Semi-convertible Hydrogel Enabled Photoresponsive Lubrication

•Endowing the capability of partly gel-sol transition to hydrogel•Exhibiting reversible appearance sol-lubricating layer triggered by UV/Vis light•Integrating responsive supramolecular network within polymer framework Supramolecular hydrogel with unique responding external stimuli has exhibited unprecedented superiority in constructing smart materials exceptional features, such as lubrication, self-healing, and high mechanical strength. The cooperation between non-covalent bonding covalent may provide one new type supramolecule-tuned functional that can switch their state solid liquid-solid under stimulus. Here, we demonstrate a semi-convertible composed stable stimuli-responsive network, which exhibits photoresponsive lubricating ability toughness. We believe this concept is now emerging from infant stage show more promising applications far beyond leading an branch interdisciplinary science integrates chemistry, hydrogel, surface science. 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(PSCH) was simple one-pot method (Figure 1). brief, mixing solution I (mixture ?-CD, AzoPB, PEG) II AAm monomers, PVA, N,N-methylenebisacrylamide, potassium persulfate, glutaraldehyde) irradiation. volume ratio (1:20, 1:25, 1:50, 1:75, 1:100), PSCHs abbreviated PSCH20, PSCH25, PSCH50, PSCH75, PSCH100. preparation three interpenetrating were networks; uncombined cis-AzoPB molecule dissociative 1i). flexible entangled networks. For gelation, ?-CDs assembled at ends chain, domains aggregated another chain form crosslink.41Li Kamachi Sol-gel inclusion ?-cyclodextrin molecular weight glycol)s solution.Polym. 1994; 26: 1019-1026Crossref (281) Scholar,42Guan J.J. X.F. J.D. Preparation action mechanism ?-cyclodextrin sulfurized isobutylene additives polyethylene glycol-600.J. Wuhan Univ. Technol. Mater 859-867Crossref (4) not distributed along whole might attributed being so long had already occurred before included middle chain. When irradiated Vis, dissociated changed its trans form, disassembled brought trans-AzoPB. transferred containing ?-CD/trans-AzoPB chains 1ii). appeared first; time increasing, further gradually inner side. Here most coiled difficult exude out entanglement resulted skeleton changing much. Therefore, no significant change observed scanning electron microscopy (SEM) S1). However, some segments or still have exposed participating PEG. treated again, cis disassembly ?-CD/AzoPB, again gel. experiment, synthesized first according previous work.36Liao 1H nuclear magnetic resonance (NMR) spectrum D2O S2) successfully. fracture increased decrease contents S3). easily destroyed bringing weak relatively unstable corresponding content these decreased slightly 94.1% 92.1% following (Table test performed ball-on-disk reciprocating tribometer. ceramic Al2O3 contact ball diameter 5 mm moved rectilinear manner sliding velocity load force. Because rich, crucial surface,43Ma L.R. 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By controlling humidity, FCs obviously either 2B). each relative setpoint 20%, 40%, 60%, 80%, 98%. 98% (0.0018 0.0014 0.0160 0.0019 irradiation) similar condition (0.0045 irradiation), closed saturated humidity. conclude benefit behavior but bring about change. experiment mainly observation behaviors PSCHs, regulated (Figures 2C 2D). kept 25 125 higher Table S2), 2C). These results consistent classic theory f = ?F (where force, ? frictional coefficient, F load). fitted showed 0.0177 0.0032 0.0033 0.0011, respectively. theoretical matched well experimental 2A. addition, pressure calculated Hertzian mechanism.45Fischer-Cripps A.C. surface.J. 1999; 34: 129-137Crossref (68) understanding process, p0, radius a, penetration depth d mechanism:p0=(6FE?2?3R2)1/3,(Equation 1) a=(3FR4E?)1/3,(Equation 2) d=?ap02E?,(Equation 3) load, R (5 mm), E? approximated low-frequency around 6 × 103 N/m2 4B). shown 1, maximal 3.27 kPa mN experiment. Moreover, 0.10 1.00 velocity. proportional when viscosity, area, thickness assumed constant.46Gong Iwasaki Kurihara Hamai Friction gels. 3. surfaces.J. 103: 6001-6006Crossref (132) 2D phenomenon different concentrations 2E). difference contents.Table 1Contact Pressure, Contact Radius, Penetration Depth BallLoad (mN)255075100125Contact (kPa)1.912.412.753.033.27Contact (mm)2.503.153.613.974.27Penetration (mm)1.251.982.603.153.66 Open table tab To identify transition, directly profiled 3A). routine histology cut slices. evaporation avoided procedure, Figures 3A 3B analyzed qualitatively. Following very quickly, soon 3 3B), reached 90 ?m Simultaneously force-distance detection terms instron testing system. 3C, curve 60 thin-tipped probe vertically 8.3 ?m/s. close zero tip contacted 3Ci); there sharp dropoff touched capillarity 3Cii); become moving layer, subsequently 3Ciii). distance layer. Comparing results, reach 3Di) 3Dii), plateau appearing. indicates 4A. good repeatability even five cycles. reversibly right side During accompanying engendered properties. 4B. seen among PSCHs. reversibility verified S6). result 4B, photoisomerization Vis. enthalpy value (?H 21.50 J/g) melt temperature (Tmelt 67.9°C) those 13.45 J/g; Tmelt 65.3°C) 4C), mechanism, designed preparing kinds polydimethylsiloxane (PDMS) surface: (1) PEG, onto PDMS substrate; (2) ?-CD/AzoPB solution; (3) coating. 0.0238 0.0007 (gel state) 0.0011 0.0002 (sol state), respectively 5A). At same time, both substrate S7), indicating (?-CD, AzoPB). interestingly, (0.0024 0.0006) (pink 5A) gel-state (1), participate 0.0187 0.0025, without (0.0259 0.0036) (0.0238 0.0007), (2). generating Generally, UV-visible investigating trans/cis derivatives. case, immersed extracted measured. adsorption peaks 330 430 nm observed, assigned ?-?? n-?? 5B).47Xie G.H. Z.J. Z.P. Kong Xiao L.P. 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Irradiation https://www.cell.com/cms/asset/44bf6a12-5186-4428-a02a-f398b65f35bc/mmc3.mp4Loading (2.57 S2. conclusion, (?-CD/PEG), polymeric (PVA PAAm), AzoPB. introduced aim Due interaction, partial PSCH. composite acted main reversibility. switchable just robotics, anti-fouling, devices. burgeoning integration science,