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[Shuntaro Uenuma](https://orcid.org/0000-0003-0693-9310), Di Liu, Kohzo Ito

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[Solvent dispersibility of two-dimensional particles with pseudo- and permanently interlocked polyethylene oxide brushes](https://mdr.nims.go.jp/datasets/a27791c2-0836-4904-b601-59965ca47263)

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Solvent dispersibility of two-dimensional particles with pseudo- and permanently interlocked polyethylene oxide brushesRSC AdvancesPAPEROpen Access Article. Published on 18 May 2026. Downloaded on 5/28/2026 3:29:38 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineView Journal  | View IssueSolvent dispersibaInternational Center for Young Scientists,1-2-1, Sengen, Tsukuba, Ibaraki 305-0047, JbDepartment of Advanced Materials Science,University of Tokyo, Kashiwa City, Chiba 27cResearch Center for Macromolecules anMaterials Science, 1-2-1 Sengen, Tsukuba, ICite this: RSC Adv., 2026, 16, 26299Received 17th January 2026Accepted 11th May 2026DOI: 10.1039/d6ra00421krsc.li/rsc-advances© 2026 The Author(s). Published byility of two-dimensional particleswith pseudo- and permanently interlockedpolyethylene oxide brushesShuntaro Uenuma, *a Di Liub and Kohzo Ito *bcThe solvent dispersibility of two-dimensional particles with pseudo- and permanently interlockedpolyethylene oxide brushes was investigated. Their dispersibility was determined by desorption orretention of the polyethylene oxide axis of two-dimensional particles. This study provides new insightinto controlling the dispersion and aggregation of particles.The dispersibility of particles with sizes ranging from severalnanometers to micrometers in solvents is important for prac-tical applications in the food industry, pharmaceuticals, nano-carriers, cosmetics, inks, and glues.1–5 van der Waalsinteractions generally occur between particles in this size range;therefore, steric repulsions of graed polymer chains are widelyused for ensuring high colloidal stability.6–8 Polymer chainscovalently graed to particles endow them with long-termstability. Meanwhile, controlling the dispersion and aggrega-tion of particles is also important for the development ofstimuli-responsive materials for environmental remediation,biological applications, sensing, and photonics.9–11 Forexample, proteins containing charged and hydrophobic groupsenable charge control in response to pH, thereby regulatingtheir dispersion and aggregation.12–14 Poly(N-iso-propylacrylamide) possesses a low critical solution temperatureof 32 °C that allows a reversible transformation between thehydrophobic aggregated and hydrophilic solvated states.15,16Photoisomerization-induced steric changes in azobenzenederivatives that occur on the particle surface can also be used tocontrol the dispersion and aggregation states.17–19Molecular architecture designs can also be used forcontrolling material properties. Mechanically interlockedstructures, such as rotaxane-type interlocked molecules,possess unique functions, which include rotating, shuttling,and location switching, owing to the mobility of the ring and/oraxis components.20–22 The design of interlocked structures doesnot compete with the introduction of functional chemicalstructures, allowing their simultaneous incorporation intoa material. Therefore, the introduction and design ofNational Institute for Materials Science,apanGraduate School of Frontier Sciences, The7-8561, Japand Biomaterials, National Institute forbaraki 305-0047, Japanthe Royal Society of Chemistryinterlocked molecular structures on the particle surface may beeffective for controlling dispersion and aggregation.Cyclodextrin-based (pseudo-)polyrotaxane self-assemblysystems are promising for the development of stimuli-responsive nano- and micro-scale materials.23–27 Our grouphas reported the fabrication of nanosheet particles witha rotaxane structure, i.e., pseudo-polyrotaxane nanosheets(PPRNS) (Fig. 1a).28 They are prepared by mixing b-cyclodextrin(b-CyD) and poly(ethylene oxide)75-b-poly(propylene oxide)29-b-poly(ethylene oxide)75 (EO75PO29EO75) in water. b-CyD selec-tively covers the central PO region and this inclusion complexassembly in a nanosheet particle consisting of a single-crystallayer of b-CyD with a thickness of 11 nm (equal to the lengthof a PO segment) and interlocked EO brushes on its surface.29,30PPRNS represent an analyzable model system with a well-dened morphology and molecular structure. In this study,we investigated the dispersion and aggregation behavior ofFig. 