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Biomedical subjects

H Iatrou

Publications and source records attributed to H Iatrou.

5 recordsLinked to original sources
PubMed2005

Tailoring the flow of soft glasses by soft additives.

We examine the vitrification and melting of asymmetric star polymer mixtures by combining rheological measurements with mode coupling theory. We identify two types of glassy states, a single glass, in which the small component is fluid in the glassy matrix of the big one, and a double glass, in which both components are vitrified. Addition of small-star polymers leads to melting of both glasses, and the melting curve has a nonmonotonic dependence on the star-star size ratio. The phenomenon opens new ways for externally steering the rheological behavior of soft matter systems.

Computer Simulation↗
PubMed2005

"Glass transition" in peptides: temperature and pressure effects.

We report on the origin of the liquid-to-glass transition in a series of oligopeptides of gamma-benzyl-L-glutamate up to the polymer (PBLG), and in Poly-Z-L-lysine (PZLL) and Polyglycine (PGly) using dielectric spectroscopy as a function of temperature and pressure. We show that temperature is the dominant control variable of the dynamics associated with the peptidic "glass transition." This is an intrinsic feature of the peptide dynamics, irrespective of the type of amino acid and of the peptide secondary structure. The influence of the type of secondary structure (alpha helix vs beta sheet) on the liquid-to-glass dynamics is discussed.

Journal Article↗
PubMed1999

Ordered bicontinuous nanoporous and nanorelief ceramic films from self assembling polymer precursors

Three-dimensional ceramic nanostructured films were produced from silicon-containing triblock copolymer films exhibiting the double gyroid and inverse double gyroid morphologies (space group Ia3d). A one-step room-temperature oxidation process that used ozonolysis and ultraviolet irradiation effected both the selective removal of the hydrocarbon block and the conversion of the silicon-containing block to a silicon oxycarbide ceramic stable to 400 degrees C. Depending on the relative volume fraction of the hydrocarbon block to the silicon- containing block, either nanoporous or nanorelief structures were fabricated with calculated interfacial areas of approximately 40 square meters per gram and pore or strut sizes of approximately 20 nanometers.

Journal Article↗
PubMedDate not supplied

Nanodomain-induced chain folding in poly(gamma-benzyl-L-glutamate)-b-polyglycine diblock copolymers.

We report on the self-assembly mechanism and dynamics in a series of poly(gamma-benzyl-l-glutamate)-b-poly(glycine) (PBLG-b-PGly) diblock copolymers within the composition range 0.67 < or = f(PBLG) < or = 0.97 and the temperature (T) range 303 < T < 433 K. Small- and wide-angle X-ray scattering, (13)C NMR, and differential scanning calorimetry are used for the structure investigation coupled with dielectric spectroscopy for both the peptide secondary structure and the associated dynamics. These techniques provide not only the nanophase morphology but also the type and persistence of peptide secondary structures. The thermodynamic confinement of the blocks within the nanodomains and the disparity in their packing efficiency results in multiple chain folding of the PGly secondary structure that effectively stabilize a lamellar morphology for high f(PBLG). Nanoscale confinement proves to be important in controlling the persistence length of secondary peptide motifs.

Magnetic Resonance Spectroscopy↗