Preparation and properties of polyelectrolyte complex sponges composed of hyaluronic acid and chitosan and their biological behaviors

Polyelectrolyte complexes (PECs) composed of chitosan and hyaluronic acid (HA) were prepared in various pH regions and at different weight ratios. At low pHs, there was a strong ionic interaction between NH groups in chitosan and both COO^? and COOH groups in HA due to the deprotonation of HA, whereas weak linkages were formed at high pHs because only the carboxyl groups of HA could interact with NH groups in chitosan. The formation of PECs resulted in a decrease in the crystallinity and thermal stability caused by the interactions between polyions. With variations in the degree of ionization of polyions at various pH conditions, novel PEC sponges were prepared by the freeze drying of PEC solutions. Furthermore, for the evaluation of the wound‐healing effect of PEC sponges with or without an antimicrobial agent (silver sulfadiazine), they were applied to a full‐skin defect of a Wistar rat in vivo. The histology and computerized morphometric analysis of the epidermal healing confirmed the proliferation of fibroblasts in the wound bed and a distinct reduction in infectious agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 925–932, 2003     

Conductivity and structure of a polyamide/silver iodide nanocomposite

In this study, the structure and properties of an organic–inorganic composite material prepared from nylon 6 doped with fine particles of silver iodide (AgI) were examined. The preparation of the composite involved the complexation of nylon 6 with polyiodide ions such as I and I by immersion in an iodine/potassium iodide (I₂–KI) aqueous solution followed by reaction in a silver nitrate (AgNO₃) aqueous solution; this resulted in the in situ formation of β-AgI fine particles within the nylon 6 matrix. The AgI content formed in the composite was dependent on the immersion temperatures of the I₂–KI and AgNO₃ solutions. Lower solution temperatures resulted in larger amounts of AgI in the composite. This method readily provided a composite with a high content of AgI in nylon 6 and a conductivity of approximately 10⁻⁵ Ω⁻¹ cm⁻¹. In a uniaxially oriented nylon 6 matrix, AgI particles precipitated with anisotropic shape, which was caused by the orientation of the precursor polyiodide ions. The structure of the oriented composite provided the anisotropic conductivity. Additionally, the composite exhibited high antibacterial properties. The procedure used in this study is considered a unique method for the preparation of organic–inorganic composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Upgrading melamine–urea–formaldehyde polycondensation resins with buffering additives. I. The effect of hexamine sulfate and its limits

Iminoamino methylene base intermediates obtained by the decomposition of hexamethylenetetramine (hexamine) stabilized by the presence of strong anions such as SO and HSO, or hexamine sulfate, were shown to markedly improve the water and weather resistance of hardened melamine–urea–formaldehyde (MUF) resins used as wood adhesives and of the wet internal bond strength performance of wood boards bonded with them. The effect was shown to be induced by very small amounts, between 1 and 5 wt % of this material on resin solid content. This strong effect allowed the use of MUF resins of much lower melamine content and also provided good performance of the bonded joints. Because the main effect was also present at the smaller proportion of hexamine as hexamine sulfate, it was not due at all to any increase in the molar ratio of the resin as a consequence of hexamine sulfate addition. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 203–214, 2003     

Poly(N‐isopropylacrylamide)‐grafted silica as a support of platinum colloids: Preparation method,characterization, and catalytic properties in hydrogenation

We investigated the composition, properties, and utility of a novel hybrid material of poly(N‐isopropylacrylamide)‐grafted silica. The modified silica was prepared in two steps: (1) grafting silane layers of active precursors, such as initiator, transfer agent or comonomer onto the silica surface by solution deposition and (2) radical polymerization of N‐isopropylacrylamide (NIPAAm) on the grafted silane layers. Thermogravimetric analysis (TGA), elemental analysis (EA), FTIR spectroscopy, and TEM were used to characterize the layer composition, structure, and chemistry, respectively. Well‐dispersed platinum colloids have been prepared on the PNIPAAm‐grafted silica via the reduction of PtCl by ethanol. The immobilized Pt colloids were found to be active and stable heterogeneous catalysts for the hydrogenation of ally alcohol in ethanol. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2678–2684, 2000     

The effect of grafted polymeric lubricant molecular weight on the frictional characteristics of nylon 6,6 fibers

