Polyelectrolyte titration using fluorescent indicator. I. Direct titration of anionic and cationic polyelectrolytes with 10−4N standard solutions

The polyelectrolyte titration, which was originally called colloid titration, is based on the stoichiometric reaction between positively charged colloidal particles and negatively charged ones. In the conventional method, the metachromatic color change of the indicator, toluidine blue, from blue to red-purple has been applied for the determination of the end point in the titration. 2.5 × 10^?3N potassium polyvinylsulfonate (KPVS) is usually used as the standard titrant. In this work, fluorescent indicators such as 6-(p-toluidino)-2-naphthalene sulfonate (TNS), acridine orange, etc., have been introduced. The fluorescence intensity was measured using the spectrophotometer equipped with magnetic stirrer and connected with a vinyl tube attached to the hand piston burette. For example, TNS is practically nonfluorescent, but it exhibits strong fluorescence when it is bound to a cationic polyelectrolyte (CP). The fluorescence of the TNS–CP complex is diminished by titration with KPVS standard solution since TNS is liberated from the complex by substitution with KPVS. After the equivalent point, the fluorescence intensity becomes constant and the end point can thus be detected by that point. It has been elucidated that the very dilute standard solution like 1 × 10^?4N can be used because the sensitivity of fluorescence detection is extremely high. © 1993 John Wiley & Sons, Inc.     

Determination of cationic polyelectrolytes using a photometric titration with crystal violet as a color indicator

The reaction of the cationic dye, crystal violet (CV) with the anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) results in a decrease of the absorbance of CV at the maximum absorption wavelength (590 nm). This change of the absorption spectra of the CV has been already applied to the determination of anionic polyelectrolytes using flow injection analysis method. In this paper, CV was applied to the indicator for the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by photometric titration, using a PVSK solution as a titrant. The end-point of the titration is detected as the break point of the titration curve. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 0 to 5×10⁻⁵ eq. mol dm⁻³ for Cat-floc, glycol chitosan and methylglycol chitosan. The effects of the concentration of CV and coexisting electrolytes in the sample solution and the effect of pH of the sample solution on the degree of the change of absorbance at the end-point were also examined.     

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.     

The characteristic fragment ions and visualization of cationic starches on pulp fiber using ToF‐SIMS

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to investigate the distribution of cationic starch on pulp fiber. To identify the characteristic fragment ions of the cationic starches, deuterium‐labeled cationic starches were prepared and analyzed using ToF‐SIMS. The starch 2‐hydroxypropyltrimethylammonium chloride derivative generated characteristic fragments at m/z 58 and 59, which were identified as [H₂C?N(CH₃)₂]⁺ and [N(CH₃)₃]^+·, respectively. The fragmentation patterns were also suggested. From the imaging analysis, the adsorption of the cationic starch on fibers was uneven on individual fibers, as well as between fibers. This may have been on account of fiber morphology and structure. On examining scanning electron microscope (SEM) images, the quaternary ammonium starch derivative (QS) did not penetrate the fiber. No migration of cationic starch was observed under various drying conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

pH敏感阳离子聚电解质凝胶的溶胀和释药性能

共聚物;pH敏感阳离子聚电解质凝胶的溶胀和释药性能     

作为电极添加剂的阳离子聚电解质的合成及性能的研究

选择Ce(SO4)2·4H2O与H2NCSNH为引发体系,控制反应温度为40℃,反应时间为6 h等工艺条件,成功合成了一种新的质子交换膜燃料电池电极添加剂-阳离子聚电解质P(AM-DMDAAC),其分子量在0.8×104～1.3×104范围内.通过测试阳离子聚电解质的电导率和研究循环伏安、热失重实验;结果发现,阳离子聚电解质P(AM-DMDAAC)有良好的电化学性能和热稳定性.     

BSA adsorption on differently charged polystyrene nanoparticles using isothermal titration calorimetry and the influence on cellular uptake

BSA adsorption onto negatively and positively charged polystyrene nanoparticles was investigated. The nanoparticles were characterized in terms of particle size, zeta potential, surface group density, and morphology. The adsorption behavior of BSA on the particle surface, as a function of pH and overall charge of the particle, was studied using ITC. Different thermodynamic data such as enthalpy changes upon binding and stoichiometry of the systems were determined and discussed. The degree of surface coverage with BSA was calculated using the thermodynamic data. The cellular uptake of particles before and after BSA adsorption was studied using HeLa cells in the presence and absence of supplemented FCS in the cell culture medium.     

