Effect of cellulose compositions and fabrication methods on mechanical properties of polyurethane-cellulose composites.

A variety of cellulose-based polymer composite materials has been developed and show different impacts on the morphologies and properties of composites. Herein, we report the morphologies and properties of composites by blending polyurethane (PU) with either ethyl cellulose (EC) or cellulose nanofiber (CNF) through either drop-casting or electrospinning process. EC is homogenously mixed with PU without microphase separation and enhanced Young's modulus of composites from 0.04 to 6.94 MPa. The CNF is heterogeneously distributed in PU/CNF composites without interference on the PU microstructure and slightly increased modulus to 0.24 MPa. While the shearing force of the electrospinning process slightly affects the PU/EC composites, it drastically enhances PU crystallinity and Young's modulus to 54.95 MPa in PU/CNF composites. A model is established to summarize the effect of cellulose additives, compositions, and processes on PU/cellulose composites, providing a comprehensive understanding for designing future cellulose composites.

Cross-Talk Immunity of PEDOT:PSS Pressure Sensing Arrays with Gold Nanoparticle Incorporation.

In this study, the cross-talk effects and the basic piezoresistive characteristics of gold nanoparticle (Au-NP) incorporated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) pressure sensing 2 × 2 arrays are investigated using a cross-point electrode (CPE) structure. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) mappings were carried out to confirm the incorporation of Au-NPs in the PEDOT:PSS films. A solution mixing process was employed to incorporate the nanoparticles. When the diameter of the Au-NPs incorporated in the PEDOT:PSS films (Au-NPs/PEDOT:PSS) was 20 nm, the piezoresistive pressure sensing 2 × 2 arrays were almost immune to cross-talk effects, which enhances the pressure sensing accuracy of the array. The Au-NPs render the PEDOT:PSS films more resilient. This is confirmed by the high plastic resistance values using a nanoindenter, which reduce the interference between the active and passive cells. When the size of the Au-NPs is more than 20 nm, a significant cross-talk effect is observed in the pressure sensing arrays as a result of the high conductivity of the Au-NPs/PEDOT:PSS films with large Au-NPs. With the incorporation of optimally sized Au-NPs, the PEDOT:PSS piezoresistive pressure sensing arrays can be promising candidates for future high-resolution fingerprint identification system with multiple-electrode array structures.

Correlation between nanoscale surface potential and power conversion efficiency of P3HT/TiO2 nanorod bulk heterojunction photovoltaic devices.

This is an in depth study on the surface potential changes of P3HT/TiO(2) nanorod bulk heterojunction thin films. They are affected by interlayer structures, the molecular weight of P3HT, the processing solvents and the surface ligands on the TiO(2). The addition of an electron blocking layer and/or the hole blocking layer to the P3HT/TiO(2) thin film can facilitate charge carrier transport and result in a high surface potential shift. The changes in surface potential of multilayered bulk heterojunction films are closely correlated to their power conversion efficiency of photovoltaic devices. Changing ligand leads to the largest change in surface potential yielding the greatest effect on the power conversion efficiency. Merely changing the P3HT molecular weight is less effective and varying the processing solvents is least effective in increasing power conversion efficiency. The steric effect of the ligand has a large influence on the reduction of charge carrier recombination resulting in a great effect on the power conversion efficiency. By monitoring the changes in the surface potential of bulk heterojunction film of multilayer structures, we have obtained a useful guide for the fabrication of high performance photovoltaic devices.