Cyclodextrin‐Based Rotaxanes: from Rotaxanes to Polyrotaxanes and Further to Functional Materials

Abstract

This minireview overviews rotaxanes and pseudorotaxanes containing cyclodextrins (CDs) as the rotor component. Since CDs interact with molecules, e.g., hydrophobic compounds of the size and shape matching their cavity, to form inclusion complexes in aqueous media, CDs are an important class of macrocyclic compounds as rotor components of rotaxanes and pseudorotaxanes. Research on CD‐based rotaxanes has begun with the synthesis of rotaxanes from low molecular weight axis molecules and then developed into the construction of molecular machines and polyrotaxanes. Recently, the research has further developed into macroscopic functional materials, e.g., slide‐ring gels, macromolecular assemblies, self‐healing materials, and soft actuators. In the present article, typical examples of CD‐based rotaxanes and pseudorotaxanes are described; synthesis of rotaxane and construction of molecular machine are described in Section 2, synthesis of polyrotaxanes is dealt with in Section 3, and development of macroscopic functional materials based on rotaxane structure is discussed in Section 4.

Confined Microenvironments from Thermoresponsive Dendronized Polymers

“…Cyclodextrins (CyDs), a class of cyclic oligosaccharides, can act as hosts with their hydrophobic cavities to confine with size‐matched hydrophobic guests to form inclusion complexes in aqueous solutions through supramolecular interaction. [ 10 ] The confinement of hydrophobic cavities guarantees the threaded structures with high stabilities to form rotaxanes or polyrotaxanes, [ 11 ] and even affords the achiral guests with induced chiralities. [ 12 ] Similarly, cyclic molecules, “Texas‐sized” molecular box, has been proven to be a versatile building block for construction of anion‐directed mechanically interlocked dynamic structures.…”

Thermally Responsive Poly(ethylene oxide)‐Based Polyrotaxanes Bearing Hydrogen‐Bonding Pillar[5]arene Rings**

“…Although a handful of host compounds were reported to bind PEOs strongly, [20–23] most of them needed their free space being activated in advance, hampering the formation of rotaxanes via a solution process. Considering the great success of supramolecular and interlocked polymer materials composed of PEOs and cyclodextrins, [24–30] alternative cyclic hosts for PEO axles are highly desirable for the further development of PEO‐based hydrogels and other functional materials.…”

Self-assembly of cyclic hexamers of γ-cyclodextrin in a metallosupramolecular framework withd-penicillamine

“…[2][3][4][5][6] These characteristic properties of CDs have widely been utilized for a variety of applications, such as optical resolution, [7][8][9] drug delivery, [10][11][12][13] and molecular machine systems. [14][15][16][17] Apart from the conventional assembly of CDs assisted by guest molecules, [15][16][17][18][19][20] the self-assembly of CDs themselves has been proposed based on NMR, TEM, and scattering techniques, in combination with molecular model calculations, since the initial report on dimer formation of CDs in solution. [21][22][23][24][25][26] However, no direct structural evidence for the self-assembly of CDs themselves has yet been obtained by means of X-ray crystallography, although a large number of crystal structures of CD molecules have been reported.…”