Reversible Topochemical Polymerization and Depolymerization of a Crystalline Three-Dimensional Porous Organic Polymer with C–C Bond Linkages

Three-dimensionally connected porous organic polymers are of interest because of their potential in adsorption, separation, and sensing, among others. When crystalline, they also afford accurate structure description, which in turn can enable particular functions. However, crystallization of three-dimensional (3D) polymers is challenging. This is especially true when targeting polymerization via stable C–C bonds, whose formation is usually irreversible and does not allow for error correction typically required for crystallization. Here, we report polyMTBA, the first 3D-connected crystalline organic polymer with permanent porosity, here formed via C–C linkages. High crystallinity is achieved by solid-state topochemical reaction within monomer MTBA crystals. polyMTBA is recyclable via thermal depolymerization and is solution-processable via its soluble monomers. These results reveal topochemical polymerization as a compelling methodology for generating stable, crystalline, and porous 3D organic frameworks.

Reversible Topochemical Polymerization and Depolymerization of a Crystalline Three-Dimensional Porous Organic Polymer with C–C Bond Linkages

Three-dimensionally connected porous organic polymers are of interest because of their potential in adsorption, separation, and sensing, among others. When crystalline, they also afford accurate structure description, which in turn can enable particular functions. However, crystallization of three-dimensional (3D) polymers is challenging. This is especially true when targeting polymerization via stable C–C bonds, whose formation is usually irreversible and does not allow for error correction typically required for crystallization. Here, we report polyMTBA, the first 3D-connected crystalline organic polymer with permanent porosity, here formed via C–C linkages. High crystallinity is achieved by solid-state topochemical reaction within monomer MTBA crystals. polyMTBA is recyclable via thermal depolymerization and is solution-processable via its soluble monomers. These results reveal topochemical polymerization as a compelling methodology for generating stable, crystalline, and porous 3D organic frameworks.

Polymeric waste valorization at a crossroads: Ten ways to bridge research on model and complex/real feedstock

The valorization of polymeric waste, such as biomass, tires, and plastics, via thermal depolymerization (i.e., pyrolysis and liquefaction) and simultaneous or subsequent catalytic treatment has gained enormous momentum. The inherent...

Methods for Producing and Practical Use of Synthesis Gas (Review)

The article details the process of gasification of fuel, which takes place inside the gas generator during synthesis gas production, gives examples of industrial application of synthesis gas obtained from coal both in Russia and abroad. Various types of gas generators are described. The calorific characteristics of synthesis gases obtained from different fuels and different methods were analyzed. What is described is a combined cycle of complex gasification of BIGCC biomass with the given example of exergetic analysis. The topic of calorie content of synthesis gas obtained during thermal depolymerization of organic fuel in the absence of oxygen is covered

Simulation and Experimental Investigation on Carbonized Tracking Failure of EPDM/BN-Based Electrical Insulation

Ethylene propylene diene monomer (EPDM) is broadly employed as an insulating material for high voltage applications. Surface discharge-induced thermal depolymerization and carbon tracking adversely affect its performance. This work reports the electrical field modeling, carbon tracking lifetime, infrared thermal distribution, and leakage current development on EPDM-based insulation with the addition of nano-BN (boron nitride) contents. Melt mixing and compression molding techniques were used for the fabrication of nanocomposites. An electrical tracking resistance test was carried out as per IEC-60587. Simulation results show that contamination significantly distorted the electrical field distribution and induced dry band arcing. Experimental results indicate that electric field stress was noticed significantly higher at the intersection of insulation and edges of the area of contamination. Moreover, the field substantially intensified with the increasing voltage levels. Experimental results show improved carbonized tracking lifetime with the addition of nano-BN contents. Furthermore, surface temperature was reduced in the critical contamination flow path. The third harmonic component in the leakage current declined with the increase of the nano-BN contents. It is concluded that addition of nano-BN imparts a better tracking failure time, and this is attributed to better thermal conductivity and thermal stability, as well as an improved shielding effect to electrical discharges on the surface of nanocomposite insulators.

Lactide Production from Polymer Waste

The method of thermal depolymerization of polylactide wastes and products from it has been studied. At a temperature of 200-250 °C and a pressure of 5-10 mbar the maximum yield of crude lactide and pure lactide is 40 and 5.5 % by weight accordingly. The addition of catalysts (Zn, ZnO, SnO, C16H30O4Sn, Sb2O3) in an amount from 0.5 to 2.0 % by weight make it possible to intensify the process and increase the monomer yield by 3-10 times. The maximum amount of lactide (~60 wt %) is achieved by using of tin octoate (1.5 % wt) as the catalyst. The findings product is a mixture that consist of D-, L-lactide (~80 wt %) and m-lactide (~4 wt %) isomers, lactic acid (~2 wt %), oligomer of lactic acid (~14 wt %), water (<1 wt %), and has a melting point 92-96 °C.