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.

Giant Grain Growth in (K,Na)NbO3 Ceramics

In this manuscript, an interesting phenomenon is reported. It has been reported that the growth of single crystals is observed in donor-doped (K,Na)NbO3 (KNN)-based ceramics. It is very interesting that the growth happens without the addition of a seed. The growth of huge grains (single crystal, approximately 30 mm,) occurs due to the abnormal grain growth (AGG) in KNN-based ceramics. In the AGG compositions, moreover, the seed plates can be synthesized by not topochemical reaction but simple molten salt synthesis (SMSS) which is a simple-and-cheap process. They can be a good candidate for the seeds at reactive templated grain growth (RTGG) or templated grain growth (TGG) process.

Intercalation-exfoliation processes during ionic exchange reaction from the sodium lepidocrocite-type titanate toward the proton-based trititanate structure

Topochemical reaction involving ionic exchange has been used to assess a large number of metastable compositions, particularly in layered metal oxides. This method encompasses complex reactions that are poorly explored,...

A Partial Anion Disorder in SrVO2H Induced by Biaxial Tensile Strain

SrVO2H, obtained by a topochemical reaction of SrVO3 perovskite using CaH2, is an anion-ordered phase with hydride anions exclusively at the apical site. In this study, we conducted a CaH2 reduction of SrVO3 thin films epitaxially grown on KTaO3 (KTO) substrates. When reacted at 530 °C for 12 h, we observed an intermediate phase characterized by a smaller tetragonality of c/a = 0.96 (vs. c/a = 0.93 for SrVO2H), while a longer reaction of 24 h resulted in the known phase of SrVO2H. This fact suggests that the intermediate phase is a metastable state stabilized by applying tensile strain from the KTO substrate (1.4%). In addition, secondary ion mass spectrometry (SIMS) revealed that the intermediate phase has a hydrogen content close to that of SrVO2H, suggesting a partially disordered anion arrangement. Such kinetic trapping of an intermediate state by biaxial epitaxial strain not only helps to acquire a new state of matter but also advances our understanding of topochemical reaction processes in extended solids.

Структурные превращения при химическом модифицировании поверхности пленки полипиромеллитимида

Using electron microscopy data, the formation of a submicron layer of polyamide acid (PAAc) on the surface of the polyiromellitimide (PI) film was studied when PI was successively treated with aqueous solutions of alkali and acid. To analyze the topology of the distribution of clusters of PAAc macromolecules on the surface of samples of modified PI film, the method of decorating PAAc with silver chloride nanoparticles was applied. The spatial distribution of the density of ensembles of decorating nanoparticles was found to be ordered. It is shown that the degree of order changes non-monotonically with increasing time of alkaline hydrolysis of PI. This change is explained by the superposition of two processes: the formation of PAAc clusters as a result of a topochemical reaction in the chains of PI macromolecules and random cluster-cluster aggregation. The centers of formation of PAAc clusters are periodically alternating microdomains – dense aggregates of PI macromolecules. The modes of obtaining an ordered PAAc cluster structure when modifying the PI surface are set.