# Fileset

[Angew Chem Int Ed - 2024 - Tateyama - Alkyl   Functional Molecular Gels  Control of Elastic Modulus and Improvement of.pdf](https://mdr.nims.go.jp/filesets/683a6cf4-a816-4e1f-8ee6-a4a6211a8321/download)

## Creator

[Akito Tateyama](https://orcid.org/0000-0002-0403-3462), [Kazuhiko Nagura](https://orcid.org/0000-0003-3910-1610), [Masamichi Yamanaka](https://orcid.org/0000-0002-6591-9005), [Takashi Nakanishi](https://orcid.org/0000-0002-8744-782X)

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Alkyl–π Functional Molecular Gels: Control of Elastic Modulus and Improvement of Electret Performance](https://mdr.nims.go.jp/datasets/65f89b9d-f251-4404-b0db-fcfdfc470170)

## Fulltext

Alkyl–π Functional Molecular Gels: Control of Elastic Modulus and Improvement of Electret PerformanceFunctional Molecular Gels Very Important PaperAlkyl–π Functional Molecular Gels: Control of Elastic Modulus andImprovement of Electret PerformanceAkito Tateyama, Kazuhiko Nagura, Masamichi Yamanaka†, and Takashi Nakanishi*Abstract: The development of optoelectronically-activesoft materials is drawing attention to the application ofsoft electronics. A room-temperature solvent-free liquidobtained by modifying a π-conjugated moiety withflexible yet bulky alkyl chains is a promising functionalsoft material. Tuning the elastic modulus (G’) is essentialfor employing optoelectronically-active alkyl–π liquidsin deformable devices. However, the range of G’achieved through the molecular design of alkyl–π liquidsis limited. We report herein a method for controlling G’of alkyl–π liquids by gelation. Adding 1 wt% low-molecular-weight gelator formed the alkyl–π functionalmolecular gel (FMG) and increased G’ of alkyl–π liquidsby up to seven orders of magnitude while retaining theoptical properties. Because alkyl–π FMGs have func-tional π-moieties in the gel medium, this new class ofgels has a much higher content of π-moieties of up to59 wt% compared to conventional π-gels of only a fewwt%. More importantly, the gel state has a 23% highercharge-retention capacity than the liquid, providingbetter performance in deformable mechanoelectric gen-erator-electret devices. The strategy used in this study isa novel approach for developing next-generation opto-electronically-active FMG materials.There is increasing demand for devices with flexiblecharacteristics such as stretchability, foldability, and deform-ability for healthcare applications, wearable sensing, andsoft robotics.[1–8] Sophisticated optoelectronically-active softmaterials with appropriate viscoelasticity are necessary fordeveloping such devices.[9–11] Alkyl–π functional molecularliquids (FMLs), which are designed as bulky yet flexiblebranched-alkyl chains attached to a π-conjugated moiety,are a promising optoelectronically-active soft material.[12–15]In addition to their liquid fluidity, alkyl–π FMLs canmaintain the optoelectronic functions inherent in the π-conjugated moieties even in the bulk neat liquid state.Attempts have been made to apply alkyl–π FMLs topractical devices such as microfluidic light-emittingdiodes[16,17] and stretchable mechanoelectric generator-elec-tret devices (MEGs).[18–21] Liquid fluidity has the advantageof shape adaptability; however, there are concerns aboutliquid leakage and bleeding from a support membrane withadsorbed liquid. Furthermore, improvements such as in-creased charge retention capability and elimination of theneed for support materials to immobilize liquid electrets arerequired, especially for MEG applications. One possiblesolution to meet these demands is to tune the elasticmodulus (G’) while preserving the softness and optoelec-tronic functionality of the alkyl–π FMLs. So far, the complexviscosity (jη* j) and G’ of alkyl–π FMLs have beencontrolled by altering the substitution position and thelength of the branched-alkyl chains.[22,23] The strategy ofincreasing G’ has also been demonstrated in the case ofalkyl–π conjugated polymer fluids,[24–26] where G’ can becontrolled by more than five orders of magnitude dependingon the branched alkyl chain length.[25] However, sincearranging the chemical structure for every alkyl–π conju-gated polymer fluid is a complicated and time-consumingprocess, a simple method of controlling G’ over a broaderrange is required to expand the usefulness of alkyl–π FMLs.In the present study, we developed alkyl–π functionalmolecular gels (FMGs), because gelation is the most helpfultechnique for dramatically adjusting G’ of liquids.