Effect of sodium poly(styrene sulfonate) on thermoreversible gelation of gelatin

The effect of an added polyanion, sodium poly(styrene sulfonate) (NaPSS), on the thermoreversible gelation and remelting of gelatin gels has been investigated by polarimetry and rheology. The presence of NaPSS can either enhance or reduce collagenlike helix formation, depending on the polymer concentration relative to that of gelatin and the gelation temperature. At temperatures < 20°C, the helical content is reduced by increasing the amount of added NaPSS, demonstrating the disruption of helical structure of gelatin by the polyanion. Synchronous measurements of optical rotation and modulus at 25°C, in both gelation and remelting, indicate that the optical rotation at the gel point for the pure gelatin is lowered on addition of NaPSS. At low frequency, the storage modulus of gelatin is increased by the addition of a small amount of NaPSS relative to that of gelatin, but decreased with excess NaPSS. The mechanical properties of gelatin with and without NaPSS will be discussed in light of the competition between network junction formation by strands of triple helices among gelatin chains and temporary ionic crosslinking between gelatin and the polyanion. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2287–2295, 1999     

Semi-Interpenetrating Hydrogels of Polyelectrolytes,Polymer-Metal Complexes and Polymer-Protected Palladium Nanoparticles

Summary: Semi-interpenetrating hydrogels (SIHs) of polyelectrolytes consisting of poly(acrylamide) hydrogel (PAAH) as matrix and sodium poly(styrenesulfonate) (NaPSS), poly(N,N′-dimethyl-N,N′-diallylammonium chloride) (PDMDAAC), stoichiometric interpolyelectrolyte complex of NaPSS-PDMDAAC, and linear polyethyleneimine-metal complexes (PMC) as well as polymer-protected palladium nanoparticles were prepared by in situ polymerization, e.g. crosslinked acrylamide chains were formed in aqueous solutions of NaPSS, PDMDAAC, NaPSS-PDMDAAC (1:1 mol/mol), PMC and palladium nanoparticles protected by poly(N-vinylpyrrolidone) (PVP), poly-(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), and linear poly(ethyleneimine) (LPEI) respectively in the presence of N,N′-methylenebisacrylamide. For each system the equilibrium swelling degree α and the parameters n and k describing the mechanism of water transport into SIHs volume was determined. Catalytic properties of SIHs were studied in allyl alcohol hydrogenation and cyclohexane oxidation reactions.     

The influence of pH on the alternate multi-layered adsorption of macrocations and macroanions on colloidal spheres

The -potential and thickness of the alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres in suspension were measured at pH values ranging from 2.8 to 10.8 via electrophoretic light-scattering measurements. Colloidal silica spheres (110 nm in diameter) were used. The macrocations used were poly(4-vinyl-N-n-butyl pyridinium bromide) (C4PVP, a strongly basic macroion) and poly (allylamine) (PAL, which is weakly basic). Sodium poly(styrene sulfonate) (NaPSS, strongly acidic) and sodium polyacrylate (NaPAA, weakly acidic) were used as macroanions. The macrocations were added first in all of the experiments. The alternate adsorption of C4PVP and NaPSS takes place for a wide range of pH values, between 2.8 and 8.7. For C4PVP + NaPAA systems, alternate layers are formed only at neutral pH values and within three to six layers. Multiple adsorption phenomena are observed at acidic and neutral pH values for PAL + NaPSS and PAL + NaPAA systems, respectively. These results strongly support the theory that the synchronous delicate balancing of the electrostatic interactions among the macrocations, the macroanions, and the colloidal spheres is important for the alternate multiple adsorption.     

Investigating the effect of mono‐ and multivalent counterions on the conformation of poly(styrenesulfonic acid) by nanopores

Polyelectrolytes are useful materials that have many technical, medical, physiological and biological applications. The properties of polyelectrolytes are determined not only by their chemical composition but also by their conformational states. However, the conformations of polyelectrolytes in solution are very difficult to characterize. Herein, we propose to use a protein nanopore to investigate the effect of mono‐ and multivalent counterions on the conformational changes of a simple polyelectrolyte, sodium poly(styrenesulfonic acid) (NaPSS). High concentration of KCl induced a conformational transition of NaPSS from “swollen random coil” form in low salt concentration to “random coil” form and was evidenced by the changes of the translocation event pattern. Addition of Mg²⁺ in buffer solution did not cause notable changes of NaPSS translocation events, but Dy³⁺ and Y³⁺ were shown to have remarkable effects on the translocation profile of NaPSS. Bridging events caused by Dy³⁺ or Y³⁺ between polyelectrolyte chains largely affected current blockage and dwell time of the translocation events. Our results provide experimental evidence for the classical theories of conformational transitions of polyelectrolytes and may find applications in many other polyelectrolyte‐related researches.     

