Entrapment and release of sodium polystyrene sulfonate (SPS) from calcium alginate gel beads

The release of sodium polystyrene sulfonate (SPS) from calcium alginate hydrogel beads has been studied. It has been shown that the structure of the cross-linked calcium alginate network is of primary importance in the retention and/or release of the SPS. This has been evidenced by studying the influence of Ca²⁺ concentration, molar masses (M_n) and the ratio of mannuronic acid/guluronic acid components. A minimum in the SPS release is observed in relation with the organization of the network structure. Conditions inducing the organization of a strong gel (e.g. high Ca²⁺ concentration for example) are not always related to a low release. A good control of release is found when a compromise between a well-structured hydrogel and sterical consideration of SPS is reached.     

SEC–MALLS analysis of cellulose using LiCl/1,3-dimethyl-2-imidazolidinone as an eluent

The lithium chloride/1,3-dimethyl-2-imidazolidinone (LiCl/DMI) solvent system for cellulose was adopted as a mobile phase of size-exclusion chromatographic (SEC) analysis of cellulose, and the applicability of this system was examined using multi-angle laser light scattering and ¹³C-NMR analysis. The results indicate that 8% (w/v) LiCl/DMI ID a true solvent for cellulose, and that cellulose molecules dissolving ID 1% (w/v) LiCl/DMI are separated orderly depending on their molecular mass (MM) or root-mean-square (RMS) radius by the SEC system. Practically, no aggregates were detected ID the dilute cellulose/LiCl/DMI solutions. Furthermore, high stability of cellulose/LiCl/DMI solutions has been demonstrated; only a few percent of decline ID average MM was observed even after storage for 6 months at room temperature. Relationships between RMS radius and MM for hardwood bleached kraft pulp ID 1% LiCl/DMI was estimated as the following equation: _g^0.59, corresponding to a Mark–Houwink–Sakurada exponent of 0.77.     

Molecular weight control of polyacrylamide with sodium formate as a chain‐transfer agent: Characterization via size exclusion chromatography/multi‐angle laser light scattering and determination of chain‐transfer constant

We discuss the synthesis and characterization of polyacrylamide (PAM) homopolymers with carefully controlled molecular weights (MWs). PAM was synthesized via free‐radical solution polymerization under conditions that yield highly linear polymer with minimal levels of hydrolysis. The MW of the PAM homopolymers was controlled by the addition of sodium formate (NaOOCH) to the polymerization medium as a conventional chain‐transfer agent. MWs and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering analysis; for polymerizations carried out to high conversion, PAM MWs ranged from 0.23 to 6.19 × 10⁶ g/mol, with most samples having PDI ≈2.0. Zero‐shear intrinsic viscosities of the polymers were determined via low‐shear viscometry in 0.514 M NaCl at 25 °C. Data derived from the polymer characterization were used to determine the chain‐transfer constant to NaOOCH under the given polymerization conditions and to calculate Mark–Houwink–Sakurada K and a values for PAM in 0.514 M NaCl at 25 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 560–568, 2003     

Radical polymerization of allylbiguanide

Monoallyl compounds are not readily homopolymerized by a conventional free‐radical mechanism. However, we successfully performed the radical polymerization of allylbiguanide hydrochloride in a concentrated acid solution (hydrochloric acid or phosphoric acid) in the presence of a radical initiator at 50 °C. The polymer product was precipitated from the reaction solution through the addition of an excess amount of acetone. The precipitated crude polymer [polyallylbiguanide (PAB)] was then purified by dialysis. PAB was confirmed by elemental analysis, infrared spectroscopy, and ¹H NMR. The molecular weight range of PAB was 10,340–113,200, and PAB exhibited a low polydispersity (weight‐average molecular weight/number‐average molecular weight = 1.04–1.68) by multi‐angle laser light scattering. The polymerization of allylbiguanide was quite sensitive to the protonic concentration of the inorganic acid. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1707–1711, 2004     