[27–30] Sincegelation has been a blind spot in the research field of alkyl–πFMLs,[12–15] we first focused on investigating the fundamentalproperties of the formed gels that use a low-molecular-weight gelator.As for device applications, we focused on MEGs. Alkyl–π FMLs have an electroactive π-moiety wrapped withinsulating alkyl chains, making them suitable for storingelectrostatic charges inside the liquid and functioning asliquid electrets.[18–20] This study revealed that gelationimproves electret performance and eliminates the need forsupporting materials in MEG devices.To control G’ of various alkyl–π FMLs such as alkylatednaphthalene (C4C8NL,[31] C10C14NL, Figures 1a-i and 1a-ii),carbazole (C2C6CZL,[32] Figure 1a-iii), dicyanostyrylbenzene[*] A. Tateyama, Prof. Dr. T. NakanishiDivision of Soft Matter, Graduate School of Life ScienceHokkaido UniversityKita 10, Nishi 8, Kita-ku, Sapporo 060-0810, JapanE-mail: NAKANISHI.Takashi@nims.go.jpA. Tateyama, Dr. K. Nagura, Prof. Dr. T. NakanishiResearch Center for Materials Nanoarchitectonics (MANA)National Institute for Materials Science (NIMS)1-1 Namiki, Tsukuba 305-0044, JapanProf. Dr. M. YamanakaMeiji Pharmaceutical University (MPU)2-522-1 Noshio, Kiyose 204-8588, Japan[†] Deceased March 12, 2024.© 2024 The Authors. Angewandte Chemie International Editionpublished by Wiley-VCH GmbH. This is an open access article underthe terms of the Creative Commons Attribution License, whichpermits use, distribution and reproduction in any medium, providedthe original work is properly cited.AngewandteChemieCommunicationswww.angewandte.orgHow to cite: Angew. Chem. Int. Ed. 2024, 63, e202402874doi.org/10.1002/anie.202402874Angew. Chem. Int. Ed. 2024, 63, e202402874 (1 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbHhttp://orcid.org/0000-0002-0403-3462http://orcid.org/0000-0003-3910-1610http://orcid.org/0000-0002-6591-9005http://orcid.org/0000-0002-8744-782Xhttps://doi.org/10.1002/anie.202402874http://crossmark.crossref.org/dialog/?doi=10.1002%2Fanie.202402874&domain=pdf&date_stamp=2024-04-10(C10C14DCBL,[22] Figure 1a-iv) and pyrene (C8C12PL, Fig-ure 1a-v) were investigated in this study. C10C14NL (Support-ing Information, Scheme S1 and Figures S1–S5) andC8C12PL (Scheme S2, Figures S6–S13) were newly synthe-sized for this study. The above compounds are solvent-freeneat liquids at room temperature and are fluorescent, e.g.,blue, green, and light blue, derived from π-conjugatedmoieties under 365 nm ultraviolet (UV) light irradiation.The gels based on alkyl–π FMLs (FMGs) were preparedaccording to the scheme shown in Figure 1d. It is knownthat gelators having hydrogen-bonding units such as N,N’-((1S,2S)-cyclohexane-1,2-diyl)didodecanamide (GA1)[33] and1-(2-benzylphenyl)-3-dodecyl urea (GA2),[34] as shown inFigures 1e and 1f, cause gelation by forming fibrous self-assembled structures in solvents. GA1, which has two amideunits and is known for effectively gelating low-polarityorganic solvents[33,35] and liquid crystals,[36,37] was first em-ployed to gelate five types of alkyl–π FMLs. In anycombination, 1 wt% GA1 was dissolved in the alkyl–πFMLs at 130 °C and formed transparent fluids. It wasconfirmed by thermogravimetric analysis (TGA) that thesealkyl–π FMLs were thermally stable at 130 °C (Figure S14and reported literature[22,31]). All combinations createdphysical gels confirmed by the vial inversion test[33–35] whencooling the mixture to room temperature. The gelationmethod successfully tuned G’ of alkyl–π FMLs by over fiveto seven orders of magnitude while maintaining the intrinsicfluorescence properties under UV light irradiation (Fig-ure 1b, 1c, 2a, and S15). Since several types of FMLs withdifferent π-moieties and substitution patterns can controldifferent physical properties and functions,[22,23,38,39] thegelation of these FMLs would benefit the future develop-ment of various applications of alkyl–π FMGs. Interestingly,the π-moiety content of the C2C6CZL/GA1 gel reached59 wt%.Among these alkyl–π FMGs, we investigated the funda-mental properties of gels based on C4C8NL and C10C14NL,the jη* j of which was 0.046 and 0.096 Pa s at 25 °C,respectively, and the effect of the alkyl chain length on thegels’ physical properties was investigated. In addition toGA1, GA2 was also tested for gelating C4C8NL andC10C14NL; thus, four alkyl–naphthalene FMGs were pre-pared. GA2 has one urea unit, and it has been reported togelate a wide range of liquids, from low-polarity organicsolvents to ionic liquids.