Structure Property Relationship of Micellar Waterborne Poly(Urethane-Urea): Tunable Mechanical Properties and Controlled Release Profiles with Amphiphilic Triblock Copolymers.

Waterborne polyurethane (WPU) has attracted significant interest as a promising alternative to solvent-based polyurethane (SPU) due to its positive impact on safety and sustainability. However, significant limitations of WPU, such as its weaker mechanical strength, limit its ability to replace SPU. Triblock amphiphilic diols are promising materials to enhance the performance of WPU due to their well-defined hydrophobic-hydrophilic structures. Yet, our understanding of the relationship between the hydrophobic-hydrophilic arrangements of triblock amphiphilic diols and the physical properties of WPU remains limited. In this study, we show that by controlling the micellar structure of WPU in aqueous solution via the introduction of triblock amphiphilic diols, the postcuring efficiency and the resulting mechanical strength of WPU can be significantly enhanced. Small-angle neutron scattering confirmed the microstructure and spatial distribution of hydrophilic and hydrophobic segments in the engineered WPU micelles. In addition, we show that the control of the WPU micellar structure through triblock amphiphilic diols renders WPU attractive in the applications of controlled release, such as drug delivery. Here, curcumin was used as a model hydrophobic drug, and the drug release behavior from WPU-micellar-based drug delivery systems was characterized. It was found that curcumin-loaded WPU drug delivery systems were highly biocompatible and exhibited antibacterial properties in vitro. Furthermore, the sustained release profile of the drug was found to be dependent on the structure of the triblock amphiphilic diols, suggesting the possibility of controlling the drug release profile via the selection of triblock amphiphilic diols. This work shows that by shedding light on the structure-property relationship of triblock amphiphilic diol-containing WPU micelles, we may enhance the applicability of WPU systems and move closer to realizing their promising potential in real-life applications.

Synthesis of Water Resistance and Moisture-Permeable Nanofiber Using Sodium Alginate-Functionalized Waterborne Polyurethane.

The development of nontoxic and biodegradable alginate-based materials has been a continual goal in biological applications. However, their hydrophilic nature and lack of spinnability impart water instability and poor mechanical strength to the nanofiber. To overcome these limitations, sodium alginate (SA) and waterborne polyurethane (WPU) were blended and crosslinked with calcium chloride; 30 wt % of SA exhibited good compatibility. Further addition of 10 wt % calcium chloride improved the water stability to an extremely humid region. Furthermore, the stress-strain curve revealed that the initial modulus and the elongation strength of the WPU/SA and WPU/CA blends increased with SA content, and the crosslinker concentration clearly indicated the dressing material hardness resulted from this simple blend strategy. The WPU/SA30 electrospun nanofibrous blend contained porous membranes; it exhibited good mechanical strength with water-stable, water-absorbable (37.5 wt %), and moisture-permeable (25.1 g/m2-24 h) characteristics, suggesting our cost-effective material could function as an effective wound dressing material.

Glycine betaine intercalated layered double hydroxide modified quaternized chitosan/polyvinyl alcohol composite membranes for alkaline direct methanol fuel cells.

Utilization of chitosan as the host polymer of anion exchange membranes (AEMs) can avoid the carcinogenic chloromethylation step which is indispensable for aromatic polymers during their quaternization process. To further improve the ionic conductivity and mechanical stability, a hydroxide ion conductor (layered double hydroxides, LDHs) was intercalated by glycine betaine and then incorporated to quaternized chitosan and polyvinyl alcohol mixed matrix to prepare AEMs. Due to intercalated organic ions, the LDHs can be homogeneously dispersed in the matrix, thus promoting the load transfer from the matrix to stiff LDHs. The tensile strength and elongation of the composite membrane (5% intercalated LDHs content) are 23.6 MPa and 51.4% which are 71% and 44% respectively higher than those of the pure QCS/PVA membrane. Moreover, the hydroxide ion conductor (LDHs) and the intercalated quaternary ammonium groups could act as new OH- conductive sites and further enhance the ionic conductivity. The membrane with 5 wt.% intercalated LDHs loading shows ionic conductivity of ˜35.7 mS cm-1 (80 °C) and peak power density of 97.8 mW cm-2 which are respectively 42% and ˜50% higher than those of the pure membrane. Furthermore, better alkaline stability was also proved in the composite system, and the ionic conductivity of the composite membrane can retain 70% (only 49% for the pure membrane) even after immersing in a 1 M KOH for 168 h.