Boundary friction between two crossed nylon 6,6 fibers has been reduced up to 6× by grafting polymeric lubricants to the surface. A modified adhesion model of friction, accommodating multiple materials on the surface, explains the variation in the friction coefficient with the molecular weight of the lubricant. The friction coefficient is proportional to the fraction of the surface covered by the grafted chain, represented by πR/A, where A is the surface area per graft site, and R_G is the radius of gyration of the lubricant. It is also shown that for larger the grafted chains, the appropriate surface area fraction depends on πR/3A. It is argued that if R_G of the grafted lubricant is larger than half the distance between graft sites, the next nearest graft site is used due to steric blocking of the nearest graft site. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 129–136, 1999     

The study of polymerization kinetics of methacrylamide by oxidation: Reduction system using potassium permanganate/glycine in aqueous medium

The polymerization kinetic of methacrylamide with the KMnO₄/glycine redox system has been investigated volumetrically at 35±0.1°C under nitrogen atmosphere in aqueous sulfuric acid medium in a dimethylsulfoxide/H₂O mixture (5% v/v). The rates of polymerization were found to obey the following equation: R_p ∝ [Methacrylamide]^1.08[Glycine]^0.44[KMnO]^0.46. A glycine end group containing polymethacrylamide was prepared by the MnO/glycine redox system under mild conditions. The reaction proceeded with radical mechanism and the overall energy of activation (E_a) was calculated to be 29.87 kJ/mol from the Arrhenius plot in the temperature range 25–50°C. Molecular weight of the polymer was determined by viscometry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3918–3924, 2003     

Effect of matrix's type on the dynamic properties for short fiber-elastomer composite

The dynamic moduli, E′ and E″, and tan δ for PET–CR, PET–EPDM, and PET–UR composites with unidirectional short fibers were studied as a function of temperature by using a Rheovibron. The temperature dependence of tan δ showed three peaks for PET–elastomer composites. The peaks at the low temperature corresponded to the main dispersion of the respective matrixes and the peak at about 140°C to the α-dispersion of PET fiber. A small and broad peak observed at a temperature between 60 and 120°C may be caused by the relaxation of the interface region between fibers and matrix. The longitudinal storage modulus for the composite E was given by the parallel model as \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm E'}_\parallel = V_f \cdot E'_f + V_m \cdot E'_m $\end{document}, where E and E are the storage moduli for fiber and matrix and V_f and V_m are the volume fraction of fiber and matrix, respectively. In the transverse direction of fibers, the composite modulus E was expressed by the logarithmic law of mixing as follows: \documentclass{article}\pagestyle{empty}\begin{document}$ \log E'_ \bot = V_f \cdot \log E'_f + V_m \cdot \log E'_m $\end{document}. The peak values of tan δ from the main dispersion of the respective matrixes were given by the equation, (tan δ_⊥max)_c/(tan δ_max)_m 1 ? β · V_f, where (tan δ_⊥max)_c and (tan δ_max)_m are the maximum values of the loss tangent for the composite and matrix, respectively, and β is coefficient depending on matrix's type. The β value of PET–CR composite is the largest one among those of the composites.     

Intrinsic birefringence of nylon 6

Different values are reported in the literature for the intrinsic birefringence of the crystalline (Δn) and the amorphous (Δn) phases in nylon 6. Mostly, these values have either been determined by extrapolation (and then it is assumed that Δn = Δn) or calculated theoretically. In this study, intrinsic birefringence values Δn and Δn for nylon 6 were determined using the Samuels two-phase model which correlates sonic modulus with structural parameters. Three series of fiber samples were used: (1) isotropic samples of different degrees of crystallinity for estimation of E and E moduli at two temperatures. The following modulus values were obtained: 1.62 × 10⁹ and 6.66 × 10⁹ N/m² for 28.5°C, and 1.81 × 10⁹ and 6.71 × 10⁹ N/m² for ?20°C; (2) anisotropic, amorphous fiber samples for estimation of Δn = 0.076 and E = 1.63 × 10⁹ N/m² at 28.5°C; (3) semicrystalline samples of various draw ratios for estimations of Δn = 0.089 and Δn = 0.078. All measurements were carried out with carefully dried samples to avoid erroneous results caused by moisture.     

