Jang-Oo Lee

Optical and Electrochemical Detection of Saccharides with Poly(aniline-co-3-aminobenzeneboronic acid) Prepared from Enzymatic Polymerization

Boronic acid-based sensors for saccharides have been developed via biocatalysis. The self-doped copolymer of poly(aniline-co-3-aminobenzeneboronic acid) [poly(aniline-co-AB)], with various mole ratios of two components, was synthesized by oxidative enzymatic polymerization using a natural biocatalyst such as horseradish peroxidase together with an anionic polyelectrolyte template (sulfonated polystyrene) under mild conditions (pH 4.5). Poly(aniline-co-AB), having an aniline boronic acid-to-aniline ratio of 1:2 on average, gave rise to a green doped polymer with absorption maxima at 745 nm. The potentiometric detection of saccharides using poly(aniline-co-AB) is presented. Characteristics of both transient and steady-state response associated with the complex formation of poly(aniline-co-AB) with various saccharides were monitored by UV-vis spectroscopy and cyclic voltammetry (CV). The results obtained from UV-vis spectroscopy and CV show that the sensitivity of enzymatically synthesized water-soluble poly(aniline-co-AB) for various saccharides was improved significantly compared to the chemically synthesized counterpart. A possible mechanism for the sensitive detection of sugar molecules by boronic acid is proposed on the basis of UV-vis and IR spectrophotometry, and four-point probe conductivity measurements.

Synthesis of polyaniline derivatives via biocatalysis

Three structurally different aniline monomers, which can not be polymerized by chemical methods, have been polymerized with horseradish peroxidase. Enzymatic synthesis of linear polyaniline requires template molecules to minimize branching in the polyaniline backbone. Monomers having methoxy and methyl blocking groups at the ortho or meta position could induce the conducting form of para-linked polyaniline without the use of an anionic template, such as SPS. A new mild peroxide, peroxyacetic acid, was identified and used to oxidize horseradish peroxidase in water.

Copolymerization of ethylene and 1,5-hexadiene by stereospecific metallocenes in the presence of Al(iBu)3/[Ph3C][B(C6F5)4]

Abstract Copolymerizations of ethylene (E) with 1,5-hexadiene (1,5-HD) has been carried out with rac-1,2-ethylenebis(1-indenyl)Zr(NMe2)2 [rac-(EBI)Zr(NMe2)2] and isopropylidene(cyclopentadienyl)(9-fluorenyl)ZrMe2 (iPr(Cp)(Flu)ZrMe2) compounds combined with Al(i-Bu)3/[Ph3C][B(C6F5)4] as a cocatalyst system. Microstructures of copolymers were determined by 1H, 13C NMR, Raman spectroscopy and X-ray diffraction (XRD). The isospecific rac-(EBI)Zr(NMe2)2/Al(i-Bu)3/[Ph3C][B(C6F6)4] catalyst showed much higher polymerization activity than syndiospecific iPr(Cp)(Flu)ZrMe2/Al(i-Bu)3/[Ph3C][B(C6F6)4] catalyst; however, the latter catalyst showed much higher comonomer reactivity, resulting in rE=17.44 and r1,5-HD=0.02(rE×r1,5-HD=0.35), than the latter catalyst showing rE=4.48 and r1,5-HD=0.12(rE×r1,5-HD=0.54). The 1,2-inserted 1,5-HD led to cyclic backbones by the intramolecular reaction. The intramolecular cyclization was independent of the polymerization temperature. Detailed investigation on the structure of copolymers by 13C NMR and distortionless enhancement by polarization transfer (DEPT) spectroscopies showed that alternating structural units become predominant as the amount of 1,5-HD incorporated into the copolymer increased. The qualitative and quantitative analyses of the structure of copolymers were also made by XRD and Raman spectroscopy.

One-step immobilization and purification of his-tagged enzyme using poly(2-acetamidoacrylic acid) hydrogel

AbstractNi2+-Complexed poly(2-acetamidoacrylic acid) (PAAA) hydrogel support was developed for the one-step immobilization and purification of recombinant histidine-tagged glutamyl aminopeptidase (His-tagged GAP). Ni2+-PAAA hydrogel was prepared from the polymerization of 2-acetamidoacrylic acid (AAA) and 2,2-[(1,4-dioxo-1,4-butanediyl) diamino] bis(2-propenoic acid) (DBDBPA) with potassium persulfate in dimethyl sulfoxide (DMSO), followed by Ni2+complexation. His-tagged GAP was immobilized directly from the cell lysate onto the Ni2+-PAAA hydrogel support and then purified. Catalytic activity of immobilized His-tagged GAP for the hydrolysis of alanylpara-nitroanilide revealed 90% conversion after 30 min of incubation, indicating sustained catalytic activity. The hydrogel-immobilized enzyme also exhibited enhanced thermal stability of sustained 70% activity after 1 h incubation at 60 °C, while the free enzyme activity was reduced to 50% at the same condition. After four cycles of hydrogel regeneration, the immobilized enzyme lost only 20% of its initial activity. Ni2+-PAAA hydrogel provided a new and convenient immobilization/purification system for His-tag enzymes through easy and simple procedures.

