Makoto Gemmei-Ide

Anti-biofouling properties of polymers with a carboxybetaine moiety.

The resistance of random copolymers of BMA and CMB against biofouling was evaluated. The amount of proteins adsorbed onto the CMB copolymers was smaller than that onto other polymers (non-ionic polymers and copolymers of ordinary ionic monomers and BMA) and decreased with an increase in the content of CMB residues. Furthermore, there was a dramatic decrease in the number of cells (platelets and fibroblasts) that adhered to the CMB copolymers compared with that to other polymers. In contrast with this, CMB copolymers were slightly perturbative to both complement and coagulation systems. However, the overall results suggest that zwitterionic moieties are effective for making polymer materials biocompatible due to their excellent anti-biofouling property.

Structure of water in the vicinity of a zwitterionic polymer brush as examined by sum frequency generation method

A zwitterionic poly(carboxymethylbetaine) (PCMB) brush was prepared on a fused quartz prism by the surface-initiated atom transfer radical polymerization (SI-ATRP) of CMB monomer. The conformation of PCMB brush and the state of water at the surface of the brush were examined using sum frequency generation (SFG) technique. The C-H stretching band of the brush, indicating the gauche defect of the brush, was affected by the contact medium such as dry nitrogen, water vapor-saturated nitrogen and liquid water. The water molecules at the PCMB-water interfaces were not largely oriented in comparison with the interfacial water of both bare and the ATRP-initiator-modified quartz prisms. The similar tendency was previously observed for water in the vicinity of water-soluble zwitterionic polymers and polymer thin films using Raman and attenuated total reflection (ATR) infrared spectroscopies, respectively. The electrical neutralization between neighboring positive and negative charges might diminish the electrostatic adsorption of water molecules to the vicinity of zwitterionic polymer brushes.

The use of a polymer inclusion membrane as a sorbent for online preconcentration in the flow injection determination of thiocyanate impurity in ammonium sulfate fertilizer

A polymer inclusion membrane (PIM) is used for the first time as a sorbent in the construction of a preconcentration column to enhance the sensitivity in flow injection analysis (FIA). The PIM-coated column is readily prepared by coating the PIM containing poly(vinyl chloride), Aliquat 336, and 1-tetradecanol onto glass beads packed in a glass tube. The determination of trace amounts of thiocyanate in ammonium sulfate fertilizer demonstrates the potential of the proposed PIM-coated column in FIA. Thiocyanate standards or samples of relatively large volume (e.g. up to 2000 µL) are injected into a nitrate carrier stream. The sample zone passes through the proposed preconcentration column where thiocyanate is concentrated in a smaller volume of a carrier solution thus resulting in up to 7.4 fold increase in sensitivity. Thiocyanate is detected spectrophotometrically after its reaction with Fe(III) downstream of the preconcentration column. The limits of detection of thiocyanate in the absence and presence of 20 g L(-1) ammonium sulfate (S/N=2) are 0.014 and 0.024 mg L(-1), respectively. Thiocyanate was successfully determined in several samples of ammonium sulfate fertilizer.

Structure of water at zwitterionic copolymer film-liquid water interfaces as examined by the sum frequency generation method.

A copolymer film composed of zwitterionic carboxymethylbetaine (CMB) and n-butyl methacrylate (BMA), Poly(CMB-r-BMA), was cast on a flat plane of an octadecyltrichlorosilane (ODS)-modified fused quartz prism with a semi-cylindrical shape. CH stretching of the polymer film and O-H stretching of water at the surface of the film were examined using the sum frequency generation (SFG) technique. The C-H stretching band of the cast film, indicating a gauche defect of the film, was affected by the contact medium including dry nitrogen, water vapor-saturated nitrogen and liquid water. In contrast, the C-H stretching of an octadecyl group introduced onto the quartz prism for stable attachment of the cast film was not significantly changed by the contact medium. The O-H stretching band indicated that water molecules at the surface of the Poly(CMB-r-BMA) film in contact with liquid water were not greatly oriented in comparison with those at the surfaces of a bare prism, an ODS SAM-modified prism, and a prism covered with a PolyBMA film or a copolymer film of BMA and methacrylic acid or 2-(dimethylamino)ethyl methacrylate. A similar small perturbation of the structure of water was previously observed in the vicinity of water-soluble zwitterionic polymers and zwitterionic copolymer films using Raman and attenuated total reflection infrared spectroscopies, respectively. A distinct effect of charge neutralization to diminish the perturbation of the structure of interfacial water around polymer materials was suggested.

Sum frequency generation study on the structure of water in the vicinity of an amphoteric polymer brush.

A polyampholyte brush was prepared on the surface of a quartz prism by surface-initiated reversible addition-fragmentation chain-transfer polymerization of methacrylic acid (MA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) at a monomer ratio of 1:1. The sum frequency generation method indicated that water molecules at the amphoteric polymer brush-water interfaces were not greatly oriented in comparison with those at the surfaces of bare quartz prisms, and negatively charged PolyMA and positively charged PolyDMAEMA brushes. The small perturbation effect of an amphoteric polymer brush on the structure of vicinal water was in accordance with the tendency of aqueous solution and thin films of amphoteric polymers observed by using Raman and infrared spectroscopies, respectively.