[34] The angular frequency (ω)-dependent rheological behavior of C4C8NL and its gel with1 wt% GA1 or GA2 were evaluated (Figure 2a). C4C8NLexhibited a loss modulus (G’’) over G’, and the slope of G’’was 1; it can be classified as a Newtonian liquid. When1 wt% of GA1 or GA2 was added to C4C8NL and formedFigure 1. a) Chemical structure of alkyl–π FML compounds utilized in this study, i) C4C8NL, ii) C10C14NL, iii) C2C6CZL, iv) C10C14DCBL, andv) C8C12PL. Photo images of b) neat liquid state of the alkyl–π FML compounds (i–v), and c) their gels formed with 1 wt% GA1, taken under365 nm UV light irradiation. Their complex viscosity (jη* j) and elastic modulus (G’) measured at 25 °C and angular frequency of ω=0.1 rads� 1 areshown in b) and c). d) Scheme of forming alkyl–π FMGs. Chemical structure of the low-molecular-weight gelators, e) GA1 and f) GA2, employed inthis study.AngewandteChemieCommunicationsAngew. Chem. Int. Ed. 2024, 63, e202402874 (2 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202402874 by Cochrane Japan, Wiley Online Library on [09/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensethe gels, G’ increased by over seven orders of magnitudeand became higher than G’’ for both cases. In addition, G’and G’’ were almost independent of ω. Figures 2b and S16ashow the strain (γ)-dependent rheology of the gels based onC4C8NL and C10C14NL, respectively, gelated by GA1 orGA2. The rheological parameters of each gel are summar-ized in Table 1. Strains below about 0.2% exhibited a linearviscoelastic region, and crossover points existed at strainsbetween about 14% and 50%. The frequency-dependentand strain-dependent rheological properties are typicalbehavior of conventional gels formed by low-molecular-weight gelators.[34,40] C4C8NL-based gels have a higher G’and a lower tan δ than C10C14NL-based gels. Since theviscosity of C4C8NL is lower than that of C10C14NL, thegelator molecules in C4C8NL seemed to diffuse more easilyin the sol–gel transition process during cooling, making itmore suitable than C10C14NL for forming a well-structuredfiber network.The fiber network structures of the gelators in C4C8NL/GA1 and C4C8NL/GA2 gels were confirmed by scanningelectron microscopy (SEM, Figure 2c) for their xerogelsprepared by extracting C4C8NL with n-hexane.[37] Thesefiber network structures contributed to the increase in G’ ofthe alkyl–π FMLs. In the C4C8NL/GA1 gel, as shown inFigure 2c-i, dense fibers were formed with an averagethickness of 95�28 nm (Figures 2c-i and S17), a similarthickness to that of the conventional organogels formed byGA1.[35] In contrast, in the xerogel prepared from theC4C8NL/GA2 gel, the average thickness of the fibers was363�113 nm (Figures 2c-ii and S17). These differences infiber thickness observed by SEM were qualitatively consis-tent with the optical (OM) and polarized optical microscopy(POM) images (Figure S18). They affected the transparencyof the gels (Figures 2c and S16b).[35,41] The C4C8NL/GA1 gelwas transparent because of the fine and thinner fibers ofGA1, whereas the C4C8NL/GA2 gel was turbid due to thethicker fibers of GA2 scattering the visible light. Theseresults are also supported by powder X-ray diffraction(PXRD) and small- and wide-angle X-ray scattering(SWAXS) measurements (Figure S19).The recovery behavior of a gel after it collapses due toan external force not only provides information about themolecular motion of the gelator but is also of practicalimportance. Hence, the thixotropy of the alkyl–naphthaleneFMGs was investigated. After applying a 100% strain (G’’>G’), the recovery rate and recovery time of G’ at 0.1% strain(G’>G’’) were analyzed. The G’ recovery rate of C4C8NL/GA1, C10C14NL/GA1, C4C8NL/GA2, and C10C14NL/GA2gels after 1 h from the 100% strain applied was confirmedto be 93%, 59%, 40%, and 24%, respectively (Figure S20).The G’ of C4C8NL gels recovered more efficiently than thatof C10C14NL gels. It is considered that the gels formed fromthe low-viscous C4C8NL, in which the gelator molecules canmove/diffuse more easily to restore the self-assembled fibernetwork structures and recover G’. The G’ recovery rates ofthe GA2 gels were slower than those of GA1. Recovery ofthese gels from the collapsed state was much slower thanthat of conventional organogels, which completes therecovery in tens of seconds to several minutes.