States of water in poly(vinyl alcohol) hydrogels

Poly(vinyl alcohol) (PVA) hydrogels with various water contents were prepared from 10 wt% aqueous solutions of mixtures of PVA and anionic poly(styrene sulfonic acid) sodium salt (NaPSS) by casting, dehydrating, and then extracting NaPSS. The existence of three types of ice were suggested by differential scanning calorimetry (DSC) measurements for every frozen hydrogel. In the frozen hydrogels the states of water, except unfrozen water, were ice of free water and disordered ice crystals. The mobility and activation energy for motion of water molecules in unfrozen hydrogels were investigated by using pulsed nuclear magnetic resonance (PNMR) measurements. It was concluded that there are two states of water in the unfrozen hydrogel, i.e. unfrozen water and disordered water which is mainly formed in narrow apertures in the hydrogel. The discrepancy between the DSC and PNMR measurements was explained by a structural transformation during cooling.     

Synchronous multilayered adsorption of macrocations and macroanions on colloidal spheres. Influence of foreign salt and basicity or acidity of the macroions

The influence of foreign salt, the basicity or the acidity of macroions and the equivalency of the number of ionic groups of macrocations and macroanions upon alternate multiple adsorption on surfaces of colloidal silica (CS91, 110 nm in diameter) and polystyrene spheres (D1A19, 220 nm) have been studied by electrophoretic light scattering measurements. The macrocations used were poly(4-vinyl-N-n-butyl pyridinium bromide (C4PVP, strongly basic), poly(4-vinyl-N-ethyl pyridinium bromide (C2PVP, strongly basic) and poly(allylamine) (PAL, weakly basic). Sodium poly(styrene sulfonate) (NaPSS, strongly acidic) and sodium polyacrylate (NaPAA, weakly acidic) were used as macroanions. The alternate adsorption disappears even in the presence of a small amount of sodium chloride. The alternate multiple adsorption takes place on the addition of C4PVP first and NaPSS next, PAL first and NaPAA next, NaPAA first and C4PVP next, and NaPAA first and PAL next on the CS91 spheres. The influence of the equivalency of the number of ionic groups of C2PVP and NaPAA has been studied for the adsorption on the D1A19 spheres. The synchronous delicate balancing of the electrostatic interactions among the macrocations, the macroanions and the surfaces of the colloidal spheres is important for the alternate multiple adsorption.     

Adsorption characteristics of stoichiometric and nonstoichiometric molecular polyelectrolyte complexes on silicon oxynitride surfaces

Adsorption properties of stoichiometric and nonstoichiometric polyelectrolyte complexes (PECs) have been investigated by means of dual polarization interferometry (DPI) and X-ray photoelectron spectroscopy (XPS). Poly(sodium styrenesulfonate) (NaPSS) of molecular weight 4300 g/mol was used as polyanion, and two bottle-brush copolymers possessing different molar ratios of the cationic segment methacryloxyethyltrimethylammonium chloride (METAC) and the nonionic segment poly(ethylene oxide) methyl ether methacrylate (PEO(45)MEMA) were used as polycations. They are referred to as PEO(45)MEMA:METAC-25 and PEO(45)MEMA:METAC-50, where the last digits denote the mol % of charged main-chain segments. The time evolution of the adsorbed amount, thickness, and refractive index of the PEC layers were determined in aqueous solution using DPI. We demonstrate that cationic, uncharged, and negatively charged complexes adsorb to negatively charged silicon oxynitride and that maximum adsorption is achieved when small amounts of PSS are present in the complexes. The surface composition of the adsorbed PEC layers was estimated from XPS measurements that demonstrated very low content of NaPSS. On the basis of these data, the PEC adsorption mechanism is discussed and the competition between PSS and negative surface sites for association with the cationic polyelectrolyte is identified as a key issue.     

