Immobilization of urease in poly(1-vinyl imidazole)/poly(acrylic acid) network

In this study, urease was immobilized in a polymer network obtained by complexation of poly(1-vinyl imidazole) (PVI) with poly(acrylic acid) (PAA). Preparation of the polymer network was monitored by FT-IR spectroscopy. Scanning electron microscopy (SEM) revealed that enzyme immobilization had a strong effect on film morphology. Proton conductivity of the PVI/PAA network was measured via impedance spectroscopy under humidified conditions. Values of the Michaelis-Menten constant (K _M) for immobilized urease were higher than for the free enzyme, indicating a decreased affinity of the enzyme to its substrate. The basic characteristics (pH_opt, pH_stability, T _opt, T _stability, reusability, and storage stability) of immobilized urease were determined. The results show that the PAA/PVI polymer network is suitable for enzyme immobilization.     

Complexation of sequence-ordered methacrylic acid copolymers with poly(4-vinylpyridine)

The complexation of three kinds of sequence-ordered acid (co)polymers with a base homopolymer was studied. The acid polymers used are poly(methacrylic acid) 1 , alternating (1:1) ethylene-methacrylic acid copolymer 2 , and periodic (2:1) ethylene-methacrylic acid copolymer 3 , and the base polymer is poly(4-vinylpyridine) 4. When mixing a methanol solution of 1, 2 , or 3 with that of 4 (0.1 M of each functional group), precipitate was formed immediately for all polymer pairs. All the precipitates contained carboxyl and pyridyl groups in ca. 1:1 molar ratio and showed IR spectra indicating the hydrogen bonding between carboxyl and pyridyl groups. When mixing dilute methanol solutions (10⁻⁴M) of the above polymer pairs, no precipitation was observed, but the extinction coefficient (ϵ_B) at 255 nm of pyridyl groups in 4 was found to increase with an increasing acid polymer concentration. This is ascribed to hydrogen bonding between carboxyl and pyridyl groups in methanol. Based on the ϵ_B variation, the order of complexation constants for acid/base polymer pairs was estimated as follows: 1/4 pair ∼ 2/4 pair ≫ 3/4 pair. © 1996 John Wiley & Sons, Inc.     

Preparation and characterization of a poly(vinylbenzyl sulfonic acid)‐grafted FEP membrane

In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP‐g‐PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base‐catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM‐EDX. A chemical stability study performed with Fenton's reagent (3% H₂O₂ solution containing 4 ppm of Fe²⁺) at 70 °C revealed that FEP‐g‐PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)‐grafted membranes (FEP‐g‐PSSA). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 563–569, 2010     

Interpolymer complex between poly(ethylene oxide) and poly(carboxylic acid)

An interpolymer complex was prepared by mixing aqueous solutions of poly(ethylene oxide) (PEO) and of a poly(carboxylic acid), i.e., poly(acrylic acid)(PAA), poly(methacrylic acid)(PMAA), or styrene-maleic acid copolymer(PSMA). The complexation mechanism was discussed on the basis of results of such experimental methods as viscosity, potentiometric titration, and turbidimetry. The hydrogen bond is primarily involved in these complexations, but the influence of hydrophobic interaction on complexation can not be ignored. If the degree of dissociation α of carboxylic acid or the degree of polymerization P_n of PEO was perceptibly changed, a stable complex was obtained at about α 0.1 or P_n (PEO) = 40 for PMAA, 200 for PAA. This fact indicates that more than a definite number of binding sites are necessary for a stable interpolymer complex to be formed and that cooperative interaction among active sites plays an important role in complex formation.     

Well‐defined amphiphilic graft copolymer consisting of hydrophilic poly(acrylic acid) backbone and hydrophobic poly(vinyl acetate) side chains

