Critical Review
Polymer Mechanochemistry on Reactive Species Generated from Mechanochemical Reactions†
Xiaolong Chen,
Hang Shen,
Zhengbiao Zhang,
Xiaolong Chen
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123 China
Search for more papers by this authorCorresponding Author
Hang Shen
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123 China
E-mail: [email protected]; [email protected]Search for more papers by this authorCorresponding Author
Zhengbiao Zhang
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123 China
E-mail: [email protected]; [email protected]Search for more papers by this authorXiaolong Chen,
Hang Shen,
Zhengbiao Zhang,
Xiaolong Chen
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123 China
Search for more papers by this authorCorresponding Author
Hang Shen
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123 China
E-mail: [email protected]; [email protected]Search for more papers by this authorCorresponding Author
Zhengbiao Zhang
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123 China
E-mail: [email protected]; [email protected]Search for more papers by this authorDedicated to the Special Issue of Emerging Themes in Polymer Science.
Abstract
Comprehensive Summary
Polymer mechanochemistry on reactive species has attracted more and more attentions over the past 20 years, as the mechanochemical generation of reactive species has a great potential in developing different polymeric materials for various purposes, such as stress detection, self-healing, self-strengthening, controllable degradation and release of small molecules. In this review, we first discuss the recent progress on polymer mechanochemistry of the reactive species that are generated from the mechanochemical reactions of mechanophores. Five types of reactive species, including radical, zwitterion, ionic, carbene and neutral intermediates, and their applications were reviewed in detail. Since mechanochemical reactions are sensitive to the mechanophore structure and polymer framework, we then discuss how mechanophore isomerism, polymer structure, polymer attachment point, and polymer architecture influence the mechanophore activation. At last, we provide our perspectives on the polymer mechanochemistry of reactive species.
Key Scientists
In the 1930s, a seminal work by Staudinger showed that the molecular weight of poly(styrene) reduced after mastication. However, polymer mechanochemistry mainly focused on the destructive effects of mechanical force, until Moore reported that the azo-mechanophore was cleaved selectively upon sonication in 2005. Afterwards, his group also found that mechanical force changed the reaction pathway of benzocyclobutene and made spiropyran display purple color under stress. In 2009, Sijbesma revealed that metal–NHC could be used as a latent catalyst to catalyze transesterification and polymerization. Subsequently, the Craig group disclosed the special mechanical reactivity of perfluorocyclobutane in 2011 and examined the influence of polymer backbone on the reactivity of epoxides in 2012. Later, they also reported that the lever-arm effect enhanced gDBC or gDCC mechanochemistry. Since 2015, Otsuka's group has developed a series of mechanophores that generated various carbon radicals and showed different colors under mechanical force. De Bo subsequently investigated the effect of regio- and stereochemistry on the reactivity of furan–maleimide adduct in 2017, and he examined the different mechanisms of the mechanical activation of tetrafluorobenzene–NHC (N-heterocyclic carbene) adduct in 2020. During that time, the Choi group explored the influence of polymer architecture on the mechanophore activation, and Robb's group utilized a furan-maleimide adduct to achieve the release of different small molecules. In 2020, Göstl and Herrmann employed the scission of the disulfide within polymers to release drugs and reporting molecules by ultrasound, and the Chen group also investigated the mechanochemistry of diselenides which afforded selenium radicals. In 2021, Boydston's group realized the “flex-activation” of NHC-carbodiimide to release NHC small molecules. Recently, the Chen group achieved multistate mechanochromism by combining two Rh structures together through a conjugated connector. In addition, Robb designed a furan-maleimide adduct to mechanically give a donor–acceptor Stenhouse adduct that reacted with different amines to display various colors. This review has focused on the chemistry of reactive species that are generated from mechanochemical reactions.
References
- 1 Chen, Y.; Mellot, G.; van Luijk, D.; Creton, C.; Sijbesma, R. P. Mechanochemical tools for polymer materials. Chem. Soc. Rev. 2021, 50, 4100–4140.
- 2 Ghanem, M. A.; Basu, A.; Behrou, R.; Boechler, N.; Boydston, A. J.; Craig, S. L.; Lin, Y.; Lynde, B. E.; Nelson, A.; Shen, H.; Storti, D. W. The role of polymer mechanochemistry in responsive materials and additive manufacturing. Nat. Rev. Mater. 2020, 6, 84–98.
- 3 Li, J.; Nagamani, C.; Moore, J. S. Polymer mechanochemistry: from destructive to productive. Acc. Chem. Res. 2015, 48, 2181–2190.
- 4 Hu, X.; Zeng, T.; Husic, C. C.; Robb, M. J. Mechanically Triggered Small Molecule Release from a Masked Furfuryl Carbonate. J. Am. Chem. Soc. 2019, 141, 15018–15023.
