Ionic Copolymers Research Articles

Solubility effects on drug transport through pH-sensitive, swelling-controlled release systems: Transport of theophylline and metoclopramide monohydrochloride

The swelling behavior of and solute transport in swellable, ionic copolymers of 2-hydroxyethyl methacrylate and methacrylic acid was studied for a wide range of copolymer compositions. The swelling behavior was determined by investigating the time-dependent change of the swelling and erosion front positions and the associated gel layer as a function of the percentage of the ionic component (MAA). Release of theophylline and metoclopramide-HCl were studied as a function of time. The swelling and release behavior were interpreted in terms of the significant solubility of the drugs tested and their possible association with the polymer matrices. It was concluded that the water uptake was mainly governed by the degree of ionization, and that the diffusion of non-ionized drugs in the hydrogels was controlled only by the volume swelling ratio of the polymer. For metoclopramide monohydrochloride, the drug diffusivity varied with copolymer composition.

Catalytic activity of cationic latices prepared according to the shot-growth method

Stable cationic latices were prepared by the shot-growth method and by use of the ionic copolymer poly(styrene-co-1-methyl 4-vinylpyridinium bromide) (PS-qPVP) as emulsifier. An increase in co-catalytic activity of the shot-growth latices in the cobalt(II)phthalocyanine-tetrasodiumsulphonate-catalysed oxidative coupling of 2-mercaptoethanol was found compared with the batch latex system. Although PS-qPVP was successfully applied as emulsifier only a moderate increase in oxidation rate was found compared with the surfactant-free system. The surface characteristics of both latex systems were investigated by ξ-potential measurement and conductometric titrations. These measurements suggest the presence of a water soluble hairy polymer shell.

Thermal stability of modified telechelic polystyrenes

AbstractThe thermal stability of telechelic polystyrenes bearing quaternary ammonium iodide or ammonium sulfonate end groups is presented. It appears that the ammonium iodide functions are stable below 200°C. Above that temperature, the polystyrene irreversibly looses its functional end groups. The weight loss then observed leads to the conclusion that a Hofmann‐type degradation mechanism is likely to take place. In contrast, the ammonium sulfonate‐terminated polystyrene begins to degrade at 180°C and leads to a polymer which is no longer end‐capped with sulfonic acid or sulfonate groups. This behavior is of importance, especially for the study of multiblock ionic copolymers which are prepared by blending two telechelic polymers, one of them bearing sulfonic acid end groups and the other one tertiary amine functional groups. © 1993 John Wiley & Sons, Inc.

Concentration of large biomolecules with hydrogels

The swelling and exclusion behavior fo crosslinked hydrogels were determined in aqueous solutions of electrolytes and in aqueous solutions of proteins and enzymes. The gels were ionic copolymers of acrylamide, ionic copolymers of N-isopropylacrylamide (NIPA) and homopolymers of NIPA. Both anionic (weak acid and strong acid) and cationic (strong base) monomers were used. Crosslinked polymer gels, whose swelling is sensitive to the temperature or concentration of the surrounding medium, can be exploited to concentrate dilute aqueous solutions of macromolecular solutes including proteins and enzymes, with no adverse effect on the activity of the enzyme. Exclusion was primarily by size and net charge although some proteins adsorbed onto the surfaces of hydrogels having the same charge. The variable with the largest effect on the size exclusion behavior of hydrogels was the monomer concentration at gel formation.

Water solubility characteristics of some ion‐containing acrylic copolymers

AbstractThe water solubility characteristics of a series of ionic copolymers of acrylic acid with acrylic esters was determined. A relationship was developed between solubility and the ionic character of the copolymers. In addition to water solubility, the effects of the composition and degree of neutralization upon other copolymer properties were also examined. Moisture effects upon the physical properties can be minimized by limiting the ionic character of the copolymer to that required for water solubility. The effects of molecular weight on the solubility and speed of dissolution was also investigated and found to have no effect, within the range of composition of the copolymers investigated.