A series of well‐defined amphiphilic graft copolymers containing hydrophilic poly(acrylic acid) (PAA) backbone and hydrophobic poly(vinyl acetate) (PVAc) side chains were synthesized via sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization followed by selective hydrolysis of poly(tert‐butyl acrylate) backbone. A new Br‐containing acrylate monomer, tert‐butyl 2‐((2‐bromopropanoyloxy)methyl) acrylate, was first prepared, which can be polymerized via RAFT in a controlled way to obtain a well‐defined homopolymer with narrow molecular weight distribution (M_w/M_n = 1.08). This homopolymer was transformed into xanthate‐functionalized macromolecular chain transfer agent by reacting with o‐ethyl xanthic acid potassium salt. Grafting‐from strategy was employed to synthesize PtBA‐g‐PVAc well‐defined graft copolymers with narrow molecular weight distributions (M_w/M_n < 1.40) via RAFT of vinyl acetate using macromolecular chain transfer agent. The final PAA‐g‐PVAc amphiphilic graft copolymers were obtained by selective acidic hydrolysis of PtBA backbone in acidic environment without affecting the side chains. The critical micelle concentrations in aqueous media were determined by fluorescence probe technique. The micelle morphologies were found to be spheres. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6032–6043, 2009     

Preparation of poly(fumaric acid) from poly(di-t-butyl fumarate) and poly(di-trimethylsilyl fumarate)

Polymerization conditions of di-t-butyl fumarate and di-trimethylsilyl fumarate were studied in detail. They cannot be polymerized by either anionic or coordination initiators, but radical and radiation polymerizations are successful. Characterization of poly(di-t-butyl fumarate), obtained thereby, with ¹H-NMR spectrum suggests that the backbone of the chain is stiff. From analysis of thermal properties of poly(di-t-butyl fumarate), it is found to be completely converted to poly(fumaric acid) by pyrolysis around 200°C. Poly(di-trimethylsilyl fumarate), on the other hand, can be quantitatively hydrolyzed with acid to the same polyacid, too. The preliminary measurement of the dissociation behaviors of poly(fumaric acid) was done by potentiometric titration, which shows that the titration curves of poly(fumaric acid) are different from those of poly(acrylic acid) and poly(maleic acid).     

Electron transfer in electroactive poly(glutamic acid)

Electroactive biopolymer was synthesized by incorporation of ferrocene moieties onto poly(glutamic acid) polymer chains. In the presence of the electron acceptor methyl viologen dichloride, the ferrocene-containing poly(glutamic acid) exhibits efficient photoinduced electron transfer. This redox-active polymer’s electrocatalytic activity for the decomposition of hydrogen peroxide and ascorbic acid was investigated by using cyclic voltammetry. As for hydrogen peroxide, the reduction peak current shows proportional response to peroxide concentration in the wide range of 10-100 mM; as for ascorbic acid, the oxidation peak current displays linear dependence on the ascorbic acid concentration under 80 mM, which could lead to the electroactive biopolymer’s applications in catalysis, photosensitizer, sensors, etc. The study could offer a strategy for developing environment-friendly electroactive and photoactive biopolymers.     

Cope elimination and complexation of poly(dimethylaminoethyl methacrylate N-oxide)

Poly(dimethylaminoethyl methacrylate N-oxide) (poly(DMAEMNO)) was prepared by oxidation of poly(dimethylaminoethyl methacrylate) with hydrogen peroxide in methanol. From thermogravimetric and IR spectroscopic investigations Cope elimination of amine oxide group in poly(DMAENO) was found to occur at 120–150°C. The postpolymerization of partially pyrolyzed polymer carrying vinyl ester group as pendant was performed with azobisisobutyronitrile at 60°C in methanol to give cross-linked polymer that was found to form hydrogel. Poly(DMAEMNO) gave metal–polymer complexes with CuCl₂, ZnCl₂, and CoCl₂. Cobalt–polymer complex had a constitution of 1:2 of metal ion to amine oxide group, while copper– and zinc–polymer complexes seemed to have structures of 1:1 and 1:2 of metal ion to amine oxide group. Furthermore, polymer complexes of poly(DMAEMNO) with poly(methacrylic acid) and poly(acrylic acid) were found to be formed by mixing aqueous solutions of both polymers and also by radical polymerization of the acid monomers in the presence of poly(DMAEMNO). From elemental analysis, thermogravimetric investigation, and measurement of turbidity it was concluded that the resulting polymer–polymer complexes contained more than one acid monomer unit per one N-oxide unit.     

Electrocatalytic Oxidation of Hydrogen Peroxide on Poly(m‐toluidine)‐Nickel Modified Carbon Paste Electrode in Alkaline Medium

The poly(m‐toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO₄, also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m‐toluidine)/modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 μM (S/N=3). The catalytic reaction rate constant, (k_h), was calculated 5.5×10² M^?1 s^?1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.     

