Preparation of High Strength and Toughness Aramid Fiber by Introducing Flexible Asymmetric Monomer to Construct Misplaced‐Nunchaku Structure

Abstract

High performance fibers with high strength and toughness have great potential in composites, but contradiction between tensile strength and elongation at break makes the preparation to become a current challenge. Herein, an asymmetric structure of more flexible diamine, 3,4′‐diaminodiphenyl ether (3,4′‐ODA), is introduced into heterocyclic aramid (PBIA) fibers to replace rigid symmetric p‐phenylenediamine (PDA). By studying the properties of copolymer (mPEBA) fibers with different ratios of diamine, it is found that the mPEBA fiber reached the optimal mechanical properties with the 30% content of 3,4′‐ODA. Compared with homopolymerized heterocyclic aramid fibers, the tensile strength and elongation at break of mPEBA fiber are improved by 26.2% and 38.7%, respectively. Results of X‐ray diffraction show that the introduction of 3,4′‐ODA structure can increase stretchability of mPEBA fibers, improving the orientation degree during hot‐drawing. Molecular dynamics simulations confirm that 3,4′‐ODA structure undergoes a conformation transformation to form a straightened chain during hot‐drawing, while symmetrical 4,4′‐diaminodiphenyl ether (4,4′‐ODA) cannot form the same conformation. The misplaced‐nunchaku structure is formed based on the special meta‐para position of 3,4′‐ODA, achieving the synergy of high strength and high toughness.

Novel, flexible, and transparent thin film polyimide aerogels with enhanced thermal insulation and high service temperature

“…108 As a result, it can act as an effective method in increasing toughness and maximum strain. 109 Following a similar strategy, in previous studies, it was shown that ODA with flexible –O– linkage can easily bend when the free rotation of the ether bond takes place. 109 This can explain the more flexible characteristic of the S1M sample compared to S2M.…”

Kevlar-like Aramid Polymers from Mixed PET Waste

“…As previously mentioned, aramid polymers are generally not characterized via GPC due to their stark insolubility in all organic solvents, with few reported exceptions. ,,− The soluble compounds typically require laborious syntheses to prepare monomers that impart some solubility to the aramid product in organic solvents. We were delighted to find an additive that provided partial or full solubility at 3 mg/mL of most of our polymeric analogues, which enabled GPC-SEC characterization of at least some of our polymers.…”

Synthesis and Characterization of Flexible Meta‐Aramid Modified with 4,4′‐Methylenedianiline

“…Several effective approaches were applied to improve the solubility of aromatic polyamide, including the introduction of flexible structural units, [20][21][22] largevolume side groups, [23,24] asymmetric structures, [25,26] or polar side groups to the backbone, [27][28][29] and the copolymerization monomers having nonplanar structures. [30,31] In addition, several methods also have been developed to improve the flexibility of PMIA.…”