Double plasma treatment-induced graft polymerization of carbohydrated monomers on poly(ethylene terephthalate) fibers

This study deals with the grafting of carbohydrate monomers on poly(ethylene terephthalate) fibers by double argon plasma treatment. Two monomers were used: allyl alpha-D-galactopyranoside and 2-methacryloxyethyl glucoside. The quantity of grafted carbohydrates was determined by phenol/sulfuric acid colorimetric titration. The graft density was observed to vary according to the monomer used. Allyl alpha-D-galactopyranoside yields to smaller graft densities compared to 2-methacryloxyethyl glucoside, suggesting transfer reactions occurring at the surface with allyl alpha-D-galactopyranoside. Fibers with the highest graft levels were obtained with the higher monomer concentration and the lower quantity of fiber treated in a plasma reactor. The grafting density can be modulated by the monomer concentration and mass of fiber exposed in the plasma reactor. For 0.5 mg of fibers, the graft densities for 23 and 68 mM allyl alpha-D-galactopyranoside are, respectively, 18 and 35 nmol/cm2. For 0.5 mg of fibers, the graft densities for 19 and 38 mM 2-methacryloxyethyl glucoside are, respectively, 150 and 250 nmol/cm2. Comparative study without the preactivation treatment shows the efficiency of the preactivation: for a mass of fiber of 0.5 mg and a 2-methacryloxyethyl glucoside concentration of 38 mM, the grafting density without plasma pretreatment is 38 nmol/cm2. Attenuated total reflectance Fourier transform infrared spectra confirmed the anchoring of the glycopolymer onto the poly(ethylene terephthalate) surfaces. Atomic force microscopy and scanning electronic microscopy pictures indicated their morphological changes.     

New methods in fluid-structure coupling with application to biomechanics

An Eulerian approach is presented for generic fluid-structure coupling of an elastic body with an incompressible fluid. We consider the coupling as a multiphysics problem where fluid-solid interfaces are captured by a level-set method. The main features of the method are its simplicity, and its natural control of mass and energy. We are indeed able to prove an energy equation which ensures in particular that the regularization of the force does not involve any energy dissipation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of High Performance Thiophene–Aromatic Polyesters from Bio-Sourced Organic Acids and Polysaccharide-Derived Diol: Characterization and Degradability Studies

In this work, the feasibility of replacing petroleum-based poly(ethylene terephthalate) (PET) with fully bio-based copolyesters derived from dimethyl 2,5-thiophenedicarboxylate (DMTD), dimethyl 2,5-dimethoxyterephthalate (DMDMT), and polysaccharide-derived 1,6-hexanediol (HDO) was investigated. A systematic study of structure-property relationship revealed that the properties of these poly(thiophene–aromatic) copolyesters (PHS(20–90)) can be tailored by varying the ratio of diester monomers in the reaction, whereby an increase in DMTD content noticeably shortened the reaction time in the transesterification step due to its higher reactivity as compared with DMDMT. The copolyesters had weight-average molar masses (Mw) between 27,500 and 38,800 g/mol, and dispersity Đ of 2.0–2.5. The different polarity and stability of heterocyclic DMTD provided an efficient mean to tailor the crystallization ability of the copolyesters, which in turn affected the thermal and mechanical performance. The glass transition temperature (T_g) could be tuned from 70–100 °C, while the tensile strength was in a range of 23–80 MPa. The obtained results confirmed that the co-monomers were successfully inserted into the copolyester chains. As compared with commercial poly(ethylene terephthalate), the copolyesters displayed not only enhanced susceptibility to hydrolysis, but also appreciable biodegradability by lipases, with weight losses of up to 16% by weight after 28 weeks of incubation.     

Impact of the Hydrolysis and Methanolysis of Bidesmosidic Chenopodium quinoa Saponins on Their Hemolytic Activity

Saponins are specific metabolites abundantly present in plants and several marine animals. Their high cytotoxicity is associated with their membranolytic properties, i.e., their propensity to disrupt cell membranes upon incorporation. As such, saponins are highly attractive for numerous applications, provided the relation between their molecular structures and their biological activities is understood at the molecular level. In the present investigation, we focused on the bidesmosidic saponins extracted from the quinoa husk, whose saccharidic chains are appended on the aglycone via two different linkages, a glycosidic bond, and an ester function. The later position is sensitive to chemical modifications, such as hydrolysis and methanolysis. We prepared and characterized three sets of saponins using mass spectrometry: (i) bidesmosidic saponins directly extracted from the ground husk, (ii) monodesmosidic saponins with a carboxylic acid group, and (iii) monodesmosidic saponins with a methyl ester function. The impact of the structural modifications on the membranolytic activity of the saponins was assayed based on the determination of their hemolytic activity. The natural bidesmosidic saponins do not present any hemolytic activity even at the highest tested concentration (500 µg·mL⁻¹). Hydrolyzed saponins already degrade erythrocytes at 20 µg·mL⁻¹, whereas 100 µg·mL⁻¹ of transesterified saponins is needed to induce detectable activity. The observation that monodesmosidic saponins, hydrolyzed or transesterified, are much more active against erythrocytes than the bidesmosidic ones confirms that bidesmosidic saponins are likely to be the dormant form of saponins in plants. Additionally, the observation that negatively charged saponins, i.e., the hydrolyzed ones, are more hemolytic than the neutral ones could be related to the red blood cell membrane structure.     