Immiscibility–miscibility phase transformation in blends of poly(ethylene succinate) with poly(L‐lactic acid)s of different molecular weights

Using differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and Fourier transformed infrared spectroscopy (FTIR), upper critical solution temperature (UCST) phase behavior with immiscibility–miscibility transformation in blends of poly(ethylene succinate) (PESu) with poly(lactic acid)s (PLAs), such as poly(D ,L ‐lactic acid) (PDLLA), poly(L ‐lactic acid) (PLLA), poly(D ‐lactic acid) (PDLA), differing in D/L configurations and molecular weights were investigated. All three binary blends of PDLLA/PESu, PLLA/PESu, and PESu/PDLA exhibit UCST behavior, which means they are immiscible at ambient temperature but can become miscible upon heating to higher temperatures at 240–268 °C depending on molecular weights. The PLLAs/PESu blends at UCST could be reverted back to the original phase‐separated morphology, as proven by solvent redissolution. The blends upon quenching from above UCST could be frozen into a quasi‐miscible state, where the Flory‐Huggins interaction parameter (χ₁₂) was determined to be a negative value (by melting point depression technique). The interaction between PDLLA and PESu in blend resulted in significant reduction in spherulite growth rate of PESu. Furthermore, blends of PESu with lower molecular weight PLLA or PDLA (M_w of PLLA and PDLA are 152,000 and 124,000 g/mol, respectively), instead of the higher M_w of PDLLA (M_w of PDLLA = 157,000 g/mol), are immiscible with UCST phase behavior, which are affected by molecular weights rather than the ratio of L/D monomer in the chemical structure of PLAs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1135–1147, 2010     

Thermosensitive behavior of amphiphilic triblock copolymers based on poly(acrylic acid) and poly(propylene oxide)

Self‐association in aqueous solution of amphiphilic poly(acrylic acid)‐b‐poly(propylene oxide)‐b‐poly(acrylic acid) (PAA‐b‐PPO‐b‐PAA) copolymers having various outer PAA block lengths are presented. These copolymers show two thermosensitive behaviors. The first one, due to hydrogen bonds between PAA and PPO resulting in large aggregates, was observed by visible spectroscopy. The second one, due to the association of PPO middle block into aggregates, was evidenced by dynamic light scattering and pyrene fluorescence. These critical temperatures both depend on the ionization and the length of PAA blocks. The characterization of the aggregates above the critical aggregation concentration by fluorescence quenching experiments showed a very low aggregation number corresponding to dimers or trimers association depending on the conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1507–1514     

New amino acid based biodegradable poly(ester amide)s via bis-azlactone chemistry

Abstract

Three new classes of the amino acid based biodegradable (AABB) polymers were synthesized via step growth polymerization of bis-azlactones and amino acid based diamine-diesters with activated fatty diester and alkylenediamine: a) poly(ester amide)s (PEAs) were obtained by polymerization of bis-azlactones with diamine-diesters, b) hydrophobically modified co-poly(ester amide)s (co-PEAs) were synthesized by copolymerization of activated fatty diacid diester and bis-azlactones with diamine-diesters, and c) poly(ester amide-co-amide)s (PEA-co-PAs) were obtained by copolymerization of alkylene diamine and diamine-diesters with bis-azlactones. The new poly(ester amide)s showed relatively low-molecular-weights (M_w within 2,800–19,600?Da, GPC in DMF), whereas the new co-poly(ester amide)s and poly(ester amide-co-amide)s exhibited high-molecular-weights (M_w within 40–100?kDa) leading to good mechanical properties. Incorporation of the bis-azlactone fragments into the poly(ester amide)s backbone increased hydrophobicity and thermal stability, whereas incorporation of diamine-diester units into the backbone of the bis-azlactone based polyamides rendered them biodegradable. Synthesized AABB polymers are potential candidates for constructing resorbable surgical and pharmaceutical devices.     

