Volume 52 Issue 10, October 2020

Drying-induced patterns, “meniscus splitting,” are introduced through a series of demonstrations using self-assembled polysaccharides as a method for the preparation of advanced biomimetic materials. Under the control of physicochemical factors, the depositing polymer bridges the gap between two substrates to make multiple nuclei at specific positions for membrane growth. By developing interfacial instability, meniscus splitting causes partitioning of a space, similar to dissipative structures seen in nature, from one space into multiple spaces.

The mechanical properties of a unidirectional carbon fiber (CF)-reinforced polyamide 6 (PA6) composite subjected to a tension perpendicular to the CFs was studied by using two types of CFs with different surface profile. The difference of local crystalline structure of PA6 among CFs can be affected to the mechanical behavior of unidirectional PA6/CF composite under transverse tension.

When the neat PMMA samples were dried at room temperature, the glass transition temperature (T_g) increases linearly with the decrease in the amount of residual solvent. However, even if the residual solvent is extrapolated to 0 wt%, the T_g is significantly lower than the bulk T_g despite no residual solvent. The T_g of heat-dried samples heat treated at 120 °C also increases linearly with decreasing residual solvent content. However, T_g was significantly different depending on the drying temperature even with the same residual solvent amount. These results indicated that the PMMA samples dried at room temperature have a distinctly different molecular mobility from the heated sample.

The molecular dynamics of PCL-grafted polyrotaxanes (PRs) homogeneously dispersed in a cross-linked epoxy network were investigated using viscoelastic mechanical measurements and relaxation time measurements with pulsed NMR spectroscopy. With increasing temperature, the PEG axial chains in the PRs exhibit a glass-rubber transition and start fluctuating in the CDs with glassy PCL graft chains, which causes viscoelastic mechanical relaxation.

Molecular structure of silica surface modifiers greatly controls the performance of silica-filled styrene-butadiene rubber (SBR) through interfacial characteristics of the composites. Soft nature of low molecular-weight hydroxyl terminated polybutadiene (HTPB) and small number of its covalent bounds to the rubber matrix was compared with large number of rigid covalent bounds made between bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) and rubber. Despite the better dispersion of silica modified with the former, the latter ensures higher transfer of stress to particles at large strains, inducing improved strength and abrasion resistance to composites.

A fluorescence film sensor film was prepared from 2,2,6,6-tetramethyl-1-piperidinyloxy radical-oxidized cellulose nanofiber, which was chemically immobilized by the Cu²⁺- or Cs⁺-selective ligand, 3,5-bis(((2-hydroxynaphthalen-1-yl)methylene)amino)benzoic acid. The potential of the current sensor is that it is a film-type sensor with facile removal from test water without leaving sensing residue in the water.