Several features of vinyl chloride–diallyl phthalate suspension copolymerization

Vinyl chloride–diallyl phthalate (VC–DAP) suspension copolymerization was carried out in a 5‐L autoclave and 200‐mL stainless steel vessel at 45°C. The apparent reactivity ratios of VC–DAP suspension copolymerization system were calculated as r_VC = 0.77 and r_DAP = 0.37. It shows that VC–DAP copolymer contains no gel when the feed concentration of DAP (f) is lower than a critical concentration (f_cr, inside the range of 0.466–0.493 mmol/mol VC at 80–85% conversion), the polymerization degree (DP) of copolymer increases with the increase of f and conversion. VC–DAP copolymer is composed of gel and sol fractions when f is larger than f_cr. The DP of sol fraction decreases as f increases, but the gel content and the crosslinking density of gel increase. The gel content also increases as conversion increases. The results also show that the index of polydispersity of molecular weight of sol changes with f, a maximum value appears when f is close to f_cr. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 156–162, 2000     

Comment

Electrolytic manganese dioxide is dissolved in the mixed non-aqueous solvent dimethyl sulfoxide–sulfur dioxide (DMSO–SO₂) to form manganese disulfate as a final product. Sulfur dioxide does not change the oxidation state of the metal cations in DMSO–SO₂ solvent. However, oxidation of sulfur(IV) to sulfur(VI) is possible. The complete MnO₂ dissolution occurs in 50 min at a stirring speed of 650 rpm, pH 1, 0.2% solids concentration, 35 × 44 mesh particle size, and 36°C. IR and FTIR evidence has been presented in favor of the formation of SO, S₂O, (CH₃)₂S⁺ as intermediate species for the proposed mechanism. In the mixed non-aqueous solvent system the kinetics of leaching is controlled by a mass transport process. The equation 1–?α–(1–α)^2/3 = kt fits the experimental data very well. This is further supported by scanning electron micrographs, which show a product layer formation on the surface of the MnO₂ particle, and by the dependence of k on 1/r.     

Melting behavior of poly(trimethylene terephthalate)

In this study, the melting behavior of isothermally crystallized polytri‐ methylene terephthalate (PTT) was investigated. Multiple melting behaviors in DSC heating trace were found because two populations of lamellar stacks were formed during primary crystallization and the recrystallization at heating process, respectively. This fact could be also confirmed from the result of optical microscopy observation. The Hoffman–Weeks equation was applied to obtain equilibrium melting temperature (T). The T value of PTT is about 525 K, which is 10 K higher than that reported. Combining the enthalpy of fusion from the DSC result and the degree of crystallinity from WAXD result, the value of the equilibrium‐melting enthalpy ΔH was deduced to be approximately 28.8 kJ mol^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2426–2433, 2002     

Adsorption of casein onto alkali treated bentonite

The adsorption measurements of casein onto alkali treated bentonite were performed at room temperature and fixed pH (11.8) with an object to study the mode of casein adsorption at the alkali treated bentonite surfaces. The adsorption isotherm was found to have a Langmuir nature. The adsorption was pH dependent and increased with a decrease in temperature. The adsorption was quite sensitive to the presence of Cl⁻, SO, and PO ions and showed many interesting variations with increasing concentrations of the added anions. Various kinetic and adsorption parameters such as the adsorption coefficient, rate constants for adsorption and desorption, diffusion constant, and penetration rate constant were calculated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1656–1663, 2000     

Synthesis of ultraviolet‐curable modified polysiloxane and its surface properties

A novel ultraviolet (UV)‐curable monomer α,ω‐dichloropolysiloxane was synthesized by the telomerization of dichlorodimethylsilane and octamethylcyclotetrasiloxane (D₄). The products with very low peel strength (<0.332 N/cm) could be used as release agents in pressure‐sensitive adhesives. Moreover, the values of the dispersion component of surface energy (γ) from the films of UV‐curable prepolymers (26.40–33.75 mJ/m²) were determined and the effects of γ on the reduction of adhesion were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2135–2139, 2002     

Development of a mechanistic model for biological nutrient removal activated sludge systems and application to a full‐scale WWTP