Continuous thermoanalysis: the essence of the method and equipment

Phase transition of the water-sodium poly(styrenesulfonate)(NaPSS) system with various water contents (W_c) ranging from 0 to 2.00 (g/g) was evaluated by differential scanning calorimetry (DSC). In the temperatures from 120 to 320K, four kinds of transitions were observed for the water-NaPSS system quenching from 320K to 120K. They were glass transition, cold-crystallization, melting, and a new transition which was considered to be that from the meso-phase to the isotropic liquid phase. From the DSC data, the phase diagram of the water-NaPSS system was obtained. At the same time, W_c was related to the weight of water calculated from the enthalpy of melting (W_f). By the subtraction of W_f from W_c, the amount of non-freezing water was calculated to be 0.57–0.68 (g/g) depending on molecular weight of NaPSS.     

Coil‐Globule Collapse in Flexible Macromolecules

The transition of a solvated flexible macromolecular chain from random coil behavior in the θ‐state to a globular compact form in the collapsed state has been the subject of extensive theoretical and experimental studies. Most of the coil‐globule transition studies of macromolecules have concentrated on the prototypical polystyrene‐cyclohexane system. However, chain contractions reported in this system have been around 75% of those in the unperturbed θ‐state. This relatively small decrease in size does not satisfy the criterion for a densely packed, collapsed globule. Experimentally, the collapse from a coil to a true compact globular state has now been established for two flexible macromolecules: poly(N‐isopropylacrylamide) in water and poly(methyl methacrylate) in various solvents. In this contribution, we review recent theoretical studies covering phenomenological and Langevin models as well as computer simulations. In addition, we outline recent experimental studies of the coil‐globule transition of various flexible polymers, copolymers, and polyelectrolytes.

Expansion factor, αequation/tex2gif-stack-1.gif, versus temperature for NaPSS in 4.17 M aqueous NaCl solution. (•): NaPSS‐1, (○): NaPSS‐2.     

Gel speciation studies-I The intrinsic dissociation constant of weakly acidic cation-exchange gels

The arid-dissociation properties of three weakly acidic cation-exchange gels, CM-Sephadex C-50-120, Biogel CM-2 and CM-Biogel A, have been studied. Each of the gels was equilibrated in sodium polystyrene sulphonate (NaPSS) solutions at three different concentration levels (0.1, 0.01 and 0.001M). The volume of the gels was measured as a function of a (their degree of neutralization), and C(p) (the NaPSS concentration); pH and pNa were also measured at each alpha-value. Intrinsic pK values of 3.25 and 4.55 have been found for CM-Sephadex C-50-120 and Biogel CM-2 respectively.     

Assessment of the diffusional behavior of polystyrene sulfonates in the dilute regime by hollow‐fiber flow field flow fractionation

We applied flow field flow fractionation in a ceramic tubular membrane to study the diffusional behavior of sodium polystyrene sulfonate (NaPSS) as a function of salt and polyelectrolyte concentrations in the dilute concentration regime. NaPSS standards were fractionated in an aqueous carrier liquid with salt concentrations of 1–100 mmol L^?1 and injected amounts of 0.2–20 μg. A sharp increase in the apparent diffusion coefficients, due to peak overloading, occurred at a critical polyelectrolyte concentration at the accumulation wall. A model has been developed that compares repulsive electrostatic interactions, calculated from the Derjaguin–Landau–Verweij–Overbeek theory, to the thermal energy. It was found that the observed critical concentration approximated the concentration of a closely packed lattice of hard spheres within an order of magnitude. The critical concentration appeared to be dependent on the salt concentration, but the influence of the molecular mass was less clear. Expressions for the migration velocity in overloaded channels were derived and confirmed experimentally for the two lowest molecular masses. Deviations occurred for high molecular mass NaPSS, possibly because of mutual attraction. These experiments confirmed the observations made by small‐angle neutron scattering and dynamic light scattering that the ordering of polyelectrolytes already occurred in the dilute regime. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1756–1765, 2001     

Micro-composite systems by in-situ formation of liquid crystal polymers in commodity polymers

In-situ formation of polyimide was carried out in solution of copolymers derived from styrene and 4-vinylpyridine. The in-situ formed polyamic acid formed a strong hydrogen-bonding with pyridine moiety of the copolymers, resulting in homogeneous solutions. Cast films obtained from the solutions were clear and transparent without phase separations, and mechanical properties of the films were much stronger than those of films from the original copolymers. In-situ polymerization of acrylamide in poly(styrene) was carried out by anionic polymerization to form Nylon 3 which was dispersed in poly(styrene) as fine particles, and mechanical properties of the poly (styrene) were greatly improved.     

