Fundamentals of Polymer Synthesis

In order to perform nearly all of our work the synthesis of well-defined polymers with controlled macromolecular structure is required. We typically synthesize new polymers using so-called “living” polymerization chemistries where due to a lack of spontaneous termination we can finely control the resulting molecular weight and molecular architecture through precise initiation of the polymerization and sequential addition of monomeric species. In order to achieve this control over the polymerization the rigorous purification of solvents and monomers is required as is a highly controlled polymerization environment which we achieve through glove box and schlenk line techniques.

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Living Polymerization
Using anionic and other living polymerizations, we can synthesize a wide variety of homopolymer and block copolymer materials with narrow molecular weight distributions (<1.1) and well-defined structures. Anionic polymerization proceeds by a chain growth mechanisms where an initiator (such as organolithiums or alkali metals) reacts with a monomer to form an active growing chain. Since the growing chains in unreactive to each other and not susceptible to other termination reactions the active species is “living.” In order to perform rigorous removal of reactive contaminants such as oxygen and water and to handle the highly pyrophoric initiators, we utilize a nitrogen environment and high-vacuum Schlenk lines as shown below. As all chains were initiated at approximately the same time and will react with monomer and grow at the same rate the resulting polymers will have approximately the same length. Once the desired conversion is achieved, the active chain ends a terminating species is added to kill the living chain. Through complete conversion and sequential monomer addition block copolymers can be synthesized and by judicious choice of terminating species chains ends can be tailored with specific functional groups for subsequent modifications.