Self-assembly of Poly(p-phenylene terephthalamide) Nanofibrils: Emergence of Structural Defects

We provide molecular level insights on the self-assembly mechanisms of poly(p-phenylene terephthalamide) (poly(PPTA)) chains in a strong solvent by using large scale molecular dynamics simulations based on a rigorous development of a coarse-grained potential model. Ordered liquid crystalline phases of poly(PPTA)_n chains facilitated by the solvent are reported for various polymer lengths, n and initial configurations. We find that the degree of hydrogen bond (H-bond) plane ordering depends sensitively on the polymer length and initial polymer alignments. Our largescale simulations suggest an increased propensity of grain boundary formation parallel to the H-bond direction with guided initial configuration. Our results reveal that the trapping of solvent nanoclusters within the ordered domains of poly(PPTA) fibrils give rise to structural defects.