Facile synthesis and characterization of soluble aramid containing polar hydroxyl side group

• Published in: Polymer (Guilford) Vol. 238; p. 124411
• Main Authors: Liu, Yadi, Zhou, Sheng, Zhao, Ning, Xu, Jian, Shen, Zhihao, Fan, Xing-He, Zhou, Qi-Feng
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 03.01.2022; Elsevier BV
• Subjects: Aramid fibers; Conjugation; Dimethyl acetamide; Dimethylformamide; Elongation; Esterification; High temperature; Hydroxyl side group; Mechanical properties; Modulus of elasticity; Molding (process); Molding processability; Molecular weight; Monomers; Nitrogen; NMR; Nuclear magnetic resonance; p-Hydroxybenzoic acid; Polymers; Size exclusion chromatography; Soluble aramid; Solution spinning; Substitution reactions; Tensile strength; Thermal resistance; Weight loss; Mechanical properties; Molding processability; Soluble aramid; Hydroxyl side group
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2021.124411

A series of aramids containing hydroxyl side group (NOM-OHc, where c is the molar fraction of hydroxyl substitution in the polymer, and c = 0, 10, 20, 40, 60, 80, 100) were synthesized by direct high-temperature polycondensation. The synthesis employed a facile process. The monomer, 4,4'-(terephthaloylbis(azanediyl))bis(2-hydroxybenzoic acid), was prepared simply via an esterification reaction. The chemical structures of the soluble aramids were confirmed by 1H NMR. And the molecular weight and mass dispersity of the aramids were obtained by size exclusion chromatography, instead of the traditional intrinsic viscosity method. The use of unsymmetrical monomers and the introduction of hydroxyl side group into the aramid structure decrease the conjugation of the polymer main chain, and thus the resulting aramid has excellent solubility in relatively polar solvents, such as N-methy-2-pyrrolidone, dimethylsulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide. As a result, the molding processability of the aramids and their composites is greatly improved. For example, films can be made by solution spinning and casting. The films have good mechanical strength, with tensile strength, tensile modulus, and elongation at break in the range of 68–95 MPa, 2.65–3.12 GPa, and 5–10%. The thermal resistance of the aramids is still quite good, with 5% weight loss temperatures in nitrogen and in air in the range of 360–430 °C. A series of aramids containing hydroxyl side group were facilely prepared, with MWs determined by SEC. They have quite good thermal stability and excellent solubility in many organic solvents. They can be easily processed into flexible polymer films with excellent mechanical properties. These aramids have potential applications in composite materials. [Display omitted] ●Aramids containing hydroxyl side group prepared by direct high-temperature polycondensation●Molecular weight and mass dispersity determined by SEC instead of traditional intrinsic viscosity method●Quite good thermal stability and excellent solubility in many organic solvents●Flexible polymer films with excellent mechanical properties easily obtained