- 5 Qi, Q.; Sekhon, G.; Chandradat, R.; Ofodum, N. M.; Shen, T.; Scrimgeour, J.; Joy, M.; Wriedt, M.; Jayathirtha, M.; Darie, C. C.; Shipp, D. A.; Liu, X.; Lu, X. Force-Induced Near-Infrared Chromism of Mechanophore-Linked Polymers. J. Am. Chem. Soc. 2021, 143, 17337–17343.
- 6 Lin, Y.; Barbee, M. H.; Chang, C.-C.; Craig, S. L. Regiochemical Effects on Mechanophore Activation in Bulk Materials. J. Am. Chem. Soc. 2018, 140, 15969–15975.
- 7 Zheng, Y.; Jiang, J.; Jin, M.; Miura, D.; Lu, F. X.; Kubota, K.; Nakajima, T.; Maeda, S.; Ito, H.; Gong, J. P. In Situ and Real-Time Visualization of Mechanochemical Damage in Double-Network Hydrogels by Prefluorescent Probe via Oxygen-Relayed Radical Trapping. J. Am. Chem. Soc. 2023, 145, 7376–7389.
- 8 Jakobs, R. T. M.; Ma, S.; Sijbesma, R. P. Mechanocatalytic Polymerization and Cross-Linking in a Polymeric Matrix. ACS Macro Lett. 2013, 2, 613–616.
- 9 Hemmer, J. R.; Rader, C.; Wilts, B. D.; Weder, C.; Berrocal, J. A. Heterolytic Bond Cleavage in a Scissile Triarylmethane Mechanophore. J. Am. Chem. Soc. 2021, 143, 18859–18863.
- 10 Staudinger, H.; Leupold, E. O. Über Isopren und Kautschuk, 18. Mitteil.: Viscositäts-Untersuchungen an Balata. Berichte der deutschen chemischen Gesellschaft (A and B Series) 2006, 63, 730–733.
- 11 Takacs, L. The historical development of mechanochemistry. Chem. Soc. Rev. 2013, 42, 7649–7659.
- 12 McFadden, M. E.; Robb, M. J. Force-Dependent Multicolor Mechanochromism from a Single Mechanophore. J. Am. Chem. Soc. 2019, 141, 11388–11392.
- 13 Qian, H.; Purwanto, N. S.; Ivanoff, D. G.; Halmes, A. J.; Sottos, N. R.; Moore, J. S. Fast, reversible mechanochromism of regioisomeric oxazine mechanophores: Developing in situ responsive force probes for polymeric materials. Chem 2021, 7, 1080–1091.
- 14 Hertel, R.; Maftuhin, W.; Walter, M.; Sommer, M. Conformer Ring Flip Enhances Mechanochromic Performance of ansa-Donor-Acceptor-Donor Mechanochromic Torsional Springs. J. Am. Chem. Soc. 2022, 144, 21897–21907.
- 15 Shen, H.; Cao, Y.; Lv, M.; Sheng, Q.; Zhang, Z. Polymer mechanochemistry for the release of small cargoes. Chem. Commun. 2022, 58, 4813–4824.
- 16 Küng, R.; Göstl, R.; Schmidt, B. M. Release of Molecular Cargo from Polymer Systems by Mechanochemistry. Chem. - Eur. J. 2022, 28, e202103860.
- 17 Hsu, T. G.; Zhou, J.; Su, H. W.; Schrage, B. R.; Ziegler, C. J.; Wang, J. A Polymer with "Locked" Degradability: Superior Backbone Stability and Accessible Degradability Enabled by Mechanophore Installation. J. Am. Chem. Soc. 2020, 142, 2100–2104.
- 18 Wang, J.; Kouznetsova, T. B.; Boulatov, R.; Craig, S. L. Mechanical gating of a mechanochemical reaction cascade. Nat. Commun. 2016, 7, 13433.
- 19 Lin, Y.; Kouznetsova, T. B.; Chang, C. C.; Craig, S. L. Enhanced polymer mechanical degradation through mechanochemically unveiled lactonization. Nat. Commun. 2020, 11, 4987.
- 20 Imato, K.; Nishihara, M.; Kanehara, T.; Amamoto, Y.; Takahara, A.; Otsuka, H. Self-healing of chemical gels cross-linked by diarylbibenzofuranone-based trigger-free dynamic covalent bonds at room temperature. Angew. Chem. Int. Ed. 2012, 51, 1138–1142.
- 21 Hager, M. D.; Greil, P.; Leyens, C.; van der Zwaag, S.; Schubert, U. S. Self-healing materials. Adv. Mater. 2010, 22, 5424–5430.
