Effect of Varying Amount of Polyethylene Glycol (PEG-600) and 3-Aminopropyltriethoxysilane on the Properties of Chitosan based Reverse Osmosis Membranes

Chitosan and polyethylene glycol (PEG-600) membranes were synthesized and crosslinked with 3-aminopropyltriethoxysilane (APTES). The main purpose of this research work is to synthesize RO membranes which can be used to provide desalinated water for drinking, industrial and agricultural purposes. Hydrogen bonding between chitosan and PEG was confirmed by displacement of the hydroxyl absorption peak at 3237 cm⁻¹ in pure chitosan to lower values in crosslinked membranes by using FTIR. Dynamic mechanical analysis revealed that PEG lowers Tg of the modified membranes vs. pure chitosan from 128.5 °C in control to 120 °C in CS-PEG5. SEM results highlighted porous and anisotropic structure of crosslinked membranes. As the amount of PEG was increased, hydrophilicity of membranes was increased and water absorption increased up to a maximum of 67.34%. Permeation data showed that flux and salt rejection value of the modified membranes was increased up to a maximum of 80% and 40.4%, respectively. Modified films have antibacterial properties against Escherichia coli as compared to control membranes.     

Bio-based sustainable films from the Algerian Opuntia ficus-indica cladodes powder: Effect of plasticizer content

The present study investigated the fabrication and characterization of bio-based sustainable films composed of a terrestrial plant raw material, namely Opuntia ficus-indica (OFI) cladodes powder (CP) and a marine seaweed derivative, namely agar (A). The effect of glycerol concentration on the properties of the casted films was evaluated at four different contents, namely 30, 40, 50 and 60 wt%. The films present UV-blocking properties, as well as moderate mechanical performance, thermal stability, and water vapor transmission rate (WVTR). The results point to an increase in thickness, elongation at break, moisture content, water solubility, and WVTR with increasing glycerol content. On the contrary, Young's modulus, tensile strength, and water contact angle decreased as glycerol concentration increased. The best combination is obtained for the film with 30% glycerol, based on an intermediate compromise between physical, mechanical, thermal, and barrier properties. All these outcomes express the potentiality of the powder obtained from grinding the OFI cladodes as raw material to produce low-cost films for the development of sustainable packaging materials.     

Hybrid anion exchange membranes with adjustable ion transport channels designed by compounding SEBS and homo-polystyrene

Hybrid anion exchange membranes (AEMs) were prepared via chemically functionalizing and crosslinking poly(styrene-b-[ethylene-co-butylene]-b-styrene) (SEBS) copolymers and low molecular weight homo-polystyrene (hPS). Via sequential chloromethylation, crosslinking, quaternization, and alkalization, a series of hPS/SEBS AEMs were obtained with varying content of hPS. Systematic structural, morphological, mechanical, absorption, and transport measurements reveal that these properties depend on the total PS content in the membranes. Particularly, increasing total PS content causes (a) PS domains in the AEMs transition the cylindrical morphology to lamella-like morphology with comparable correlation length; (b) Young's modulus, water uptake, swelling ratio, ionic exchange capacity and ionic conductivity of the AEMs, and T_g of PS phase increase. In addition, the alkaline stability of the hPS/SEBS AEMs is also improved by addition of hPS. These findings suggest that the proposed method can develop high performance SEBS AEMs that are suitable for fuel cell applications.     

Effects of different porous fillers on interfacial properties of poly (vinyl alcohol) hybrid films

Poly(vinyl alcohol) (PVA)-based hybrids have demonstrated broad liquid separation applications but separation performances are constrained by the compatibility between fillers and polymer, and thus it is essential to study the interfacial properties of these hybrids. In this work, PVA hybrids with four different porous fillers have been fabricated and characterized with Fourier transform infrared, X-ray diffraction, Scanning electron microscope, swelling and contact angle tests. Swelling results show that PVA has a degree of swelling (DS) of 79% in water but the swelling is compressed after adding fillers and the DS for PVA hybrids has decreased by 19%, 17%, 15%, and 9% for 30 wt% loading of ZIF-8, UiO-66, Hβ and ZSM-5, respectively. For methanol and its 10 wt% aqueous solution, similar swelling results are obtained due to mutual interactions among the filler, polymer and test liquids. Based on water and glycerol contact angle results, the surface energy of PVA is estimated to be 40.56 Nm⁻¹ and it drops to 27.39 Nm⁻¹ after adding less hydrophilic ZIF-8 or rise to 48.56 Nm⁻¹ after introducing more hydrophilic ZSM-5. The high-film hydrophilicity and then large surface energy have rendered methanol/water sorption selectivity of PVA hybrids decrease to some extent or vice versa.     

Preparation and characterization of poly(vinyl alcohol)/gum tragacanth/cellulose nanocomposite film

The effects of gum tragacanth obtained from two species of Astragalus Gossypinus (GT-G) and A. Parrowianus (GT-P) at two levels of 10% and 30% combined with cellulose nanofibers (CNF; 5%) on the physico-mechanical and structural properties of polyvinyl alcohol (PVA) nanocomposite film were investigated in this study. The water solubility and water vapor permeability of the films decreased with increasing the content of both gums, especially in the film containing 30% GT-P. The highest values of the tensile strength (39.3 MPa) and elongation at break (445%) belonged to the treatment containing 10% GT-P (90/10P/0). The FTIR and DSC analyses confirmed good interactions between GT and PVA in the 90/10P/0 treatment. SEM images indicated the dense structure of this film as the optimum treatment. Although the presence of CNF in the films containing GT-G improved some properties, especially the Young modulus, it impaired all the functional properties of nanocomposite GT-P film.     