Optimization of Lignin–Cellulose Nanofiber-Filled Thermoplastic Starch Composite Film Production for Potential Application in Food Packaging

The optimization of the production of thermoplastic starch (TPS) bionanocomposite films for their potential application in food packaging was carried out, according to the Box–Wilson Central Composite Design (CCD) with one center point, using Response Surface Methodology (RSM) and fillers based on lignin and nanofiber, which were derived from bamboo plant. The effects of the fillers on the moisture absorption (MAB), tensile strength (TS), percent elongation (PE) and Young’s modulus (YM) of the produced films were statistically examined. The obtained results showed that the nanocomposite films were best fitted by a quadratic regression model with a high coefficient of determination (R²) value. The film identified to be optimum has a desirability of 76.80%, which is close to the objective function, and contained 4.81 wt. % lignin and 5.00 wt. % nanofiber. The MAB, TS, YM and PE of the identified film were 17.80%, 21.51 MPa, 25.76 MPa and 48.81%, respectively. The addition of lignin and cellulose nanofiber to starch composite was found to have reduced the moisture-absorption tendency significantly and increased the mechanical properties of the films due to the good filler/matrix interfacial adhesion. Overall, the results suggested that the produced films would be suitable for application as packaging materials for food preservation.     

Influence of salts on hydrophobically end-capped polyethylene oxides in aqueous solution

The influence of four different salts (NaCl, KBr, CaCl₂ and MgCl₂) on the associative behaviour of poly(ethylene oxide) (POE with M=32000g/mol) hydrophobically end-capped with hexadecyl groups in aqueous solutions was investigated. Phase diagrams were obtained, structural properties were established by small angle neutron scattering (SANS) measurements and studies on the viscoelastic properties of the solutions were performed by low-shear viscosity and dynamic stress experiments. The influence of the four salts is compared as well as the difference of the interactions obtained with and without salts.     

Study of the solid-state hydrolysis of chitosan in presence of HCl

Chemical depolymerization of chitosan was obtained in the solid state by means of gaseous HCl. This new method allowed us to simultaneously form the hydrochloric salt and saturate the hydration water with acid. The depolymerization was carried out by keeping the product at a given temperature for the desired time. The measurements of the molecular weight distributions demonstrated the ability to control the reaction and produce oligomers with chosen dimensions. This solid-state hydrolysis favors the presence of a four-fold distribution that can be related to the original morphology and crystallinity of the initial material. The effects of the hydrolysis on the crystallinity, the crystalline structure, and the supramolecular order of the obtained chitosans were also studied. Finally, the washing of the hydrolyzed products in concentrated alkaline or acidic media allowed us to eliminate the lowest DPs and thus to narrow the molecular weight distribution. In this case, the crystallinity was also increased up to values beyond 70%. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3181–3191, 1997     

Rapid adsorption enthalpy surface sampling (RAESS) to characterize nanoporous materials

Molecular adsorption in nanoporous materials has many large-scale industrial applications ranging from separation to storage. To design the best materials, computational simulations are key to guiding the experimentation and engineering processes. Because nanoporous materials exist in a plethora of forms, we need to speed up the existing simulation tools to be able to screen databases of hundreds of thousands of structures. Here, we describe a new algorithm that quickly calculates adsorption enthalpies by sampling the surface of the material instead of the whole porous space. This surface sampling has been tested on the CoRE MOF 2019 database and has been proven to be more than 2 orders of magnitude faster than the gold standard method (Widom insertion), with an acceptable level of error on an enthalpy value of 0.34 kJ mol⁻¹, and is therefore proposed as a valuable addition to the high-throughput screening toolbox.

To speed up the calculation of adsorption enthalpy, a new algorithm changes the 3D problem into 2D sampling. It reduces the computational cost of large-scale screening of nanoporous materials for applications like fluid separation and storage.