- 22 Wang, S.; Urban, M. W. Self-healing polymers. Nat. Rev. Mater. 2020, 5, 562–583.
- 23 Matsuda, T.; Kawakami, R.; Namba, R.; Nakajima, T.; Gong, J. P. Mechanoresponsive self-growing hydrogels inspired by muscle training. Science 2019, 363, 504–508.
- 24 Verstraeten, F.; Gostl, R.; Sijbesma, R. P. Stress-induced colouration and crosslinking of polymeric materials by mechanochemical formation of triphenylimidazolyl radicals. Chem. Commun. 2016, 52, 8608–8611.
- 25 Seshimo, K.; Sakai, H.; Watabe, T.; Aoki, D.; Sugita, H.; Mikami, K.; Mao, Y.; Ishigami, A.; Nishitsuji, S.; Kurose, T.; Ito, H.; Otsuka, H. Segmented Polyurethane Elastomers with Mechanochromic and Self-Strengthening Functions. Angew. Chem. Int. Ed. 2021, 60, 8406–8409.
- 26 Chen, Z.; Mercer, J. A. M.; Zhu, X.; Romaniuk, J. A. H.; Pfattner, R.; Cegelski, L.; Martinez, T. J.; Burns, N. Z.; Xia, Y. Mechanochemical unzipping of insulating polyladderene to semiconducting polyacetylene. Science 2017, 357, 475–479.
- 27 Izak-Nau, E.; Campagna, D.; Baumann, C.; Göstl, R. Polymer mechanochemistry-enabled pericyclic reactions. Polym. Chem. 2020, 11, 2274–2299.
- 28 Wiggins, K. M.; Brantley, J. N.; Bielawski, C. W. Polymer Mechanochemistry: Force Enabled Transformations. ACS Macro Lett. 2012, 1, 623–626.
- 29 Lenhardt, J. M.; Ogle, J. W.; Ong, M. T.; Choe, R.; Martinez, T. J.; Craig, S. L. Reactive cross-talk between adjacent tension-trapped transition states. J. Am. Chem. Soc. 2011, 133, 3222–3225.
- 30 Hickenboth, C. R.; Moore, J. S.; White, S. R.; Sottos, N. R.; Baudry, J.; Wilson, S. R. Biasing reaction pathways with mechanical force. Nature 2007, 446, 423–427.
- 31 Peterson, G. I.; Choi, T. L. The influence of polymer architecture in polymer mechanochemistry. Chem. Commun. 2021, 57, 6465–6474.
- 32 Melville, H. W.; Murray, A. J. R. The ultrasonic degradation of polymers. Trans. Faraday Society 1950, 46, 996–1009.
- 33 Sohma, J. Mechanochemistry of polymers. Prog. Polym. Sci. 1989, 14, 451–596.
- 34 Kim, T. A.; Lamuta, C.; Kim, H.; Leal, C.; Sottos, N. R. Interfacial Force-Focusing Effect in Mechanophore-Linked Nanocomposites. Adv. Sci. 2020, 7, 1903464.
- 35 Silberstein, M. N.; Min, K.; Cremar, L. D.; Degen, C. M.; Martinez, T. J.; Aluru, N. R.; White, S. R.; Sottos, N. R. Modeling mechanophore activation within a crosslinked glassy matrix. J. Appl. Phys. 2013, 114, 023504.
- 36 Silberstein, M. N.; Cremar, L. D.; Beiermann, B. A.; Kramer, S. B.; Martinez, T. J.; White, S. R.; Sottos, N. R. Modeling mechanophore activation within a viscous rubbery network. J. Mech. Phys. Solids 2014, 63, 141–153.
- 37 Traeger, H.; Kiebala, D. J.; Weder, C.; Schrettl, S. From Molecules to Polymers—Harnessing Inter- and Intramolecular Interactions to Create Mechanochromic Materials. Macromol. Rapid Commun. 2020, 42, 2000573.
- 38 Encina, M. V.; Lissi, E.; Sarasúa, M.; Gargallo, L.; Radic, D. Ultrasonic degradation of polyvinylpyrrolidone: Effect of peroxide linkages. J. Polym. Sci.: Polym. Lett. Ed. 1980, 18, 757–760.
- 39 Lu, Y.; Sugita, H.; Mikami, K.; Aoki, D.; Otsuka, H. Mechanochemical Reactions of Bis(9-methylphenyl-9-fluorenyl) Peroxides and Their Applications in Cross-Linked Polymers. J. Am. Chem. Soc. 2021, 143, 17744–17750.
- 40 Klussmann, M. Alkenyl and Aryl Peroxides. Chemistry 2018, 24, 4480–4496.