Water-repellent films from corn protein and tomato cutin

Flexible and hydrophobic biobased films were obtained using zein esterified with methanol and para-toluene (p-toluene) sulfonic acid, cutin from tomato peels and ethanol. Esterification was confirmed by proton nuclear magnetic resonance and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR). Non-modified zein films were brittle and hydrophilic. ATR-FTIR demonstrated that zein esterification increased zein hydrophobicity. Without cutin, esterified zein films were hydrophobic but brittle. Addition of cutin yielded films that were flexible and hydrophobic, as demonstrated by contact angle measurements. Principal component analysis (PCA) of ATR-FTIR data showed that intensities at 3195 cm⁻¹ and 3490 cm⁻¹ were correlated to the relative hydrophobicity of zein films. PCA also showed that films of esterified zein and cutin were more hydrophobic than their counterparts (non-modified zein without cutin). Optical and scanning electron microscopy demonstrated that esterified zein was compatible with cutin and yielded cohesive films, which did not fracture upon bending.     

Enzymatic degradability and release properties of graphene oxide/silk fibroin nanocomposite films

The structure evolution of silk fibroin (SF) in the nanocomposite films with graphene oxide (GO) was investigated and related to the enzymatic degradability and release property. The interaction with GO was found to induce conformation transition of SF from random coil to β-sheet. However, the surface binding constrained the rearrangement of the silk chains, leading to a decrease of β-sheet when GO content was more than 1.0%. The crystal structure of SF played a key role in the degradation of GO/SF composites. The preferential degradation of the hydrophilic blocks resulted in a faster degradation of SF films with higher β-sheet content. The addition of GO to SF matrix led to a slower release and a reduction of the burst release of RhB, the model compound. The release profile was well fitted to the Rigter–Peppas equation, from which the characteristic constant decreased and the diffusional exponent increased with increasing GO content but quickly leveled off when GO content was more than 1.0%. Degradation of the composites had little influence on the characteristic constant of RhB release, however, led to an increased diffusional exponent, which was more evident for the composites with higher β-sheet content.     

Poly (vinyl alcohol)/polylactic acid blend film with enhanced processability,compatibility, and mechanical property fabricated via melt processing

Poly (vinyl alcohol)/polylactic acid (PVA/PLA) blend film, which is environment friendly and has potential applications in food and electronic packaging fields, was fabricated by melt extrusion casting. Fourier transform infrared spectroscopy analysis confirmed the formation of the hydrogen bonding between PLA and PVA, which improved the compatibility of PLA with PVA, making PLA uniformly dispersed in PVA matrix as small spheres, even when PLA content increase to 15 wt%. In this way, the original hydrogen bond network among PVA was disturbed and the chain mobility of PVA was activated, endowing PVA/PLA blends with lower melt viscosity than bot modified PVA and PLA, and the blend films with the increased crystallinity, mechanical property, and water resistance. Compared with PVA film, the crystallinity, tensile strength and Young's modulus of the blend film with 15 wt% PLA, respectively, increased by 15.1%, 9 and 51 MPa, and the water contact angle enlarged from 23° to 60°.     

Bi-layer gelatin active films with “Pitanga” leaf hydroethanolic extract and/or natamycin in the second layer

Research on biopolymers-based active films produced with natural antioxidants and/or antimicrobials has gained attention over the last few years; however, anti-mold activity has been less studied than those of anti-bacteria. The aim of this work was the development and characterization of bi-layer films based on gelatin with natamycin and/or “Pitanga” leaf hydroethanolic extract in the second thin layer in order to determine the effects of these bioactive compounds on bi-layered film properties. The films were characterized regarding their moisture content and solubility in water, optical properties, microstructure, mechanical and thermal properties, water contact angle, water vapor permeability, UV/visible light transmission, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and antioxidant and anti-mold activities. Active films presented activity against Penicillium spp and Aspergillus niger and demonstrated antioxidant activity, as measured by ABTS ^•+ and DPPH ^• methods. Neither additive used in the films' second layer significantly affected the films' moisture content, thermal properties or the molecular interactions of the polymer matrix, assessed by FTIR, although some mechanical properties were affected, and the water contact angle. In conclusion, bi-layer films have reduced the quantity of additives required to maintain the antioxidant and anti-mold activities, as compared to similar monolayer films of the same thickness.     

Temperature and processing effects on lithium ion conductivity of solution-deposited lithium zirconium phosphate (LiZr2P3O12) thin films

Lithium zirconium phosphate (LiZr₂P₃O₁₂) thin films have been prepared on platinized silicon substrates via a chemical solution deposition approach with processing temperatures between 700°C and 775°C. Films that were subject to a single high-temperature anneal were found to crystallize at temperatures above 725°C. Crystallization was observed in films annealed after each deposited layer at 700°C and above. In both cases, grain size was found to increase with annealing temperature. Ion conductivity was found to increase with annealing temperature in singly annealed films. In per-layer annealed films ion conductivity was found to initially increase then decrease with increasing annealing temperature. A maximum ion conductivity of 1.6 × 10⁻⁶ S/cm was observed for the singly annealed 775°C condition, while a maximum ion conductivity of 5.8 × 10⁻⁷ S/cm was observed for the 725°C per-layer annealed condition. These results are consistent with an increasing influence of cross-plane, internal interface resistance and vapor phase carrier loss in the per-layer annealed samples. This work demonstrates that post-deposition processing methods can strongly affect the ion conducting properties of LiZr₂P₃O₁₂ thin films.