Effect of thermal treatment on cation local structure in manganese-neutralized sulfonated polystyrene ionomers

Two sets of manganese-neutralized sulfonated polystyrenes, at 2.6 and 7.6 mol % sulfonation, were subjected to three sample treatments: solvent casting from tetrahydrofuran/water, solvent casting followed by annealing, and compression molding. Both as-cast samples were void of ionic aggregates, as evidenced by the absence of a peak in their small-angle X-ray scattering (SAXS) patterns. Upon annealing, the SAXS peak appeared, indicating the formation of ionic aggregates. The compression-molded 7.6 mol % material also exhibited the SAXS peak, while the compression-molded 2.6 mol % material did not, possibly due to a slower rate of aggregation in the lower ion content material. The local coordination structure about the Mn2+ cation was examined by extended X-ray absorption fine structure (EXAFS) spectroscopy and found to be nearly identical for all six samples despite the differences in the state of aggregation. That the local structure is unaffected by the microdomain structure reflects the difference in size scale probed by SAXS and EXAFS. When a nonionic monomer is copolymerized with a small amount of ionic comonomer, profound changes in prop- erties are observed relative to the nonionic parent polymer. The ionic copolymers, termed ionomers, typically contain less than 10 mol % of a sulfonic or carboxylic acid-bearing monomer and are neutralized with metal cations. The marked increases in, for example, modulus and tear and abrasion resistance and the dramatic alterations in ion- transport propertie~l-~ that occur in these materials are now accepted as being due to aggregation of the ionic groups4i5 into microdomains. Because of the small size of these ionic aggregates, diffraction techniques can reveal little regarding their in- ternal structure. On the other hand, extended X-ray ab- sorption fine structure (EXAFS) spectroscopy is a powerful technique for determining the local atomic environment about a specific atom and has been profitably applied to numerous ionomers.6-17 The EXAFS signal is a modula- tion of the X-ray absorption coefficient on the high-energy side of an element's absorption edge, and it contains in- formation on the coordination shells surrounding that atom. The type and number of atoms in a shell, as well as the distance to and disorder within a shell, are reflected in the EXAFS data. As such, EXAFS can probe the en- vironment around ions that reside in ionic aggregates, as well as dispersed ionic groups and even ions in solution.1° One ionomer that has been studied in detail by nu- merous in~estigators~~~ ~~'~~~~~~

Interfacial adhesion between ionic copolymers and high‐modulus surface‐treated carbon fibers

AbstractHigh‐modulus carbon‐fiber‐reinforced thermoplastic composites typically fail at the interface due to poor adhesion between fiber and matrix. To increase interfacial strength, the research described herein focuses on modifying the fiber surface (via high‐temperature acid treatment or zinc electrolysis) to facilitate chemical functional groups on the fiber that might increase fiber‐matrix inter‐actions. The thermoplastic matrix materials used in this study were random copolymers of ethylene and methacrylic acid in which the carboxyl groups in the methacrylic acid segments were neutralized with either sodium or zinc counterions. Mechanical tests were performed to determine the macroscopic effects of fiber pretreatment on the ultimate mechanical properties of the composites. Fabrication was designed such that fiber‐matrix separation provides the dominant contribution to mechanical gracture. Composites containing fibers treated with nitric acid, or a mixture of nitric and sulfuric acids exhibit a 20 to 25 percent increase in transverse (tensile) fracture stress relative to composites fabricated with as‐received fibers. Scanning electron microscopy of the fiber‐matrix interface at fracture allows one to “zoom‐in” and obtain qualitative details related to adhesion. Fracture surface micrographs of the above‐mentioned acid‐treated fiber‐reinforced composites reveal an increase in the amount of matrix material that adhered to the fiber surface relative to the appearance of the fracture surface of composites fabricated with as‐received fibers. The presence of acid functionality in the matrix, rather than the divalent nature of the zinc counterions, produces the largest relative enhancement of transverse (tensile) fracture stress in the above‐mentioned composites containing surface‐treated carbon fibers.

A humidity sensor using ionic copolymer and its application to a humidity-temperature sensor module

A humidity-temperature sensor module with a frequency output signal was fabricated by integrating a humidity sensor, temperature sensor and measuring circuit on a ceramic substrate. The humidity sensor had a copolymer of ionic and non-ionic monomers as its humidity-sensitive material, and a chip thermistor served as the temperature sensor. The measuring circuit was an astable multivibrator, and the humidity and temperature sensors were used as circuit elements to determine the oscillation frequency. Operation of the humidity-sensing circuit was evaluated on the basis of an analysis of the frequency dependence of the humidity sensor impedance. In the derivation of the humidity-oscillation frequency characteristics from the impedance data, a model that expresses the humidity sensor impedance by the bulk resistance of the humidity-sensitive material gave relatively good agreement with expe The fabricated module offers superior long-term stability. Changes in humidity-oscillation frequency and temperature-oscillation frequency characteristics were less than ±3% r.h. and ±0.1 °C, respectively, after more than two years in an open laboratory atmosphere.

