Characterization of a resorbable poly(ester urethane) with biodegradable hard segments.

The rapid growth of regenerative medicine and drug delivery fields has generated a strong need for improved polymeric materials that degrade at a controlled rate into safe, non-cytotoxic by-products. Polyurethane thermoplastic elastomers offer several advantages over other polymeric materials including tunable mechanical properties, excellent fatigue strength, and versatile processing. The variable segmental chemistry in developing resorbable polyurethanes also enables fine control over the degradation profile as well as the mechanical properties.

Optical switching in chiropticenes.

Chiropticenes are a novel class of predesigned chiral molecular switches that are triggered and controlled by a combination of both light and electric field. Chiropticenes contain an optically active (chiral) center and, as a consequence, provide two accessible equal energy bistable states resembling the molecular elements of binary logic. Structural engineering of the basic switch design is investigated to modulate the thermal and optical switching behavior of the resulting compounds.

New Thiophene-Pyrrole-Derived Annulenes Containing 6 and 10 Heterocyclic Units.

A series of thiophene-pyrrole-derived annulenes containing either 6 (9a-c) or 10 (14a,band 17) heterocyclic units and 2 vinylene bridges have been synthesized from the appropriate dialdehydes or tetraaldehydes by the McMurry coupling reaction. All of these annulenes except 17 contain one or two intramolecular aliphatic chains linking the pyrrole units. Spectroscopic properties of these annulenes show no evidence for overall aromaticity or antiaromaticity, although the nature of the aliphatic bridge has a small but definite effect on the UV-visible spectra and electrochemical properties of the compounds.