TEMPO-mediated Oxidation of Native Cellulose: SEC–MALLS Analysis of Water-soluble and -Insoluble Fractions in the Oxidized Products

Linter cellulose was suspended in water and oxidized by the NaClO/NaBr/2,2,6,6-tetramehylpiperidine-1-oxy radical (TEMPO) system at pH 10.5 (TEMPO-mediated oxidation), and the oxidized products were separated into several fractions by filtration and centrifugation, depending on their particle sizes and apparent water-solubility. The major fraction (>ca. 80 mass % of the original linter cellulose) is the filter paper-trapped fibers, which can form inter-fiber hemiacetal linkages when handsheets are prepared thereof. Size-exclusion chromatographic analysis with multi-angle laser light scattering detection (SEC–MALLS) of these fibrous fractions dissolved in 0.5% LiCl/N,N-dimethylacetamide (DMAc) showed that some depolymerization occurred on cellulose chains during the TEMPO-mediated oxidation. On the other hand, the apparently water-soluble fractions (<ca. 20 mass % of the original linter cellulose) in the TEMPO-oxidized linter cellulose consisted of small amounts of colloidal particles having the cellulose I crystal structure, which came off from linter cellulose by the TEMPO-mediated oxidation and were mixed in the apparently water-soluble fraction even after filtration using 0.45 μm membrane. The presence of such colloidal cellulose crystals in the water-soluble fractions of the TEMPO-oxidized linter cellulose brings about anomalous bimodal SEC-elution patterns and extremely large molecular-mass values calculated from the SEC–MALLS data. Truly water-soluble cellouronic acid and/or over-oxidized compounds having glucuronic acid and hexeneuronic acid units are also present in the water-soluble fractions.     

Determination of engineered nanoparticles on textiles and in textile wastewaters

Textile materials with engineered nanoparticles (ENPs) have excellent properties as they are antibacterial, antimicrobial, water resistant and protective. The textile industry has recognized the importance and the advantages of ENPs, so they comprise one of the fastest developing branches of processing.The most important sources of ENPs released to the environment from textiles are textile-industry wastewaters and waters from large hospital or hotel laundries. In addition, waste textile materials coated with ENPs present a threat to the environment, if such materials are not properly handled and disposed of after use.Currently, the toxicity and the potential harm of ENPs widely applied on textiles are not thoroughly investigated and/or eliminated. Consequently, there is an urgent need to define the most appropriate analytical methods for monitoring ENPs on textiles.This review presents the most important techniques for monitoring ENPs on textile materials and in textile-wastewater samples, from the perspective of protecting the environment and human health.     

Melt rheology of long-chain-branched polypropylenes

Rheological properties of long-chain-branched isotactic polypropylene (PP) via copolymerization with a very small amount of nonconjugated α,ω-diene monomer using metallocene catalyst system in both linear and nonlinear regions were investigated, comparing with conventional linear and long-chain-branched PP modified at postreactor. Although comonomer incorporation was equal to 0.05 mol% or less, it caused high molecular weight, broad molecular weight distribution, and long-chain branching. A detailed study on the effect of diene incorporation on the polymer properties was conducted, comparing with modified PP in postreactor. Polymer chain microstructures were characterized by gel permeation chromatography with multiangle laser light scattering (MALLS), differential scanning calorimetry, and rheological means: dynamic viscoelasticity, step-strain, uniaxial elongational flow measurements, and large amplitude oscillatory shear. The PP, which incorporated a small amount of diene monomer, showed significantly improved viscoelastic behaviors. The diene-propylene copolymer containing long-chain branches showed extremely long relaxation mode under shear and outstanding viscosity increase under elongational flow, so-called strain hardening. The difference in microstructure of diene-propylene copolymer with modified PP with long-chain branches is investigated by MALLS and rheological characterizations.     