In wastewater treatment plants (WWTPs) the production of nitrite as an intermediate in the biological nutrient removal (BNR) process has been widely observed, but not been taken into account by most of the conventional activated sludge models yet. This work aims to develop a mechanistic mathematical model to evaluate the BNR process after resolving such a problem. A mathematical model is developed based on the Activated Sludge Model No.3 (ASM3) and the EAWAG Bio‐P model with an incorporation of the two‐step nitrification–denitrification, the anoxic P uptake, and the associated two‐step denitrification by phosphorus accumulating organisms. The database used for simulations originates from a full‐scale BNR municipal wastewater treatment plant. The influent wastewater composition is characterized using batch tests. Model predictions are compared with the measured concentrations of chemical oxygen demand (COD), NH‐N, NO‐N, NO‐N, PO‐P, and mixed liquid volatile suspended solids. Simulation results indicate that the calibrated model is capable of predicting the microbial growth, COD removal, nitrification and denitrification, as well as aerobic and anoxic P removal. Thus, this model can be used to evaluate and simulate full‐scale BNR activated sludge WWTPs. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Solution and diffusion properties of cyclohexane,cyclohexanol, and cyclohexanone in poly(ethylene glycol) by inverse gas chromatography

The solution and diffusion properties of cyclohexane, cyclohexanol, and cyclohexanone in poly(ethylene glycol) (PEG) and crosslinked PEG have been studied in the temperature range of 368.15 to 403.15 K using inverse gas chromatography (IGC) technique. The infinite dilute activity coefficient (Ω) and diffusion coefficient (D) have been determined for the above solvent/polymer systems. Accordingly, several thermodynamic functions, the diffusion pre‐exponential factor, and activation energy have been attained. The results showed a decrease in Ω and an increase in D with rising temperature. The order of the relative magnitude of Ω and D of the solvents were explained by comparing their interactions with the polymer and their collision diameters, respectively. Moreover, Ω and D in crosslinked PEG were smaller than those in PEG at various temperatures. The analysis of Ω, the infinite dilute selectivity and capacity showed the possibility of using crosslinked PEG as an appropriate membrane material for the separation of cyclohexane, cyclohexanol, and cyclohexanone mixture. A thermodynamic study also implied that the solvent sorptions in the polymers were all enthalpically driven in the experimental range. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Mass transport process for the adsorption of Cr(VI) onto water‐insoluble cationic starch synthetic polymers in aqueous systems

Dynamic adsorption behaviors between Cr(VI) ion and water‐insoluble amphoteric starches was investigated. It was found that the HCrO ion predominates over the initial pH ∼ 2–4, the CrO ion predominates over the initial pH ∼ 10–12, and both ions coexist over the initial pH ∼ 6–8. The sorption process occurs in two stages: the external mass transport process occurs in the early stage and the intraparticle diffusion process occurs in the long‐term stage. The diffusion coefficient of the early stage (D₁) is larger than that of the long‐term stage (D₂) for the initial pH 4 and pH 10. The diffusion rate of HCrO ion is faster than that of CrO ion for both processes. The D₁ and D₂ values are ∼ 1.38 × 10⁻⁷–10.1 × 10⁻⁷ and ∼ 0.41 × 10⁻⁷–1.60 × 10⁻⁷ cm² s⁻¹, respectively. The ion diffusion rate in both processes is concentration dependent and decreases with increasing initial concentration. The diffusion rate of HCrO ion is more concentration dependent than that of CrO ion for the external mass transport process. In the intraparticle diffusion process, the concentration dependence of the diffusion rate of HCrO and CrO ions is about the same. The external mass transport and intraparticle diffusion processes are endothermic and exothermic, respectively, for the initial pH 4 and pH 10. The k_d values of the external mass transport and intraparticle diffusion processes are ∼ 15.20–30.45 and ∼ −3.53 to −12.67 kJ mol⁻¹, respectively. The diffusion rate of HCrO ion is more temperature dependent than that of CrO ion for both processes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2409–2418, 1999     

The effect of poly(vinyl alcohol) hydrolysis on the properties of its blends with nylon 6

