Harry R. Allcock

Polymer Synthesis, Materials Chemistry, and Biomedicine

The use of fundamental chemistry to advance the fields of polymers, materials, and biomedicine is a major emphasis in modern research. Professor Harry Allcock and his students are exploring novel approaches to these subjects by the synthesis and study of new classes of high polymers and advanced materials using the techniques of organic, organometallic, and inorganic chemistry.

High polymers are long chain macromolecules that are the constituents of many useful materials. Depending on their molecular structures, different polymers can have properties, such as liquid crystallinity, high strength or elasticity, catalytic activity, unusual optical or electrical properties, or special biomedical qualities.

Most conventional polymers are derived entirely from petroleum. They are inexpensive, but they have a relatively restricted range of properties. For example, in general, they lack the thermal stability of ceramics, the long-term electrical behavior of silicon or metals, the "optical switching" behavior of inorganic solids, or the biocompatibility of living tissues and ceramic materials.

The research in the Allcock group involves the design and synthesis of new polymers that contain organic components, together with heteroelements such as phosphorus, silicon, boron, or transition metals. The aim is to combine the most advantageous properties found in organic polymers with the special properties imparted by the heteroelements. For example, our research team has developed synthesis routes to a broad range of new polymers that have backbones of the types shown in 1-3, and with organic or organometallic side units attached to these backbones. By varying the side group structure, it is possible to bias the properties toward those of elastomers or structural materials, liquid crystalline polymers, semiconductors, high refractive index glasses, ceramics, inert biomedical materials, or biologically active polymers. Other polymers with carbon or sulfur in the backbone, as well as phosphorus and nitrogen, are also under development, in addition to copolymers with organic and silicone macromolecules. (see Diagram)

There are three general aspects to nearly all the research topics in this program:

(1) The development of new synthesis methodology starting at the level of small molecules and progressing to macromolecules. Much of this work involves the development of organic substitution methods or organometallic reaction chemistry, and contains a high component of molecular design based on ongoing structure-property studies.

(2) Characterization and molecular structure determination of the new compounds by techniques such as NMR, IR, gel permeation chromatography, X-ray diffraction, molecular mechanics-molecular graphics, etc. The aim of this aspect is to relate the unique properties found for the new polymers to their molecular structures.

(3) Examination of the materials' properties (i.e., solid state properties) of the new polymers, again with a view to developing structure-property relationships that will aid future research. Techniques such as thermal analysis, electrical and optical behavior, scanning electron microscopy, X-ray photoelectron spectroscopy, and biocompatibility studies are examples of the approaches used. This phase of each project often involves collaborations with other research groups that have specialized experience in materials' or medical-oriented techniques. For instance, our work on nonlinear optical materials, composite materials, ceramics, semiconductors, membranes, bioerodible polymers, bioactive surfaces, fuel cell membranes, and solid polymeric battery electrolytes is conducted through collaborations with groups at other universities and in industrial laboratories. Examples of the medical-oriented research are the development of new polymers for microencapsulation of drugs or vaccines and materials for tissue engineering and bone regeneration.

Overall, the research in this program provides training in the ways that fundamental synthetic, mechanistic, and structural chemistry can be utilized in polymer chemistry and materials science. It also offers opportunities for an understanding of long-range practical topics that a student will almost certainly encounter in a professional scientific career.