Search

Lithium bis(diisopropylphosphino)amide LiN[P(i-Pr)2]2 reacts with SnCl2 or GeCl2·dioxane in the presence of excess n-BuLi to produce the bicyclic compounds {MN[P(i-Pr)2]2}2 (M = Sn, Ge) which feature Sn22+ or Ge22+ units bridged by phosphorus. When paired with B(C6F5)3 in THF, the Lewis-basic M22+ complexes participate in a THF ring-opening reaction. Quite surprisingly, in the absence of THF one para-F atom from B(C6F5)3 is activated and displaced to B while a new M–C bond is formed. Each of these complexes, as well as Cl2Sn{N[P(i-Pr)2]2}2 and {ClSnN[P(i-Pr)2]2}2 were characterized by a combination of multi-nuclear NMR spectroscopy and single-crystal X-ray diffraction.

In this paper, we developed an exact analytical 3D elasticity solution to investigate mechanical behavior of a thick multilayered anisotropic fiber-reinforced pressure vessel subjected to multiple mechanical loadings. This closed-form solution was implemented in a computer program, and analytical results were compared to finite element analysis (FEA) calculations. In order to predict through-thickness stresses accurately, three-dimensional finite element meshes were used in the FEA since shell meshes can only be used to predict in-plane strength. Three-dimensional FEA results are in excellent agreement with the analytical results. Finally, using the proposed analytical approach, we evaluated structural damage and failure conditions of the composite pressure vessel using the Tsai–Wu failure criteria and predicted a maximum burst pressure.

Photoluminescence (PL) of single poly(3-hexylthiophene) (P3HT) J-aggregate nanofibers (NFs) exhibits strong quenching under intensity-modulated pulsed excitation. Initial PL intensities (I(0)) decay to steady-state levels (ISS) typically within ∼ 1-10 μs, and large quenching depths (I(0)/I(SS)2) are observed for ∼ 70% of these NFs. Similar studies of polymorphic, H-aggregate type P3HT NFs show much smaller PL quenching depths (I(0)/I(SS) ≤ 1.2). P3HT chains in J-type NF π-stacks possess high intrachain order, which has been shown previously to promote the formation of long-lived, delocalized polarons. We propose that these species recombine nongeminately to triplets on time scales of1 ns. The identity of triplets as the dominant PL quenchers was confirmed by subjecting NFs to oxygen, resulting in an instantaneous loss of triplet PL quenching (I(0)/I(SS) ∼ 1). The lower intrachain order in H-type NFs, similar to P3HT thin-film aggregates, localizes excitons and polarons, leading to efficient geminate recombination that suppresses triplet formation at longer time scales. Our results demonstrate the promise of self-assembly strategies to control intrachain ordering within multichromophoric polymeric aggregate assemblies to tune exciton coupling and interconversion processes between different spin states.