Seiko Nemoto

Studies on the Adsorption Property and Structure of Polyamine-Ended Poly(ethylene glycol) Derivatives on a Gold Surface by Surface Plasmon Resonance and Angle-Resolved X-ray Photoelectron Spectroscopy

The adsorption properties and structure of polyamine-ended poly(ethylene glycol) (PEG) derivatives on a flat gold surface were studied by means of surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS) using PEG(5k)-block-poly[2-(N,N-dimethylamino)ethyl methacrylate](7.5k) [PEG-b-PAMA(5k/7.5k)] and pentaethylenhexamine-ended PEG(5k) [N6-PEG(5k)], which had 48 and 6 amino groups at the omega-end, respectively. The SPR analysis showed that the amount of PEG-b-PAMA(5k/7.5k) adsorbed onto the gold surface was not affected by the change in pH, and the desorption of this copolymer from the surface was not observed upon the addition of a solution at high salt concentration. The angle-resolved XPS (ARXPS) analysis revealed the structure of the PEG-b-PAMA polymer layer constructed on the gold surface: the PAMA segments were concentrated and located at the interface between the PEG layer and the gold surface. On the other hand, in the case of the PEG-graft-PAMA copolymer (PAMA-g-PEG)-modified gold surface, both the PAMA and the PEG segments homogeneously migrated to all regions of the constructed copolymer layer. The adsorbed amounts of N6-PEG(5k) under different pH conditions were constant and 2-3 times higher than those caused by the adsorption of single amino group-terminated PEG(5k) [PEG-NH(2)(5k)] and hydroxyl group-terminated PEG(5k) [PEG-OH(5k)]. The N6-PEG(5k)-modified gold surface showed a higher nonfouling property toward the adsorption of bovine serum albumin compared with the bare and the N6-modified gold surface. These results indicate that polyamine-ended PEGs were strongly immobilized onto the gold surface by polyamine anchors, even though electrostatic interaction between the polyamine and the gold substrate was not the dominant factor in this adsorption event. Furthermore, the formation of an almost complete phase-separated PEG/polyamine layer on the gold surface by polyamine-ended PEGs was strongly suggested.

Hybridization of sugar alcohols into brucite interlayers via a melt intercalation process.

We report the preparation of organic-brucite (BR) hybrids using harmless sugar alcohols (xylitol, XYL, and sorbitol, SOR). Since XYL and SOR are solid materials at room temperature, the hybridization was investigated by comparing two separate methods, hydrothermal treatment and melt mixing. BR-sugar alcohol hybrids were successfully prepared by a melt intercalation method at 175 °C. X-ray diffraction and Fourier transform infrared spectroscopy analyses indicated that organic molecules were intercalated into the brucite layers, overcoming the barrier of hydroxyl bonds between the BR layers. Moreover, X-ray photoelectron spectroscopy and thermal analyses showed that the intercalated materials at 175 °C resulted in the formation of covalent Mg-O-C bond linkages on the interlayer surface of BR.

The Role of Claysphere under the Environmental Condition on the Earth's Surface

The low soil fertility in semi-arid land requires effective soil improvement measures. To elucidate a possible relationship between dominant minerals and organic materials that improves soil fertility in semi-arid land, several experiments is carried out using kaolinite and urea. The reaction rate of urea-kaolinite complex is determined using XPS and XRD. It is confirmed that the intercalated urea is easily released from the structure of urea-kaolinite complex after dissolution experiments. Soil-forming minerals and native organic polymer compounds which contain nitrogen distributes in semi-arid soil. We will carry out a study at semi-arid land whether complexes will be able to support more efficient agricultural productivity and to determine the applicability of the results obtained to low-fertility areas.