Aqueous solutions of amphiphilic polysaccharides: Concentration and temperature effect on viscosity

Approaching disorder-tolerant semiconducting polymers

Doping has been widely used to control the charge carrier concentration in organic semiconductors. However, in conjugated polymers, n-doping is often limited by the tradeoff between doping efficiency and charge carrier mobilities, since dopants often randomly distribute within polymers, leading to significant structural and energetic disorder. Here, we screen a large number of polymer building block combinations and explore the possibility of designing n-type conjugated polymers with good tolerance to dopant-induced disorder. We show that a carefully designed conjugated polymer with a single dominant planar backbone conformation, high torsional barrier at each dihedral angle, and zigzag backbone curvature is highly dopable and can tolerate dopant-induced disorder. With these features, the designed diketopyrrolopyrrole (DPP)-based polymer can be efficiently n-doped and exhibit high n-type electrical conductivities over 120 S cm⁻¹, much higher than the reference polymers with similar chemical structures. This work provides a polymer design concept for highly dopable and highly conductive polymeric semiconductors.

In conjugated polymers, n-doping is often limited by the tradeoff between doping efficiency and charge carrier mobilities, since dopants often randomly distribute within polymers, leading to significant structural and energetic disorder. Here, the authors screen a large number of polymer building block combinations and explore the possibility of designing n-type conjugated polymers with good tolerance to dopant-induced disorder.

A sustainable and nondestructive method to high-throughput decolor Lycium barbarum L. polysaccharides by graphene-based nano-decoloration

Lycium barbarum L. polysaccharides (LBPs) with outstanding biological activities are of increasing interest. Traditional purification approaches are time-consuming and often involve toxic solvents that destroy the functionality and structure of polysaccharides. Herein, we report a sustainable and nondestructive strategy for purifying LBPs using graphene-based nano-decoloration. The amination of graphene oxide (GO) enables the resulted aminated reduced GO (NH₂-rGO) with abundant sp²-hybridized carbon domains, displaying high adsorption capacity toward pigments in crude polysaccharides. As such, within 5 min, NH₂-rGO can highly effectively and fast to decolor LBPs, with a high decoloration ratio of 98.72% and a high polysaccharides retention ratio of 95.62%. Importantly, compared with traditional decoloration methods, NH₂-rGO is nondestructive toward LBPs and has good reusability. Moreover, it exhibited widespread-use decoloration performance to decolor several common plant species. Overall, our proposed nano-decoloration approach is a general-purpose, sustainable, and nondestructive method to purify LBPs.

Mechanistic modelling of fluid bed granulation, Part I: Agglomeration in pilot scale process

The present study aims to develop a mechanistic model to predict the performance of a fluid bed granulation process. Therefore, the behavior of the bed was investigated experimentally for various operating conditions. It was observed that the granule Loss on Drying (LoD) and granule size are strongly interrelated. In detail, the maximum final granule size was observed at an intermediate final LoD. Consequently, there is an optimum spray rate and inlet temperature with respect to the granule size. Besides, it was demonstrated that the experiments delivering lower LoD result in a more elongated final granule. Aimed at enabling the prediction of the bed performance numerically, a single-compartment, population-balance-based model was developed and validated against experimental data. The model parameters associated with the growth rate of granule were estimated and mechanistically correlated to the relevant operating conditions. Detailed analysis of the experimental results suggested that these model parameters may be partially connected to the granule LoD. Subsequently, in order to examine the accuracy of the developed model, a simulation was performed for a new set of operating conditions not previously accounted for in the correlations. The comparison of the simulated bed performance, when compared to the experimental results, proved with reasonable accuracy the reliability of the developed model in predicting the temporal evolution of granule size. Therefore, this study can be a step forward in developing a stand-alone granulation model, via modeling heat and mass transfer, to simulate evaporation and drying in a fluid bed granulator.

O-(2-Hydroxyethyl)cellulose–derived Surfactants Prepared by Microwave–assisted Transesterification

A series of polymeric surfactants were prepared from O-(2-hydroxyethyl)cellulose (HEC, DS = 1) by transesterification of methyl laurate and the complex of methyl esters of rape seed oil fatty acids in the H2O/DMF system using microwave irradiation as heating source. The obtained derivatives were characterized by FTIR spectroscopy and viscometry, and their surfaceactive, foaming, emulsification and performance properties evaluated. The results indicate that under microwave heating water-soluble HEC-fatty acid esters with very low degree of esterification can be obtained in a few minutes and at temperatures not exceeding 100°C. The derivatives exhibited foaming ability and significant emulsifying efficiency for ‘oil in water’-type emulsions comparable to that of commercial surfactants as well as a good washing power and very high antiredeposition efficiency.

A comparison of the activation energy of viscous flow for hen egg-white lysozyme obtained on the basis of different models of viscosity for glass-forming liquids

The paper presents the results of viscosity determinations on aqueous solutions of hen egg-white lysozyme at a wide range of concentrations and at temperatures ranging from 5°C to 55°C. On the basis of these measurements and different models of viscosity for glass-forming liquids, the activation energy of viscous flow for solutions and the studied protein, at different temperatures, was calculated. The analysis of the results obtained shows that the activation energy monotonically decreases with increasing temperature both for solutions and the studied protein. The numerical values of the activation energy for lysozyme, calculated on the basis of discussed models, are very similar in the range of temperatures from 5°C to 35°C.

Viscometric study of pectin. Effect of temperature on the hydrodynamic properties

Hydrodynamic properties are important parameters affecting the performance of pectin. This polysaccharide is used as a thickening and gelling agent in food and pharmaceutical industries. The most common and economical of the hydrodynamic properties is the determination of viscosity, in which are determined the intrinsic viscosity and the diffusion coefficient. They indirectly measure the molecular weight (M(w)); hydrodynamic radius (R(H)); number of Simha, (ν(a/b)); Perrin parameter (P); Scheraga-Mandelkern parameter (β); and Flory parameters (ϕ(0) and P(0)). All the hydrodynamic parameters are dependent on temperature. Normally these parameters are reported at a temperature of 25°C, which limits their application to different temperatures. This work studies pectin dependence on temperature, finding that this biopolymer in aqueous solution presents a conformation of rod-like with ν(a/b)=10.5, and a value from 0.8232 to 0.8129. Pectin behavior in this system indicates that it behaves like a colloidal particle that tends to compact with increasing temperature (R(H) decrease). The molecular weight calculated for pectin is 180,000 g/mol. Mark-Houwink-Sakurada (M-H-S) equation constants, a and k, for pectin in water solvent-temperature systems have been already reported.

Bile Acids as Building Blocks of Amphiphilic Polymers. Applications and Comparison with Other Systems

This review deals with the use of bile acids as building blocks of amphiphilic polymers. These natural polyfunctional organic molecules have been employed in the synthesis of macromolecules combining hydrophilic and hydrophobic sequences. The two main synthetic strategies are radical (co)polymerization after attachment of a vinyl group onto the bile acid and molecule grafting of bile acid onto a hydrophilic polymer. The physicochemical properties of the resulting polymers both as bulk materials and in aqueous solution are reviewed and compared with polymers of other structures. Whenever possible, semiquantitative correlations are established and discussed.