Calorimetric determination of surfactant/polyelectrolyte binding isotherms

Mixing of oppositely charged surfactants and polyelectrolytes in aqueous solutions leads to cooperative surfactant adsorption onto the polyelectrolyte chains. Experimental determination of surfactant/polyelectrolyte binding isotherms is usually done using custom-built surfactant-ion-specific electrodes. As an alternative, we present an indirect isotherm approximation method that uses conventional isothermal titration calorimetry (ITC). The calorimetric data is fitted to the two-binding-state Satake-Yang adsorption model, which quantifies the extent of binding in terms of the binding constant (Ku) and the cooperativity parameter (u). This approach is investigated using two surfactant/polyelectrolyte mixtures: sodium perfluorooctanoate (FC7) and N,N,N-trimethylammonium derivatized hydroxyethyl cellulose (UCARE Polymer JR-400), whose binding behavior follows the Satake-Yang model, and dodecyltrimethylammonium bromide (DTAB) and poly(styrenesulfonate) (NaPSS), whose behavior deviates dramatically from the Satake-Yang model. These studies demonstrate that, in order to apply the indirect ITC method of binding isotherm determination, the surfactant/polyelectrolyte adsorption process must have no more than two dominant binding states. Thus, the technique works well for the FC7/JR-400 mixture. It fails in the case of the DTAB/NaPSS adsorption, but its mode of failure offers insight into the multiple-binding-state adsorption mechanism.     

线性聚酯酰胺对聚碳酸亚丙酯的改性

通过己内酯和氨基己酸开环、缩合反应制备了酯段含量为81%的线性聚酯酰胺（PEA）,并用熔融共混的方法制备了PEA/聚碳酸亚丙酯（PPC）共混物,考察了PEA的引入对共混体系相容性、热力学稳定性和机械性能的影响。 结果表明,PEA与PPC之间有较好的相容性,共混物的热力学稳定性比PPC有显著提高,当PEA质量分数为3%时,共混体系的起始分解温度（T-5%）和最大分解速率时的温度（Tmax）比PPC分别提高了52.7%和46.4%。 通过调节PEA的含量可以使共混体系同时达到增强和增韧的效果。     

A NOVEL RESISTIVE HUMIDITY SENSOR BASED ON SODIUM POLYSTYRENESULFONATE/TiO_2 NANOCOMPOSITES

A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO_2 nanocomposites,and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis (<4% RH) andquicker response (absorption: less than 2 s; desorption: less than 20 s) in comparison with sensor composed of NaPSS. Theeffect of concentration of NaPSS and TiO_2 on humidity response of sensors was discussed.     

Humidity sensors using in situ synthesized sodium polystyrenesulfonate/ZnO nanocomposites

Thin film humidity sensors have been prepared using in situ synthesized inorganic/organic nanocomposites of sodium polystyrenesulfonate (NaPSS) and ZnO. Its humidity sensing characteristics and the sensing mechanism have been investigated by measuring the complex impedance spectra of the sensor at different humidities. The logarithm of the impedance of sensor based on composite film changes linearly by four-orders of magnitude over almost whole humidity range (11-97% RH). Furthermore, the sensor exhibits a quick response (absorption: 2 s, desorption: 2 s) and small hysteresis (less than 2% RH). The composite film shows better sensing properties than NaPSS film, such as better linearity, quicker response. Explanation to the improvement is attempted by taking into account of the composition and structure of the nanocomposites.     

