Stimuli-Responsive Molecular and Macromolecular Systems Controlled by Rotaxane Molecular Switches

Abstract

Synthesis and dynamic nature of molecular and macromolecular systems controlled by rotaxane molecular switches are discussed. Rotaxane molecular and macromolecular switches including those working without solvent were synthesized mainly using sec-ammonium salt/crown ether couples. A linear polymer possessing a crown ether/sec-ammonium salttype [1]rotaxane moiety at the chain terminal was prepared by the rotaxane-linking of single polymer chain, and applied to the linear polymercyclic polymer topology transformation. Successful synthesis of macromolecular [2]rotaxane (M2R) possessing single polymer axle and one crown ether wheel made possible a variety of unique applications such as development of topology-transformable polymers and rotaxane cross-linked polymers (RCPs) by connecting polymer chains to the components of M2R. The pronounced dynamic nature of these polymer systems is quite interesting and is expected to afford much useful information for designing novel stimuli-responsive molecules, polymers, and polymer materials.

Switchable Polymer Materials Controlled by Rotaxane Macromolecular Switches

“…Structure- and/or property-changeable systems driven by various stimuli are attractive for the design of stimuli-responsive materials, which usually require dynamic or structure-changeable molecular units. Dynamic units that use mechanical linkages have attracted considerable attention because of their scientific interest and actual applications, such as in smart devices and materials. − Specifically, rotaxane linkages are most promising because in rotaxanes there are no interactions between the components, which are also characterized by high mobility. Therefore, molecules containing rotaxane-linked units frequently exhibit unique properties that have not been previously reported.…”

“…To construct these dynamic systems, RMSs are essential and depend on the development of macromolecular [2]rotaxanes (M2Rs). 11 The change of M2Rs to RMSs and their application to topologytransformable polymers as stimuli-responsive materials are the main topics of this Outlook, which also discusses how the polymer chain mobility affects the polymer properties. An illustrative description of the contents of this Outlook is summarized in Figure 3.…”

“…This article primarily focuses on the construction and function of such dynamic macromolecular systems that can undergo dynamic structure or topological changes to induce changes in properties and/or functions. To construct these dynamic systems, RMSs are essential and depend on the development of macromolecular [2]­rotaxanes (M2Rs) . The change of M2Rs to RMSs and their application to topology-transformable polymers as stimuli-responsive materials are the main topics of this Outlook, which also discusses how the polymer chain mobility affects the polymer properties.…”

Semirotaxanes and unsymmetrical rotaxanes from substituted benzylammonium salts and dibenzo-24-crown-8

“…Similar to pseudorotaxanes, semirotaxanes are important parts of supramolecular chemistry research because this is the route to mechanically interlocked systems that cannot dethread without covalent bond cleavage. Such interlocked structures have been widely used in molecular machines [12][13][14][15][16][17][18][19][20][21][22][23][24] and systems that can be controlled by external stimuli, 25,26 such as electrochemistry, 27,28 pH, [28][29][30][31] etc. 32,33 It has been known for more than two decades that dibenzo-24-crown-8 (DB24C8) and its derivatives form stable pseudorotaxanes with secondary ammonium salts driven by hydrogen bonding and ion-dipole interactions in low-polarity solvents, 34,35 such as acetone and acetonitrile.…”

Interfacial nanoarchitectonics for responsive cellular biosystems

“…From the nanoscale to macroscopic scale, conversions of materials, signals, and information are keys for functions in many cases, including regulation of material functions by external stimuli [ [1] , [2] , [3] ], energy production from external energy sources [ [4] , [5] , [6] ], energy management on external input [ [7] , [8] , [9] , [10] ], various information conversions from inputs to outputs [ [11] , [12] , [13] ], and controls of biological responses [ [14] , [15] , [16] , [17] ]. The design and fabrication of functional materials and systems for these conversions with high efficiency and desired specificity are crucial matters for various social demands such as energy [ [18] , [19] , [20] ], environmental [ [21] , [22] , [23] , [24] ], and biomedical [ [25] , [26] , [27] ] issues.…”