淀粉基阳离子絮凝剂的研制及性能测试

用可溶性淀粉为原料,通过接枝改性合成了一种淀粉基阳离子絮凝剂(MSF),其最佳制备工艺条件为:淀粉与丙烯酰胺的质量比为1:2,引发剂用量为0.6 g,反应温度为50 ℃,接枝时间为3.5 h;阳离子化条件为:甲醛和二甲胺摩尔比为1.0:1.4,反应时间2.5 h,反应温度50 ℃.产物结构经FTIR证实.用其处理番茄废水后,废水的透光率提高了78.2%、TOC下降了22.5%、COD下降了37.25%,结果表明该产品对高浓度有机废水的絮凝性能优于聚丙烯酰胺高分子絮凝剂(PAM).     

A digital image-based method for determining of total acidity in red wines using acid-base titration without indicator

This work proposes the use of digital image-based method for determination of total acidity in red wines by means of acid-base titration without using an external indicator or any pre-treatment of the sample. Digital images present the colour of the emergent radiation which is complementary to the radiation absorbed by anthocyanines present in wines. Anthocyanines change colour depending on the pH of the medium, and from the variation of colour in the images obtained during titration, the end point can be localized with accuracy and precision. RGB-based values were employed to build titration curves, and end points were localized by second derivative curves. The official method recommends potentiometric titration with a NaOH standard solution, and sample dilution until the pH reaches 8.2-8.4. In order to illustrate the feasibility of the proposed method, titrations of ten red wines were carried out. Results were compared with the reference method, and no statistically significant difference was observed between the results by applying the paired t-test at the 95% confidence level. The proposed method yielded more precise results than the official method. This is due to the trivariate nature of the measurements (RGB), associated with digital images.     

Preparation and characterization of hybrid cationic hydroxyethyl cellulose/sodium alginate polyelectrolyte antimicrobial films

This study aimed to develop polyelectrolyte‐structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic hydroxyethyl cellulose was synthesized and characterized by Fourier‐transform infrared, ¹H NMR, and ¹³C NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte‐structured antimicrobial food packaging materials were prepared using hydroxyethyl cellulose, cationic hydroxyethyl cellulose, and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by thermal gravimetric analysis and differential scanning calorimetry. Surface morphology of samples was investigated by SEM. The obtained results prove that produced food packaging materials have good thermal and antimicrobial properties, and they can be used as food packaging material in many industries.     

Synthesis of nanocomposites from cationic polyacrylamide and modified carbon black: Application as flocculants for oily sludge suspension

Carbon black was modified using various liquid‐phase oxidation methods (modified carbon black = m‐CB, m = (1, 2, 3): 1, sulfuric acid/potassium permanganate method; 2, nitric acid method; 3, hydrogen peroxide method). With acetone–ethylene glycol as initiator, dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) as monomer, cationic polyacrylamide (CPAM) was prepared by UV excitation of the monomer. The m‐CB/CPAM nanocomposites were synthesized using a hydrothermal method. The factors that affected the molecular weight of CPAM were investigated, including the total monomer concentration, the dosage of the complex initiator, the mass ratio of m_AM:m_DMDAAC and the UV irradiation time. The chemical structures and morphologies of the samples were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental composition, X‐ray diffraction and scanning electron microscopy. 1‐CB/CPAM was utilized to flocculate oil sludge suspension, and the effects of 1‐CB quality, 1‐CB/CPAM dosage, temperature and pH value on the flocculation performance of 1‐CB/CPAM were investigated. The flocculation mechanism of 1‐CB/CPAM was also analyzed. The results show that 1‐CB/CPAM has an outstanding flocculation effect, and it flocculates oil sludge particles by adsorption bridging and charge neutralization in acidic and alkaline conditions.     

