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Stronger aramids through molecular design and nanoprocessing

Abstract:

We introduce oligo-(1,6-pyrene terephthalamide, oPyrTA) as an oligoamide model for Kevlar®. Through comparison with an oligo-(p-phenylene terephthalamide, oPTA) of similar molecular weight, this work shows that the incorporation of polycyclic aromatic pyrene moieties improves drastically the mechanical properties of the structure, increasing elastic nanoindentation-determined modulus and hardness by factors of 1.9 and 4.3, respectively. Liquid deprotonated dispersions of oPyrTA nanofibers were used as nanoscale building blocks for producing large-surface, free-standing oligomer macroscopic nanofilms. This 2D assembly leads to further significant improvements in reduced modulus and hardness (more than twice) compared to the starting oligomer macroscale fibres, due to a better re-organizational arrangement of the oPyrTA nanofibers in the nanofilms, formed under 2D spatial confinement.