Host Structural Flexibility

Intercalation reactions involve the reversible insertion of foreign ions or molecules into a host species in which, ideally, the basic structure of the host is not disrupted. As the name implies such reactions were once considered to be confined to layered structures where the guest species was inserted into the van der Waals gap. However, modern intercalation chemistry includes numerous examples of three-dimensional host structures flexible enough to accommodate the guest. 

Along this line, several new linear hosts and flexible cyclic hosts having a C2-symmetry axis (bisDPGP, bisTAGP, and bisTMGP Scheme 8) have been designed and synthesized based on the structural feature of the highly selective MeFruNys." However, these tailor-made flexible hosts prove less effective than MeFruNys as chiral selector (Table 15). 

To date, organometallic guests have been intercalated almost exclusively into layered host lattices. The structural flexibility of the layer structures, with their ability to adapt to the geometry of the inserted guest species by free adjustment of the interlayer separation, is presumably responsible for this observation. It is remarkable that in spite of the differences in composition and detail of the sheet unit structures, the basic chemical reactivity of these phases... 

Two common piezoelectric materials are polymers (polyvinylidene fluoride, PVDF) and c mics (lead zirconate titanate, PZT). The polymer materials are soft and flexible however have lower dielectric and piezoelectric properties than ceramics. Conventional piezoelectric ceramic materials are rigid, heavy and can only be produced in block form. Ceramic materials add additional mass and stiffiiess to the host structure, especially when working with flexible/lightweight materials. This and their fragile nature limit possibilities for wearable devices. Comparisons of several piezoelectric materials are presented in Table 1. 

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