Effect of hydrophilic block end groups and block junction on block copolymer self-assembly in solution

Surface-mediated self-assembly of click-reactive cello-oligosaccharides for fabricating functional nonwoven fabrics

Polymer fabrics are versatile materials used in various fields. Surface modification methods for hydrophobic polymer fibers have been developed to endow the materials with water wettability and functionality. Nevertheless, it remains a challenge to freely introduce functional groups to polymer fiber surfaces in a simple manner. Herein, we report the decoration of nonwoven fabric surfaces with azidated cello-oligosaccharide assemblies via molecular self-assembly. Cello-oligosaccharides with a terminal azido group were enzymatically synthesized and allowed to self-assemble in polyolefin, polyester, and vinylon nonwoven fabrics. It was found that the functional oligosaccharides formed bark-like assemblies on the nonwoven fiber surfaces, probably through heterogeneous nucleation. The hydrophilic oligosaccharide assemblies made the hydrophobic nonwoven surfaces water-wettable. Moreover, the azido group at oligosaccharide terminal was available for the post-functionalization of the modified nonwovens. In fact, an antigen was successfully conjugated to the modified nonwovens via the click chemistry. The antigen-conjugated nonwovens were useful for the specific and quantitative detection of a corresponding antibody. Our findings demonstrate the great potential of cello-oligosaccharide assembly for the functionalization of fabrics and other polymeric materials.

Prismatic Block Copolymer Hexosomes

Cubosomes and hexosomes are recent solution morphologies with an ordered porous structure and are observed for lipids and amphiphilic block copolymers (BCPs) with high hydrophobic fractions. Whereas lipid hexosomes typically exhibit a prismatic shape, BCP hexosomes have so far only been observed as closed microspheres where inner channels are not connected to the surrounding medium. Here, we describe the formation of flat, prismatic BCP hexosomes with pronounced faceting and a highly ordered lattice of hexagonally packed channels. We assemble polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP or SV) into the hexosome framework using polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) as a macromolecular surfactant in low-χ solvents. During solvent exchange, SV-rich domains form through liquid-liquid phase separation, followed by solidification and confined assembly within these domains. Since the final solvent (acetone) has a very low χ parameter toward PS and P4VP (equaling low interfacial tension), solidification of the hexosome occurs under confinement conditions that we term "supersoft". The low interfacial tension allows the stabilization of the hexagonal-prismatic shape, which originates from the hexagonal lattice of channels. Increasing the interfacial tension with polar cosolvents at some point dominates the particle shape, resulting in deformation of prismatic BCP hexosomes into spinning-top structures. The use of low-χ solvents for confined assembly of BCPs may allow the formation of unusual particle shapes simply by tuning the polymer-solvent interaction.

Sensing interface based on electrodeposited Cu-BTC microporous film for electrochemical detection of the painkiller paracetamol

The use of metal-organic framework materials in electrochemical sensors has been gaining more attention in the last few years due to their highly porous structure and electrocatalytic activity. In this work, a novel paracetamol electrochemical sensor based on a Cu-BTC microporous film electrochemically grown onto glassy carbon electrode was introduced. The Cu-BTC film was deposited directly onto the electrode surface via an electrochemical approach using a Et₃N probase to accelerate the growth of Cu-BTC. The fast growth enables the formation of a microporous structure with better adsorption of targeted molecules. The two-dimensional arrangement of units made of dimeric copper cations coordinated to carboxylate anions helped to improve the electrochemical conductivity and electron transfer rate at the electrode surface (charge transfer resistance was dramatically decreased from 2173 Ω to 86 Ω). The electrocatalytic activity of copper ion centers in Cu-BTC was studied with peak separation between oxidation and reduction peaks of pseudo-redox paracetamol molecules much shortened (from 629 mV to 87 mV). Consequently, the sensing parameters (sensitivity and detection limit) of the as-prepared paracetamol sensor were considerably improved. Further works need to be conducted on tailoring ligand structure in order to much improve the electrical conductivity of metal-organic frameworks for sensing purposes.