[42,43]The thermal stability of the obtained gels exhibited asimilar trend to conventional organogels, such as concen-tration dependency (Figure S21) and weakening of thehydrogen bondings in the sol–gel transition (Figure S22).[44]The molecular dynamics of the gelated alkyl–naphthaleneliquid molecules were evaluated by diffusion coefficient (D)measurement of the 1H NMR stimulated echo method.[45–47]D is an index representing the degree of translationalmotion of a molecule. Figure 3a shows the D of C4C8NLmolecules depending on the gelator concentration. C4C8NLexhibited a D of 1.67×10� 11 m2s� 1. In the gel state, Ddecreased with an increase in the concentration of thegelator. Interfacial interactions near the gelator fibers couldreduce the translational motion of C4C8NL molecules. In thecase of C10C14NL, D did not decrease significantly aftergelation, and little difference was observed between thegelator species types (Figure S23). This may be due to thehigher viscosity, i.e., slower translational motion of C10C14NLcompared to C4C8NL, which makes it less susceptible to thegelator. In the C4C8NL/GA2 gel, the D of C4C8NL is largerthan that of the C4C8NL/GA1 gel. This can be understoodfrom the size of the gel fibers in their gels. The assembledthinner fibers of GA1 have a more extensive interface areaFigure 2. a) Angular frequency (ω)-dependent rheological behavior ofC4C8NL, 1 wt% C4C8NL/GA1 gel, and 1 wt% C4C8NL/GA2 gel. b) Strain(γ)-dependent rheological behavior of 1 wt% C4C8NL/GA1 gel and1 wt% C4C8NL/GA2 gel. c) Scanning electron microscopy (SEM)images of xerogels prepared from i) 1 wt% C4C8NL/GA1 gel andii) 1 wt% C4C8NL/GA2 gel. Inset photo images are the correspondinggels under visible light.Table 1: G’, G’’, tan δ, and crossover point of the gels based on C4C8NLand C10C14NL with 1 wt% GA1 or 1 wt% GA2.C4C8NL/GA1C10C14NL/GA1C4C8NL/GA2C10C14NL/GA2G’ (kPa) [a] 28.7 13.5 20.8 19.3G’’ (kPa) [a] 3.82 2.36 5.22 5.18tan δ[a,b] 0.133 0.176 0.251 0.268Crossover point (%) [c] 39.1 41.9 48.9 14.0[a] Strain=0.1%, Angular frequency=6.3 rad s� 1. [b] tan δ=G’’/G’.[c] γ value when G’=G’’ in strain sweep measurement.AngewandteChemieCommunicationsAngew. Chem. Int. Ed. 2024, 63, e202402874 (3 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202402874 by Cochrane Japan, Wiley Online Library on [09/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensebetween the fibers and the C4C8NL molecules compared tothat of the C4C8NL/GA2 gel. Notably, the liquid moleculesin the gels under any condition showed a D of about 80–90% compared to that of the neat liquid. Alkyl–π FMLsoften exhibit functionalities unique to their fluidity, such assolvent functions and structural transitions.[39,48–54] Sincefluidity is generally maintained even in the gel state, thesealkyl–π FMGs are expected to exhibit functionalities basedon the fluidity peculiar to alkyl–π FMLs.Optical properties of neat alkyl–naphthalene liquids arealso retained in the gel state. Solvent-free alkyl–naphthaleneliquids show a broad fluorescence peak compared to thedilute solution state (0.1 mM) in n-hexane due to theirexcimeric luminescence.[31] The absorption and fluorescencespectra of the gels exhibited almost identical features tothose of the liquids (Figures 3b, S16c, and S24). Thefluorescence lifetime and quantum yield were also lessaffected by gelation (Figure S25, Tables S1 and S2). Inconventional π-gels consisting of organic solvent and gelatorowning π-moieties, the content of the π-moieties is only afew wt% in the gels.[28,29] In contrast, alkyl–π FMGs arepresumed to exhibit high functionality due to their highcontent of π-moieties. Regarding this point, we comparedthe fluorescence intensity between a conventional organogeland the C4C8NL/GA1 gel. The content of the naphthylmoieties in organogels obtained by gelating n-hexane with 1and 3 wt% of a gelator containing naphthyl groups (GA3,[55]Figure S26a) was only 0.2 and 0.6 wt%, respectively. Incontrast, the C4C8NL/GA1 gel had a 40 wt% content ofnaphthyl moiety in the gel and emitted stronger fluorescenceunder UV light irradiation (Figures S26b–c). In addition,conventional organogels turn into xerogels in the air withina few hours because of the volatilization of organic solvents(Figure S26d). In contrast, alkyl–π FMLs have a low-volatility; thus, the FMGs can be stably handled in the airfor a long period, i.e., over 10 months in the dark at roomtemperature (23�3 °C, Figure S16d).Among the alkyl–π FMLs, C8C12PL is suitable for anelectret application because a relatively wide π-conjugatedunit is entirely covered with insulating alkyl chains (Fig-ure S27a and Table S3), as reported in the electretization ofalkyl–porphyrin[20] and alkyl–fullerene liquids.