Supramolecular Chirality in Achiral Polyfluorene: Chiral Gelation, Memory of Chirality, and Chiral Sensing Property

Abstract

Producing supramolecular chirality from achiral π-conjugated polymers toward preferred chiral memory, effective circularly polarized luminescence, and chiral sensor is extremely important in design of functional chiral materials. Proposed herein is an effective protocol to generate and memorize the supramolecular chirality formed from achiral poly­(9,9-dioctyl­fluorene) (PF8) induced by chiral solvation. The process of chiral supramolecular assembly was monitored by UV–vis spectroscopy, circular dichroism (CD), and fluorescent spectroscopy. Achiral PF8 dissolved in neat (R)-(+)-limonene (1R) and (S)-(−)-limonene (1S) underwent chiral sol–gel transition at −20 °C. PF8 aggregates revealed intense CD and circularly polarized luminescence (CPL) signals due to β-phase, exhibiting absolute dissymmetry ratio of ≈2 × 10–3 at 430–470 nm. The supramolecular chirality of PF8 aggregates can be perfectly memorized in solid film even near decomposition temperature (300 °C), comparing favorably with that from chiral polyfluorene. Atomic force microscopy (AFM) inferred helically distorted PF8 aggregate motifs responsible for the CD and CPL functionality. Furthermore, the first chiral sensor to detect nonracemic limonene molecules employing achiral PF8 spin-cast film from CHCl3 solution was achieved.

Supra‐dendron Gelator Based on Azobenzene–Cyclodextrin Host–Guest Interactions: Photoswitched Optical and Chiroptical Reversibility

“…Light is one of the most important stimuli since it is easily controlleda nd is largely nondestructive. [21][22][23][24][25] In order to realize chiroptical switching based on azobenzene, it is important to transfer chirality to the azobenzene moiety,s ince azobenzene itself is achiral.D uring such chiral transfer,s elf-assembly of the component molecules is necessary.H owever,i nm any cases, although strong p-p interactions between azobenzene moieties can assist self-assembly, they often cause irreversibility of the trans-cis isomerization. Photochromic groups, such as azobenzene, spiropyran, or dithienylethene, have been incorporated into the gels through covalent bonds or by as upramolecular approach.…”

Helicity Control of Triphenylamine‐Based Supramolecular Polymers: Correlation between Solvent Properties and Helicity in Supramolecular Gels

“…The chemical shift of the TPA aromatic protons of 1 was also larger than that of the terpyridine protons of 1 ( Figure S8), indicating strong p-p stacking between the TPAc omponents (as compared with the terpyridine components). In contrast, the chemical shift of the amide protons of the alanine moiety of 1 in [D 8 ]THF was nearly same as that of the achiral amide protons attached to the TPAc omponent ( Figures 4B,D), suggesting that both chiral and achiral amide moieties formed intermolecular hydrogen bonds with- www.chemeurj.org out any interference of solvent molecules. Additionally,t he chemicals hift of the terpyridine protons was 7-10 times larger than that of the TPAp rotons ( Figure S9).…”

“…[1][2][3][4][5] It plays ak ey role in many advanced functions in life. During the past two decades, there has been considerable researcho n the helicala rchitectureb ecause of its structural beauty,v ital roles in biologicals ystems, [6][7][8] and potentialf or practicala pplication, such as chiral separation [9][10][11][12][13] and asymmetric catalysis. [14][15][16][17][18] The helix is intrinsically chiral and is alwayse ither leftor right-handed.…”

Chiral Solvation Induced Supramolecular Chiral Assembly of Achiral Polymers

“…Meanwhile, many diverse factors, such as tersolvent composition, solvent polarity, polymer molecular weight, alkyl chain length, limonene enantiopurity, solution temperature, clockwise and counter-clockwise stirring, and aggregate size are confirmed to influence the magnitude of the induced CD and/or CPL amplitude. Through theoretical calculation, they assume that the inherent twisting ability (H-H repulsion) between the near- Zhang et al demonstrated that solvent chirality can be transferred to the aggregates of many optically inactive π-conjugated polymers with different backbone structures, such as main chain azo-containing polyfluorene (F8AZO), poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PF8), poly(9,9-di-noctylsila-fluorenyl-2,7-diyl) (PSi8), poly(9-(1-octylnonyl)-9H-carbazole-2,7-diyl) (PCz8), P(F8-alt-Si8), P(F8-alt-Cz8), and P(Si8-alt-Cz8), hyperbranched PF8s, side chain azo-containing polymers PAzoMA, P(AzoMA-rans-MMA), and star side-chain Azo polymers (star PAzoMAs) as shown in Figure 6 [69,[72][73][74][75][76]. Optically active F8AZO aggregates were successfully generated by the chirality transfer from (S)-and (R)-limonene, demonstrated by the intense ICD signals corresponding to F8AZO in the visible region [69].…”

“…This novel element-dependent chiroptical inversion and structural dependence of π-conjugated polymers with the help of limonene chirality in aggregation states pave a new way for designing chiroptical functional polymers. Furthermore, they successfully constructed the supramolecular chirality for CDsilent PF8 by cooling its limonene solution at low temperature [74]. More interestingly, the supramolecular chirality can be transferred to solid films and be perfectly memorized.…”