Poly(ethylene-<i>co-</i>propylene macromonomer)s:  Synthesis and Evidence for Starlike Conformations in Dilute Solution

Abstract

By use of two sequential coordination−insertion polymerizations, a series of ethylene- co -propylene-based comb polymers was synthesized. First, poly(ethylene- co -propylene) macromonomers featuring one unsaturated chain end were synthesized using a titanium bis(phenoxyimine) catalyst. The macromonomers were then homopolymerized using a living nickel α-diimine catalyst. The molecular weights and corresponding number of arms for each poly(macromonomer) were determined using size-exclusion chromatography with viscometry detection and universal calibration. Viscosity−molecular weight conformation plots for the poly(macromonomer)s revealed compact solution structures. Furthermore, viscometric radii for each poly(macromonomer) ( R v ) and corresponding linear macromonomer ( R v ) a were determined and the ratio ( R v )/( R v ) a for each pair was compared to those of a variety of polyisoprene-based star polymers with similar functionality. The comparison revealed that despite the obvious comb topology of the poly(macromonomer)s their dilute solution conformations correspond reasonably well to the bona fide polyisoprene stars.