[18] Sincebleeding causes a problem when forming MEGs with alkyl–π FMLs,[20] fabrication with the gel state is advantageous forconstructing highly durable MEGs. First, we evaluated thecharge retention capacity. The polyurethane (PU) non-woven fabric impregnated with C8C12PL (Figure S28) andC8C12PL/GA1 (1 wt%) gel (Figure S29) was electrified bypositive corona discharging at 100 °C for 30 min, and thencharging was continued for over 30 min until cooling toroom temperature (Figure S27b). C8C12PL/GA1 gel exhib-ited an electrical charge of 0.12 Cm� 3, approximately 24%larger than C8C12PL (0.097 Cm� 3), and had a longer chargeretention (Figure 4a). Since GA1 alone shows only a littlecharge retention, enhancement of electret performance bygelation is considered to result from the increase in G’. Inthis positive corona discharging process, electrificationoccurs during the process from sol to gel transition; there-Figure 3. a) Diffusion coefficient of C4C8NL depending on the concen-tration of GA1 and GA2. b) Normalized absorption (solid lines) andfluorescence (FL) spectra (dashed lines) of 0.1 mM dilute solution ofC4C8NL in n-hexane, solvent-free C4C8NL, 1 wt% C4C8NL/GA1 gel, and1 wt% C4C8NL/GA2 gel.Figure 4. a) Changes over time in the charge amount of nonwovenfabric containing C8C12PL liquid and C8C12PL/GA1 gel after coronadischarge measured by a Coulomb meter. b) Device structure andphoto image of MEG. c) Mechanism of mechanoelectric generation.Waveform of open-circuit voltage of MEGs fabricated with d) C8C12PL,1 wt% C8C12PL/GA1 gel e) with and f) without supporting fabric, whencontinuous vibration (frequency=16.7 Hz) was applied.AngewandteChemieCommunicationsAngew. Chem. Int. Ed. 2024, 63, e202402874 (4 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202402874 by Cochrane Japan, Wiley Online Library on [09/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensefore, charged species, e.g., N2+*, O2+*, H3O+*, could beefficiently captured in the C8C12PL/GA1 gel, resulting inhigher electret performance. The charge density of theC8C12PL/GA1 gel was three times higher than that of atypical stretchable polymer electret (0.04 Cm� 3).[56]MEGs were fabricated using PU nonwoven fabricimpregnated with C8C12PL and C8C12PL/GA1 gel (Fig-ure 4b). The PU nonwoven fabric was sandwiched betweendeformable silver electrodes and a PU masking layer. Thedevice was approximately 130 mg in weight and 200 μm inthickness. Figure 4c explains the mechanism of mechano-electric generation. When a force is applied to push thedevice, the distance between the electrodes is reduced,resulting in an electric current. The device formed with theC8C12PL/GA1 gel exhibited an open-circuit voltage (Voc)about 83�4% higher than the C8C12PL-based MEG undera continuously applied 16.7 Hz vibration (Figures 4d, 4e, andS30a, Table S4). Regarding the change in Voc over the courseof days, the gel device maintained a higher Voc than theliquid one (Figure S31). When we utilize liquid materials forelectrets,[18,20] we must impregnate them into the nonwovensupporting fabric to prevent short circuits due to contactbetween the electrodes (Figure S30b). In contrast, there isno contact between electrodes even without the supportingfabric in the case of gels with improved elasticity comparedto liquids, and it showed a vibration power generationfunction of 64�5% Voc compared to the device withsupporting fabric (Figure 4f and Table S4). When a vibrationof 16.7 Hz was applied to the C8C12PL/GA1 gel in a vial, thegel shape was maintained (Supplementary movies S1 andS2). In addition, the Voc of the gel device was almostconstant even when the continuous vibration was applied for10 min (Figure S30c). Therefore, during the MEG operation,gel collapse may not occur. Importantly, no liquid leakagefrom the gel MEG devices was observed. Furthermore, sincethe gel MEG device is deformable, it worked even whenfolded or bent (Figures S30d–h). Since C8C12PL/GA1 acts asa matrix for stably storing charged species, degradation orelectrochemical reaction in C8C12PL/GA1 due to coronadischarging was not confirmed (Figures S32 and S33a).Therefore, C8C12PL/GA1 can be extracted from