Directed Orientation of Oligo(phenylene ethynylene)s Using Ureas or Urethanes in Rod–Coil Copolymers

Abstract

Interchromophoric interactions between oligo(phenylene ethynylene)s incorporated in copolymers in solution as well as in solid state are investigated using UV/Vis and IR spectroscopy. One promising strategy to enable strong interchromophoric interactions is the introduction of hydrogen‐bonding moieties. Together with the tendency of the chromophores to self‐assemble via π–π‐stacking a dense packing of the chromophores within a polymer film can be achieved. In order to demonstrate this strategy, oligo(phenylene ethynylene)s are used as monomers for copolymers using the highly efficient blocked isocyanate route and polymer films are prepared by spin coating technique. The copolymers are prepared by an in situ deprotection of a pyrazol protected bis‐isocyanate functionalized rigid chromophore followed by subsequent polyaddition using a bis‐amine or bis‐alcohol linker unit. The specific introduction of urea as well as urethane moieties enhances coplanarization of the chromophores in the polymer films into well‐organized structures, which can be characterized based on their specific optical properties.

Optimizing the self‐assembly of conjugated polymers and small molecules through structurally programmed non‐covalent control

“…Hydrogen bonding interactions can enforce coplanarity of conjugated oligomers such as oligo (phenylene-ethynylenes) and other linear conjugated networks with dynamic covalent linkages (Figure 1). [24][25][26][27] For more rigid frameworks, intermolecular interactions between molecules are more prominent. 28,29 Latent hydrogen bonding, in which hydrogen bond donors are suppressed through thermally cleavable substituents, can further tune the rigidity of already-cast materials.…”

“…As with polymers, the intramolecular configuration, as well as the intermolecular assembly of oligomers can impact the semiconducting abilities of conjugated oligomers. Hydrogen bonding interactions can enforce coplanarity of conjugated oligomers such as oligo (phenylene‐ethynylenes) and other linear conjugated networks with dynamic covalent linkages (Figure 1) 24–27 . For more rigid frameworks, intermolecular interactions between molecules are more prominent 28,29 .…”

Side Chain Regioisomers that Dictate Optical Properties and Mechanofluorochromism through Crystal Packing

“…As they are not coupled to the conjugated system, incorporating directional interactions into side chains enables structural control that is orthogonal to the function of the main chain and broadly applicable for many classes of main chain structures. − Analogous to the design in Chart , our group’s previous work has demonstrated side chain engineering for guiding optical and responsive properties in phenylene-ethynylenes (PEs) via electron-poor fluoroarene pendants that cofacially stack with arenes in the PE chromophore (ArF–ArH interactions). − This robust aromatic stacking interaction is useful in a variety of contexts to direct molecular packing. − To accommodate these interactions, the PE linkages twist out of coplanarity by at least 55°, reducing conjugation. In addition, these ArF–ArH interactions insulate the PE chromophores from each other by blocking regions of overlap that are otherwise required for through-space coupling.…”

Photophysics of a Bis‐Furan‐Functionalized 4,7‐bis(Phenylethynyl)‐2,1,3‐benzothiadiazole: A Building Block for Dynamic Polymers

“…Films exhibit very similar absorption properties as samples in solution (Figure ), i. e., no change in the position of the absorption maximum (Table ), but show a very distinct broadening of the lowest energy absorption band of several 100 cm −1 (Table S1). While spectral broadenings of the absorption spectra of films of AEs have already been observed, their interpretation is not straight forward. Aggregation of chromophores can be excluded, as spectra of, e. g., dialkoxy‐substituted AE aggregates show distinct and sharp absorption bands .…”