Potentiometric titration of anionic polyelectrolytes using a cationic surfactant solution as a titrant and a titrant-sensitive plasticized poly(vinyl chloride) membrane electrode

A potentiometric titration method for the direct determination of anionic polyelectrolytes using a plasticized poly(vinyl chloride) membrane electrode is described. A cationic surfactant solution is used as titrant. The method is based on ion association between the anionic polyelectrolyte in the sample and the cationic surfactant in the titrant. The end-point is detected as a sharp potential change due to an increase in the concentration of the free cationic surfactant at the equivalence point. The sharpness of the titration curve at the end-point is compared for several cationic surfactants; a solution of stearyltrimethylammonium ion has been found to be superior. Received: 8 October 1996 / Revised: 17 December 1996 / Accepted: 18 December 1996     

Potentiometric back-titration of sulfate ion using a tetraphenylborate derivative as a titrant and a titrant-sensitive plasticized poly(vinyl chloride) membrane electrode

A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode without added ion-exchanger is described. A solution of a derivative of tetraphenylborate is used as titrant. The method is based on the ion association between an excess of 2-aminoperimidinium added to the sulfate containing sample and the tetraphenylborate derivative in the titrant. The titration end-point is detected as a sharp potential change due to an increase in the concentration of the free tetraphenylborate derivative at the equivalence point. The sharpness of the titration curve at the end-point is compared for two tetraphenylborate derivatives. Good results are obtained with a solution of sodium tetrakis (4-fluorophenyl) borate.     

Potentiometric back-titration of sulfate ion using a tetraphenylborate derivative as a titrant and a titrant-sensitive plasticized poly(vinyl chloride) membrane electrode

A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode without added ion-exchanger is described. A solution of a derivative of tetraphenylborate is used as titrant. The method is based on the ion association between an excess of 2-aminoperimidinium added to the sulfate containing sample and the tetraphenylborate derivative in the titrant. The titration end-point is detected as a sharp potential change due to an increase in the concentration of the free tetraphenylborate derivative at the equivalence point. The sharpness of the titration curve at the end-point is compared for two tetraphenylborate derivatives. Good results are obtained with a solution of sodium tetrakis (4-fluorophenyl) borate. Received: 9 March 1998 / Revised: 21 April 1998 / Accepted: 25 April 1998     

End-point detection of the potentiometric titration of anionic polyelectrolytes using an anionic surfactant-selective plasticized poly (vinyl chloride) membrane electrode and an anionic surfactant as a marker ion

A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to dodecylbenzenesulfonate (DBS) ion is applied to the determination of anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) by potentiometric titration, using a poly (diallyldimethylammonium chloride) (Cat-floc) solution as a titrant. The end-point of the titration is detected as the potential jump of the plasticized PVC membrane electrode caused by decrease in the concentration of DBS ion added to the sample solution as a marker ion, due to the ion association reaction between the DBS ion and Cat-floc. The effects of the concentration of DBS ion, coexisting surfactants and electrolytes in the sample solution and pH of the sample on the degree of the potential jump at the end-point were examined. A linear relationship between the concentration of anionic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2 × 10^–5 to 4 × 10^–4 N for PVSK, alginate, and carrageenan. Received: 30 April 1998 / Revised: 6 July 1998 / Accepted: 11 August 1998     

End-point detection of the potentiometric titration of anionic polyelectrolytes using an anionic surfactant-selective plasticized poly (vinyl chloride) membrane electrode and an anionic surfactant as a marker ion

A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to dodecylbenzenesulfonate (DBS) ion is applied to the determination of anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) by potentiometric titration, using a poly (diallyldimethylammonium chloride) (Cat-floc) solution as a titrant. The end-point of the titration is detected as the potential jump of the plasticized PVC membrane electrode caused by decrease in the concentration of DBS ion added to the sample solution as a marker ion, due to the ion association reaction between the DBS ion and Cat-floc. The effects of the concentration of DBS ion, coexisting surfactants and electrolytes in the sample solution and pH of the sample on the degree of the potential jump at the end-point were examined. A linear relationship between the concentration of anionic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2 × 10^–5 to 4 × 10^–4 N for PVSK, alginate, and carrageenan.     