COMPLEXATION BEHAVIOR OF POLY(ACRYLIC ACID) AND POLY(ETHYLENE OXIDE) IN WATER AND WATER-METHANOL

To investigate the effects of solvent type and temperature on the interpolymer complexation via hydrogen bonding, a study was made on the complex system of poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) in two kinds of solvent systems, pure water and water-MeOH (30 wt%) mixed solvent, at various temperatures using the Ubbelohde viscometer, pH-meter, and UV spectrophotometer. The repeating unit mole ratio at the most optimum complexation as confirmed by the reduced viscosity measurement was shifted from [PEO]/[PAA] ≈ 1.25:1 to 1.5:1 by the addition of methanol to water. From the UV measurement, the deviation from the “isosbestic point” (where the absorbance of the solution remains constant) has presented another evidence for the solvent effect on complexation. In addition, the analysis of the changes in thermodynamic properties upon complexation as well as the fraction of carboxyls associated with PEO oxygens and the complex stability constant as estimated by potentiometric titration at several temperatures reveals that the complex formation in mixed solvent became more unfavorable compared to that in pure solvent at high temperatures above 30°C. This could be explained by considering that in water the hydrophobic interaction as well as the hydrogen bonding may greatly contribute to the stabilization of the polymer complex formed, while in water-methanol the main stabilizing force would be the hydrogen bonding alone.

Thermoreversible Gelation of Poly(Vinylidene Fluoride) in Propylene Carbonate

Abstract Thermoreversible gelation of poly(vinylidene fluoride) (PVDF) in propylene carbonate (PC) solutions at relatively low concentrations (0.5–3.5 wt.%) has been studied in terms of the gelation time (or rate) as a function of temperature and polymer concentration. A master curve could be made for the gelation time–temperature curves using the temperature shift based on the difference in the gel melting temperature (T m g) at different PVDF concentrations. The apparent activation energy of gelation was estimated to be proportional to (T m g − T)−1.8. The gel melting enthalpy (ΔH m g) determined from the modified Eldrige–Ferry equation was 18.67 kJ/mol. In dried gel films many spherulites connected by tie molecules were observed by scanning electron microscopy (SEM). From the wide angle x‐ray diffraction (WAXD) measurement, crystallites from PVDF gels were found to consist only of the γ‐type crystal with the TTTGTTTG¯ conformation, irrespective of the polymer concentration. As judged from the results obtained, the gelation of PVDF in PC seems to proceed mainly via liquid–liquid phase separation (even if followed by crystallization in the final stage) within the concentration range covered. #Dedicated to Prof. Won‐Jei Cho on the occasion of his retirement.

Reactive processing of recycled polycarbonate/acrylonitrile butadiene styrene.

Cellular phone housings were ground to make original particulates using a knife mill. Foams and adhesives with a lighter density than water were removed from ground mixtures using a sink-float process in water; ground metals, button rubbers, and wires were separated from desired materials by using a sink float process in salt All housing materials, consisting of seven thermoplastics included in cellular phone housings, showed better tensile properties than pure housing materials made of polycarbonate/acrylonitrile butadiene styrene, but they only had about half of the impact strength. In contrast, the low impact strength for all housing materials was improved by adding 25 wt % polyethylene elastomer and/or 2.4 wt % ground epoxy circuit boards for batch mixing. Impact strengths, tensile strengths, and the energy absorption ability of all housing materials were improved by adding 5.4wt% glycidyl methacrylate for twin screw extrusion.

Effect of the polar groups in the non-degenerate π-conjugated pendant of vinyl copolymers

The interest of coploymeric electroluminescent diodes (PELDs) has much increased to improve the quantum efficiency. To understand charge transport and EL properties of the copolymer with non-degenerate π-conjugated pendants, new vinyl copolymers for light-emitting diodes with polar groups were prepared by radical copolymerization of vinyl(9-carbazole) and vinyl derivatives such as vinyl-benzyl chloride, styrene, (4-methyl)styrene.

Effect of molecular structure on complexation between acidic- and basic-polypeptides in solution

Interpolymer complex formation between basic polypeptides, poly(L-proline) Form I [PLP(I)], Form II [PLP(II)] and poly-4-hydroxy-L-proline (PHLP), and acidic polypeptides, poly(L-glutamic acid) (PLGA), poly(D- glutamic acid) (PDGA) and poly(L-aspartic acid) (PLAA), has been studied in water-methanol (1:2 v/v) mixed-solvent by viscometry, potentiometry, light scattering and circular dichroism (CD) measurements. It has been found that polymer complexes between basic- and acidic- polypeptides are formed via hydrogen bonding with a stoichiometric ratio of basic/acidic polypeptides = 1:2 (in unit mole ratio) and that PLP(II) forms polymer complex more favorably with PLGA than with PLAA, and the complex of PLP(II) with PLGA is also more favorable than the complex formation of PHLP with PLGA. In addition, the complex formation is highly dependent on the conformation, especially the optical structure of the component polymers, i.e., the stereoselective complexation is observed. The PLGA having a right-handed helix at pH 3.2 formed the complex favorably and quickly with left-handed helix PLP(II), whereas PDGA having a left-handed helix at pH 3.2 favorably formed the complex with right-handed helix PLP(I).

Steady, elongational flow of dilute solutions of once-bent, once-broken, and deformable rod polymers

Calculations have been made for steady–state elongational flows of dilute solutions of polymer molecules modelled as rods decorated with beads that interact frictionally with the solvent. The models are chosen to mimic structural and dynamic features of real polymer molecules. In one model, the rods are rigid and bent at one point. In another, they are broken into two parts and then hinged together. The third model is a flexible rod that forms a circular arc with a variable radius of curvature. The elongational (Trouton) viscosity and the flow birefringence have been calculated as functions of the model parameters. Numerical results are presented for a large range of deformation rates.