Highly Thermally Stable, Reversible, and Flexible Main Chain Type Benzoxazine Hybrid Incorporating Both Polydimethylsiloxane and Double-Decker Shaped Polyhedral Silsesquioxane Units through Diels-Alder Reaction.

This work synthesizes a new bifunctional furan derivative (PDMS-FBZ) through a sequence of hydrosilylation of nadic anhydride (ND) with polydimethylsiloxane (PDMS), reaction of the product with p-aminophenol to form PDMS-ND-OH, and its subsequent Mannich reaction with furfurylamine and CH2 O. Then, the main chain-type copolymer PDMS-DABZ-DDSQ is prepared through a Diels-Alder (DA) cycloaddition of PDMS-FBZ with the bismaleimide-functionalized double-decker silsesquioxane derivative DDSQ-BMI. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirm the structure of this PDMS-DABZ-DDSQ copolymer; differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) reveal it to have high flexibility and high thermal stability (Tg = 177 °C; Td10 = 441 °C; char yield = 60.1 wt%); contact angle measurements reveal a low surface free energy (18.18 mJ m-2 ) after thermal ring-opening polymerization, because the inorganic PDMS and DDSQ units are dispersed well, as revealed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This PDMS-DABZ-DDSQ copolymer possesses reversible properties arising from the DA and retro-DA reactions, suggesting its possible application as a functional high-performance material.

Efficient adsorption and photocatalytic degradation of water emerging contaminants through nanoarchitectonics of pore sizes and optical properties of zirconium-based MOFs.

Over the past decades, the presence of pharmaceutical emerging contaminants in water bodies is receiving increasing attention due to the high concentration detected from wastewater effluent. Water systems contain a wide range of components coexisting together, which increases the difficulty of removing pollutants from the water. In order to achieve selective photodegradation and to enhance the photocatalytic activity of the photocatalyst on emerging contaminants, a Zr-based metal-organic framework (MOF), termed VNU-1 (VNU represents Vietnam National University) constructed with ditopic linker 1,4-bis(2-[4-carboxyphenyl]ethynyl)benzene (H2CPEB), with enlarged pore size and ameliorated optical properties, was synthesized and applied in this study. When compared to UiO-66 MOFs, which only had 30% photodegradation of sulfamethoxazole, VNU-1 had 7.5 times higher adsorption and reached 100% photodegradation in 10 min. The tailored pore size of VNU-1 resulted in size-selective properties between small-molecule antibiotics and big-molecule humic acid, and VNU-1 maintained high photodegradation performance after 5 cycles. Based on the toxicity test and the scavenger test, the products after photodegradation had no toxic effect on V. fischeri bacteria, and the superoxide radical (·O2-) and holes (h+) generated from VNU-1 dominated the photodegradation reaction. These results demonstrate that VNU-1 is a promising photocatalyst and provide a new insight for developing MOF photocatalyst to remove emerging contaminants in the wastewater systems.

Double-Decker-Shaped Polyhedral Silsesquioxanes Reinforced Epoxy/Bismaleimide Hybrids Featuring High Thermal Stability.

In this study, we synthesized bismaleimide into a functionalized double-decker silsesquioxane (DDSQ) cage. This was achieved by hydrosilylation of DDSQ with nadic anhydride (ND), reacting it with excess p-phenylenediamine to obtain DDSQ-ND-NH2, and treating with maleic anhydride (MA), which finally created a DDSQ-BMI cage structure. We observed that the thermal decomposition temperature (Td) and char yield were both increased upon increasing the thermal polymerization temperature, and that these two values were both significantly higher than pure BMI without the DDSQ cage structure since the inorganic DDSQ nanoparticle could strongly enhance the thermal stability based on the nano-reinforcement effect. Based on FTIR, TGA, and DMA analyses, it was found that blending epoxy resin with the DDSQ-BMI cage to form epoxy/DDSQ-BMI hybrids could also enhance the thermal and mechanical properties of epoxy resin due to the organic/inorganic network formation created by the ring-opening polymerization of the epoxy group and the addition polymerization of the BMI group due to the combination of the inorganic DDSQ cage structure and hydrogen bonding effect. The epoxy/DDSQ-BMI = 1/1 hybrid system displayed high Tg value (188 °C), Td value (397 °C), and char yield (40.4 wt%), which was much higher than that of the typical DGEBA type epoxy resin with various organic curing agents.