usedelectrets and employed as an ingredient in electrets again(Figure S33b).In conclusion, we developed a method for controlling G’of alkyl–π FMLs by gelation, i.e., the formation of alkyl–πFMGs. Blue, green, and light blue fluorescent alkyl–π FMLswere gelated by low-molecular-weight gelators havinghydrogen-bonding units. The G’ of these liquids wereincreased by five to seven orders of magnitude whileretaining their optical properties. The sol–gel transitiontemperature and rheological properties can be modulated bythe alkyl chain length of the alkyl–π FMLs and the speciesof the gelators; however, D of more than 80% compared tothe liquids was preserved in the gels. This suggests that thefluidity of the liquid molecules is well maintained in the gelstate, although G’ of the materials changes significantly. Thealkyl–pyrene FMG worked for mechanoelectric generationwithout liquid leakage and even without supporting fabric,and its performance was remarkably improved comparedwith the device with the liquid. Using gelation, G’ of thealkyl–π FMLs could be adjusted to a region close to therange of G’ of human body organs (101 to 105 Pa).[57]Therefore, this technique will expand the potential of alkyl–π FMLs/FMGs for biological applications. To further expandthe types of alkyl–π FMGs and realize more advancedfunctions, it is necessary to introduce stimuli-responsiveunits into gelator molecules.[58–66] These attempts will enablethe development of novel alkyl–π FMGs that can be appliedto various fields such as healthcare, sensing, and soft-robotics.AcknowledgementsThis work was supported by the World Premier Interna-tional Research Center Initiative (WPI), MEXT, Japan. Wethank Ms. Keiko Sano and Dr. Xiao Zheng (NIMS) for theircooperation in the synthesis of C8C12PL and C10C14DCBL,respectively, Dr. Naoaki Kuwata (NIMS) for assistance withthe diffusion coefficient measurement, and Dr. AkiraShinohara (NIMS) for insightful discussions.Conflict of InterestThere are no conflicts to declare.Data Availability StatementThe data that support this study are available in thesupplementary material of this article.Keywords: π-gels · functional molecular liquids ·low-molecular-weight gelators · luminescence · electretmaterials[1] C. Majidi, Adv. Mater. Technol. 2018, 1800477.[2] T. Someya, Z. Bao, G. G. Malliaras, Nature 2016, 540, 379–385.[3] C. Wang, C. Wang, Z. Huang, S. Xu, Adv. Mater. 2018, 30,1801368.[4] Y. Jiang, Z. Zhang, Y.-X. Wang, D. Li, C.-T. Coen, E. Hwaun,G. Chen, H.-C. Wu, D. Zhong, S. Niu, W. Wang, A. Saberi, J.-C. Lai, Y. Wu, Y. Wang, A. A. Trotsyuk, K. Y. Loh, C.-C.Shih, W. Xu, K. Liang, K. Zhang, Y. Bai, G. Gurusankar, W.Hu, W. Jia, Z. Cheng, R. H. Dauskardt, G. C. Gurtner, J. B.-H.Tok, K. Deisseroth, I. Soltesz, Z. Bao, Science 2022, 375, 1411–1417.[5] J. Xu, S. Wang, G.-J. N. Wang, C. Zhu, S. Luo, L. Jin, X. Gu,S. Chen, V. R. Feig, J. W. F. To, S. Rondeau-Gagné, J. Park,B. C. Schroeder, C. Lu, J. Y. Oh, Y. Wang, Y.-H. Kim, H. Yan,R. Sinclair, D. Zhou, G. Xue, B. Murmann, C. Linder, W. Cai,J. B.-H. Tok, J. W. Chung, Z. Bao, Science 2017, 355, 59–64.[6] C. Larson, B. Peele, S. Li, S. Robinson, M. Totaro, L. Beccai,B. Mazzolai, R. Shepherd, Science 2016, 351, 1071–1074.[7] M. Ha, S. Lim, H. Ko, J. Mater. Chem. B 2018, 6, 4043–4064.[8] W.-C. Gao, J. Qiao, J. Hu, Y.-S. Guan, Q. Li, ResponsiveMater. 2024, 2, e20230022.AngewandteChemieCommunicationsAngew. Chem. Int. Ed. 2024, 63, e202402874 (5 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202402874 by Cochrane Japan, Wiley Online Library on [09/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://doi.org/10.1038/nature21004https://doi.org/10.1126/science.abj7564https://doi.org/10.1126/science.abj7564https://doi.org/10.1126/science.aah4496https://doi.org/10.1126/science.aac5082https://doi.org/10.1039/C8TB01063C[9] A. Shinohara, Z. Guo, C. Pan, T. Nakanishi, Org. Mater. 2021,3, 309–320.[10] S. E. Root, S. Savagatrup, A. D. Printz, D. Rodriquez, D. J.Lipomi, Chem. Rev. 2017, 117, 6467–6499.[11] X. Hu, B. Lei, S.-S. Li, L.-J. Chen, Q. Li, Responsive Mater.2023, 1, e20230009.[12] A. Ghosh, T. Nakanishi, Chem. Commun. 2017, 53, 10344–10357.[13] F. Lu, T. Nakanishi, Adv. Opt. Mater. 2019, 7, 1900176.[14] F. Lu, T. Nakanishi, Sci. Technol. Adv. Mater. 2015, 16, 014805.[15] Functional Organic Liquids (Ed.: T. Nakanishi), Wiley-VCH,Weinheim 2019.[16] T. Kasahara, S. Matsunami, T. Edura, J. Oshima, C. Adachi, S.Shoji, J. Mizuno, Sens. Actuators A Phys. 2013, 195, 219–223.