Synthesis of cationic water‐soluble copolymers and hydrogels based on [2‐(methacryloyloxy)ethyl]trimethylammonium chloride and 2‐hydroxyethylacrylate and their complex formation with poly(acrylic acid)

Water‐soluble cationic copolymers and hydrogels were synthesized by radical copolymerization of [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT) and 2‐hydroxyethylacrylate (HEA). The kinetics of copolymerization has been studied and the reactivity ratios were determined. It was found that MADQUAT exhibits higher reactivity in copolymerization. The complexation between linear MADQUAT‐HEA and linear poly(acrylic acid) (PAA) has been studied in aqueous solutions at different pH. It results in the formation of insoluble polyelectrolyte complexes, whose composition and stability to aggregate depends on MADQUAT content in copolymers and pH. The hydrogels were synthesized by three‐dimensional radical copolymerization of MADQUAT and HEA in the presence of a crosslinker. The effects of the feed mixture composition on yield and swelling properties of the hydrogels were studied. The interactions of these hydrogels with linear PAA result in formation of gel–polyelectrolyte complexes and contraction of the samples. It was found that the contraction depends on copolymer composition, PAA molecular weight, and solution pH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44:845–853, 2006     

Synthesis and characteristics of the poly(carboxybetaine)s and the corresponding cationic polymers

Two types of carboxybetaines and their corresponding cationic monomers and polymers are synthesized in this study. Comparing the chemical shifts of the methylene groups in the cationic monomers and carboxybetaines in both ¹H- and ¹³C-NMR spectra reveal that the respective methylene groups are clearly distinguished from their chemical shifts in ¹H- and ¹³C-NMR spectra. The solubilities, moisture regain properties, and solution properties of the poly(carboxybetaine)s and cationic polymers are investigated in relation to their molecular structures. Because the cationic polymers were ionized in an aqueous solution, the cationic polymers were more soluble than the poly(carboxybetaine). For the various functional groups of poly(carboxybetaine)s and cationic polymers, the order of tendency for moisture regain is  COO >  CONH . Results obtained from the reduced viscosity for cationic poly(TMMPAMS) are reversed from that for zwitterionic poly(DMAEAPL). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3527–3536, 1997     

Surface modification of poly(dimethylsiloxane) microchips using a double-chained cationic surfactant for efficiently resolving fluorescent dye adsorption

This paper described a double-chained cationic surfactant, didodecyldimethylammonium bromide (DDAB), for dynamic surface modification of poly(dimethylsiloxane) (PDMS) microchips to reduce the fluorescent dyes adsorption onto the microchannel. When DDAB with a high concentration was present as the dynamic modification reagent in the running and sample buffer, it not only reversed the direction of electroosmotic flow, but also efficiently suppressed fluorescent dyes pyronine Y (PY) or rhodamine B (RB) adsorption onto the chip surface. In addition, vesicles formed by DDAB in the buffer with higher surface charge density and electrophoretic mobility could provide wider migration window and potential for the separation of compounds with similar hydrophobicity. Factors affecting modification, such as pH and concentrations of the buffer, DDAB concentration in the buffer were investigated. Compared with commonly used single-chained cetyltrimethylammonium bromide, DDAB provided a better modification performance. Furthermore, PY and RB were separated successfully on a PDMS microchip at the appropriate conditions with DDAB.     

Selective uptake of different proteins by annealed and quenched cationic spherical polyelectrolyte brushes

The selective uptake of bovine serum albumin (BSA) and β-glucosidase (β-G) by annealed and quenched cationic spherical polyelectrolyte brushes (SPB) was systematically studied by combining turbidimetric titration, dynamic light scattering and small angle X-ray scattering (SAXS). These two kinds of SPB consist of a same polystyrene core and a dense shell of poly (2-aminoethyl methacrylate hydrochloride) (PAEMH) and poly [2-(methacryloyloxy) ethyl] trimethylammonium chloride (PMAETA), respectively. Results reveal that the adsorption/desorption of proteins on SPB can be easily controlled by changing external conditions (pH and ionic strength). For a particular annealed or quenched SPB, there is a significant difference of the interaction pH regions between the brush and the two proteins, and this difference can be tuned by ionic strength. At low ionic strength, quenched brushes were more suitable for selective adsorption of BSA and β-G, while annealed brushes performed better at high ionic strength. SAXS analysis demonstrated that volume exclusion effect played a remarkable role in protein uptake by both SPB, and larger proteins were more likely to be adsorbed on the outer layer of the brush. The unique core-shell structure and controllable chain types make SPB an excellent candidate in selective adsorption/separation of proteins of different sizes.     

