Quaternized polysulfone-based nanocomposite membranes and improved properties by intercalated layered double hydroxide

Biomaterials Based on Organic Polymers and Layered Double Hydroxides Nanocomposites: Drug Delivery and Tissue Engineering

The development of biomaterials has a substantial role in pharmaceutical and medical strategies for the enhancement of life quality. This review work focused on versatile biomaterials based on nanocomposites comprising organic polymers and a class of layered inorganic nanoparticles, aiming for drug delivery (oral, transdermal, and ocular delivery) and tissue engineering (skin and bone therapies). Layered double hydroxides (LDHs) are 2D nanomaterials that can intercalate anionic bioactive species between the layers. The layers can hold metal cations that confer intrinsic biological activity to LDHs as well as biocompatibility. The intercalation of bioactive species between the layers allows the formation of drug delivery systems with elevated loading capacity and modified release profiles promoted by ion exchange and/or solubilization. The capacity of tissue integration, antigenicity, and stimulation of collagen formation, among other beneficial characteristics of LDH, have been observed by in vivo assays. The association between the properties of biocompatible polymers and LDH-drug nanohybrids produces multifunctional nanocomposites compatible with living matter. Such nanocomposites are stimuli-responsive, show appropriate mechanical properties, and can be prepared by creative methods that allow a fine-tuning of drug release. They are processed in the end form of films, beads, gels, monoliths etc., to reach orientated therapeutic applications. Several studies attest to the higher performance of polymer/LDH-drug nanocomposite compared to the LDH-drug hybrid or the free drug.

3D nanoflower-like layered double hydroxide modified quaternized chitosan/polyvinyl alcohol composite anion conductive membranes for fuel cells

To solve the trade-off problem among ionic conductivity, mechanical and chemical stability of anion exchange membranes (AEMs), quaternized chitosan (QCS) was first prepared and then was blended with polyvinyl alcohol (PVA) to improve mechanical strength of QCS. Afterwards, three-dimensional (3D) hierarchical flower-like layered double hydroxides (LDHs) were prepared via one-pot ethylene glycol-assisted solvothermal method, and then were incorporated into QCS/PVA blend matrix to fabricate composite AEMs. By constructing 3D hierarchical structure, the active sites of LDH nanosheets are fully exposed, thus impressive ion conductivity, alkali and fuel resistant ability of LDH nanosheets can be rationally utilized. The composite membrane displayed the maximum OH^- conductivity of 25.7 mS cm^-1, which was 48.6 % higher than that of the pristine membrane. Alkaline stability measurement proved that the composite membranes kept residual ionic conductivity of as high as 92 % after immersion in a 2 M KOH for 100 h. Due to the decreased methanol permeability and increased conductivity, the composite membrane with 6% LDHs content exhibited a peak power density of 73 mW cm^-2 at 60 °C, whereas the pristine membrane demonstrated only 40 mW cm^-2.

Quaternized Polysulfone Cross-Linked N,N-Dimethyl Chitosan-Based Anion-Conducting Membranes

Anion-conducting membranes were obtained following the cross-linking of 1,4-diazoniabicycle[2.2.2]octane functionalized-polysulfone with N,N-dimethyl chitosan (DMC). The ionic conductivity of the composite membranes was controlled by the amount of DMC. The influence of the amount of DMC on water uptake, swelling ratio, and ionic conductivity of the obtained membrane was studied. The membrane with 2 wt% DMC exhibited an ionic conductivity of 54 mS/cm and 94 mS/cm at 25 °C and 70 °C, respectively. The membrane showed good dimensional stability under hydrated conditions. A urea/O₂ fuel cell, built using the composite membrane, exhibited a peak power density of 4.4 mW/cm² with a current density of 16.22 mA/cm² at 70 °C.