Engineering Responsive Polymer Building Blocks with Host–Guest Molecular Recognition for Functional Applications

Abstract

CONSPECTUS: All living organisms and soft matter are intrinsically responsive and adaptive to external stimuli. Inspired by this fact, tremendous effort aiming to emulate subtle responsive features exhibited by nature has spurred the invention of a diverse range of responsive polymeric materials. Conventional stimuli-responsive polymers are constructed via covalent bonds and can undergo reversible or irreversible changes in chemical structures, physicochemical properties, or both in response to a variety of external stimuli. They have been imparted with a variety of emerging applications including drug and gene delivery, optical sensing and imaging, diagnostics and therapies, smart coatings and textiles, and tissue engineering. On the other hand, in comparison with molecular chemistry held by covalent bonds, supramolecular chemistry built on weak and reversible noncovalent interactions has emerged as a powerful and versatile strategy for materials fabrication due to its facile accessibility, extraordinary reversibility and adaptivity, and potent applications in diverse fields. Typically involving more than one type of noncovalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic association, electrostatic interactions, van der Waals forces, and π-π stacking), host-guest recognition refers to the formation of supramolecular inclusion complexes between two or more entities connected together in a highly controlled and cooperative manner. The inherently reversible and adaptive nature of host-guest molecular recognition chemistry, stemming from multiple noncovalent interactions, has opened up a new platform to construct novel types of stimuli-responsive materials. The introduction of host-guest chemistry not only enriches the realm of responsive materials but also confers them with promising new applications. Most intriguingly, the integration of responsive polymer building blocks with host-guest recognition motifs will endow the former with further broadened responsiveness to external stimuli and accordingly more sophisticated functions. In this Account, we summarize recent progress in the field of responsive polymeric materials containing host-guest recognition motifs with selected examples and highlight their versatile functional applications, whereas small molecule-oriented host-guest supramolecular systems are excluded. We demonstrate how the introduction of host-guest chemistry into conventional polymer systems can modulate their responsive modes to external stimuli. Moreover, the responsive specificity and selectivity of polymeric systems can also be inherited from the host-guest recognition motifs, and these features provide extra advantages in terms of function integration. The following discussions are categorized in terms of design and functions, namely, host-guest chemistry toward the fabrication of responsive polymers and assemblies, optical sensing and imaging, drug and gene delivery, and self-healing materials. A concluding remark on future developments is also presented. We wish th...

Adamantylated trisimidazolium-based tritopic guests and their binding properties towards cucurbit[7]uril and β-cyclodextrin

“…Additionally, the ROESY spectrum ( Fig. 3b) was recorded for a mixture containing 1 and b-CD in a 1:5 molar ratio to observe the intermolecular interactions between adamantane hydrogen atoms H(a), H(b), and H(c) and inner b-CD hydrogen atoms H(3) and H (5). Therefore, we can deduce from the 1 H NMR titration experiment and ROESY spectrum that the adamantane cage was included into the b-CD cavity to form the 1@b-CD 3 complex, similarly to 1@CB7 3 .…”

“…Besides micelles, dendritic polymers, and membrane vesicles, hydrogels have been designed to store, deliver or release active compounds under the control of external stimuli such as pH, light, temperature or concentration of additional compounds [1][2][3][4][5][6][7][8]. Because the host-guest concept is one of the most popular approaches in this research area [9], either the guest or the host binding motifs are used for the preparation of the building blocks.…”

Advanced Polymer-Surfactant Systems via Self-Assembling

“…host molecules) consisting of two or more entities connected via noncovalent interactions in a highly controlled and cooperative manner. These host-guest inclusions are relatively stable and provide reliable and robust connections for the fabrication of stimuli-responsive supramolecular systems [8]. Cyclodextrins (CDs) are the most used and affordable hosts in the field of inclusion chemistry [7,9,10].…”

“…self-healing) after exposure to externally applied stimuli or shear forces increasing the life span of these materials [8,7]. The self-healing capability is highly dependent on the noncovalent connections in the polymer backbone and on the decomplexation and complexation of the supramolecular system [7,8,11,12].…”

“…self-healing) after exposure to externally applied stimuli or shear forces increasing the life span of these materials [8,7]. The self-healing capability is highly dependent on the noncovalent connections in the polymer backbone and on the decomplexation and complexation of the supramolecular system [7,8,11,12]. Therefore, supramolecular chemistry built on weak and reversible noncovalent interactions has emerged as a powerful and versatile strategy to design and fabricate materials with extraordinary reversibility and adaptivity with potential applications in diverse fields [8].…”