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Block Copolymer Synthesis

Because they are very sensitive to oxygen and acidic protons (water, alcohols etc.) it is necessary to exclude any impurities. This can be achieved by using vacuum or working in inert atmosphere (glovebox). Our group is equipped with three high vacuum lines and a glove box which are used for polymerizations of various monomer liquids and gases. Some typical polymers made by anionic polymerization are polystyrene, poly(ethylene oxide) and block copolymers like poly(styrene-blockisoprene), PS-b-PI and poly(isoprene-block-ethylene oxide), PI-b-PEO.

Our group synthesizes block copolymers in order to direct the structure of hybrid materials and to study complex fluids. Most of our polymerization reactions are done through either anionic polymerization or living radical polymerization.

Anionic Synthesis

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Wiesner Research Group - Cornell University

Anionic Polymerization

The most widely used technique for the preparation of model block copolymers is living anionic polymerization. The active centers in an anionic polymerizations are highly reactive carbanions.

Atomic Transfer Living Radical Polymerization (ATRP)

Another commonly used technique for block copolymer preparation is ATRP. An equilibrium reaction between an alkyl halide (P-X) and a transition metal (Mt) creates a low concentration of radicals to enable polymerization (+M) while limiting unwanted termination reactions.

ATRP

ATRP is both versatile and robust in that it can polymerize most vinyl monomers and is tolerant of water as well as many side groups. ATRP has been used to create block copolymers such as poly(n-butyl acrylate-block-styrene), PBA-PS.

Combination of Anionic and ATRP Techniques

Recent studies demonstrate that the combination of anionic polymerization and controlled radical polymerization of vinyl monomers is not only a viable as well as a simpler alternative to a purely anionic route, but it also allows one to prepare unprecedented, copolymer structures. Well-defined polymeric architectures have been engineered via this novel route. Our group has synthesized amphiphilic triblock terpolymers by combining anionic polymerization and ATRP. More details on this work may be found on our Triblock Copolymers page.

Selected References

K. Matyjaszewski. "Transition metal catalysis in controlled radical polymerization: atom transfer radical polymerization." Chem. Eur. J. 5(11), 1999, 3095-3102.