Conductometric titration of pindolol and propranolol using ammonium reineckate and potassium tetracyanonickelate

A simple and sensitive conductometric method for the determination of 2–24 mg of pindolol and propranolol hydrochlorides using ammonium reineckate and potassium tetracyanonickelate in an ethanol-water mixture is described. The effect of the solvent ratio, reagent concentration, time and temperature on the shape of the titration curve is studied. Statistical treatment of the experimental results indicates that the method is precise and accurate. The accuracy of the method is indicated by the excellent recovery (98.2–101.2%) and the precision is supported by the low standard deviation value < 0.10. The sensitivity of the proposed method is discussed and the results are compared with the pharmacopoeial non-aqueous titration method.     

Propenyl ethers. II. Study of the photoinitiated cationic polymerization of propenyl ether monomers

The results of studies of the photoinitiated cationic polymerization of mono-, di-, and multifunctional propenyl ethers are reported in this article. Real-time infrared spectroscopy and differential scanning photocalorimetry were used to determine the reactivity of the monomers with respect to each other and in relation to other types of cationically polymerizable monomers. Propenyl ethers were observed to be highly reactive monomers in photoinitiated cationic polymerization undergoing very high conversions to polymer at very short irradiation times. Attempts were also made to correlate the structures of these monomers with their reactivity as well as to examine the effects of various experimental parameters on their photopolymerization. © 1993 John Wiley & Sons, Inc.     

Transition metal-catalyzed tandem isomerization and cationic polymerization of allyl ethers. II. Structural and mechanistic studies

In the presence of organosilanes, dicobalt octacarbonyl catalyzes the polymerization of alkyl allyl ethers to give high molecular weight polymers. This article reports the results of a detailed mechanistic study of this new polymerization reaction. The evidence obtained in this study supports a stepwise process involving first, the reaction of dicobalt octacarbonyl with an organosilane to form HCo(CO)₄ and R₃SiCo(CO)₄. In subsequent steps, HCo(CO)₄ isomerizes the allyl ether to a 1-propenyl ether and then this compound is polymerized by the formal transfer of a silyl cation from R₃SiCo(CO)₄. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1985–1997, 1997     

Theoretical approach to cationic polymerization of alkenylfurans. II. Ab initio and semiempirical study of relevant steps in the reaction mechanism

SCF ab initio and AM1 semiempirical calculations with full geometry optimization have been carried out to model the initial steps of alkenylfuran cationic polymerization. Semiempirical procedures have been used to model propagation steps. Proton affinities of the relevant neutral species as well as the heats of formation of probable dimers were calculated. The results allow the explanation of the experimental behavior. The capabilities of the employed methods to describe these type of processes is discussed. It is confirmed that competition between vinyl and ring site attacks is the most important feature in these systems. © 1992 John Wiley & Sons, Inc.     

Conformation and Aggregation Behavior of Polyelectrolyte with Primary Amino Pendant Groups in Water or THF/Water Binary Solvent Mixture and Their Effect on the Morphology of AOT Vesicles in Aqueous Media

Cationic polyelectrolyte with primary amine pendant groups, poly (4-vinyl benzyl amine hydrochloride salt) (poly (4-VBAHS)), was characterized by static light scattering. Using light scattering measurement, the conformation transition of poly (4-VBAHS) chains in pure water, and THF/H₂O (v/v: 1/3) binary solvent mixture was discussed. Concentration-dependent multiple morphologies including interpenetrating networks, tubular micelles, branched micelles, hexagonal phases, vesicles, and needle crystals were observed by TEM. In addition, effect of poly (4-VBAHS) on the morphology, stability, and critical vesicle/micelle concentration of anionic surfactant sodium bis (2-ethylhexyl) sulfosucciante vesicles were detected using dynamic light scattering, zeta potential, surface tension, and transmission measurements.