Nanoporous, honeycomb-structured network fibers spun from semiflexible, ultrahigh molecular weight, disubstituted aromatic polyacetylenes: Superhierarchical structure and unique optical anisotropy

A diaryl-substituted polyacetylene, poly[1-(trimethylsilyl)phenyl-2- phenylacetylene] (PTMSDPA), provided nanoporous, honeycomb-structured network fibers by electrospinning the chloroform solution with about 1.6 wt % polymer. The PTMSDPA fibers formed a nanoporous, honeycomb-network structure. These fibers emitted an intense yellowish green light. The main axis of yellowish green emission in the fiber appeared to be perpendicular to the fiber axis. The polarization ratio (I_⊥/I) in fluorescence (FL) attained a value of ∼4.7 and the FL peak band of the perpendicular axis (λ _max = 548 nm) was slightly red-shifted by 9 nm compared to that of the parallel one (λ_max = 539 nm). The ultrahigh M_w of 8.0 × 10⁵ and the relatively high α value of 0.765 were responsible for the lyotropic liquid crystallinity of PTMSDPA. The weak charge separation within the repeat unit of PTMSDPA was assumed to be responsible for the unique optical anisotropy of strong emission perpendicular to the fiber axis.