Flow injection determination of anionic polyelectrolytes using an anionic surfactant-selective plasticized poly(vinyl chloride) membrane electrode detector

 A potentiometric flow injection method for the determination of anionic polyelectrolytes utilizing a flow-through type surfactant-selective electrode detector is described. The method is based on the detection of the concentration increase of anionic surfactant liberated from a reagent stream containing an ion associate between cationic polyelectrolyte, poly(diallyldimethylammonium chloride) and anionic surfactant, dodecylbenzenesulfonate, which is caused by the formation of a polyion complex between cationic and anionic polyelectrolytes. The response of the electrode detector as a peak-shaped signal was obtained for injected anionic polyelectrolyte samples. A linear relationship was found to exist between peak height and the logarithmic concentration of potassium poly (vinyl sulfate) (PVSK) with a slope of 30 mV decade^-1 in a concentration range of 1.0×10^-4 to 1.0×10^-3 mol/L. Identical relationships were obtained for sodium alginate and carageenan (also anionic polyelectrolytes) as for PVSK but with a lower sensitivity. The detection limit for PVSK was 2.5×10^-5 mol/L. The relative standard deviation for 5 injections of a 2.5×10^-4 mol/L PVSK solution was 1.3% and the sampling rate was ca. 10 samples h^-1. Received: 9 April 1996/Revised: 8 July 1996/Accepted: 14 July 1996     

Potentiometric titration of polyhexamethylene biguanide hydrochloride with potassium poly(vinyl sulfate) solution using a cationic surfactant-selective electrode.

A potentiometric titration method using a cationic surfactant as an indicator cation and a plasticized poly(vinyl chloride) membrane electrode sensitive to the cationic surfactant is proposed for the determination of polyhexamethylene biguanide hydrochloride (PHMB-HCl), which is a cationic polyelectrolyte. A sample solution of PHMB-HCl containing an indicator cation (hexadecyltrimethylammonium ion, HTA) was titrated with a standard solution of an anionic polyelectrolyte, potassium poly(vinyl sulfate) (PVSK). The end-point was detected as a sharp potential change due to an abrupt decrease in the concentration of the indicator cation, HTA, which is caused by its association with PVSK. The effects of the concentrations of HTA ion and coexisting electrolytes in the sample solution on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of PHMB-HCl and the end-point volume of the titrant exists in the concentration range from 2.0 x 10(-5) to 4.0 x 10(-4) M in the case that the concentration of HTA is 1.0 x 10(-5) M, and that from 1.0 x 10(-6) to 1.2 x 10(-5) M in the case that the concentration of HTA is 5.0 x 10(-6) M, respectively. The proposed method was applied to the determination of PHMB-HCl in some contact-lens detergents.     

Potentiometric flow-injection determination of boron by using a flow-through tetrafluoroborate ion-selective poly(vinyl chloride) membrane electrode

A highly sensitive tetrafluoroborate ion-selective poly(vinyl chloride) membrane electrode was constructed and applied to a detector in the flow-injection determination of boron. Boron at the 10 ng ml^?1 level can be determined by converting it to tetrafluoroborate ion in a flow of hydrofluoric acid. A sampling rate of 30 h^?1 was achieved with a relative standard deviation of less than 2%.     

Use of marker ion and cationic surfactant plastic membrane electrode for potentiometric titration of cationic polyelectrolytes

A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to stearyltrimethylammonium (STA) ion is applied to the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by potentiometric titration, using a potassium poly (vinyl sulfate) (PVSK) solution as a titrant. The end-point of the titration is detected as the potential change of the plasticized PVC membrane electrode caused by decrease in the concentration of STA ion added to the sample solution as a marker ion due to the ion association reaction between the STA ion and PVSK. The effects of the concentration of STA ion, coexisting electrolytes in the sample solution and pH of the sample on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2×10⁻⁵ to 4×10⁻⁴ N for Cat-floc, glycol chitosan, and methylglycol chitosan.     

