Biomedical subjects

Patrick T Mather

Publications and source records attributed to Patrick T Mather.

4 recordsLinked to original sources

PubMed2006

Molecular dynamics simulations of multilayer polyelectrolyte films: effect of electrostatic and short-range interactions.

The effect of the strength of electrostatic and short-range interactions on the multilayer assembly of oppositely charged polyelectrolytes at a charged substrate was studied by molecular dynamics simulations. The multilayer buildup was achieved through sequential adsorption of charged polymers in a layer-by-layer fashion from dilute polyelectrolyte solutions. The strong electrostatic attraction between oppositely charged polyelectrolytes at each deposition step is a driving force behind the multilayer growth. Our simulations have shown that a charge reversal after each deposition step is critical for steady multilayer growth and that there is a linear increase in polymer surface coverage after the first few deposition steps. Furthermore, there is substantial intermixing between chains adsorbed during different deposition steps. We show that the polymer surface coverage and multilayer structure are each strongly influenced by the strength of electrostatic and short-range interactions.

Journal Article↗

PubMed2005

Liquid-crystalline supramolecular polymers formed through complementary nucleobase-pair interactions.

We report how the placement of nucleobase units, thymine, or N6-(4-methoxybenzoyl)adenine, onto the ends of a mesogenic core, bis-4-alkoxy-substituted bis(phenylethynyl)benzene, affects the properties of these materials. We show that addition of these bulky polar groups significantly reduces the range of liquid-crystalline behavior of these compounds. However, mixing two complementary nucleobase-containing AA- and BB-type monomer units together does result in the formation of stable, thermotropic liquid-crystalline (LC) phases. Hydrogen bonding is shown to play an important role in the formation of these LC phases, consistent with the formation of oligomeric or polymeric hydrogen-bonded aggregates. X-ray analyses of these mixed materials are consistent with the formation of smectic C phases.

Adenine↗

PubMed2005

Molecular dynamics simulations of layer-by-layer assembly of polyelectrolytes at charged surfaces: effects of chain degree of polymerization and fraction of charged monomers.

We performed molecular dynamics simulations of the electrostatic assembly of multilayers of flexible polyelectrolytes at a charged surface. The multilayer build-up was achieved through sequential adsorption of oppositely charged polymers in a layer-by-layer fashion from dilute polyelectrolyte solutions. The steady-state multilayer growth proceeds through a charge reversal of the adsorbed polymeric film which leads to a linear increase in the polymer surface coverage after completion of the first few deposition steps. Moreover, substantial intermixing between chains adsorbed during different deposition steps is observed. This intermixing is consistent with the observed requirement for several deposition steps to transpire for completion of a single layer. However, despite chain intermixing, there are almost perfect periodic oscillations of the density difference between monomers belonging to positively and negatively charged macromolecules in the adsorbed film. Weakly charged chains show higher polymer surface coverage than strongly charged ones.

Journal Article↗

PubMed2003

Shape memory effect exhibited by smectic-C liquid crystalline elastomers.

It was long expected and recently shown that main-chain liquid crystalline elastomers (MC-LCEs) may serve as high performance soft actuators due to a coupling of their intrinsic characteristics of high, yet labile, ordering and network strain. Here, we present the synthesis of new siloxane-based smectic MC-LCEs. These new materials exhibit a unique thermomechanical behavior known as the shape memory effect, which has never been observed before in such LCEs. To achieve targeted transition temperatures required for facile actuation at low temperatures, specifically temperatures ranging from 15 to 65 degrees C, we have designed and prepared such elastomers incorporating two distinct mesogenic groups, termed 5H and 5tB, coupled with hydride-terminated poly(dimethylsiloxane) spacers.

Journal Article↗