Small-angle neutron scattering study of micellization of ionic copolymers in aqueous solutions. The effects of side-chain length and molecular weight

Small-angle neutron scattering study of micellization of ionic copolymers in aqueous solutions. The effects of side-chain length and molecular weight

Controlled Activity Polymers. V. Copolymers of 2-(1-Naphthylacetyl) Ethyl Acrylate with Hydrophilic Comonomers: Release Behavior

Abstract Release properties of the copolymers of 2-(1-naphthylacetyl)ethyl acrylate with hydrophilic comonomers of known molecular weight have been studied as a function of pH, composition, comonomer type, and copolymer microstructure. Fluorescence and solid-state 13C-NMR studies have also been performed. Neighboring group effects for the hydrolysis were observed by the concentration of auxin released; the release mechanism differed with the comonomer type. In addition, the release behavior of the ionic copolymers is affected by the presence of intramolecular hydrophobic interactions.

Adiabatic Compressibility and Apparent Molal Volume of Ionic Monomers, Polymers, and Copolymers in Aqueous and Nonaqueous Solutions

Abstract In this review we are primarily concerned with the use of apparent molal volume and apparent molal compressibility of polyelectrolytes along with their corresponding monomers in elucidating the ion-ion and ion-solvent interactions in aqueous and nonaqueous solutions. Though the main emphasis will be given to synthetic polyelectrolytes, the biochemical significant (natural) ones are not excluded altogether. It is hoped that this information will provide researchers with up-to-date knowledge of the subject matter and give a new impetus to further study on the subject. Most of the works on molal volumes and ultrasonic velocity measurements were confined up to the middle sixties to solutions of simple electrolytes. These works gave valuable information about the structure of solutions as well as about the fundamental properties of solutions.

ChemInform Abstract: REVERSIBLE OXYGEN BINDING BY THE COMPLEX OF POLY(2‐METHYL‐1‐VINYLIMIDAZOLE) AND HEME IN COLD AQUEOUS MEDIA

AbstractPoly‐[Q‐methyl‐1‐vinylimidazol] (Molgewicht l0") formt mit Häm in wäßriger Ethylenglykollösung einen stabilen finffach‐ koordinierten Komplex, der bei ‐30°C ein Sauerstoffaddukt bildet, während für Häm‐ Komplexe mit niedrigerem Molekulargewicht und für den sechsfach‐koordinierten Komplex mit Poly‐[l‐vinylimidazol] eine reversible Oxidation beobachtet wurde.

Reversible oxygen binding by the complex of poly(2-methyl-1-vinylimidazole) and heme in cold aqueous media

Poly(2-methyl-1-vinylimidazole), molecular weight > 104, forms a stable five-co-ordinated complex with heme in aqueous ethylene glycol solution. This complex gave an oxygen adduct at –30 °C, whereas an irreversible oxidation was observed for low-molecular-weight heme complexes with 2-methyl-imidazoles and for the six-co-ordinated heme complex with poly(1-vinylimidazole). Oxygenation was also observed for heme complexes with copolymers of 2-methyl-1-vinylimidazole but not for those with ionic copolymers. The lifetime of the oxygen adduct decreased with increasing hydrogen-ion concentration and upon adding alcohol or urea. Oxygen-binding and -dissociation rate constants and oxygen-binding equilibrium constants were also measured in cold aqueous media.