[17] N. Kobayashi, T. Kasahara, T. Edura, J. Oshima, R. Ishimatsu,M. Tsuwaki, T. Imato, S. Shoji, J. Mizuno, Sci. Rep. 2015, 5,14822.[18] R. K. Gupta, M. Yoshida, A. Saeki, Z. Guo, T. Nakanishi,Mater. Horiz. 2023, 10, 3458–3466.[19] A. Shinohara, M. Yoshida, C. Pan, T. Nakanishi, Polym. J.2023, 55, 529–535.[20] A. Ghosh, M. Yoshida, K. Suemori, H. Isago, N. Kobayashi, Y.Mizutani, Y. Kurashige, I. Kawamura, M. Nirei, O. Yamamuro,T. Takaya, K. Iwata, A. Saeki, K. Nagura, S. Ishihara, T.Nakanishi, Nat. Commun. 2019, 10, 4210.[21] Z. Guo, Y. Patil, A. Shinohara, K. Nagura, M. Yoshida, T.Nakanishi, Mol. Syst. Des. Eng. 2022, 7, 537–552.[22] X. Zheng, K. Nagura, T. Takaya, K. Hashi, T. Nakanishi,Chem. Eur. J. 2023, 29, e202203775.[23] F. Lu, T. Takaya, K. Iwata, I. Kawamura, A. Saeki, M. Ishii, K.Nagura, T. Nakanishi, Sci. Rep. 2017, 7, 3416.[24] V. C. Wakchaure, S. D. Veer, A. D. Nidhankar, V. Kumar, A.Narayanan, S. S. Babu, Angew. Chem. Int. Ed. 2023, 62,e202307381; Angew. Chem. 2023, 135, e202307381.[25] Z. Guo, A. Shinohara, C. Pan, F. J. Stadler, Z. Liu, Z.-C. Yan,J. Zhao, L. Wang, T. Nakanishi, Mater. Horiz. 2020, 7, 1421–1426.[26] A. Shinohara, C. Pan, Z. Guo, L. Zhou, Z. Liu, L. Du, Z. Yan,F. J. Stadler, L. Wang, T. Nakanishi, Angew. Chem. Int. Ed.2019, 58, 9581–9585; Angew. Chem. 2019, 131, 9682–9686.[27] R. Laishram, S. Sarkar, I. Seth, N. Khatun, V. K. Aswal, U.Maitra, S. J. George, J. Am. Chem. Soc. 2022, 144, 11306–11315.[28] S. Panja, D. J. Adams, Chem. Soc. Rev. 2021, 50, 5165–5200.[29] S. S. Babu, V. K. Praveen, A. Ajayaghosh, Chem. Rev. 2014,114, 1973–2129.[30] R. G. Weiss, J. Am. Chem. Soc. 2014, 136, 7519–7530.[31] B. Narayan, K. Nagura, T. Takaya, K. Iwata, A. Shinohara, H.Shinmori, H. Wang, Q. Li, X. Sun, H. Li, S. Ishihara, T.Nakanishi, Phys. Chem. Chem. Phys. 2018, 20, 2970–2975.[32] E. Hendrickx, B. D. Guenther, Y. Zhang, J. F. Wang, K. Staub,Q. Zhang, S. R. Marder, B. Kippelen, N. Peyghambarian,Chem. Phys. 1999, 245, 407–415.[33] K. Hanabusa, M. Yamada, M. Kimura, H. Shirai, Angew.Chem. Int. Ed. 1996, 35, 1949–1951; Angew. Chem. 1996, 108,2086–2088.[34] T. Komiyama, Y. Harada, T. Hase, S. Mori, S. Kimura, M.Yokoya, M. Yamanaka, Chem. Asian J. 2021, 16, 1750–1755.[35] H. Nakagawa, M. Fujiki, T. Sato, M. Suzuki, K. Hanabusa,Bull. Chem. Soc. Jpn. 2017, 90, 312–321.[36] T. Kato, T. Kutsuna, K. Hanabusa, M. Ukon, Adv. Mater.1998, 10, 606–608.[37] K. Yabuuchi, A. E. Rowan, R. J. M. Nolte, T. Kato, Chem.Mater. 2000, 12, 440–443.[38] Y. Yamamoto, F. Lu, T. Nakanishi, S. Hayashi, J. Phys. Chem.B 2023, 127, 4870–4885.[39] A. Tateyama, T. Nakanishi, Responsive Mater. 2023, 1,e20230001.[40] H. Sawada, M. Yamanaka, Chem. Asian J. 2018, 13, 929–933.[41] J. N. Loos, C. E. Boott, D. W. Hayward, G. Hum, M. J.Maclachlan, Langmuir 2021, 37, 105–114.[42] A. Dawn, H. Kumari, Chem. Eur. J. 2018, 24, 762–776.[43] Y. Ohsedo, M. Oono, A. Tanaka, H. Watanabe, New J. Chem.2013, 37, 2250.[44] N. Mohmeyer, H.-W. Schmidt, Chem. Eur. J. 2007, 13, 4499–4509.[45] J. Kowalczuk, A. Rachocki, M. Bielejewski, J. Tritt-Goc, J.Colloid Interface Sci. 2016, 472, 60–68.[46] M. Yemloul, E. Steiner, A. Robert, S. Bouguet-Bonnet, F.Allix, B. Jamart-Grégoire, D. Canet, J. Phys. Chem. B 2011,115, 2511–2517.[47] J. Kowalczuk, S. Jarosz, J. Tritt-Goc, Tetrahedron 2009, 65,9801–9806.[48] M. J. Hollamby, M. Karny, P. H. H. Bomans, N. A. J. M.Sommerdjik, A. Saeki, S. Seki, H. Minamikawa, I. Grillo, B. R.Pauw, P. Brown, J. Eastoe, H. Möhwald, T. Nakanishi, Nat.Chem. 2014, 6, 690–696.[49] S. S. Babu, M. J. Hollamby, J. Aimi, H. Ozawa, A. Saeki, S.Seki, K. Kobayashi, K. Hagiwara, M. Yoshizawa, H. Möhwald,T. Nakanishi, Nat. Commun. 2013, 4, 1969.[50] S. S. Babu, J. Aimi, H. Ozawa, N. Shirahata, A. Saeki, S. Seki,A. Ajayaghosh, H. Möhwald, T. Nakanishi, Angew. Chem. Int.Ed. 2012, 51, 3391–3395; Angew. Chem. 2012, 124, 3447–3451.[51] A. Ikenaga, Y. Akiyama, T. Ishiyama, M. Gon, K. Tanaka, Y.Chujo, K. Isoda, ACS Appl. Mater. Interfaces 2021, 13, 47127–47133.[52] K. Isoda, Y. Sato, D. Matsukuma, ChemistrySelect 2017, 2,7222–7226.[53] T. Ogoshi, K. Maruyama, Y. Sakatsume, T. Kakuta, T.Yamagishi, T. Ichikawa, M. Mizuno, J. Am. Chem. Soc. 2019,141, 785–789.[54] X. Zheng, R. K. Gupta, T. Nakanishi, Curr. Opin. ColloidInterface Sci. 2022, 62, 101641.[55] X. Wang, P. Duan, M. Liu, Chem. Asian J. 2014, 9, 770–778.[56] S. Zhang, Y. Wang, X. Yao, P. L. Floch, X. Yang, J. Liu, Z.Suo, Nano Lett. 2020, 20, 4580–4587.