Micellar polymerisation of ionic surfactants studied by conductimetry

The micellar polymerisation of ionic surfactants such as allyldodecyl-dimethylammonium bromide and 3-dodecyl-1-vinyl imidazolium iodide has been studied by conductimetry in aqueous solution. The polymerisation was carried out using two different sources of γ rays directed into solutions of surfactant above the critical micellar concentration. Conductimetry is shown to be a very good physicochemical method for analysis of these solutions. The results showed different behaviour for the two surfactants, which has highlighted a change in the structure of their aggregates which led to the assumption of an interaction between the polymers of high mass and different products of the polymerisation (oligomers, products of degradation, monomers etc.). Ultrafiltration experiments coupled with ¹H-NMR and conductivity analysis confirm these assumptions.     

Characterization of micellar systems produced by new amphiphilic conjugates of poly(ethylene glycol)

This study proposes polymeric micelles produced using new amphiphilic conjugates between amino- or carboxy-mPEG₂₀₀₀ and three different α-lipoamino acids (PEG-LAA). The characterization of these colloidal systems showed CMC values, in the order of 10^?5?M, that are interesting in the view of an in vivo administration. The PEG-LAA micelles also showed a good stability at 37?°C and upon dilution in aqueous media. Using a colored probe as a model lipophilic compound, the loading efficiency and in vitro release profile were also outlined.     

Acid-base determination of lubricating oils

The base content, total base number (TBN), has been determined for a range of petroleum products and used engine oils, by both potentiometric and conductimetric methods. Titration values depend both on the method of detection and solvent media used. A conductimetric titration method for TBN is described based upon IP 177 and 276 (ASTM D-664 and 2896) solution chemistry. The results of the conductimetric titration TBN determinations are compared with those from IP 177 and IP 276 potentiometric determinations to show that the TBN order of magnitude is IP 276 (potentiometric) > conductimetric > IP 177 (potentiometric). The conductimetric method equilibrates very rapidly and is suitable for automatic titrimeters. Results for new and used oils determined by these different titration methods are discussed. Conductimetric detection for TBN determination uses standard IP method reagents and solvents and is an alternative to the trisolvent TBN method.     

Application of Conductimetry for Evaluation of Lactic Starter Cultures in Soymilk

ABSTRACT: :
Soymilk (SM), a potential culture medium for applying conductimetric techniques to evaluate the behavior of probiotic lactobacilli and bifidobacteria was examined. Media LAPTg, LM, and SM was standardized for the growth of Lactobacillus fermentum and Bifidobacterium longum. A dilution of 1/100 for L. fermentum and 1/1 for B. longum were considered optimal to obtain a detection time (DT) between 5 and 10 min. The relationship between the initial number of cells and the DT was linear throughout the incubation period considered (40 h). The effect of temperature (30, 37, and 42 °C) on the metabolic activity of the cells was also determined after 40 h of fermentation. The higher metabolic changes were observed at 42 °C with conductance values from 600 to 800 μS and DT of 5-7 min. Results obtained were confirmed by viable counts.     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements Part 4. Radical polymerization of acrylic acid in the presence of poly(vinyl alcohol): characterization of resulting polymer blends

The radical polymerization of acrylic acid in the presence of poly(vinyl alcohol) as a template in aqueous solution has been studied using conductimetry, which shows template influences on the reaction rate. A comparison is made between data obtained by differential scanning calorimetry and infrared spectroscopy for poly(acrylic acid)–poly(vinyl alcohol) blends prepared either by template polymerization or by casting of the preformed polymers. Evidence for more significant interpolymer interactions in blends prepared by template polymerization than in those obtained by simple mixing is given. © 2001 Society of Chemical Industry     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. Part 1. Radical polymerization of sodium acrylate

The radical homopolymerization of sodium acrylate in water in the presence of potassium peroxodisulphate as initiator was investigator through the use of conductimetry and dilatometry. The kinetics were monitored while varying either the monomer concentration or temperature. Initial rate and order of reaction were determined with good accuracy in a comparative way. The conductimetric method proved superior in monitoring the reaction progress at temperatures higher than 50°C, allowing the activation energy of the reaction to be determined. © 1999 Society of Chemical Industry     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. 2. Radical polymerization of sodium methacrylate in the presence of poly(allylamine) hydrochloride

The polymerization of sodium methacrylate in water was investigated using conductimetry and dilatometry. Conductimetry was shown to be a reliable tool for the determination of the kinetic parameters of the blank polymerization (order of reaction with respect to monomer and initiator, activation energy). The conductimetric investigation of template polymerization of the acrylic monomer onto poly(allylamine) hydrochloride at low monomer concentration indicates that the reaction proceeds by a ‘zip’ mechanism. © 1999 Society of Chemical Industry     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. Part 3. Radical polymerization of acrylic acid in the presence of poly(N‐vinylpyrrolidone)

Conductimetry was used for monitoring the radical polymerization of a weak electrolyte (acrylic acid) in aqueous solution and for determination of the kinetic parameters of the reaction (reaction order with respect to monomer, activation energy). The results obtained were consistent with those determined by other techniques (such as dilatometry) or expected from theory. Dilatometric and conductimetric measurements were also used to study the template polymerization of acrylic acid onto poly(N‐vinylpyrrolidone). Results indicate that the reaction proceeds according to a pick‐up mechanism. Complexes between poly(acrylic acid) and poly(N‐vinylpyrrolidone) were always isolated in equimolar composition of the two polymers, regardless of the polymerization mixture composition. Spectroscopic evidence of the existence of strong interaction and intimate mixing of the two polymers in the complexes was found. An influence of the template molecular weight on the chain length of the forming poly(acrylic acid) was detected by means of viscometry. © 2000 Society of Chemical Industry     

Dextran–rare earth ion interactions. I. Dynamics in aqueous solutions

The interaction of light-lanthanoid cations (La³⁺, Ce³⁺, and Nd³⁺) with dextran in aqueous solutions was studied by viscosimetric, turbidimetric, and conductimetric methods. The effects of the type of the cation and the concentration of the cation on the interaction mechanism were investigated. Viscosity behavior of the solutions was interpreted using the Huggins and Kraemer equations; intrinsic viscosities and the slopes were calculated. The results found from the Huggins and Kraemer approaches accorded well. The order of interaction was determined as La³⁺ > Ce³⁺ > Nd³⁺. In all experimental methods applied, a critical concentration of the Ln³⁺ ion (≈0.08 mol Ln³⁺/L) was noted at which the observed property showed a significant change. Up to this critical concentration, viscosities of the dextran/Ln³⁺ solutions decreased and after making an outstanding turn at this point increased toward higher concentrations. Turbidimetric and precipitation experiments gave opposite results as expected but the same order for the cation and the same value of critical concentration. The results obtained from the application of a mathematical model to the precipitation data verified the conclusions attained by viscosimetry and conductimetry. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 323–329, 2001