ESI‐MS and MALLS analysis of quaternary structure of molluscan hemocyanins

The understanding of the function of macromolecular complexes is mainly related to a precise knowledge of their structure. Recently, the development of suitable mass spectrometric techniques (electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization (MALDI)) and multi‐angle laser light scattering has enabled mass determination of native complexes and of their subunits. By these techniques, the structure and association/dissociation behavior of huge molecules of molluscan Octopus vulgaris, Sepia officinalis and Rapana venosa have been characterized. Molecular masses of the native and dissociated molecule of cephalopodan Hcs O. vulgaris (3545 and 359.3 kDa, respectively) and S. officinalis (4134 and 443.8 kDa, respectively) revealed that only one type subunit organizes their molecules, while the presence of two isoforms with different masses (422.8 and 400.0 kDa) has been determined for gastropodan R. venosa Hc, aggregated into didecamers. The difference of their structural subunits was also established after limited proteolysis with TPCK‐trypsin. Eight functional units (FUs) with masses of ~ 50 kDa were isolated from both subunits of RvH and isoform of Sepia officinalis, while seven FUs were purified from OvH. Further characterization of proteins by ESI‐mass spectrometry (MS) and MALDI‐MS, methods gave insights into post‐translational modifications such as glycosylation. Glycosylation of O. vulgaris and S. officinalis Hcs was suggested based on the differences (11.6 and 40.0 kDa, respectively) between the masses measured by ESI‐MS and those calculated by their gene sequences. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of the Molar Mass and the Radius of Gyration, Together with their Distributions for Methylhydroxyethylcelluloses

Three molar mass series were produced by different methods of degradation (namely ultrasonic (seven samples), oxidation (seven samples) and autoclaving (eight samples)) from a methylhydroxyethylcellulose (MHEC) sample with an average degree of substitution (DS) of 1.3, a molar degree of substitution (MS) of 0.46, a radius of gyration of 67 nm and a weight-average molar mass, M _w, of 318,000 g/mol. The degraded samples were characterized in terms of their molar mass and particle size together with their respective distributions with a hyphenated apparatus consisting of size exclusion chromatography and multi-angle laser light scattering and concentration detector (SEC/MALLS/DRI) at 25 °C in 0.1 M NaNO₃ solution (with 200 ppm NaN₃ as antibactericide). The refractive index increment was determined as dn/dc = 0.135 cm³/g. It was possible to reduce the weight-average molar mass down to approximately 10% of the initial molar mass using all the methods. In a comparison of the three degradation methods it was shown that only ultrasonic degradation retains the monomodal distribution, whereas the other two degradation methods yield a bimodal molar mass distribution. Consequently, only ultrasonic degradation represents a suitable method for producing homologous molar mass series. An R _G–M relationship of R _G = 0.0511 × M ^0.56 was established for the sample used in this case, and from this it was possible to calculate an []–M relationship of [] = 0.3587 × M ^0.68.     

Novel cationic and amphiphilic pullulan derivatives I: Synthesis and characterization

Cationic amphiphilic modified pullulan’s were obtained in two steps: firstly the synthesis of diethylaminoethylpullulan (DEAE-Pullulan) with DS₀ = 0.80 in water (all degrees of substitution (DS) are calculated in anhydroglucose units (AGU)) followed by the incorporation of different alkyl chains (C₁₀, C₁₂ and C₁₆) using Hoffmann alkylation reaction. Three alkylated derivatives (Y-Cx-DEAE-Pullulan) were produced with a degree of substitution of alkyl chains (Y = 100 DS_Cx) of 40 in the case of C10 and C12 and 20 in the case of C16. The three samples contained two functional types: an amine function (DS_N), dependent on pH and a quaternary ammonium function (DS_N+) linked to a hydrophobic alkyl chain (DS_Cx). Chemical characterizations were carried out by conductimetric measurements, elemental analysis and ¹H NMR. The amphiphilic and associative properties have been confirmed by flow field flow fractionation (F4) coupled on-line with multi-angle laser light scattering (MALLS). The intermolecular associations were observed for DEAE-Pullulan and Y-Cx-DEAE-Pullulan in 0.1 M LiNO₃.