- 41 Cohen, N. Revised Group Additivity Values for Enthalpies of Formation (at 298 K) of Carbon–Hydrogen and Carbon–Hydrogen–Oxygen Compounds. J. Phys. Chem. Ref. Data 1996, 25, 1411–1481.
- 42 Iozzi, M. F.; Helgaker, T.; Uggerud, E. Assessment of theoretical methods for the determination of the mechanochemical strength of covalent bonds. Mol. Phys. 2009, 107, 2537–2546.
- 43 Li, Y.; Nese, A.; Matyjaszewski, K.; Sheiko, S. S. Molecular Tensile Machines: Anti-Arrhenius Cleavage of Disulfide Bonds. Macromolecules 2013, 46, 7196–7201.
- 44 Fritze, U. F.; von Delius, M. Dynamic disulfide metathesis induced by ultrasound. Chem. Commun. 2016, 52, 6363–6366.
- 45 Shi, Z.; Wu, J.; Song, Q.; Gostl, R.; Herrmann, A. Toward Drug Release Using Polymer Mechanochemical Disulfide Scission. J. Am. Chem. Soc. 2020, 142, 14725–14732.
- 46 Huo, S.; Zhao, P.; Shi, Z.; Zou, M.; Yang, X.; Warszawik, E.; Loznik, M.; Goestl, R.; Herrmann, A. Mechanochemical bond scission for the activation of drugs. Nat. Chem. 2021, 13, 131–139.
- 47 Shi, Z.; Song, Q.; Gostl, R.; Herrmann, A. Mechanochemical activation of disulfide-based multifunctional polymers for theranostic drug release. Chem. Sci. 2020, 12, 1668–1674.
- 48 Takahashi, A.; Goseki, R.; Ito, K.; Otsuka, H. Thermally Healable and Reprocessable Bis(hindered amino)disulfide-Cross-Linked Polymethacrylate Networks. ACS Macro Lett. 2017, 6, 1280–1284.
- 49 Kida, J.; Aoki, D.; Otsuka, H. Self-Strengthening of Cross-Linked Elastomers via the Use of Dynamic Covalent Macrocyclic Mechanophores. ACS Macro Lett. 2021, 10, 558–563.
- 50 Kildahl, N. K. Bond Energy Data Summarized. J. Chem. Educ. 1995, 72, 423.
- 51 Xia, J.; Zhao, P.; Pan, S.; Xu, H. Diselenide-Containing Polymeric Vesicles with Osmotic Pressure Response. ACS Macro Lett. 2019, 8, 629–633.
- 52 Wu, Q.; Yuan, Y.; Chen, F.; Sun, C.; Xu, H.; Chen, Y. Diselenide-Linked Polymers under Sonication. ACS Macro Lett. 2020, 9, 1547–1551.
- 53 Krishnakumar, B.; Sanka, R. V. S. P.; Binder, W. H.; Parthasarthy, V.; Rana, S.; Karak, N. Vitrimers: Associative dynamic covalent adaptive networks in thermoset polymers. Chem. Eng. J. 2020, 385, 123820.
- 54 Zheng, J.; Png, Z. M.; Ng, S. H.; Tham, G. X.; Ye, E.; Goh, S. S.; Loh, X. J.; Li, Z. Vitrimers: Current research trends and their emerging applications. Mater. Today 2021, 51, 586–625.
- 55 Berkowski, K. L.; Potisek, S. L.; Hickenboth, C. R.; Moore, J. S. Ultrasound-Induced Site-Specific Cleavage of Azo-Functionalized Poly(ethylene glycol). Macromolecules 2005, 38, 8975–8978.
- 56 Kim, G.; Wu, Q.; Chu, J. L.; Smith, E. J.; Oelze, M. L.; Moore, J. S.; Li, K. C. Ultrasound controlled mechanophore activation in hydrogels for cancer therapy. Proc. Natl. Acad. Sci. U. S. A. 2022, 119, e2109791119.
- 57 Holbrook, K. A.; Parry, K. A. W. Kinetics of the gas-phase unimolecular thermal isomerisation of 1,1-dichloro-2,3-dimethylcyclopropane. Part I. cis-1,1-Dichloro-2,3-di-methylcyclopropane. J. Chem. Soc. B 1970, 1019–1021.
- 58 Lenhardt, J. M.; Ong, M. T.; Choe, R.; Evenhuis, C. R.; Martinez, T. J.; Craig, S. L. Trapping a diradical transition state by mechanochemical polymer extension. Science 2010, 329, 1057–1060.