Synthesis and characterization of polyimide containing PEG/PDMS amphiphilic conetworks by hydrosilylation: Correlation between structure and properties

Soluble poly(imide‐siloxane)s were obtained by carefully designing the synthesis and introducing poly(ethylene glycol) (PEG) units, thereby making the system amphiphilic in nature. The solubility of the synthesized PEG containing poly(mide‐siloxane)s (PPIS) in various solvents was tested and their thermal properties were investigated. Polymeric siloxane networks were prepared by combining imide groups and hydrophilic PEG components with sufficient variability in their composition to analyze their physicochemical details. The amine groups of the imides were varied in their rigidity and bulkiness, and their effect on the mechanical and thermal properties was studied. Here we have also examined the surface property of the networks through contact angle measurements, morphology through SEM, existence of amorphous nature by WAXD, and their structure–property relationships were correlated. The thermal analysis revealed the phase separation of the three components poly(dimethyl siloxane) (PDMS), PEG, and imide, showing a tricomponent amphiphilic conetworks. The mechanical properties were found to be improved by the phase separated PPIS containing more rigid imide groups. The overall properties of the amphiphilic conetwork has the features of differing hydrophilicity, mobility, and morphology distributed across a matrix, which has a microphase separated design suitable for gas separation and biomedical applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1707–1726, 2007     

Formation Mechanism and Tensile Mechanical Properties of Poly(acrylamide-co-octylphenol polyoxyethylene (10) acrylate) Hydrophobic Association Hydrogels With High Toughness

Poly(acrylamide-co-octylphenol polyoxyethylene (10) acrylate) hydrophobic association hydrogels, which is abbreviated to poly(AM-co-OP10/AC) HA-gels, were prepared through micellar copolymerization of acrylamide (AM) and a small amount of octylphenol polyoxyethylene (10) acrylate (OP10/AC) in the presence or absence of sodium dodecyl sulfate (SDS). For poly(AM-co-OP10/AC) HA-gels, formation mechanism was discussed in detail, which can reasonably explain the reason that tensile mechanical properties of the hydrogels (containing SDS) are much higher than those of the hydrogels (not containing SDS). In addition, according to the tensile experimental results of poly(AM-co-OP10/AC) HA-gels, the effect of composition content in the initial solutions on tensile mechanical properties was investigated in detail. The results clearly indicate tensile strength, elastic modulus and elongations for poly(AM-co-OP10/AC) HA-gels strongly depended on composition content in the initial solutions.     

TUNED MECHANICAL PROPERTIES ACHIEVED BY VARYING POLYMER STRUCTURE — KNOWLEDGE THAT GENERATES NEW MATERIALS FOR TISSUE ENGINEERING

By changing both the monomer composition and the polymer structure, we have varied the mechanical properties of resorbable polymers. The polymers were synthesized by ring-opening polymerization using L-lactide （LLA）, ε-caprolactone （εCL）, trimethylene carbonate （TMC） and 1,5-dioxepan-2-one （DXO） as monomers. Well-defined triblock copolymers, microblock copolymers and networks have been evaluated, and comparisons between them show that it is possible to tune the mechanical properties. Triblock copolymers with an amorphous middle block of poly（1,5-dioxepan-2- one） （PDXO） and semi-crystalline end-blocks of poly（ε-caprolactone） （PCL） were stronger and had a higher strain at break than triblock copolymers with poly（L-lactide） （PLLA） as end-blocks. Polymers with both DXO and TMC in the amorphous middle-block and PLLA as end-blocks showed a lower stress at break, but the material gained elasticity, a property which is very valuable in tissue engineering. Mechanical properties of networks, synthesized by a novel method, containing PDXO and PCL are also presented. Although it is difficult to compare them with the uncross-linked polymers, this is an additional way to modify and widen the properties.     

Synthesis and Properties of Novel Thermoplastic Poly(ester-ether-imide) Elastomers Derived from 4,4′-bis(N-trimellitimide)-diphenylether Unit with Excellent Thermal Stability

The novel poly(ester-ether-imide)s (PEEIs) were synthesized by 1, 6-hexanediol (HD), poly(tetramethylene glycol) (PTMG1000) and imide dicarboxylic acid was prepared from 1,2,4-trimellitic anhydride (TMA) and 4,4′-oxydianiline (ODA) by the traditional chemical two-step method. The structures of synthesized imide dicarboxylic acid and poly(ester-ether-imide)s were confirmed by FT-IR and ¹H-NMR spectroscopy, respectively. The intrinsic viscosities, thermal properties, dynamic mechanical properties, mechanical properties and solubility of these polymers were characterized. The results indicate that these polymers have good solubility, exhibit excellent thermal stability owing to the introduction of imide units, and the tensile strength of PEEIs increases with increasing the number of imide groups while maintaining the good elasticity of the polymers.