Interactions of temperature-responsive anionic polyelectrolytes with a cationic surfactant

The interactions of temperature-responsive copolymers of sodium 2-acrylamido-2-methyl-1-propanesulfonate (AMPS) and N-isopropylacrylamide (NIPAM) with a cationic surfactant, dodecyltrimethylammonium chloride (DTAC), have been studied. The content of AMPS in the copolymers ranged from 1.1 to 9.6 mol%. The surface activity was higher for the polymers with lower AMPS content. It was found that DTAC undergoes association with the polymer chain, forming mixed polymer-surfactant micelles. The values of cac for the polymers were found in fluorescence studies using pyrene as the fluorescent probe. They were in the range 0.9-3.6x10(-3) M and were lower for polymers with higher AMPS content. An increase in DTAC concentration up to about its cmc results in a decrease of the LCST (lower critical solution temperature) of the copolymers, while further increase above the cmc results in an increase of the LCST. The minimum value of LCST in the presence of the surfactant is lower than the LCST of NIPAM homopolymer.     

Biodegradation of plasticized poly(vinyl chloride) containing cellulose

The plasticized poly(vinyl chloride) (PVC‐P) and its blend with cellulose (PVC‐P/cell) were prepared by means of extrusion. The samples were then biodegraded in forest soil as well as in soil enriched with cellulolytic microorganisms. Moreover, the samples were vaccinated with chosen species of fungi whose direct effect on polymer was then observed. The course of biodegradation was monitored in terms of, and by means of the following: weight loss, carbon dioxide evolved, attenuated total reflectance infrared (FTIR‐ATR) spectroscopy, gel permeation chromatography (GPC), as well as visual and microscopic observation (OM, SEM). The mechanical properties of samples were studied using the standard tensile tests. It was found that biodegradation in soil occurs in PVC‐P and this process is accelerated in the composition of PVC‐P with cellulose. The biodecomposition yield of PVC‐P/cellulose blends (calculated as relative percentage weight loss) is several dozen times higher than that of PVC‐P. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 903–919, 2007     

Dynamic mechanical properties of plasticized poly(vinyl chloride)

The complex compliance in extension of gels of poly(vinyl chloride) (PVC) in di(2-ethylhexyl) phthalate (DOP) and in tricresyl phosphate (TCP) was measured over the frequency range from 0.6 to 0.006 cps and the temperature range from ?66 to 65°C: the weight fractions of DOP and TCP in the gels were 0.32, 0.40, 0.49, and 0.59. Measurements were carried out in an apparatus using forced low-frequency longitudinal osillations. Data for the gels could not be combined by the method of reduced variables, since there were gradual changes with decreasing temperature, attributable to an increase in crystallinity. Application of the reduction method of Ninomiya and Ferry for solutions of crystalline polymers was found to be successful. The apparent melting temperatures (T′_m) were obtained from the temperature dependence of the vertical shift factors. An apparent heat of fusion of ca. 120 cal/mole of monomer unit was found. This melting range was in agreement with that of secondary crystallinity in plasticized PVC reported in calorimetric studies by Juijn. With decreasing temperature, two phenomena occurred in the temperature range from T_g + ca. 80°C to T_g: the vitrification of a concentrated amorphous solution and the slight crystallization of the polymeric component. The larger the difference between T_g and T′_m the broader the primary dispersion zone on the frequency scale. This broadening effect was explained as due to the difference in dependence of T_g and T′_m on plasticizer concentration, without any need to consider any specific interaction between plasticizer and PVC.     

Determination of sulfate ion by potentiometric back-titration using sodium tetrakis (4-fluorophenyl) borate as a titrant and a titrant-sensitive electrode

A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode sensitive to a titrant is described. The method is based on ion association between the excess of 2-aminoperimidinium added to the sulfate ion in the sample and sodium tetrakis (4-fluorophenyl) borate (FPB) in the titrant. The titration end-point was detected as a sharp potential change due to an increase in the concentration of the free FPB at the equivalence point. The end-point was detected even in the presence of a 20-fold excess of common cations and anions relative to the concentration of the sulfate ion within approximately 2% of titration error. A linear relationship between the concentration of the sulfate ion and the end-point volume of the titrant exists in the sulfate ion concentration range from 2x10(-4) to 3x10(-3) mol l(-1) using 10(-2) mol l(-1) FPB solutions as the titrant. The present method could be applied to determine sulfate ions in sea water.     