- 59 Imato, K.; Kanehara, T.; Ohishi, T.; Nishihara, M.; Yajima, H.; Ito, M.; Takahara, A.; Otsuka, H. Mechanochromic Dynamic Covalent Elastomers: Quantitative Stress Evaluation and Autonomous Recovery. ACS Macro Lett. 2015, 4, 1307–1311.
- 60 Imato, K.; Irie, A.; Kosuge, T.; Ohishi, T.; Nishihara, M.; Takahara, A.; Otsuka, H. Mechanophores with a reversible radical system and freezing-induced mechanochemistry in polymer solutions and gels. Angew. Chem. Int. Ed. 2015, 54, 6168–6172.
- 61 Sumi, T.; Goseki, R.; Otsuka, H. Tetraarylsuccinonitriles as mechanochromophores to generate highly stable luminescent carbon- centered radicals. Chem. Commun. 2017, 53, 11885–11888.
- 62 Ishizuki, K.; Oka, H.; Aoki, D.; Goseki, R.; Otsuka, H. Mechanochromic Polymers That Turn Green Upon the Dissociation of Diarylbibenzothiophenonyl: The Missing Piece toward Rainbow Mechanochromism. Chemistry 2018, 24, 3170–3173.
- 63 Ishizuki, K.; Aoki, D.; Goseki, R.; Otsuka, H. Multicolor Mechanochromic Polymer Blends That Can Discriminate between Stretching and Grinding. ACS Macro Lett. 2018, 7, 556–560.
- 64 Kawasaki, K.; Aoki, D.; Otsuka, H. Diarylbiindolinones as Substituent-Tunable Mechanochromophores and Their Application in Mechanochromic Polymers. Macromol. Rapid Commun. 2019, 41, 1900460.
- 65 Sakai, H.; Aoki, D.; Seshimo, K.; Mayumi, K.; Nishitsuji, S.; Kurose, T.; Ito, H.; Otsuka, H. Visualization and Quantitative Evaluation of Toughening Polymer Networks by a Sacrificial Dynamic Cross-Linker with Mechanochromic Properties. ACS Macro Lett. 2020, 9, 1108–1113.
- 66 Kida, J.; Aoki, D.; Otsuka, H. Mechanophore activation enhanced by hydrogen bonding of diarylurea motifs: An efficient supramolecular force-transducing system. Aggregate 2021, 2, e50.
- 67 Kawasaki, K.; Aoki, D.; Otsuka, H. Diarylbiindolinones as Substituent-Tunable Mechanochromophores and Their Application in Mechanochromic Polymers. Macromol. Rapid Commun. 2020, 41, 1900460.
- 68 Klajn, R. Spiropyran-based dynamic materials. Chem. Soc. Rev. 2014, 43, 148–184.
- 69 Davis, D. A.; Hamilton, A.; Yang, J.; Cremar, L. D.; Van Gough, D.; Potisek, S. L.; Ong, M. T.; Braun, P. V.; Martinez, T. J.; White, S. R.; Moore, J. S.; Sottos, N. R. Force-induced activation of covalent bonds in mechanoresponsive polymeric materials. Nature 2009, 459, 68–72.
- 70 Gossweiler, G. R.; Kouznetsova, T. B.; Craig, S. L. Force-rate characterization of two spiropyran-based molecular force probes. J. Am. Chem. Soc. 2015, 137, 6148–6151.
- 71 Sun, C.; Zhang, S.; Ren, Y.; Zhang, J.; Shen, J.; Qin, S.; Hu, W.; Zhu, S.; Yang, H.; Yang, D. Force-Induced Synergetic Pigmentary and Structural Color Change of Liquid Crystalline Elastomer with Nanoparticle-Enhanced Mechanosensitivity. Adv. Sci. 2022, 9, 2205325.
- 72 Clough, J. M.; Kilchoer, C.; Wilts, B. D.; Weder, C. Hierarchically Structured Deformation-Sensing Mechanochromic Pigments. Adv. Sci. 2023, 10, 2206416.
- 73 Li, M.; Zhang, Q.; Zhou, Y.-N.; Zhu, S. Let spiropyran help polymers feel force! Prog. Polym. Sci. 2018, 79, 26–39.
- 74 Zhang, H.; Gao, F.; Cao, X.; Li, Y.; Xu, Y.; Weng, W.; Boulatov, R. Mechanochromism and Mechanical-Force-Triggered Cross-Linking from a Single Reactive Moiety Incorporated into Polymer Chains. Angew. Chem. Int. Ed. 2016, 55, 3040–3044.
- 75 Wang, Z.; Ma, Z.; Wang, Y.; Xu, Z.; Luo, Y.; Wei, Y.; Jia, X. A Novel Mechanochromic and Photochromic Polymer Film: When Rhodamine Joins Polyurethane. Adv. Mater. 2015, 27, 6469–6474.