Crystal growth of ice Ih by revapor-deposition and diffusion suppression of monomolecular water in a polymer solid: spectroscopic observation of phase transition of water sorbed into solid polystyrene.

Monomolecular water in a solid polymer, which has no effective hydrogen bonding sites, was revealed by temperature-variable Fourier transform infrared spectroscopy to be condensable and crystallizable. Ice Ih formed in the polymer matrix was grown by vapor deposition and was reduced by sublimation. Moreover, rapid cooling induced crystal growth by vapor deposition during heating (revapor-deposition). These results indicate the requirement of a change in the generally accepted understanding of the thermal responses of water in a polymer matrix and give rise to a problem for general interpretation of the category of water in a polymer matrix based on calorimetrical analysis at very low water contents.

Binding of β-amyloid to sulfated sugar residues in a polymer brush.

A glycopolymer obtained by living radical polymerization of glucose-carrying vinyl monomer was sulfated and accumulated as a polymer brush on a gold colloid-immobilized glass. Binding processes of various proteins to sulfated glucose residues in the brush were examined by the increase in absorbance with a help of localized surface plasmon resonance. β-Amyloid protein (Aβ) bound to the sulfated glycopolymer brush, whereas no binding to the non-sulfated one. An AFM image of Aβ aggregates on the sulfated brush was ellipsoidal, whereas no-shaped aggregation of Aβ on the poly(methacrylic acid) and poly[2-(dimethylamino)ethyl methacrylate] brushes. The present results indicate the importance of balance between electrostatic attraction and repulsion in the folding-aggregation phenomena of Aβ at the surface of glycopolymers.

Structure of Water in the Vicinity of Amphoteric Polymers as Revealed by Vibrational Spectroscopy

The water incorporated in a thin film of amphoteric terpolymers composed of various ratios of methacrylic acid (MA), N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) and n-butyl methacrylate was analyzed using the band shapes of the O–H stretching in the infrared spectra. At an early stage of sorption of water into the polymer film, the O–H stretching band for the water incorporated in the film with comparative contents of MA and DMAPMA residues was similar to that for bulk water. These results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the hydrogen-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups. The number of platelets adhered to the film with comparative contents of MA and DMAPMA residues was relatively the smallest among the examined terpolymer films, which suggested a correlation between the mildness of the charge-balanced polymeric materials to the structure of incorporated water and their blood-compatibilities. In addition, the structure and hydrogen bonding of water in an aqueous solution of co-polymers composed of various ratios of MA and DMAPMA or [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were also analyzed using the contours of the O–H stretching in the polarized Raman spectra. The number of hydrogen bonds disrupted due to the presence of one monomer residue (N corr value) for PolyMA was largely positive, and with an increase in the content of the DMAPMA or MAPTAC residues, the N corr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the N corr value increased again. This is in a significant contrast with the largely positive N corr values for the homo-polymers (PolyMA, PolyDMAPMA and PolyMAPTAC), and other ordinary polyelectrolytes. The effect of the charge-balanced co-polymer on the hydrogen-bonded network structure of vicinal water observed by Raman spectroscopy was in accordance with that of the charge-balanced terpolymer film observed by infrared spectroscopy.

Recrystallization of water in non-water-soluble (meth)acrylate polymers is not rare and is not devitrification.

Change in the state of water sorbed into four kinds of non-water-soluble poly(meth)acrylates with low water content by temperature (T) perturbation was examined on the basis of T variable mid-infrared (MIR) spectroscopy. Many studies using differential scanning calorimetry suggested that there was no change in the state. T dependence of their MIR spectra, however, clearly demonstrated various changes in the state. Furthermore, recrystallization, which was crystallization during heating, was observed in all four polymers. The recrystallization observed in this study was not devitrification, which is the change in the state from glassy water to crystalline water, but vapor deposition during heating (vapor re-deposition). There were only two reports about recrystallization of water in a non-water-soluble polymer before this report; therefore, it might be considered to be a rare phenomenon. However, as demonstrated in this study, it is not a rare phenomenon. Recrystallization (vapor re-deposition) of water in the polymer matrices is related to a balance between flexibility and strength of the electrostatic interaction sites of polymer matrices but might not be related to the biocompatibility of polymers.

Water structure at the interfaces between a zwitterionic self-assembled monolayer/liquid water evaluated by sum-frequency generation spectroscopy.

A silane coupling agent having a zwitterionic end group was covalently bound to a semi-cylindrical fused silica prism for sum-frequency generation (SFG) analyses and to a flat glass for estimating biological affinity. It was found that total intensity of the -derived from water in contact with a positively or negatively charged SAM-modified surface and a bare silica prism. These results indicated that water molecules in the vicinity of the zwitterionic SAM-modified surface are not strongly oriented in comparison with those of lopsidedly charged SAMs and bare silica. Moreover, the zwitterionic SAM surface suppressed non-specific adsorption of bovine serum albumin in contrast to the significant adsorption to lopsidedly charged SAMs and the bare cover glass. On the other hand, fibroblasts gradually adhered to the SAM surfaces and extended regardless of the electrical charge of the SAM, though the number of cells that adhered to the zwitterionic SAM was the smallest. The results strongly suggested that the charge neutralization of a solid material surface is very important for anti-biofouling properties.