β-Strand inspired bifacial π-conjugated polymers

Abstract

β-Strand inspired bifacial π-conjugated polymers that are soluble despite the absence of pendant solubilizing chains are reported. Precise tunability of the bifacial monomer height enables control of polymer solubility and intermolecular interactions.

Cycloparaphenylene-Norbornene Monomers Afford Access to Carbon Nanohoop-Based Polymers

“…In poly [8]CPP-random- [10]CPP, the fluorescence of the smaller hoops dominates the overall emission spectrum, indicating energy transfer between the hoop units. A related effect was recently observed in a heterocatenane composed of [9]CPP and [12]CPP. [41] Our observation of energy transfer in CPP copolymers suggests that CPP units can play a role in advanced emissive materials composed of multiple fluorophores.…”

“…For example, unlike in their linear counterparts, the HOMO-LUMO energy gap of CPPs decreases as the number of linked benzene rings decreases. This trend is also reflected in the red-shifting fluorescence emission as the hoop size decreases- [12]CPP has an emission maximum at 450 nm while [7]CPP emits at 587 nm. [19] Small structural changes, such as incorporation of donoracceptor motifs [20] or shifting the position of a bond, [21] can also be used to tune the electronics and optical properties of these molecules.…”

“…Properties intrinsic to each type of macrocyclic unit, such as intrinsic porosity and affinity for guest molecules, make macrocycle-based polymers extremely well-suited for relevant challenges such as ion sensing [5] and pollutant sequestration. [7,8,10,11] Cyclic side chains can also improve polymer solubility, [12] an advantage for materials processing. In a recent addition to this area, Hawker and coworkers showed that macrocyclic alkyl side chains in polymers retain the hydrophobicity of their linear counterparts while increasing the amorphous character of the polymers.…”

A twist in the non-slanted H-mers to control π-conjugation in 2-dimensions and optical properties

“…Based on our previous studies on cyclophane-based polymers, bifacial cyclophanes are shown to hinder p-p-interactions. 34 Even though the cyclophanes in H-mers are located only at the periphery and not on the benzimidazole and the rungs, they are efficient in masking the p-surface of H-mers and hindering p-p interactions in the aggregated state. In addition to this, the twist between the strands and rung in the H-mers also hinders the intermolecular p-p aggregation in thin films and therefore results in no significant changes in the absorption spectra of H-mers in solution and thin films.…”

“…The benzimidazole H-mers synthesized so far use conventional pendant solubilizing chains to impart solubility. 24 To obtain soluble H-mers, herein, we have employed bifacial cyclophanes that were reported by our group recently 34 and were shown to impart solubility to polymers without the need for pendant solubilizing chains. All the H-mers are readily soluble without heating in chloroform and dichloromethane.…”