Effective Conversion of Amide to Carboxylic Acid on Polymers of Intrinsic Microporosity (PIM-1) with Nitrous Acid

Abstract

Carboxylate-functionalised polymers of intrinsic microporosity (C-PIMs) are highly desirable materials for membrane separation applications. The recently reported method to afford C-PIMs was via an extensive base hydrolysis process requiring 360 h. Herein, a novel and effective method to convert PIM-CONH2 to C-PIM using nitrous acid was studied. The chemical structure of C-PIM was characterised by 1H NMR, 13C NMR, FTIR, elemental analysis, UV-Vis, TGA and TGA-MS. Complete conversion from amide to carboxylic acid groups was confirmed. Decarboxylation of C-PIM was also successfully studied by TGA-MS for the first time, with a loss of m/z 44 amu (CO2) observed at the first degradation stage. TGA also revealed decreased thermal stability of C-PIM relative to PIM-CONH2 under both N2 and air atmosphere. Gel permeation chromatography (GPC) analysis showed continuous molecular weight degradation of C-PIM with extended reaction time. Aromatic nitration was also observed as a side reaction in some cases.

Hybrid Fluorescent Poly(silsesquioxanes) with Amide- and Triazole-Containing Side Groups for Light Harvesting and Cation Sensing

“…The lower thermal stability of LPSQ-amide-Py may be explained by decarboxylation of side chains. Such phenomena were observed for carboxylate-functionalized polymers at 250–370 °C [ 48 ]. It corresponds both to the observed T d1 (260–300 °C) and the extent of the process illustrated by the peak at T d = 360–380 °C.…”

New Antiadhesive Hydrophobic Polysiloxanes

“…• C and may be correlated to the decarboxylation of side -COOH groups [42,43]. Thermal decomposition of P-2 and P-3 is more complicated due to the more complex composition of the side groups.…”

Effective enhancement of selectivities and capacities for CO2 over CH4 and N2 of polymers of intrinsic microporosity via postsynthesis metalation

“…To accurately evaluate effect of incorporation of metal ions into the PIM backbone, high purity carboxylated PIM (C‐PIM) is required as a starting material. In 2018, our group reported a fast and efficient route to high purity C‐PIM via the nitrous acid hydrolysis of amide‐containing PIM‐1 (PIM‐CONH 2 ) 11 . The sodium ion metallated PIM (designated as C‐PIM‐Na) was then prepared by reacting a slightly excess of sodium hydroxide with C‐PIM in methanol solution.…”