[57] T. R. Cox, J. T. Erler, Dis. Models Mech. 2011, 4, 165–178.[58] M. Martínez-Abadía, R. K. Dubey, M. Fernández, M. Martín-Arroyo, R. Aguirresarobe, A. Saeki, A. Mateo-Alonso, Chem.Sci. 2022, 13, 10773–10778.[59] M. Kawaura, T. Aizawa, S. Takahashi, H. Miyasaka, H.Sotome, S. Yagai, Chem. Sci. 2022, 13, 1281–1287.[60] S. M. M. Reddy, P. Dorishetty, G. Augustine, A. P. Desh-pande, N. Ayyadurai, G. Shanmugam, Langmuir 2017, 33,13504–13514.[61] S. Mukherjee, T. Kar, P. K. Das, Chem. Asian J. 2014, 9, 2798–2805.[62] M. K. Nayak, J. Photochem. Photobiol. A 2011, 217, 40–48.[63] C. Vijayakumar, V. K. Praveen, A. Ajayaghosh, Adv. Mater.2009, 21, 2059–2063.[64] T. Kitahara, N. Fujita, S. Shinkai, Chem. Lett. 2008, 37, 912–913.[65] K. Yabuuchi, Y. Tochigi, N. Mizoshita, K. Hanabusa, T. Kato,Tetrahedron 2007, 63, 7358–7365.[66] S. J. George, A. Ajayaghosh, Chem. Eur. J. 2005, 11, 3217–3227.Manuscript received: February 8, 2024Accepted manuscript online: March 21, 2024Version of record online: April 10, 2024AngewandteChemieCommunicationsAngew. Chem. Int. Ed. 2024, 63, e202402874 (6 of 6) © 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH 15213773, 2024, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/anie.202402874 by Cochrane Japan, Wiley Online Library on [09/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttps://doi.org/10.1021/acs.chemrev.7b00003https://doi.org/10.1039/C7CC05883Ghttps://doi.org/10.1039/C7CC05883Ghttps://doi.org/10.1088/1468-6996/16/1/014805https://doi.org/10.1016/j.sna.2012.12.031https://doi.org/10.1039/D3MH00485Fhttps://doi.org/10.1038/s41428-022-00725-whttps://doi.org/10.1038/s41428-022-00725-whttps://doi.org/10.1039/D1ME00180Ahttps://doi.org/10.1039/D0MH00029Ahttps://doi.org/10.1039/D0MH00029Ahttps://doi.org/10.1002/anie.201903148https://doi.org/10.1002/anie.201903148https://doi.org/10.1002/ange.201903148https://doi.org/10.1021/jacs.2c03230https://doi.org/10.1021/jacs.2c03230https://doi.org/10.1039/D0CS01166Ehttps://doi.org/10.1021/cr400195ehttps://doi.org/10.1021/cr400195ehttps://doi.org/10.1021/ja503363vhttps://doi.org/10.1039/C7CP05584Fhttps://doi.org/10.1016/S0301-0104(99)00049-Xhttps://doi.org/10.1002/anie.199619491https://doi.org/10.1002/anie.199619491https://doi.org/10.1002/ange.19961081719https://doi.org/10.1002/ange.19961081719https://doi.org/10.1002/asia.202100433https://doi.org/10.1246/bcsj.20160360https://doi.org/10.1002/(SICI)1521-4095(199805)10:8%3C606::AID-ADMA606%3E3.0.CO;2-Thttps://doi.org/10.1002/(SICI)1521-4095(199805)10:8%3C606::AID-ADMA606%3E3.0.CO;2-Thttps://doi.org/10.1021/cm9904887https://doi.org/10.1021/cm9904887https://doi.org/10.1021/acs.jpcb.2c08385https://doi.org/10.1021/acs.jpcb.2c08385https://doi.org/10.1002/asia.201800217https://doi.org/10.1021/acs.langmuir.0c02464https://doi.org/10.1002/chem.201703374https://doi.org/10.1039/c3nj00450chttps://doi.org/10.1039/c3nj00450chttps://doi.org/10.1002/chem.200601154https://doi.org/10.1002/chem.200601154https://doi.org/10.1016/j.jcis.2016.03.033https://doi.org/10.1016/j.jcis.2016.03.033https://doi.org/10.1021/jp200281fhttps://doi.org/10.1021/jp200281fhttps://doi.org/10.1016/j.tet.2009.09.073https://doi.org/10.1016/j.tet.2009.09.073https://doi.org/10.1038/nchem.1977https://doi.org/10.1038/nchem.1977https://doi.org/10.1021/acsami.1c13119https://doi.org/10.1021/acsami.1c13119https://doi.org/10.1002/slct.201701412https://doi.org/10.1002/slct.201701412https://doi.org/10.1021/jacs.8b12253https://doi.org/10.1021/jacs.8b12253https://doi.org/10.1016/j.cocis.2022.101641https://doi.org/10.1016/j.cocis.2022.101641https://doi.org/10.1002/asia.201301518https://doi.org/10.1021/acs.nanolett.0c01434https://doi.org/10.1242/dmm.004077https://doi.org/10.1039/D2SC02637Fhttps://doi.org/10.1039/D2SC02637Fhttps://doi.org/10.1039/D1SC06246Hhttps://doi.org/10.1021/acs.langmuir.7b03453https://doi.org/10.1021/acs.langmuir.7b03453https://doi.org/10.1002/asia.201402358https://doi.org/10.1002/asia.201402358https://doi.org/10.1016/j.jphotochem.2010.09.014https://doi.org/10.1002/adma.200802932https://doi.org/10.1002/adma.200802932https://doi.org/10.1246/cl.2008.912https://doi.org/10.1246/cl.2008.912https://doi.org/10.1016/j.tet.2007.03.121https://doi.org/10.1002/chem.200401178https://doi.org/10.1002/chem.200401178 Alkyl–π Functional Molecular Gels꞉ Control of Elastic Modulus and Improvement of Electret Performance Acknowledgements Conflict of Interest Data Availability Statement