An investigation of the properties of the blends of nylon 6 (PA6) and poly(vinyl alcohol) (PVA) with varying degrees of hydrolysis was conducted. A near disappearance of the characteristics of the α‐form PVA crystals, crystallization exotherms, and hydrogen‐bonded hydroxyl groups and the tensile properties originally associated with the PVA molecules of PA6_xPVA PA6_xPVA, and PA6_xPVA specimens was observed as the PVA contents of the specimens became equal to or less than their corresponding ‘‘critical’’ values at 16.7 wt%, 33.3 wt%, and 50 wt%, respectively. These results support the idea that PVA molecules are miscible with PA6 molecules to some extent at the molecular level as the PVA contents of the blends become equal to or less than their corresponding critical PVA contents. In this article, we have proposed the possible reasons accounting for these properties of the PA6_xPVA_y series specimens with a varying degree of hydrolysis. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Poly(2‐hydroxyethylmethacrylate)/chitosan dye and different metal‐ion‐immobilized interpenetrating network membranes: Preparation and application in metal affinity chromatography

Composite membranes were synthesized with 2‐hydroxyethylmethacrylate and chitosan (pHEMA/chitosan) via an ultraviolet‐initiated photopolymerization technique in the presence of an initiator (α,α′‐azobisisobutyronitrile). The interpenetrating network (IPN) membranes were improved by the immobilization of dye molecules via hydroxyl and amino groups on the membrane surfaces from the IPNs. A triazidine dye (Procion Green H‐4G) was covalently immobilized as a ligand onto the IPN membranes. The protein showed various affinities to different chelated metal ions on the membrane surfaces that best matched its own distribution of functional sites, resulting in a distribution of binding energies. In support of this interpretation, two different metal ions, Zn(II) and Fe(III), were chelated with the immobilized dye molecules. The adsorption and binding characteristics of the different metal‐ion‐chelated dye‐immobilized IPN membranes for the lysozyme were investigated with aqueous solutions in magnetically stirred cells. The experimental data were analyzed with two adsorption kinetic models, pseudo‐first‐order and pseudo‐second‐order, to determine the best fit equation for the adsorption of lysozyme onto IPN membranes. The second‐order equation for the lysozyme–dye–metal‐chelated IPN membrane systems was the most appropriate equation for predicting the adsorption capacity for all the tested adsorbents. The reversible lysozyme adsorption on the dye‐immobilized and metal‐ion‐chelated membranes obeyed the Temkin isotherm. The lysozyme adsorption capacity of the pHEMA/chitosan dye, pHEMA/chitosan dye–Zn(II), and pHEMA/chitosan dye–Fe(III) membranes were 2.54, 2.85, and 3.64 mg cm^?2, respectively. The nonspecific adsorption of the lysozyme on the plain pHEMA/chitosan membrane was about 0.18 mg cm^?2. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1843–1853, 2003     

Preparation and solid‐state nuclear magnetic resonance characterization a styrene/butadiene/acrylonitrile (ABS)/poly(vinyl chloride) (PVC)/gypsum ternary system

Polymer blends were prepared to obtain a new material with specific characteristics. To prepare a miscible polymer blend, it is necessary to evaluate the chemical structure and molecular dynamics of all polymers involved and to thereby establish a structure–property relationship for these materials. In this work, ternary blends for application in plates chromatography were formed with styrene/butadiene/acrylinotrile (ABS), poly(vinyl chloride) (PVC), and gypsum, and were studied by solid‐state carbon‐13 nuclear magnetic resonance (¹³C NMR). Magic‐angle spinning (MAS), cross‐polarization magic‐angle spinning (CPMAS), variable contact time (VCT), and proton spin‐lattice relation time in the rotating frame (Tρ) were the techniques used to evaluate the miscibility, homogeneity, and compatibility of polymer blends at the molecular level. From the values of Tρ, it was verified that ABS/PVC/gypsum formed good polymer blends with some specific physical interaction at the molecular level. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 293–296, 2003     

New‐type sulphonated polymer surfaces for improving blood compatibility

A new‐type sulphonated polymer surface obtained by the solution technique is reported. The surface properties of the modified polymer surfaces are characterized by SEM and ESCA, and their in vitro blood compatibility is evaluated in terms of TT, PRT, PTT, and platelet adhesion. The modified polymer surface is found to be the least thrombogenic when the modifying polymer molecule contains hydrophilic PEO chains. The PEO chains can serve as “spacers” inserted into the film surface and SO group. This kind of polymer surface is easily mobile for reconstructing to carry out the function of the SO group and PEO chains. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2826–2831, 1999