FUNCTIONAL POLYMER LABORATORY

Noncoherent low-power photon upconversion has been realized in solid thin films composed of an ethyleneoxide/epichlorohydrin copolymer doped with palladium octaethylporphyrin (PdOEP) and 9,10-diphenylanthracene (DPA). Selective excitation of PdOEP at 544 nm generates easily visualized DPA fluorescence in the blue with noncoherent light sources under ambient laboratory conditions.  The work, published in the Journal of the American Chemical Society, is a collaboration with Felix N. Castellano's group at Bowling Green State University.

Upon self-assembly, certain photoluminescent chromophores exhibit pronounced changes of their optical absorption properties. The integration of these dyes into a polymer matrix allows facile monitoring of external stimuli, for example mechanical stress, temperature history, or - as shown in this new paper published in the Journal of Materials Chemistry - exposure to moisture. The work was selected for the cover of the august issue of the journal. A US patent that broadly covers this technology has just been issued to Case Western Reserve University.

For more information click here.

Upon self-assembly, certain photoluminescent chromophores exhibit pronounced changes of their optical absorption properties. The integration of these dyes into a polymer matrix allows facile monitoring of external stimuli, for example mechanical stress, temperature history, or exposure to chemicals. A US patent that broadly covers this technology has just been issued to Case Western Reserve University.

For more information click here.

Pictures: Brent Crenshaw

March 2007: van den Berg, O.; Capadona, J. R; Weder, C.; Preparation of Homogeneous Dispersions of Tunicate Cellulose Whiskers in Organic Solvents; Biomacromolecules 2007, 8, 1353 - 1357.

The incorporation of nanoparticles into polymers is a design approach that is employed in all areas of materials science.  Cellulose nanofibers, also referred to as ‘whiskers’, offer intriguing mechanical properties, are readily obtained from renewable bio-sources such as wood, cotton, or tunicates and are attracting significant attention. Due to their high specific surface area and energy, nanoparticles usually have a strong tendency for aggregation, which makes it difficult to homogeneously disperse them in polymeric hosts. We reported on the dispersability of cellulose whiskers in a range of ‘new’ solvents. For more information click here. Pictures: Otto van den Berg, Jeffrey R. Capadona March 2007: Crenshaw, B.; Burnworth, M.; Khariwala, D.; Hiltner, P.A.; Mather, P.T.; Simha, R.; Weder, C.; Deformation-Induced Color Changes in Mechanochromic Polyethylene Blends; Macromolecules 2007, 40, 2400-2408.        Upon self-assembly, certain oligo(phenylene vinylene) chromophores exhibit pronounced changes of their optical absorption properties.  The integration of these dyes into a polymer matrix allows facile monitoring of mechanical stress or temperature history and is the basis for a versatile and general new approach for thermochromic and mechanochromic materials. A detailed and systematic investigation of mechanochromic, melt-processed blends between a series of polyethylenes (PE) with crystallinities ranging from 9 to 66 % and two excimer-forming, photoluminescent oligo(phenylene vinylene) dyes is described in this recent paper. For more information click here. Picture: Brent Crenshaw

Upon self-assembly, certain oligo(phenylene vinylene) chromophores exhibit pronounced changes of their optical absorption properties. The integration of these dyes into a polymer matrix allows facile monitoring of mechanical stress or temperature history and is the basis for a versatile and general new approach for thermochromic and mechanochromic materials.

For more information click here.

Picture: Jill Kunzelman.

Highly selective detection of chemical warfare agent mimics can be achieved by judicious combination of carefully designed fluorescent ligands and metal ions. Designed sensor arrays of these multi-metal/multi-ligand systems represent a modular and versatile approach for the detection of organophosphates and other analytes.

For more information click here.

Picture: Dan Knapton / Mark Burnworth.

Because of excimer formation, the emission characteristics of blends of conventional polymers and minute amounts of photoluminescent oligo(phenylene vinylene)s (OPV) dyes depend on the extent of aggregation of the luminescent dye molecules, which in turn can depend on a variety of external stimuli.

This effect may be exploited for the design of molecular sensors that are easily integrated into a polymer of interest and allow one to monitor mechanical deformation or - as shown in our latest paper that reports the investigation of PET/sensor blends - exposure above a threshold temperature.

Time-temperature indicators or time-temperature integrators based on our new materials change their fluorescence color in a predictable manner, if exposed exposure above a threshold temperature. The temperature regime and switching speed ican be minutely controlled.

For more information click here.

Picture: Maki Kinami / Brent Crenshaw.