AMPHIPHILIC BLOCK-COPOLYMERS BY SEQUENTIAL LIVING CATIONIC POLYMERIZATION - SYNTHESIS AND CHARACTERIZATION OF POLY(ISOBUTYLENE-B-METHYL VINYL ETHER)

The living polymerization of methyl vinyl ether (MeVE) was achieved us ing initiators obtained by capping 2,4,4-trimethyl-2-chloropentane (TM PCl) with 1,1-diphenylethylene (DPE), or 1,1-ditolylethylene (DTE) in conjunction with TiCln(OEt)(4-n) (n = 2-2.4) coinitiator in CH2Cl2/hex anes (60/40 v/v) solvent mixture at 0 degrees C. Sequential block copo lymerization of isobutylene (IB) with MeVE has also been accomplished. Well-defined living poly(isobutylene) (PIE) was first prepared at -80 degrees C in the presence of TiCl4, followed by capping with DPE or D TE. Then, Ti(OEt)(4) was added to reduce the Lewis acidity followed by the addition of MeVE, and the temperature was raised to 0 degrees C. Well-defined PIB-PMeVE diblock copolymers with controlled molecular we ight and narrow molecular weight distribution (M(w)/M(n) < 1.1) have b een obtained, with the virtual absence of homopolymer contaminants. Ac cording to differential scanning calorimetry, the diblock copolymers e xhibit two T(g)s, suggesting microphase separation. PIB-PMeVE diblock copolymers with similar to 50/50 w/w composition were insoluble in wat er but soluble in methanol. The diblock copolymer with 80 wt % PMeVE c ontent was soluble in water, exhibited excellent surfactant properties (critical micelle concentration = 2.3 x 10(-5) M), and produced stabl e emulsions of oil in water (average particle size similar to 200 nm).