Shinya Teramachi

Structure and enzymatic degradation of poly(3-hydroxybutyrate) copolymer single crystals with an extracellular PHB depolymerase from Alcaligenes faecalis T1.

Lamellar single crystals of four random copolymers of (R)-3-hydroxybutyrate with different hydroxyalkanoates: poly(3-hydroxybutyrate-co-8 mol%-3-hydroxyvalerate) (P(3HB-co-8%-3HV)), poly(3-hydroxybutyrate-co-10 mol%-4-hydroxybutyrate) (P(3HB-co-10%-4HB)), poly(3-hydroxybutyrate-co-8 mol%-3-hydroxyhexanoate) (P(3HB-co-8%-3HH)) and poly(3-hydroxybutyrate-co-10 mol%-6-hydroxyhexanoate) (P(3HB-co-10%-6HH)), were grown from dilute solutions of chloroform and ethanol. All single crystals have lath-shaped morphology and the second monomer units seem to be excluded from the P(3HB) crystal, on the basis of the electron diffraction diagrams. The enzymatic degradation of P(3HB-co-8%-3HH) and P(3HB-co-10%-6HH) single crystals was investigated with an extracellular PHB depolymerase from Alcaligenes faecalis T1. Adsorption of an extracellular PHB depolymerase, examined using an immuno-gold labelling technique, demonstrated a homogeneous distribution of enzyme molecules with a low concentration on the crystal surfaces. Enzymatic degradation of single crystals progressed from the edges and ends of crystals to yield narrow cracks along their long axes and the small crystal fragments. Lamellar thicknesses of single crystals and molecular weights of copolymer chains remained unchanged during the enzymatic hydrolysis. The above results support the hypothesis that the hydrophobic adsorption of the enzyme contributes to increase the mobility of molecular chains of single crystals and generate the disordered chain-packing regions. The active-site of PHB depolymerase takes place preferentially at the disordered chain-packing regions of crystal edges and ends with endo-exo enzymatic hydrolysis behaviour, termed processive degradation.

Compositional fractionation of poly(methyl methacrylate)-graft-polydimethylsiloxane by reversed-phase high-performance liquid chromatography

The results are reported of the compositional fractionation of poly(methyl methacrylate)-graft-polydimethylsiloxane (PMMA-graft-PDMS) by high-performance liquid chromatography (h.p.l.c.) of reversed-phase adsorption mode. Graft copolymers with different compositions were prepared by the radical copolymerization of PDMS macromonomer with MMA, using azobisisobutyronitrile as the initiator in benzene at 60°C. The gradient h.p.l.c. measurements were made using a prepacked column of octyl-modified silica gel, with tetrahydrofuran and acetonitrile as eluents. Detection was performed by an evaporative light-scattering detector. The PMMA-graft-PDMS samples were eluted from the components of higher PMMS contents to those of lower PMMA contents, according to reversed-phase adsorption. The present graft copolymers were separated according to their chemical compositions.

Determination of chemical composition distribution of poly(methyl methacrylate)-graft-polystyrene prepared from ω-p-vinylbenzyl polystyrene macromonomer by adsorption high-performance liquid chromatography

Abstract Chemical composition distributions (CCDs) of poly(methyl methacrylate)- graft -polystyrene samples with different compositions and conversions synthesized from methyl methacrylate and ω-vinylbenzyl polystyrene macromonomer were determined by high-performance liquid chromatography using both reversed-phase and normal-phase adsorption modes. The good agreement between CCDs obtained by both modes showed that the molecular-weight effect on the CCDs is negligible. All samples have broad CCDs. As the macromonomer content increases, the CCD becomes sharper. These results are in accordance with the theoretical predictions. As the conversion increases at the same feed composition, the CCD becomes broader towards the low-macromonomer-content side, which is in contrast to the CCDs of the samples obtained previously from ω-methacryloyl polystyrene macromonomer

Sample remaining in an ODS column after compositional fractionation of copolymers by high-performance liquid chromatography

Abstract High-performance liquid chromatography is very effective for the compositional fractionation of copolymers. Octadecyl-modified silica gel (ODS) has been used as a packing material for fractionation in the reversed-phase (RP) adsorption mode. In the compositional fractionation of the samples of copoly-(methyl methacrylate-styrene) by RP gradient elution through ODS column, it was found that small peaks were observed with blank elution just after the sample measurement and a perfect baseline was recovered after several blank elutions.

Comparison of Chemical Composition Distributions of Poly(methyl methacrylate)-graft-polydimethylsiloxane by High-Performance Liquid Chromatography and Demixing-Solvent Fractionation

Abstract Poly(methyl methacrylate)-graft-polydimethylsiloxane (PMMA-graft-PDMS) samples with different compositions were prepared by radical copolymerization of PDMS macromonomer with methyl methacrylate. The chemical composition distributions (CCDs) of the graft copolymer samples were determined by the high-performance liquid chromatography (HPLC) based on the reversed-phase adsorption mode, using a prepacked column of butyl-modified silica gel and the linear gradient elution of acetonitrile and tetrahydrofuran. The CCD of one of the graft copolymer samples was also determined by the demixing-solvent fractionation using the demixing-solvent pair of dimethylsulfoxid-tetrachloroethylene reported by Stejskal et al. The CCD by HPLC was in good agreement with theoretical CCD, while the CCD by the demixing-solvent fractionation was narrower than those by the HPLC and the theoretical calculation.

Comparison between Successive Precipitation and Column Elution Methods in Compositional Fractionation of Copolymers

Abstract In order to compare the efficiencies of successive precipitation and column elution methods in compositional fractionation, mixtures of two styrene-acrylonitrile random copolymers with different chemical compositions were fractionated by the two methods by using the methyl ethyl ketone-cyclohexane system. The compositional distribution curve determined by each method was compared with the curve calculated from a theory on compositional fractionation. The value of a parameter K, which shows the efficiency of compositional fractionation, was determined to have the best agreement between the experimental and calculated curves. It was found that the column elution method is more effective than the successive precipitation method.