Volume 51 Issue 11, November 2019

Water desalination through a reverse osmosis (RO) membrane is an important technology for producing pure water from seawater. High-performance membrane materials have been extensively developed because these materials are useful as core elements in practical water separation processes. Bridged polysilsesquioxane (PSQ)-derived membranes are promising candidates for robust RO membranes because they exhibit high thermal stability and chlorine resistance compared to conventional aromatic polyamide membranes. This review reports on our recent studies involving the development of RO membranes based on bridged PSQs.

This focus review provides an overview of the formation and functions of surface-segregated monolayers (SSMs) on organic semiconductor films. Careful design of SSM molecules allows the formation of highly ordered surface monolayers with high coverage densities. SSMs can be used to induce changes in the molecular structure and the orientation in the bulk film. SSMs can be used to change the interfacial properties of organic/metal and organic/organic interfaces in various organic electronic devices. These modifications can drastically alter the performance of devices, demonstrating the general importance of interfaces.

Melanin, a black component of human hair, plays an important role in bright structural colorations in nature. Polydopamine-based artificial melanin particles, inspired by natural melanin and its important role in structural coloration, were used to produce bright structural colors by controlling light reflection and absorption. A variety of structural coloration characteristics have become possible through our investigations of the assembly structure, composition, shape, and application of artificial melanin particles.

Radical copolymerization of N-substituted maleimides and olefins provides AAB sequence-controlled copolymers by penultimate unit control. In this study, we investigated the steric, resonance, and polar effects of N-substituents on sequence control during copolymerization of various N-substituted maleimides with diisobutene and limonene in chloroform at 60 °C, and concluded that less bulky and more electron-donating substituents effectively induced the penultimate unit effect. We also demonstrated that 2:1 sequence-controlled maleimide copolymers was efficiently produced during radical copolymerization of limonene and N-phenylmaleimides with an electron-donating substituent.

We carried out the conventional radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization of di(1-adamantyl) fumarate, bis(3,5-dimethyl-1-adamantyl) fumarate, 1-adamantyl isopropyl fumarate, and 3,5-dimethyl-1-adamantyl isopropyl fumarate. Triblock copolymers consisting of rigid and flexible segments were synthesized by the RAFT polymerization of 2-ethylhexyl acrylate using poly(dialkyl fumarate)s as the macro-chain transfer agents. The excellent thermal stability of the adamantane-containing poly(dialkyl fumarate)s was confirmed by thermogravimetric analysis. The alignment of the rigid poly(dialkyl fumarate)s chains in the solid-state was revealed by X-ray diffraction.

The relaxation behavior of random copolymers of diisopropyl fumarate (DiPF) with 1-adamantyl acrylate (AdA) and n-butyl acrylate with various compositions was investigated using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The β relaxation temperature systematically shifted depending on the glass transition temperature of the counterpart copolymers, and the merging of the α and β processes at an intermediate composition was also observed. Thus, the random copolymerization of DiPF and acrylates enables us to fine tune the properties associated with the β relaxation of DiPF segments.

The nucleating effect of silk fibroin nanodisc on the crystallization behavior of poly(l-lactic acid) (PLLA) was investigated by polarizing optical microscope observations and the differential scanning calorimetry measurements. The experimental results show that the small amount of SFN (only 1%) reduces the induction period and the crystallization half-time while it increases the final degree of crystallinity. It was found that the SFN works as a nucleation agent by increasing the number of nuclei about four times while it does not change the growth rate of spherulites.

A triple-helical peptide, H-(Pro-Pro-Gly)₁₀-OH (PPG10) forms complex with NaHeparin in aqueous NaCl at ionic strengths of 20 and 50 mM and at 15 °C. The triple helix of PPG10 in the resulting complex is appreciably stabilized and the melting temperature of the triple helix is considerably higher than without NaHeparin. Analyses of the scattering function of the complex indicate that the molecular shape is substantially different from that of the previously investigated complex, suggesting specific attractive interactions between PPG10 and NaHeparin.

We synthesized cellulose nanofiber (CNF) modified with 9,9′-bis(aryl)fluorene, possessing cardo moieties (BCNF), and evaluated the properties of its polyamide 6/66 (PA) composites. As a result, it was revealed that BCNF was well dispersed in PA and had a strong reinforcing effect—even in a temperature range above the glass transition temperature—compared with unmodified CNF. This is attributed to the improvement of the interface affinity between BCNF and PA derived from the bulky and hydrophobic structure of BPFG.

In this work, MgO₂ NPs has been prepared in-situ onto the PVDF matrix to obtain an electroactive and high dielectric composite thin film. A simple, low-cost, solid-state integrated device utilizing the synthesized composite film as the active material is fabricated named as “self-charging photo power bank” (SPPB). The device shows notably high values of energy densities, power densities, and areal capacitances. The device also holds an appreciable long-term recycling capability and has powered electronic gadgets like LEDs and digital table clock.

Soybean protein isolate (SPI) was bonded to carboxymethyl cellulose (CMC) by a hydrazine bond to prepare SPI-CMC carriers for pesticide applications. AVM/SPI-CMC was obtained by encapsulating avermectin (AVM) with SPI-CMC through thermal denaturation. SPI-CMC could improve the anti-UV performance of AVM and slow down the decomposition rate of AVM. The hydrazone bond and carboxyl groups showed pH responsiveness, which could release drugs rapidly in an acidic environment. Environmentally friendly SPI-CMC could protect and release pesticides continuously, which could improve the efficiency of pesticides.

We developed biobased nanocapsules with enzymatic degradability, which were generated by the layer-by-layer deposition of enzymes and polypeptide over a liposome. Our developed nanocapsules exhibited layer-specific degradation by enzymes, which enables the release of cargo through degradation of the capsule wall as well as accumulation and targeting of nanocapsules through the emergence of surface properties and functionalities such as bone-targeting ability and cell-penetrating ability by unveiling an inner polymer layer.

Bridged polysilsesquioxane membranes have been expected as robust RO membranes for water desalination. However, water permeability of the membranes was not sufficiently high. In the present work, we studied interfacial copolymerization of bis[(triethoxysilyl)propyl]amine (BTESPA) and bis(triethoxysilyl)ethane (BTESE), which resulted in ~10 times higher water permeance of the membrane than that of the BTESPA homopolymer membrane with keeping NaCl rejection at nearly the same level. It was also found that the copolymerization with BTESE improved the thermal stability and chlorine resistance of the membranes.