Xiaodeng Yang

A simple and convenient method to synthesize N-[(2-hydroxyl)-propyl-3-trimethylammonium] chitosan chloride in an ionic liquid.

N-[(2-Hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride (HTCC) was synthesized through nucleophilic substitution of 2,3-epoxypropyltrimethyl ammonium chloride (EPTAC) onto chitosan using ionic liquid of 1-allyl-3-methylimidazole chloride (AmimCl) as a homogeneous and green reaction media. The chemical structure of HTCC was confirmed by FTIR, (1)H NMR and (13)C NMR. The FTIR peak intensity of amino group at 1595 cm(-1) decreased and that of [Formula: see text] at 1475 cm(-1) increased with the increase of reaction time, confirming the substitution of EPTAC on CS. The degree of substitutions (DS) were calculated from the integral area of (1)H NMR, and the optimum reaction condition was obtained, namely, reaction time of 8h, temperature of 80°C and [Formula: see text] of 3/1. The degree of crystallinity and thermal properties of HTCC were characterized by XRD, TG, DSC, and DMA methods. Data from XRD, TG, DSC and DMA show that the degree of crystallinity, thermal stability, as well as glass transition temperature of HTCC decreased with the increase of DS. The reaction mechanism of chitosan with EPTAC in AmimCl was elucidated by performing density functional theory (DFT) calculations.

Effects of chitosan quaternary ammonium salt on the physicochemical properties of sodium carboxymethyl cellulose-based films

The effects of N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC) on the physicochemical properties of sodium carboxymethyl cellulose (CMC)-based films were investigated. The prepared HTCC/CMC film-forming solutions (FFSs) with varying mass ratios exhibited shear-thinning behavior and typical pseudo-plasticity. The highest apparent viscosity and lowest crossover frequency was obtained for the HTCC/CMC FFS with a mass ratio of 10%, due to the formation of the strongest intermolecular interactions, which also led to the best mechanical properties. Furthermore, the effects of temperature and degree of substitution of HTCC on the composite film properties were also investigated. Structural property assessment by FTIR, SEM, and DSC showed a clear interaction between HTCC and CMC, leading to the formation of a new composite material with enhanced physicochemical properties. The data demonstrate the importance of HTCC in CMC-based films for food and drug packaging.

Theoretical study of the reaction of chitosan monomer with 2,3-epoxypropyl-trimethyl quaternary ammonium chloride catalyzed by an imidazolium-based ionic liquid

The molecular mechanism of the graft reaction of 2,3-epoxypropyl-trimethyl quaternary ammonium chloride with chitosan monomer was investigated by performing density functional theory (DFT) calculations. The calculated results show that the -NH2 group of chitosan monomer is more reactive than its -OH and -CH2OH groups, and the graft reaction on the -NH2 group is calculated to be exothermic by 20.5kcal/mol with a free energy barrier of 42.6kcal/mol. The reaction cannot benefit from the presence of the intruded water molecule, but can be considerably assisted by 1-allyl-3-methylimidazolium chloride ([Amim]Cl) ionic liquid. The reaction catalyzed by the ion-pair is calculated to be exothermic by 36.5kcal/mol and the barrier is reduced to 29.3kcal/mol, which are further corrected to 28.0 and 29.1kcal/mol by considering the solvent effect of [Amim]Cl ionic liquid. Calculated results verified the experimental finding that imidazolium-based ionic liquids can promote the reaction of chitosan with epoxy compounds.

Rheological properties of N-[(2-hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride

N-[(2-hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride (HTCC) was synthesized using 1-allyl-3-methylimidazole chloride (AmimCl) as a homogeneous green reaction media. The effects of polymer concentration, temperature, cation valence, anion type and concentration of inorganic salt, and degree of substitution (DS) on the rheological properties of HTCC were investigated. The apparent viscosity indicated that HTCC solution was a typical pseudoplastic fluid, which could be described by Ostwald de Waele and Cross-empirical models. The viscoelastic properties showed the formation of gel-like structures. Temperature showed slight effect on the apparent viscosity of HTCC solution, while the DS of HTCC showed remarkable effect on the apparent viscosity. At a low shear rate, the apparent viscosities of HTCC solution increased firstly with an increase of cNaCl from 0 to 40mmol/L, and then decreased with further increasing cNaCl to 60mmol/L. At a high shear rate, the opposite trends were observed. The variation of HTCC molecular construction under different inorganic salt conditions was confirmed by scanning electron microscopy, meanwhile, the variation mechanism was proposed.