1 (a) Schematic of PPRNS formation. (b) Schematics of thedispersion behavior of PPRNS and capped PPRNS in solvents. Thedispersion and aggregation of PPRNS are governed by the retention(left) or desorption (center) of EO75PO29EO75 from the b-CyD crys-talline core, while capped PPRNS retain EO75PO29EO75 in varioussolvents, resulting in stable dispersion (right).RSC Adv., 2026, 16, 26299–26302 | 26299http://crossmark.crossref.org/dialog/?doi=10.1039/d6ra00421k&domain=pdf&date_stamp=2026-05-16http://orcid.org/0000-0003-0693-9310http://orcid.org/0000-0002-1798-3811http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d6ra00421khttps://pubs.rsc.org/en/journals/journal/RAhttps://pubs.rsc.org/en/journals/journal/RA?issueid=RA016029RSC Advances PaperOpen Access Article. Published on 18 May 2026. Downloaded on 5/28/2026 3:29:38 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlinePPRNS and axis-end-capped PPRNS (capped PPRNS) containingpseudo- and permanently interlocked EO brushes in varioussolvents, focusing on the behavior of the axis polymer (Fig. 1b).Amine-terminated EO75PO29EO75 was used for the preparationof PPRNS, enabling subsequent capping via a click reactionbetween the NH2 groups and bulky trimethylolpropane tri-glycidyl ether in water.30 The results revealed that the dispersionand aggregation of PPRNS are governed by the retention anddesorption of EO75PO29EO75 from the CyD crystalline core andthat the capped PPRNS can hold the EO75PO29EO75 in varioussolvents, resulting in good dispersion.The solvent for PPRNS and capped PPRNS was varied fromwater to organic solvents following the procedure described inFig. 2a, and their dispersibility was evaluated via opticalmicroscopy (OM, SI S3). The behaviors of PPRNS and cappedPPRNS in various solvents are summarized in Table 1. ThePPRNS aggregated in many types of organic solvents, while thecapped PPRNS exhibited good dispersion in almost all solvents,with the exception of hexane. The speeds of formation ofFig. 2 (a) Solvent exchange protocol for transferring the PPRNS dispersioof particles collected via centrifugation (dissolved in DMSO-d6), and scheand (c) organic solvents (acetone and 15C5E) are shown. The numbers in timages.26300 | RSC Adv., 2026, 16, 26299–26302aggregation were typically very fast (immediately aer theaddition, within several seconds).As representative examples, PPRNS aggregation in acetoneand its dispersion in water and 15C5E are shown in Fig. 2b andc. The precipitated PPRNS were collected via centrifugation, andits composition was analyzed using 1H nuclear magnetic reso-nance (NMR). For PPRNS in water, the integral of the b-CyDpeak was set to 100 as the standard, and that of the axis CH3signal was 70. Meanwhile, for PPRNS in acetone, the integral ofthe axis was signicantly reduced (6, Fig. 2c). This indicates thedesorption of EO75PO29EO75 from the b-CyD cavity, which leadsto particle aggregation. The desorption is caused by the highaffinity of the axis for acetone. The EO75PO29EO75 in b-CyDcavity is thought to be replaced with solvent molecules. Aerbeing dispersed in acetone, PPRNS was dissolved in water,which also support that the fact of desorption of EO75PO29EO75.Meanwhile, PPRNS in 15-crown-5 ether (15C5E) (bulky liquid)was well dispersed (Fig. 2c) over one week. The 1H NMR resultsindicated that the axis polymer was retained within the PPRNSstructure (Fig. 2c). This likely occurs because 15C5E has highn from water to various organic solvents. OM images, 1H NMR spectramatics of the dispersion or aggregation behavior of PPRNS in (b) waterhe 1H NMR spectra represent integral values. The scale bar applies to all© 2026 The Author(s). Published by the Royal Society of Chemistryhttp://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d6ra00421kTable 