Chu-Hua Lu

The Self‐Assembled Structure of the Diblock Copolymer PCL‐b‐P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane

This paper describes the miscibility and self-assembly, mediated by hydrogen-bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(ε-caprolactone)-block-(4-vinyl pyridine)] (PCL-b-P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen-bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP-POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long-range order, such as cylindrical and spherical structures, at relatively low OP-POSS contents, and short-range order or disordered structures at higher OP-POSS contents. Analyses performed using differential scanning calorimetry, wide-angle X-ray diffraction, and FT-IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen-bond acceptors toward the OH group of OP-POSS than are the CO groups of the PCL block, thereby resulting in excluded and confined PCL phases.

Supramolecular ionic strength-modulating microstructures and properties of nacre-like biomimetic nanocomposites containing high loading clay

In this study, we prepare thick nacre-like polymer clay nanocomposite films by a simple solution casting method. Nanoclay sheets with soft polymer coatings are used as ideal building blocks with intrinsic hard/soft character. The water-soluble poly(vinyl alcohol) (PVA) was chosen as an organic binder to connect each smectic clay sheet in the form of a nacre-like microstructure. The polymer-clay composite is in the form of a membrane in which the clay sheets are like stacked bricks. In addition, when applying normal stress larger than the yield stress—about 40 MPa—white shear bands develop at strains larger than 10%, much like the conditions where crazing of organic PVA is suppressed by inorganic fillers of clay sheets. Their corresponding microstructure and mechanical properties are studied using wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques and a tensile testing machine and are discussed in detail.