Rheology and viscosity scaling of gelatin/1-allyl-3-methylimidazolium chloride solution

Gelatin/1-allyl-3-methylimidazolium chloride solutions are prepared by using the ionic liquid 1-allyl-3-methylimidazolium chloride as solvent. The rheological properties of the gelatin solutions have been investigated by steady shear and oscillatory shear measurements. In the steady shear measurements, the gelatin solutions with high concentration show a shear-thinning flow behavior at high shear rates, while another shear thinning region can be found in the dilute gelatin solutions at low shear rates. The overlap concentration of gelatin in [amim]Cl is 1.0 wt% and the entanglement concentration is a factor of 4 larger (4.0 wt%). The high intrinsic viscosity (295 mL/g) indicates that the gelatin chains dispersed freely in the ionic liquid and no aggregation phenomenon occurs in dilute gelatin solution. The frequency dependences of modulus changed obviously with an increase in gelatin concentration. The empirical time-temperature superposition principle holds true at the experimental temperatures.

Viscometric Properties of Carboxymethylchitosan Solutions

The viscosity of carboxymethylchitosan solutions was measured via an Ubbelohde viscometer. The effect of carboxymethylchitosan concentration, pH of the carboxymethylchitosan solution, and concentration of added NaCl and CaCl2 on the reduced viscosity of the carboxymethylchitosan solutions were comparatively investigated. The results showed that the reduced viscosity of the carboxymethylchitosan solution decreased with the increase of carboxymethylchitosan concentration. The reduced viscosity of carboxymethylchitosan decreased with the addition of NaCl and CaCl2, and CaCl2 affected the viscosity more significantly than NaCl. With the increase of pH, the reduced viscosity first decreased and then increased. The interaction between Ca2+ ions and carboxymethylchitosan was studied by means of dynamic light scattering and scanning electron microscopy.

Aggregation behavior and adsorption properties of salt-free catanionic surfactant mixtures containing tetradecyltrimethyl ammonium salts

ABSTRACT The aggregation behavior of salt-free catanionic surfactants, tetradecyltrimethyl ammonium hydroxide (TTAOH)/fatty acid (FA) including octanoic acid (OA), decylic acid (DA) and lauric acid (LA) in aqueous solutions were studied. The critical micelle concentration(cmc), surface tension at cmc (γcmc), surface excess (Гmax), mean molecular surface area (Amin), adsorption efficiency (pc20) and surface tension reduction effectiveness (πcmc) were obtained from surface tension isotherms. The influence of temperature on the surface tension of salt-free TTAOH/FA (TTAOF) systems was investigated. Data of adsorption dynamics indicated that at fixed adsorption time, the order of adsorption capacity was TTAOH < TTAOH/OA (TTAOO) < TTAOH/DA (TTAOD) < TTAOH/LA (TTAOL). The adsorption process of salt-free TTAOF was adsorption-controlled. The complex and storage moduli increased with increasing oscillation frequency, however, the loss modulus showed the opposite trend. The complex modulus passed through a maximum value with increasing concentration of salt-free surfactant TTAOF. The adsorbed TTAOF layer was elastic, and the elasticity increased with increasing hydrocarbon chain length of FA. GRAPHICAL ABSTRACT

Interaction Between GMAC-m-CS and Surfactants: Surface Tension and Conductivity Methods

Glycidyl trimethyl ammonium chloride-modified chitosan (GMAC-m-CS) was synthesized through nucleophilic substitution of GMAC on CS in isopropanol dispersed system, which was characterized by FTIR and 1H NMR methods. The interaction between GMAC-m-CS and surface active ILs −1-dodecyl (tetradecyl and hexadecyl)-3-methylimidazolium bromide (CnmimBr, n = 12, 14, 16) was studied by surface tension and conductivity methods. The amount of CnmimBr adsorbed on GMAC-m-CS increases first with raising temperature, and then decreases, which reaches the largest amount at 30°C. The amount increases with the increase of alkyl chain length. The surface tension reducing capabilities of GMAC-m-CS/CnmimBr systems increase with temperature, however, decrease with the increase of GMAC-m-CS concentration. The aggregation processes of C14mimBr in solutions without GMAC-m-CS and with high concentration of GMAC-m-CS were entropy driven; however, it is enthalpy driven in solutions with low concentration of GMAC-m-CS. Based on the analysis of properties of GMAC-m-CS/CnmimBr, the interaction model of GMAC-m-CS/ILs was proposed. GRAPHICAL ABSTRACT

Synthesis of a Novel Class of Organosilicon Quaternary Ammonium Gemini Surfactants

A novel class of organosilicon quaternary gemini surfactants alkanediyl-α, ω-bis(methyl-dimethoxy-silopropyl-diethyl ammonium bromide) was synthesized with N,N-diethyl-aminopropyl-methyl-dimethoxysilane and α, ω-dibromoalkane as the raw materials, where the N,N-diethyl-aminopropyl-methyl-dimethoxysilane was synthesized by reacting diethylamine with γ-chloropropylmethyldimethoxysilane. The effects of various solvents on the conversion rate of the reaction and on purification of surfactants were investigated. The structures of the organosilicon quaternary ammonium gemini surfactants were determined by means of 1H NMR and elemental analysis. The properties of aqueous solution were measured with electrical conductivity and viscosity methods.