Structure and sorption properties of the polyion complex between poly(acrylic acid) and poly(4-vinylpyridine)

A polyion complex was formed from poly(acrylic acid) (PAA) and poly(4-vinylpyridine) (PVP). Its structure and composition were examined by means of infrared spectroscopy (IR), x-ray photoelectron spectroscopy (XPS), and elemental analysis. The polyion complex was obtained by dissolving PAA and PVP together in methanol. The composition of the polyion complex was independent of stirring speed, mixing sequence, and standing time after mixing. However, the composition depended on the concentrations and the ratio of the components in the reaction mixture. Excess of PAA in the product was observed when concentrated solutions (2.0 × 10^?1M) were used for the preparation or when an excess of PAA was added to PVP. The sorption of water vapor by an equimolar PAA/PVP complex at 293 and 303 K was higher than that by the pure components, especially in the low- and middle-pressure regions. In the high-pressure region, however, the uptake was not affected by the complex formation. While hydrogen bond interactions in general decrease sorption, Coulombic interactions between polymer chains increased the sorption capacity.     

Cobalt‐mediated radical polymerization routes to poly(vinyl ester) block copolymers

Cobalt‐mediated radical polymerizations (CMRPs) utilizing redox initiation are demonstrated to produce poly(vinyl ester) homopolymers derived from vinyl pivalate (VPv) and vinyl benzoate (VBz), and their block copolymers with vinyl acetate (VAc). Combining anhydrous Co(acac)₂, lauroyl peroxide, citric acid trisodium salt, and VPv at 30 °C results in controlled polymerizations that yield homopolymers with M_n = 2.5–27 kg/mol with M_w/M_n = 1.20–1.30. Homopolymerizations of scrupulously purified VBz proceed with lower levels of control as evidenced by broader polydispersities over a range of molecular weights (M_n = 4–16 kg/mol; M_w/M_n = 1.34–1.65), which may be interpreted in terms of the decreased nucleophilicity of these less electron donating propagating polymer chain ends. Based on these results, we demonstrate that sequential CMRP reactions present a viable route to microphase separated poly(vinyl ester) block copolymers as shown by small‐angle X‐ray scattering analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Proton transfer involving nucleic acids: A temperature-jump study of the systems sulphonephthaleins–double stranded poly(A) and sulphonephthaleins–double stranded poly(C)

The kinetics of proton transfer between poly(A—AH) (partially protonated double-stranded polyadenylic acid) and CPR (chlorophenol red), and between poly(C—H—C) (partially protonated double-stranded polycytidylic acid) and the indicators CPR, BCP (bromocresol purple), and BCG (bromocresol green) have been investigated at 25°C and ionic strength 0.1 M (NaClO₄) by the temperature-jump method. The acidic proton of poly(C—H—C) is engaged in a hydrogen bond (N₃H⁺––––N₃) which is believed to contribute to stabilizing the double-strand conformation, whereas the acidic proton of poly(A—A—H) does not form hydrogen bonds. The analysis of the dependence of the relaxation times on the concentrations of the reactants has enabled the evaluation of the rate constants for the direct proton transfer and for the protolysis paths. The rate constants for proton recombination with the deprotonated forms of the polynucleotides and the indicators are of the order of magnitude expected for diffusion controlled processes involving oppositely charged ions (k₂=(0.2−1.6)×1010 M⁻¹s⁻¹). The direct proton transfer from poly(C—H—C) to BCG is thermodynamically disfavored and its rate constant, k₁, is lower than k₂ by about three orders of magnitude. The (thermodynamically favored) proton transfers from poly(A—A—H) to CPR and from poly(C—H—C) to CPR and BCP are characterized by similar values of k₁. This result indicates that the hydrogen bonds in poly(C—H—C) are very weak and suggests that the stabilization of the double-stranded conformation of this polynucleotide could be ascribed to the large number of hydrogen bonds rather than to their specific strength. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 161–169, 1998.     

Synthesis and pH-sensitive micellization of doubly hydrophilic poly(acrylic acid)-b-poly(ethylene oxide)-b-poly(acrylic acid) triblock copolymer in aqueous solutions

A doubly hydrophilic triblock copolymer poly(acrylic acid)-b-poly(ethylene glycol)-b-poly(acrylic acid) (PAA-b-PEO-b-PAA) with M _w/M _n = 1.15 was synthesized by atom transfer radical polymerization of t-butyl acrylate (tBA), followed by acidolysis of the PtBA blocks. The pH-sensitive micellization of PAA-b-PEO-b-PAA in acidic solution was investigated by potentiometric titration, fluorescence spectrum, dynamic light scattering and zeta potential. The pK _a was 6.6 and 6.0 in deionized water and in 0.1 mol/L NaCl solution, respectively. The copolymer formed micelles composed of a weakly hydrophobic core of complexed PAA and PEO and a hydrophilic PEO shell in 1 mg/mL solution at pH < 5.5 due to hydrogen bonding. The critical micelle concentration was 0.168 mg/mL at pH 2.0. At pH < 4.5, steady and narrow distributed micelles were formed. Increasing pH to 5.0, unsteady and broad distributed micelles were observed. At pH > 5.5, the micelle was destroyed owing to the ionization of the PAA blocks.     

