Thermal Cross Linking of Novel Azide Modified Polymers of Intrinsic Microporosity—Effect of Distribution and the Gas Separation Performance

Abstract

The synthesis of polymers of intrinsic microporosity (PIM) modified with azide groups, the cross linkage by nitrene reaction and their performance as gas separation membranes are reported. The azide modification of the spirobisindane units in the polymer backbone was done by post functionalization of methylated spirobisindane containing polymers. These polymers differ in distribution and concentration of the azide group containing spirobisindane units by applying perfectly alternating and randomly distributed copolymers along the polymer chains. To investigate the influence of concentration of the azide groups, additionally the homopolymer of methylated spirobisindane was synthesized and subjected to identical treatments and characterizations as both copolymers. Cross linkage by nitrene reaction was examined by different temperature treatments at 150, 200, 250 and 300 °C. Characterization of the new polymers was performed by NMR, SEC and FT-IR. Furthermore, the crosslinking process was investigated by means of solid state NMR, TGA-FTIR, DSC and isoconversional kinetic analysis performed with TGA. Gas permeability of CO2, N2, CH4, H2 and O2 was determined by time lag experiments and ideal selectivities for several gas pairs were calculated. The two azide groups per repeating unit degrade during thermal treatments by release of nitrogen and form mechanically stable PIM networks, leading to an increase in gas permeability while selectivity remained nearly constant. Measured diffusivity and solubility coefficients revealed differences in the formation of free volume elements depending on distribution and concentration of the azide groups. Aging studies over about five months were performed and physical aging rates (βP) were evaluated with regard to the concentration and distribution of curable azide functionalities. Subsequently, the enhanced sieving effect during aging resulted in membrane materials that surpassed the Robeson upper bound in selected gas pairs.

Reactive Multifunctional Polymer Films Using Thermally Stimulated Cascade-like Reactions: Potential Strategy Employing Modified ortho-Allylation in Polyimides

“…Crosslinking, herein, appears to be one of the utmost important techniques for materials improvement since mechanical properties, chemical resistance, thermal stability, and application-specific properties such as swelling and porosity can be manipulated . Several concepts for such crosslinking reactions are known, such as allyl crosslinking, , click-chemistry, ,− such as thiol–ene , and Diels–Alder reactions, as well as a set of 1,3-dipolar cycloadditions, ,− often with azide functionalities, and also esterification ,− and radical crosslinking. ,− ,, Widely described reactive and crosslinked polymeric systems are, for instance, polybenzoxazines, which are easily synthesized by reactions of a primary amine, phenolic derivative, and aldehyde followed by crosslinking via ring-opening reactions. − Polybenzoxazines can be used to prepare tandem- or cascade reaction systems, other examples are Wagner-Jauregg reactions in allylated bismaleimides. − A cascade reaction is defined as a chemical reaction sequence comprising at least two consecutive reactions, in which each step requires the chemical transformation of the previous step. These steps proceed in many cases via intramolecular reactions but might also occur intermolecularly.…”

An Electrochemical Investigation into the Redox Properties of Push‐Pull Dibenzodioxins and Comparative Analysis with Analogous Heteroacenes

“…Hence, they are used to prepare porous organic polymers (POPs); including PIMs (polymers of intrinsic microporosity) [4a–g] . In addition, thermally cross‐linkable PIMs with azide groups and dibenzodioxin units in the backbone have been reported [4c] and their performance as gas separation membranes were tested [4d–e] . Highly stable, porous, and recyclable polyarylether‐covalent organic frameworks based on dibenzodioxins were engineered and demonstrated for removal of antibiotics from water over wide pH ranges [4h] …”

Postsynthetically Modified Polymers of Intrinsic Microporosity (PIMs) for Capturing Toxic Gases

“…Polymers of intrinsic microporosity (PIMs), a subclass of porous organic polymers, have demonstrated their potential for use in a wide array of applications related to gas separations − and the degradation of toxic chemicals . PIMs possess high surface area due to the inefficient packing of the non-network polymer chains with their rigid and contorted structures. − Moreover, the non-network PIMs can be dissolved in common organic solvents, providing an opportunity for further processing into different forms such as films, coatings, or fibers.…”

“…PIMs possess high surface area due to the inefficient packing of the non-network polymer chains with their rigid and contorted structures. − Moreover, the non-network PIMs can be dissolved in common organic solvents, providing an opportunity for further processing into different forms such as films, coatings, or fibers. In PIM-1, the first reported family member of PIMs (shown in Figure a), the nitrile group in the backbone can be readily functionalized with various organic groups to selectively capture targeted species. − , Given their high porosity and ease of functionalization with acidic or basic groups, combined with good processability, we envisioned PIMs as potential adsorbents for capturing toxic industrial gases (TICs), such as NH 3 or SO 2 . While the vast majority of PIM studies focus on CO 2 capture or CO 2 /CH 4 and CO 2 /N 2 gas separations, − few studies have been reported using PIMs as adsorbents for capturing other acidic or basic gas molecules .…”

“…In PIM-1, the first reported family member of PIMs (shown in Figure a), the nitrile group in the backbone can be readily functionalized with various organic groups to selectively capture targeted species. − , Given their high porosity and ease of functionalization with acidic or basic groups, combined with good processability, we envisioned PIMs as potential adsorbents for capturing toxic industrial gases (TICs), such as NH 3 or SO 2 . While the vast majority of PIM studies focus on CO 2 capture or CO 2 /CH 4 and CO 2 /N 2 gas separations, − few studies have been reported using PIMs as adsorbents for capturing other acidic or basic gas molecules . To our surprise, although basic amidoxime functionalities in porous polymers have revealed their great affinity toward acidic CO 2 gas, , interactions with other acidic gas molecules, such as SO 2 , have not yet been explored.…”