A chlorate ion-selective electrode based on a poly(vinyl chloride)-matrix membrane

An electrode has been prepared, consisting of a PVC membrane containing Corning 477316 nitrate liquid ion-exchanger in the chlorate form, which responds to chlorate ions. It has a faster response (1-2 sec) and lower limit of detection (3 x 10(-5)M) than the nitrate electrode for chlorate determination. Selectivity coefficients for the electrode towards several other ions have been measured.     

Microcrystalline and three-dimensional network structure of plasticized poly(vinyl chloride)

Three-dimensional networks can be formed in plasticized poly(vinyl chloride) by chain entanglements and crystallites introduced in the system during the fusion and annealing processes. The fusion conditions influence the mechanical stability of the plasticized polymers, by establishing regions where one-phase systems are observed. During annealing at temperatures of between 170 and 190 °C, for up to 9 minutes, maximum degree of crystallinity of 0.079 was detected for samples plasticized with 20 wt% di-2-ethyl-hexyl-phthalate. Experimental analysis of mechanical properties and analysis of stress relaxation experiments showed that rubber elasticity theories could be applied with some approximation to plasticized PVC to analyze the structure of the three-dimensional networks formed.     

Potentiometric titration of cyanide and chloride, using the silver specific-ion electrode as an indicator

Conditions are given for consecutive potentiometric titration of cyanide and chloride in mmole amounts, a silver-specific electrode being used as indicator electrode.     

Compatibility of iron-containing polymeric additives with a cable-grade plasticized poly(vinyl chloride)

Several linear polymeric ferrocene compounds with $\text{M}{}_{\mathrm{<mtext>n</mtext>}}$ in the range 1200–3000 have been compounded with a cable-grade, DIOP-plasticized PVC at concentrations of 1–5%; two non-polymeric ketoferrocenes and a heteroferrocene have been included for comparison. Moulded sheets, prepared from the compounded materials, have been evaluated for compatibility by visual inspection, from analyses prior to and after a heat aging treatment, and from stress-strain data. Best performance with respect to all three compatibility criteria has been observed for a poly(ferrocenylenemethylene) with $\text{M}{}_{\mathrm{<mtext>n</mtext><mtext>\; =\; 2400</mtext>}}$, which shows excellent compatibility up to a loading of 9%. Good performance has also been demonstrated for a number of related polymers substituted at the bridging carbon atom. These findings suggest promising applications for selected polymeric ferrocenes as multifunctional additives for PVC-based engineering and biomedical materials.     

Interaction of cationic surfactant and anionic polyelectrolytes in mixed aqueous solutions

Surfactant–polymer interactions in aqueous solutions have been studied using dynamic surface tension, polyelectrolyte titration, nephelometric turbidity, and dynamic light scattering. For the preparation of complexes, a technical cationic surfactant was used in combination with two poly(maleic acid-co-polymers) of similar structure but different hydrophobicity. The dynamic surface tensions of mixed solutions as functions of surfactant concentration at constant polyelectrolyte content, as well as changes in the surface activity due to the influence of polyanion at constant surfactant concentration are discussed in terms of a complex or aggregate formation in the bulk phase. The interaction of the surfactant with poly(maleic acid-alt-propene) (P-MS-P) and poly(maleic acid-alt--methylstyrene) (P-MS-MeSty), respectively, is strong in both cases and results in the formation of nanoparticles with properties depending on the composition of the corresponding mixture.     

Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium-Schiff's base complex

A PVC membrane electrode based on a cadmium-salen (N,N'-bis-salicylidene-1,2-ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5-11.0. It has a linear response to thiocyanate from 1.0 x 10(-6) to 1.0 x 10(-1) mol L(-1) with a slope of 59.1 +/- 0.2 mV per decade, and a detection limit of 7 x 10(-7) mol L(-1). This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.     

Fourier-transform infrared study of orientation in pure and plasticized poly(vinyl chloride)

Fourier-transform infrared spectroscopy has been used for the study of orientation of pure and plasticized PVC. The results show that orientation is independent of experimental conditions (temperature, strain rate, plasticizer) in the homogeneous deformation range. Such behavior is explained by the existence of a fringe micellar-type network with physical crosslinks. The network is partially destroyed during stretching. Furthermore, the orientation of the carbonyl group of the plasticizer is connected with PVC chain orientation.