ساختارهای فرامولکولی متشکل از γ-سیکلودکسترین
Abstract
1- Introduction
2- Result and discussion
3- Conclusion
4- Experimental section
References
Abstract
To construct well-defined microstructures, strict controls of the temperature and sophisticated techniques are generally required because microstructure formation is usually based on crystallization, which easily results in a kinetic trap of disordered structures. Herein, we report the formation of various microstructures such as rods, cubes, plates, and nanosheets via supramolecular self-assembly between γ-cyclodextrin (CD) and polyethers in water without temperature change. We revealed the relationships between the guest polymer structures and the resulting microstructure: (1) Short guest homopolymers lead to the formation of rod microstructures, whilst long congeners result in plates. (2) A hydrophilic backbone polymer is necessary to isolate the plates in water, otherwise hydrophobic interaction leads to aggregation of the plates and the formation of polycrystalline γ-CD complexes. (3) Spatial confinement of the γ-CDs on the central segment of a guest triblock copolymer plays a key role in the fabrication of nanosheets with uniform thickness.
Introduction
Non-covalent supramolecular self-assembly has attracted much research attention because of the potential to produce complicated nanoand micro-sized structures on a large scale via simple experimental procedures [1]. The nano- and micro-structures fabricated via supramolecular self-assembly can be controlled by designing the molecular structure of the components, and change dynamically depending on the surrounding conditions [2–7]. Therefore, supramolecular self-assembly has been utilized for the fabrication of many kinds of applied materials with specific structures, such as lipid bilayer membranes [8,9], selfassembled monolayers [10,11], and metal-organic frameworks [12–15]. Many researchers have dedicated their efforts to fabricating various morphologies by manipulating supramolecular self-assembly behavior [16–21], as the properties of materials are strongly dependent on the geometry of the nano- and micro-sized structures [22–25]. In general, complicated steps for synthesis of the components, strict temperature control, and sophisticated techniques are required for manipulation of the structures, especially in the case of the self-assembly of organic components [20,26–29]. This is mainly because well-ordered self-assembled microstructures usually arise from the crystallization of a certain part of the components. Because crystallization is a kinetically dominated phenomenon, the rapid formation of microstructures is likely to result in kinetic trapping of the disordered microstructure consisting of polycrystals. We have focused on the complexation-induced crystallization of cyclodextrins (CDs) in order to form ordered microstructures. CDs are torus-shaped oligosaccharides; there are three kinds of commercially available CDs, i.e., α-CD, β-CD, and γ-CD, classified by the ring size.