Preparation and microstructural analysis of poly(lactic‐alt‐glycolic acid)

Alternating copolymers of glycolic (G) and lactic (L) acid were prepared by the condensation of the preformed dimers: L_LG and L_racG. By size exclusion chromatography (THF, PS standards), poly(L_LG) exhibited a molecular weight (M_n) of 15.6 kg mol^?1, with a weight average molecular weight (M_w) of 26.9 kg mol^?1 and a PDI of 1.72. The M_n for poly(L_racG) was 9.2 kg mol^?1, with a M_w of 12.9 kg mol^?1 and a PDI of 1.40. The NMR spectra of poly(L_LG) were consistent with an isotactic microstructure. NMR spectra of the racemic poly(L_racG) were consistent with an atactic structure. The methylene region of the ¹H NMR spectrum showed a tetrad level of resolution of the nearby stereochemical relationships, for example, iii. Resonances for other groups in both the ¹H and ¹³C NMR spectra gave only a triad level of resolution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4704–4711, 2008     

Oxidative degradation of poly(isophthaloylhydrazine‐1,2‐diyl)s

The condensation polymerization of isophthalodihydrazide and diphenyl isophthalate affords poly(isophthaloylhydrazine‐1,2‐diyl). High‐molecular‐weight poly(5‐tert‐butylisophthaloylhydrazine‐1,2‐diyl) is prepared by the polycondensation of 5‐tert‐butylisophthalodihydrazide and bis(4‐nitrophenyl) 5‐tert‐butylisophthalate in NMP at 100 °C. T_d of the poly(diacylhydrazine) is observed above 300 °C. No T_g is observed below T_d. The high‐molecular‐weight poly(diacylhydrazine) exhibits a film‐forming ability. The poly(diacylhydrazine) decomposes on treatment with an oxidant such as sodium hypochlorite solution to obtain the corresponding carboxylic acid and nitrogen. However, poly(diacylhydrazine) was stable to oxygen and hydrogen peroxide even in the presence of transition metal ions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6255–6262, 2008     

Stereoregular poly(styrenesulfonic acid)

A convenient method is described for the preparation of poly(n-propyl p-vinylbenzene sulfonate) by using the monomer, n-propyl p-vinylbenzene sulfonate and butyllithium initiation in tetrahydrofuran at ?75°C. The structure of this polymer enables complete hydrolysis to the corresponding poly(styrenesulfonic acid), which was characterized with respect to molecular weight and sulfonic acid content. The polyacid was shown by potentiometric titration to be strongly ionophoric.     

Synthesis of poly(succinimide) by bulk polycondensation of L‐aspartic acid with an acid catalyst

The bulk polycondensation of L ‐aspartic acid (ASP) with an acid catalyst under batch and continuous conditions was established as a preparative method for producing poly(succinimide) (PSI). Although sulfuric acid, p‐toluenesulfonic acid, and methanesulfonic acid were effective at producing PSI in a high conversion of ASP, o‐phosphoric acid was the most suitable catalyst for yielding PSI with a high weight‐average molecular weight (M_w) in a quantitative conversion; that is, the M_w value was 24,000. For the continuous process using a twin‐screw extruder at 3.0 kg · h⁻¹ of the ASP feed rate, the conversion was greater than 99%, and the M_w value was 23,000 for the polycondensation with 10 wt % o‐phosphoric acid at 260°C. Sodium polyaspartate (PASP‐Na) originating from the acid‐catalyzed polycondensation exhibited high biodegradability and calcium‐ion‐chelating ability. The total organic carbon value was 86 ∼ 88%, and 100 g of PASP‐Na chelated with 5.5 ∼ 5.6 g of calcium ion, which was similar to the value for PASP‐Na from the acid‐catalyzed polycondensation with a mixed solvent © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 117–122, 2000