Chain propagation/step propagation polymerization: synthesis of defect-free telechelomers

Abstract

Defect-free poly(oxyethylene-bZock-pivalolactone) telechelomers, represented by (OE)a4-(P VL)m, where m = 5,12, and 16, were synthesized by sequential anionic ring-opening polymerization of ethylene oxide and pivalolactone with hydroxypivalic acid. These telechelomers exhibited excellent microphase separation, allowing both the hard and soft segments to crystallize. Essentially complete microphase separation occurs for m = 12 and 16, and the sample with m = 5 showed some microphase mixing in the hard phase.Step polymerization of the (OE)a4-(PVL)m telechelomers was achieved by alanine-mediated melt esterification with titanium tetrabutoxide added in catalytic amounts, producing low molecular weight segmented copolymers, represented by [(OE)M-(PVL)m]p. For example, melt esterification of the sample with m = 16 produced the pentamer, [(OE^-iPVLheb, with Mn = 16 000.