Changes in Electrical Resistance of Ionic Copolymers Caused by Moisture Sorption and Desorption

Changes in Electrical Resistance of Ionic Copolymers Caused by Moisture Sorption and Desorption

Preparation and Copolymerization of Methacrylate-Terminated Ionic Liquid Rubbers

Abstract Preparation of methacrylate-terminated ionic liquid rubbers (MTILR) was investigated by the addition reaction of partially neutralized carboxyl-terminated liquid rubbers (PNCTLR) with glycidyl methacrylate. The PNCTLR were prepared from a polymer of butadiene (BD) (Hycar CTB 2000X162) and a copolymer of BD-acrylonitrile (Hycar CTBN 1300X8) by partial neutralization with MgO and CaO. The metal carboxylate groups of PNCTLR catalyzed the reaction. The Mg carboxylate group showed higher catalytic activities than the Ca carboxylate group. The MTILR obtained were copolymerized with styrene. The novel ionic copolymers obtained were evaluated for their physical properties. The copolymers containing Mg showed better physical properties than their reference copolymers not containing ionic links, an effect of introducing metal. The Ca-containing copolymers showed poor physical properties, probably due to lower interionic attraction of Ca2+, to heterogeneity of the systems, and to lower overall cross-linking...

Oxygenation of the Heme-Complex Bound to Polymeric 2-Methylimidazoles

Oxygenation of the heme complex of poly(1-vinyl-2-methylimidazole) (PMI) was studied in organic solvents containing 10 vol% water at −30°C. The life-time of the oxygen adduct was prolonged in 10 vol% water/N,N–dimethylacetamide and N-methylpyrrolidone but oxygenation was not observed in the following 10 vol% water/alcohols: ethanol, butanol, and ethylene glycol. This shows a correlation to the proton accepting ability of organic solvents. The oxygen adduct was formed even in an aqueous medium for the heme complexes bound to poly(1-vinyl-2-methylimidazole-co-N,N,-dimethylacrylamide) and poly(1-vinyl-2-methylimidazole-co-1-vinyl-pyrrolidone) at −30°C but not for heme complexes bound to the ionic copolymers: poly(1-vinyl-2-methylimidazole-co-methacrylic acid) and poly(1-vinyl-2-methylimidazole-co-1-vinyl-2-methyl-3-benzylimidazolium chloride).

Polyelectrolyte behaviour of acrylonitrile methallylsulphonate copolymers in dimethylformamide

The properties in organic solvent (DMF) of two ionic copolymers are investigated and compared to those of polyelectrolytes in aqueous solutions. First, the viscometric behaviour is disccussed: it is demonstrated that [η] varies linearly with C −1 2 T , where C T is the ionic concentration of the solution. At infinite salt concentration we obtain data in agreement with unperturbed dimensions. Using isoionic dilution, we deduce ø p , the osmotic coefficient. From osmometry, the dependence of ø p on the concentration is obtained and compared to the theoretical value. In the presence of neutral salt, the osmotic pressure is determined as a function of salt and polymer concentrations. The results are interpreted in terms of a Donnan equilibrium.

Chain interactions in diphilic copolymer acid and salt solutions

IR spectroscopy and viscometry have been used to study the effects of chain interactions on the hydrodynamic dimensions of acrylic acid-styrene (AA-,St) copolymers, or the ionomers based on them, in mixed solvents (toluene with pyridine and other amines). The extent of the macromolecular coiling of the acid form of copolymer in a neutral solvent depends on the content of AA chain units and the relative number of hydrogen bonds between the chains. The reactions of the AA chain units with amines leads to a formation of molecular and ionic complexes which are in equilibrium with each other and are displaced at 25°C towards paired ions in the case of primary and secondary amines. The macromolecular shrinkage in volume in the presence of amines is due to the formation of association compounds by the paired ions by a dipole-dipole mechanism. The COOH group substitutions by metal cations strengthens the chain interactions and produces further coil shrinkage due to associate-cluster formations, these then combining as four ionic copolymer chain units.

Cation motion in ionic copolymers

Far infrared bands for the motion of Li +, Na + and CS + in the field of side groups and paraffinic elements of ethylene-methacrylate ionic copolymers, and a preliminary evaluation of the force field for the vibrations of those ions are reported.

Preparation and properties of ionic oxymethylene copolymers

AbstractOxymethylene copolymers containing pendant ionic groups have been prepared and some of their properties examined. The ionic copolymers differ from non‐ionic copolymers in that the crystalline order is poorer, which results in increased transparency and ductility and in decreased stiffness and strength. The reduction of crystalline order is dependent upon the rate of cooling from the melt. Melt viscosity and temperature dependence of melt viscosity of ionic copolymers are higher than those of non‐ionic copolymers. Introduction of ionic groups also increases water sensitivity. Ionic oxymethylene copolymers neutralized with divalent cations were examined briefly, and these show some unusual aging effects.