1 Dispersibility of PPRNS and capped PPRNS in a series of solventsaH2O 15C5Ef MeOH EtOH Acetone THFg DEGDMEh CHCl3 EtOAci PGMEAj Hexane DMSOPPRNS B B ×b ×b ×c ×c ×c ×d ×d ×d ×d DissolvedCapped PPRNS B B B B B B B Be Be Be ×e Dissolveda B: Dispersed. ×: not dispersed. b Gradual morphological change to large crystal. c Axes were desorbed. d Low affinity of solvents for water is onereason for aggregation. e Solvents were changed from MeOH (miscible for both organic solvents and water). f 15-Crown-5-ether. g Tetrahydrofuran.h Diethylene glycol dimethyl ether. i Ethyl acetate. j Propylene glycol 1-monomethyl ether 2-acetate.Paper RSC AdvancesOpen Access Article. Published on 18 May 2026. Downloaded on 5/28/2026 3:29:38 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlineaffinity for the EO segment but cannot enter the b-CyD cavityowing to steric hindrance. As a result, the axial structure inPPRNS is maintained, leading to high dispersibility of PPRNS.As a prerequisite for the dispersibility of PPRNS, the EOsegmentsmust be solvated; however, this can lead to desorptionof EO75PO29EO75 from the b-CyD cavity, as observed in PPRNSdispersed in acetone. Because many types of organic solventmolecules are smaller than the b-CyD cavity, they can readilyenter the cavity unless this process is highly unfavorable,leading to the desorption of the axis polymer and PPRNSaggregation. In contrast, 15C5E and water are unique solventsthat keep PPRNS well dispersed. Although both solvents cansolvate EO brushes, their penetration into the b-CyD cavity isenergetically unfavorable, owing to steric hindrance for 15C5Eand strong hydrogen bonding among water molecules forwater.31,32Next, the capped PPRNS was prepared by end-capping viaa click reaction between NH2 groups of PPRNS and bulky tri-methylolpropane triglycidyl ether in neutral water at roomtemperature.30 Its dispersibility was investigated (solventexchange to a water-immiscible solvent was performed usingthe capped PPRNS dispersion in MeOH, which is miscible withboth water and the organic solvent). The capped PPRNSexhibited good dispersibility in a range of organic solvents (OMimages of capped PPRNS in acetone are shown in Fig. 3a, whilethose in other organic solvents are presented in SI S3). Forcapped PPRNS in acetone, compositional analysis via 1H NMRindicated the retention of EO75PO29EO75 (Fig. 3b). These resultsFig. 3 (a) Schematic of the synthesis of capped PPRNS from PPRNSand OM images of capped PPRNS dispersed in acetone. (b) 1H NMRspectrum of capped PPRNS in DMSO-d6 (the numbers denote theintegrals). (c) Schematic of the PPRNS dispersion in acetone.© 2026 The Author(s). Published by the Royal Society of Chemistrysuggest that the permanent interlocking of EO75PO29EO75endows PPRNS with high dispersibility in various solvents byretaining the axis (Fig. 3c). Consistent with this interpretation,the capped PPRNS did not disperse in hexane (SI S3), where thePEO brushes are not solvated.The morphology of PPRNS in ethanol (EtOH) and methanol(MeOH) was slowly changed from nanosheet to microcrystal (SIS2). This slow transformation (from 5 to 60 min) is probablycaused by the balance among the low solubility of b-CyD, thelow binding constant of the b-CyD cavity with MeOH and EtOH,and the slow axis desorption. Accurate prediction of PPRNSbehavior requires additional quantitative studies. In contrast toPPRNS, the capped PPRNS particles remained stable for overone week.Changing the solvent of PPRNS from water to CHCl3, EtOAc,PGMEA, or hexane induced aggregation. The immiscibility ofthese solvents with water makes the solvent exchange imper-fect, and this is probably one reason for the aggregation.Despite being immiscible, for PPRNS in CHCl3, compositionalanalysis (1H NMR) indicated the desorption of the axis of PPRNS(the integral ratio of the axis CH3 signal to the b-CyD signal wasreduced from 70/100 to 21/100 aer solvent exchange). Thisimplies that PPRNS aggregate in water-immiscible organicsolvents that have high affinity for the axis polymer, even if thesolvent exchange proceeds successfully.The dispersion and aggregation behavior of PPRNS andcapped PPRNS in various organic solvents have been system-atically investigated. Based on these ndings, the factors thatdetermine the dispersion, aggregation, and structural behaviorof PPRNS are outlined below.