In Situ Complex with by‐product HCl and Release Chloride Ions to Dissolve Aramid

Abstract

Because of the strong hydrogen-bond interaction among macromolecular chains, the addition of chloride salts is generally needed to offer Cl ions for the dissolution of aromatic polyamides. In this paper, poly-(benzimidazole-terephthalamide) which complexed with by-product HCl during polymerization (PABI-HCl) was prepared and imidazole compound as cosolvent was added into dimethylacetamide (DMAc) to dissolve PABI-HCl. Due to stronger affinity to protons, imidazole compound could in-situ complex with HCl of PABI-HCl and form imidazolium hydrochloride. Then imidazolium hydrochloride would ionize and produce much free Cl ions which acted as stronger hydrogen-bond acceptor to disrupt interaction among macromolecular chains. As a result, solubility of PABI-HCl in DMAc was improved significantly in existence of small amount of imidazole compound. Moreover, DMAc-imidazole mixture was utlized for synthesis of different kinds of aramids and no precipitation was observed with progress of the reaction. So the mixture was suitable to be utlized as solvent for polymerization of aramid.

Synthesis of polyaramids in γ-valerolactone-based organic electrolyte solutions

“…Liu et al made a similar discovery in their work on the synthesis of the polyaramid poly-(benzimidazole-terephthalamide). [44][45] They found that the addition of imidazole or sodium acetate to scavenge in-situ the released HCl greatly increased the solubility of their polyaramids.…”

C−N Coupling Reactions on Graphene with Aromatic Macromolecules and the Spatial Conformation of Grafted Macromolecules

“…Based on the nucleophilic behavior,i ti sc rucial to enhance the nucleophilicity of the benzimidazole moiety to achieveC À Nc oupling on graphene with highere fficiency.I nm ost cases, DMAc rather than DMSO, with addition of lithium chloride (LiCl;D MAc/LiCl for short altogether), is the commonly used solventt od issolve aromatic polyamide. [15] Therefore, it seems unsuitable to enhance the reaction efficiency by changingt he solvents. Alternatively,t he enhancement of nucleophilicity could be achieved by adding ab asic catalyst.…”

Improving Interfacial and Compressive Properties of Aramid by Synchronously Grafting and Crosslinking

“…Para‐aramid fibers such as Kevlar or Twaron have been widely applied in fiber‐reinforced composites and engineering materials due to their excellent mechanical properties and heat‐resistance . However, chemically inert surface and low compressive strength of aramid are two major problems for its application in reinforcing materials .…”