- 76 Wang, T.; Zhang, N.; Dai, J.; Li, Z.; Bai, W.; Bai, R. Novel Reversible Mechanochromic Elastomer with High Sensitivity: Bond Scission and Bending-Induced Multicolor Switching. ACS Appl. Mater. Interfaces 2017, 9, 11874–11881.
- 77 Khang, T. M.; Huang, R.; Khan, A.; Chuang, W.-T.; Quoc Nhien, P.; Cuc, T. T. K.; Hue, B. T. B.; Wei, K.-H.; Li, Y.-K.; Lin, H.-C. Reversible Ratiometric Mechanochromic Fluorescence Switching in Highly Stretchable Polyurethane Elastomers with Ultratoughness Enhanced by Polyrotaxane. ACS Mater. Lett. 2022, 4, 2537–2546.
- 78 Wu, M.; Li, Y.; Yuan, W.; De Bo, G.; Cao, Y.; Chen, Y. Cooperative and Geometry-Dependent Mechanochromic Reactivity through Aromatic Fusion of Two Rhodamines in Polymers. J. Am. Chem. Soc. 2022, 144, 17120–17128.
- 79 Hu, H.; Cheng, X.; Ma, Z.; Wang, Z.; Ma, Z. A double-spiro ring-structured mechanophore with dual-signal mechanochromism and multistate mechanochemical behavior: non-sequential ring- opening and multimodal analysis. Polym. Chem. 2022, 13, 5507–5514.
- 80
He, W.; Yuan, Y.; Wu, M.; Li, X.; Shen, Y.; Qu, Z.; Chen, Y. Multicolor chromism from a single chromophore through synergistic coupling of mechanochromic and photochromic subunits. Angew. Chem. Int. Ed. 2023, 135, e202218785.
10.1002/ange.202218785 Google Scholar
- 81 Robb, M. J.; Kim, T. A.; Halmes, A. J.; White, S. R.; Sottos, N. R.; Moore, J. S. Regioisomer-Specific Mechanochromism of Naphthopyran in Polymeric Materials. J. Am. Chem. Soc. 2016, 138, 12328–12331.
- 82 McFadden, M. E.; Barber, R. W.; Overholts, A. C.; Robb, M. J. Naphthopyran molecular switches and their emergent mechanochemical reactivity. Chem. Sci. 2023, 14, 10041–10067.
- 83 Shiraki, T.; Diesendruck, C. E.; Moore, J. S. The mechanochemical production of phenyl cations through heterolytic bond scission. Faraday Discuss. 2014, 170, 385–394.
- 84 Diesendruck, C. E.; Peterson, G. I.; Kulik, H. J.; Kaitz, J. A.; Mar, B. D.; May, P. A.; White, S. R.; Martinez, T. J.; Boydston, A. J.; Moore, J. S. Mechanically triggered heterolytic unzipping of a low-ceiling-temperature polymer. Nat. Chem. 2014, 6, 623–628.
- 85 Barbee, M. H.; Wang, J.; Kouznetsova, T.; Lu, M.; Craig, S. L. Mechanochemical Ring-Opening of Allylic Epoxides. Macromolecules 2019, 52, 6234–6240.
- 86 Choudhury, N.; Kim, A.; Kim, M.; Kim, B. S. Mechanochemical Degradation of Poly(vinyl chloride) into Nontoxic Water-Soluble Products via Sequential Dechlorination, Heterolytic Oxirane Ring-Opening, and Hydrolysis. Adv. Mater. 2023, 35, 2304113.
- 87 Díez-González, S.; Nolan, S. P. Stereoelectronic parameters associated with N-heterocyclic carbene (NHC) ligands: A quest for understanding. Coordin. Chem. Rev. 2007, 251, 874–883.
- 88 Sentman, A. C.; Csihony, S.; Waymouth, R. M.; Hedrick, J. L. Silver(I)-carbene complexes/ionic liquids: novel N-heterocyclic carbene delivery agents for organocatalytic transformations. J. Org. Chem. 2005, 70, 2391–2393.
- 89 Piermattei, A.; Karthikeyan, S.; Sijbesma, R. P. Activating catalysts with mechanical force. Nat. Chem. 2009, 1, 133–137.
- 90 Jakobs, R. T. M.; Sijbesma, R. P. Mechanical Activation of a Latent Olefin Metathesis Catalyst and Persistence of its Active Species in ROMP. Organometallics 2012, 31, 2476–2481.
- 91 Michael, P.; Binder, W. H. A Mechanochemically Triggered "Click" Catalyst. Angew. Chem. Int. Ed. 2015, 54, 13918–13922.