(1) Affinity of solvent for PEO brushes: the solvent shouldhave high affinity with the PEO moieties for dispersion. Inhexane, capped PPRNS aggregate because of the poor solvationof the PEO brush.(2) Retention and desorption of the axis polymer: for PPRNSin solvents that are good for PEO brushes, retention of the axispolymer within the cavity of the b-CyD crystal is crucial formaintaining dispersion. In contrast, PPRNS aggregate when theaxis polymer is desorbed.(3) Balance between axis-polymer retention and desorption:the stability of the axis polymer in the cavity of the b-CyD crystalis determined by the balance between the dissolution of thepolymer from the cavity and the subsequent occupation of thecavity by solvent molecules. In most solvents, PPRNS aggregateas a result of axis-polymer dissolution with subsequent occu-pation by solvent molecules. In contrast, PPRNS retained theRSC Adv., 2026, 16, 26299–26302 | 26301http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d6ra00421kRSC Advances PaperOpen Access Article. Published on 18 May 2026. Downloaded on 5/28/2026 3:29:38 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlineaxis polymer and remained well dispersed in water and 15C5E,likely because these solvents do not penetrate the b-CyD cavity.(4) End-capping: end-capping of the axis in PPRNS preventsdesorption of the axis polymer from the cavity of the b-CyDcrystal, resulting in stable dispersion in a wide range ofsolvents.(5) Dissolution in DMSO: both PPRNS and capped PPRNSdissolve in DMSO owing to the high solubility of b-CyD. Thisenables compositional analysis of PPRNS and capped PPRNSvia solution 1H NMR.(6) Morphological transformation in ethanol or methanol: inethanol or methanol, both the axis polymer and b-CyD of PPRNSmay slowly dissolve, causing morphological transformationinto large crystals. Further dynamic and kinetic analysis wouldbe required to clarify these processes.In this study, we examined the dispersion behavior of PPRNSand capped PPRNS, which are two-dimensional particlesfeaturing pseudo- and permanently interlocked PEO brushes.The well-denedmorphology andmolecular structure of PPRNSenabled analysis of their dispersion and aggregation behavior,providing a foundation for interpretating, predicting, andcontrolling the dispersibility of particles with interlocked(including entangled) polymers. This study provides a newinsight into controlling the dispersion and aggregation ofparticles.Conflicts of interestThere are no conicts to declare.Data availabilityThe data supporting the ndings of this study are availablewithin the article or its supplementary information (SI).Supplementary information is available. See DOI: https://doi.org/10.1039/d6ra00421k.References1 E. J. W. Verwey, J. Phys. Colloid Chem., 1947, 51, 631–636.2 F. Liu, D. J. McClements, C. Ma and X. Liu, Annu. Rev. FoodSci. Technol., 2023, 14, 35–61.3 M. J. Mitchell, M. M. Billingsley, R. M. Haley, M. E. Wechsler,N. A. Peppas and R. Langer, Nat. Rev. Drug Discovery, 2021,20, 101–124.4 L. Salvioni, L. Morelli, E. Ochoa, M. Labra, L. Fiandra,L. Palugan, D. Prosperi and M. Colombo, Adv. ColloidInterface Sci., 2021, 293, 102437.5 M. Aguirre, N. Ballard, E. Gonzalez, S. Hamzehlou,H. Sardon, M. Calderon, M. Paulis, R. Tomovska, D. Dupin,R. H. Bean, T. E. Long, J. R. Leiza and J. M. 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Published by the Royal Society of Chemistryhttps://doi.org/10.1039/d6ra00421khttps://doi.org/10.1039/d6ra00421khttp://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d6ra00421k Solvent dispersibility of two-dimensional particles with pseudo- and permanently interlocked polyethylene oxide brushes Solvent dispersibility of two-dimensional particles with pseudo- and permanently interlocked polyethylene oxide brushes Solvent dispersibility of two-dimensional particles with pseudo- and permanently interlocked polyethylene oxide brushes Solvent dispersibility of two-dimensional particles with pseudo- and permanently interlocked polyethylene oxide brushes