McGowan Institute for Regenerative Medicine
affiliated faculty member Tara Meyer, PhD (pictured), associate professor in the department of chemistry at the University of Pittsburgh, and her co-workers recently reported on the preparation of repeating sequence poly(lactic-co-glycolic acid) copolymers. In their work, the strategy for producing these repeating sequence copolymers involved the assembly by condensation polymerization of pre-formed segmers comprising high degree of sequence- and stereo-control.
In cooperation with guest-editors Hans Börner (Humboldt University, Berlin) and Jean-Francois Lutz (Institut Charles Sadron, Strasbourg) Macromolecular Rapid Communications published a special issue representing the avant-garde in the field of “precision macromolecular chemistry.” The trends highlighted in this topical issue constituted unquestionably the core of a new discipline in the field of polymer science. Dr. Meyer and her team’s paper entitled “Periodic Incorporation of Pendant Hydroxyl Groups in Repeating Sequence PLGA Copolymers” appeared in this special issue.
The Meyer Group is interested in the design and synthesis of polymeric and composite materials with the potential for high level application. A particular focus of the group is synthesis of repeating sequence copolymers (RSCs) which exhibit sequence-dependent properties. RSCs suitable for use in the biomedical and electronics fields are under development. The group is also interested in the preparation of oligomeric and polymeric systems for mercury sensing and in the creation of stimuli sensitive composites. In her lab, Dr. Meyer’s research interests include:
Synthesis of repeating sequence copolymers for biomedical applications
The preparation of plastics that behave like metals is one of the most exciting frontiers of polymer chemistry. We are interested in using metal-catalyzed couplings to assemble polymers with conducting and magnetic properties. A specific system that we are currently investigating involves the preparation of polyanilines with unique architectures. By studying a variety of these materials we hope to develop a set of structure/property relationships that will contribute to the development of new technologies, such as transparency-thin displays and LED's.
One pot reactions that form both new carbon-carbon and carbon-heteroatom bonds
Although the ability of transition metals to catalyze regio- and stereo-selective carbon-carbon bond formation is widely exploited, only recently have researchers truly begun to take advantage of the power of transition metals to make carbon-heteroatom bonds, particularly bonds to more ìexoticî main group elements from rows 3 and below in the periodic table. We have recently developed and reported a new palladium catalyzed regio- and stereo-selective chalcogenide-element addition (Y = Se, G = N) to terminal alkynes in the presence of carbon monoxide producing ‚-selenyl acrylamides. Typical yields are 65-85%. The selenyl group, of course, provides many opportunities for subsequent functionalization. The modularity of the reaction is particularly appealing because it could easily allow for the creation of a small library of closely related derivatives. The reaction tolerates a range of alkynyl substrates as well as differing substitutions on the sulfenamide nitrogen.
Synthesis of conducting and magnetic polymers
Bone tissue engineering has the potential to heal difficult fractures, particularly those associated with diseases such as osteoporosis. The development of good scaffolds is critical to the success of this treatment. Ideally these scaffolds should provide mechanical support, encourage proper cell differentiation and proliferation, and degrade to give non-toxic by-products. The need for biocompatibility severely limits the types of monomers that can be used in the synthesis of polymeric biomaterials used as temporary scaffolds in tissue engineering. It is, therefore, attractive to develop materials with a wide range of mechanical properties made from multiple combinations of building blocks that are known to be non-toxic. The most widely used scaffolding to date are polymers derived from lactic and glycolic acids and their copolymers. These materials are FDA-approved for a variety of uses in the human body and are known to degrade hydrolytically to their biocompatible components. Although a wide variety of polymers and copolymers are known for these monomers, there has never been an attempt to examine RSCs where the block size is small, i.e. (GGGLLLLL)n or (GLLLLLL) (G = glycolic acid monomer, L = lactic acid monomer). There are several advantages to RSCs including uniformity of hydrolytic degradation, the potential to add regularly spaced tethered groups, and the improvement of mechanical properties.
Illustration: McGowan Institute for Regenerative Medicine.
The Meyer Group
Bio: Dr. Tara Meyer
Abstract (Macromolecular Rapid Communications, Special Issue: Precision Macromolecular Chemistry, Volume 32, Issue 2, pages 220–225, January 17, 2011)