- 92 Nixon, R.; De Bo, G. Three concomitant C-C dissociation pathways during the mechanical activation of an N-heterocyclic carbene precursor. Nat. Chem. 2020, 12, 826–831.
- 93 Shen, H.; Larsen, M. B.; Roessler, A. G.; Zimmerman, P. M.; Boydston, A. J. Mechanochemical Release of N-Heterocyclic Carbenes from Flex-Activated Mechanophores. Angew. Chem. Int. Ed. 2021, 60, 13559–13563.
- 94 Klukovich, H. M.; Kean, Z. S.; Iacono, S. T.; Craig, S. L. Mechanically induced scission and subsequent thermal remending of perfluorocyclobutane polymers. J. Am. Chem. Soc. 2011, 133, 17882–17888.
- 95 Ramirez, A. L.; Kean, Z. S.; Orlicki, J. A.; Champhekar, M.; Elsakr, S. M.; Krause, W. E.; Craig, S. L. Mechanochemical strengthening of a synthetic polymer in response to typically destructive shear forces. Nat. Chem. 2013, 5, 757–761.
- 96 Wang, J.; Piskun, I.; Craig, S. L. Mechanochemical Strengthening of a Multi-mechanophore Benzocyclobutene Polymer. ACS Macro Lett. 2015, 4, 834–837.
- 97 Hu, X.; Zeng, T.; Husic, C. C.; Robb, M. J. Mechanically Triggered Release of Functionally Diverse Molecular Payloads from Masked 2-Furylcarbinol Derivatives. ACS Cent. Sci. 2021, 7, 1216–1224.
- 98 Overholts, A. C.; Razo, W. G.; Robb, M. J. Mechanically gated formation of donor-acceptor Stenhouse adducts enabling mechanochemical multicolour soft lithography. Nat. Chem. 2023, 15, 332.
- 99 Odell, J. A.; Keller, A. Flow-induced chain fracture of isolated linear macromolecules in solution. J. Polym. Sci., Part B: Polym. Phys. 1986, 24, 1889–1916.
- 100 Wang, J.; Kouznetsova, T. B.; Niu, Z.; Ong, M. T.; Klukovich, H. M.; Rheingold, A. L.; Martinez, T. J.; Craig, S. L. Inducing and quantifying forbidden reactivity with single-molecule polymer mechanochemistry. Nat. Chem. 2015, 7, 323–327.
- 101 Barbee, M. H.; Kouznetsova, T.; Barrett, S. L.; Gossweiler, G. R.; Lin, Y.; Rastogi, S. K.; Brittain, W. J.; Craig, S. L. Substituent Effects and Mechanism in a Mechanochemical Reaction. J. Am. Chem. Soc. 2018, 140, 12746–12750.
- 102 Nixon, R.; De Bo, G. Isotope Effect in the Activation of a Mechanophore. J. Am. Chem. Soc. 2021, 143, 3033–3036.
- 103 Klein, I. M.; Husic, C. C.; Kovacs, D. P.; Choquette, N. J.; Robb, M. J. Validation of the CoGEF Method as a Predictive Tool for Polymer Mechanochemistry. J. Am. Chem. Soc. 2020, 142, 16364–16381.
- 104 Kryger, M. J.; Munaretto, A. M.; Moore, J. S. Structure-mechanochemical activity relationships for cyclobutane mechanophores. J. Am. Chem. Soc. 2011, 133, 18992–18998.
- 105 Stevenson, R.; De Bo, G. Controlling Reactivity by Geometry in Retro-Diels-Alder Reactions under Tension. J. Am. Chem. Soc. 2017, 139, 16768–16771.
- 106 Wang, J.; Kouznetsova, T. B.; Kean, Z. S.; Fan, L.; Mar, B. D.; Martinez, T. J.; Craig, S. L. A remote stereochemical lever arm effect in polymer mechanochemistry. J. Am. Chem. Soc. 2014, 136, 15162–15165.
- 107 O'Bryan, G.; Wong, B. M.; McElhanon, J. R. Stress sensing in polycaprolactone films via an embedded photochromic compound. ACS Appl. Mater. Interfaces 2010, 2, 1594–1600.
- 108 Konda, S. S.; Brantley, J. N.; Varghese, B. T.; Wiggins, K. M.; Bielawski, C. W.; Makarov, D. E. Molecular catch bonds and the anti-Hammond effect in polymer mechanochemistry. J. Am. Chem. Soc. 2013, 135, 12722–12729.
- 109 Ribas-Arino, J.; Shiga, M.; Marx, D. Mechanochemical transduction of externally applied forces to mechanophores. J. Am. Chem. Soc. 2010, 132, 10609–10614.
