Shinya Teramachi | PubMed Health

PubMed2005

Direction of temperature gradient for normal-phase temperature gradient interaction chromatography in polystyrene fractionation.

Temperature gradient interaction chromatography (TGIC) is a powerful technique for molecular weight fractionation of polymers, in which the interaction strength is controlled by varying the column temperature. In the present paper, the effects of the sign of the temperature dependence of the retention and the direction of the temperature gradient (raising or lowering) on TGIC in the normal-phase mode were studied for the molecular weight fractionation of polystyrene samples in organic mobile phases. It was found that a positive temperature gradient was effective in the system consisting of amino-modified silica (NH(2)) column and the eluent mixture of tetrahydrofuran and n-hexane where retention decreased with increasing temperature. A negative temperature gradient was effective for the systems consisting of a bare-silica column//chloroform/n-hexane and NH(2)-column//chloroform/n-hexane, where retention increased with increasing temperature. Increasing retention with increasing temperature has been found, so far, only for a water-soluble polymer (PEO) in an aqueous mobile phase in RP-TGIC.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Morphology and enzymatic degradation of oriented thin film of ultrahigh molecular weight poly[(R)-3-hydroxybutyrate].

Thin films of ultrahigh molecular weight poly[(R)-3-hydroxybutyrate] (P(3HB)) were sheared and isothermally crystallized at 100 degrees C. Transmission electron microscopy and atomic force microscopy (AFM) observations revealed that thick fibrous textures, on which lamellae are overgrown normal to the long axis of the fibril, run parallel to the shearing direction. A selected area electron diffraction pattern taken from the fibrils exhibits a fiber pattern of P(3HB) alpha-modification, and the crystallographic c-axis (chain axis) of P(3HB) is set parallel to the long axis of the fibril. In situ AFM observations of enzymatic degradation for the thin film were performed with an extracellular P(3HB) depolymerase from Ralstonia pickettii T1 in a buffer solution. The film surface and thickness became rougher and thinner, respectively, with time after adding the enzyme. During the degradation, fine shish-kebab structures appeared gradually. This fact supports that the amorphous region in the film is preferentially degraded rather than the crystalline one by the depolymerase. The in situ AFM observations also revealed that one thick fibril in the original film is composed of three different states, namely, finer fibril (shish), stacked lamellae (kebab) in edge-on state, and the surrounding amorphous phase.

Hydroxybutyrates↗