Synthesis of Copolymers by Living Carbanionic Alternating Copolymerization

The synthesis and characterization of copolymers from styrene and 1,3-pentadiene (two isomers) are reported. Styrene/1,3-pentadiene (1:1) copolymerization with carbanion initiator yield living, well-defined, alternating (r1 = 0.037, r2 = 0.056), and highly stereoregular copolymers with 90%-100% trans-1,4 units, designed Mn s and low ÐM s (1.07-1.17). The first-order kinetic resolution and NMR spectra demonstrate that the copolymers obtained possess strictly alternating structure containing both 1,4- and 4,1-enchaiments. Also a series of copolymers with varying degrees of alternation are synthesized from para-alkyl substituted styrene derivatives and 1,3-pentadiene. The degree of alternation is strongly dependent on the polarity of solvent, reaction temperature, type of trans-cis isomer of 1,3-pentadiene and para-substituted group in styrene. The macro zwitterion forms (SPC) through the distribution of electronic charges from the donor (1,3-pentadiene) to the acceptor (styrenes) are proposed to interpret the carbanion alternating copolymerization mechanism. Owing to the versatility of the carbanion-initiating reaction, the present alternating strategy based on 1,3-pentadiene (especially cis isomer) can serve as a powerful tool for precise control of polymer chain microstructure, architecture, and functionalities in one-pot polymerization.