- 110 Dopieralski, P.; Anjukandi, P.; Rückert, M.; Shiga, M.; Ribas–Arino, J.; Marx, D. On the role of polymer chains in transducing external mechanical forces to benzocyclobutene mechanophores. J. Mater. Chem. 2011, 21, 8309–8316.
- 111 Klukovich, H. M.; Kean, Z. S.; Black Ramirez, A. L.; Lenhardt, J. M.; Lin, J.; Hu, X.; Craig, S. L. Tension trapping of carbonyl ylides facilitated by a change in polymer backbone. J. Am. Chem. Soc. 2012, 134, 9577–9580.
- 112 Klukovich, H. M.; Kouznetsova, T. B.; Kean, Z. S.; Lenhardt, J. M.; Craig, S. L. A backbone lever-arm effect enhances polymer mechanochemistry. Nat. Chem. 2013, 5, 110–114.
- 113 Jiang, S.; Zhang, L.; Xie, T.; Lin, Y.; Zhang, H.; Xu, Y.; Weng, W.; Dai, L. Mechanoresponsive PS-PnBA-PS Triblock Copolymers via Covalently Embedding Mechanophore. ACS Macro Lett. 2013, 2, 705–709.
- 114 Church, D. C.; Peterson, G. I.; Boydston, A. J. Comparison of Mechanochemical Chain Scission Rates for Linear versus Three-Arm Star Polymers in Strong Acoustic Fields. ACS Macro Lett. 2014, 3, 648–651.
- 115 Oka, H.; Imato, K.; Sato, T.; Ohishi, T.; Goseki, R.; Otsuka, H. Enhancing Mechanochemical Activation in the Bulk State by Designing Polymer Architectures. ACS Macro Lett. 2016, 5, 1124–1127.
- 116 Peterson, G. I.; Lee, J.; Choi, T.-L. Multimechanophore Graft Polymers: Mechanochemical Reactions at Backbone–Arm Junctions. Macromolecules 2019, 52, 9561–9568.
- 117 Li, Y.; Niu, Z.; Burdynska, J.; Nese, A.; Zhou, Y.; Kean, Z. S.; Dobrynin, A. V.; Matyjaszewski, K.; Craig, S. L.; Sheiko, S. S. Sonication-induced scission of molecular bottlebrushes: Implications of the "hairy" architecture. Polymer 2016, 84, 178–184.
- 118 Watabe, T.; Ishizuki, K.; Aoki, D.; Otsuka, H. Mechanochromic dendrimers: the relationship between primary structure and mechanochromic properties in the bulk. Chem. Commun. 2019, 55, 6831–6834.
- 119 Watabe, T.; Aoki, D.; Otsuka, H. Enhancement of Mechanophore Activation in Mechanochromic Dendrimers by Functionalization of Their Surface. Macromolecules 2021, 54, 1725–1731.
- 120 Noh, J.; Peterson, G. I.; Choi, T.-L. Mechanochemical Reactivity of Bottlebrush and Dendronized Polymers: Solid vs. Solution States. Angew. Chem. Int. Ed. 2021, 60, 18651–18659.
- 121 Zhang, H.; Diesendruck, C. E. Accelerated Mechanochemistry in Helical Polymers. Angew. Chem. Int. Ed. 2022, 61, e202115325.
- 122 Wang, L.-J.; Zhou, X.-J.; Zhang, X.-H.; Du, B.-Y. Enhanced Mechanophore Activation within Micelles. Macromolecules 2016, 49, 98–104.
- 123 Xuan, M.; Fan, J.; Khiem, V. N.; Zou, M.; Brenske, K.-O.; Mourran, A.; Vinokur, R.; Zheng, L.; Itskov, M.; Goestl, R.; Herrmann, A. Polymer Mechanochemistry in Microbubbles. Adv. Mater. 2023, 35, 2305130.
- 124 Li, J.; Hu, B.; Yang, K.; Zhao, B.; Moore, J. S. Effect of Polymer Grafting Density on Mechanophore Activation at Heterointerfaces. ACS Macro Lett. 2016, 5, 819–822.
- 125 Qiu, W.; Gurr, P. A.; Qiao, G. G. Regulating Color Activation Energy of Mechanophore-Linked Multinetwork Elastomers. Macromolecules 2020, 53, 4090–4098.
- 126 Park, J.; Lee, Y.; Barbee, M. H.; Cho, S.; Cho, S.; Shanker, R.; Kim, J.; Myoung, J.; Kim, M. P.; Baig, C.; Craig, S. L.; Ko, H. A Hierarchical Nanoparticle-in-Micropore Architecture for Enhanced Mechanosensitivity and Stretchability in Mechanochromic Electronic Skins. Adv. Mater. 2019, 31, 1808148.
