH(OR). Subsequent amidation of the pendant malonic ester in R" with H2NC(CH2OH)3 in the presence of anhydrous K2CO3 in dimethyl sulfoxide led to polymer 3. A similar reaction in methanol, on the other hand, gave another block polymer (4), [-CH2CH(OCH2CH2R')-]m[-CH2CH(OR)-]n (R'= CH(CONHC(CH2OH)3)COO-K+), with one carboxylate anion and three hydroxyl groups per pendant R'. These amphiphilic block polymers (3 and 4) were soluble in water and lowered the surface tension of their aqueous solutions (0.1 wt %, 25-degrees-C) to a minimum 40 dyn/cm. Observation by transmission electron microscopy revealed that these block copolymers form molecular assemblies that include lamellae and vesicles (for m = 5, n = 12) and phase-separated microdomains (for m = 30-100, n congruent-to 10 or 50).