Facially amphiphilic (FA) phenylene ethynylene (PE) polymers that self-assemble in aqueous solution were studied by small-angle X-ray diffraction (SAXD) and found to self-assemble into bilayers with a fully extended backbone. The resulting bilayers have long-range liquid-crystalline order. This self-assembly is programmed into the molecule by placing polar and nonpolar groups at precise locations so that they segregate onto opposite sides of the molecular structure. The absence of FA patterning generated an amorphous sample confirming the importance of this programmed amphiphilicity in the self-assembly process. Facially amphiphilic patterning represents a new design criterion for supramolecular chemistry, illustrated here in the observation of molecular ordering into bilayers reminiscent of self-assembled structures commonly found in biology, including amphiphilic beta-sheet polypeptides and phospholipid bilayers. 相似文献
A sterically encumbered m‐terphenyl oxacyclophane substituted with two aryl iodide substituents has been prepared as a versatile monomer for the preparation of π‐conjugated polymers. The monomer has been used to prepare a poly(p‐phenylene ethynylene) derivative (P1) incorporating oxacyclophane units as canopies that shield one side of the π‐system from inter‐chain interactions. The photophysical properties of P1 in dilute solution compare well to those of a poly(p‐phenylene ethynylene) derivative (P2) that lacks the canopy. The presence of the steric canopy leads to a diminished inter‐chain interaction in the solid state and enhances the kinetic response of P1 to vapors of nitro‐organics such as TNT, presumably by increasing the permeability of P1 to these analytes over that of P2.
The optical properties of a series of π-conjugated phenylene-ethynylene oligomers (OPEs) have been studied by advanced quantum chemical methods. The ground state and lowest singlet excited state geometries of unsubstituted and different electron donor and acceptor groups substituted OPEs are optimized by density functional theory and configuration interaction singles methods. The absorption and emission spectra of unsubstituted and substituted OPEs have been calculated using the time-dependent density functional theory (TDDFT) method. The results of theoretical calculations are in good agreement with the available experimental results. It has been found that the substitution of electron donating and withdrawing groups in the phenyl ring and conjugation length of the OPEs has significantly affect both the absorption and emission spectra 相似文献