Highly effective binding of neutral dinitriles by simple alkyl-substituted pillar[5]arenes and the formation of interpenetrated geometries are reported. The resulting host-guest complexes represent one of the most efficient recognition motifs based on pillararenes.

A simple bis(imidazolium) dication, 1,4-bis[N-(N'-hydroimidazolium)]butane, can act as a new template for formation of [2]pseudorotaxane with pillar[5]arene, in which the dethreading/rethreading process can be controlled by addition of base and acid. The effect on the association constant of both the solvent and counterion is also described.

The binding behavior of substituted 1,4-bis(pyridinium)butane derivatives (X-Py(CH(2))(4)Py-X, X = H, 2-methyl, 3-methyl, 4-methyl, 2,6-dimethyl, 4-pyridyl, and 4-COOEthyl) 1(2+)-7(2+), with negatively charged carboxylatopillar[5]arene (CP5A) has been comprehensively investigated by (1)H NMR and 2D ROESY and UV absorption and fluorescence spectroscopy in aqueous phosphate buffer solution (pH 7.2). The results indicated that the position of the substituents attached on pyridinium ring dramatically affects the association constants and binding modes. 3- and 4-Substituted guests (1(2+), 3(2+), 4(2+), 6(2+), 7(2+)) form [2]pseudorotaxane geometries with CP5A host, giving very large association constants (>10(5) M(-1)), while 2,6-dimethyl-substituted 5(2+) forms external complex with relatively small K(a) values [(2.4 ± 0.3) × 10(3) M(-1)] because the 2,6-dimethylpyridinium unit is too bulky to thread the host cavity. Both of the binding geometries mentioned above are observed for 2(2+), having one methyl group in the 2-position of pyridinium. Typically, the association constant of [2]pseudorotaxane 1(2+)⊂CP5A exceeds 10(6) M(-1) in water, which is significantly higher than those of previously reported analogues in organic solvents. The remarkably improved complexation of bis(pyridinium) guests by the anionic host was due to electrostatic attraction forces and hydrophobic interactions.

Simple alkyl-substituted pillar[5]arenes can form stable interpenetrated complexes with neutral bis(imidazole) guests utilizing multiple C-H···O(N) hydrogen bond and C-H···π interactions.

A novel water-swellable rubber (WSR) has been prepared by blending chlorobutadiene rubber (CR), reactive clay and other additives with crosslinked sodium polyacrylate (CSP), which was modified by interpenetrating polymer networks (IPNs) technology with crosslinked P(AA-co-BA). The structure of WSR was characterized by scanning electron microscopy (SEM). The mechanical properties, water-swelling ratio by mass, and the percentage loss of CSP in the WSR were investigated. The results showed that the modified CSP grains can be dispersed well in the CR, and that it resulted in increase of mechanical properties and water-swelling ratio and in decrease of percentage loss of CSP, compared with the unmodified one. When the percentage content of crosslinked P(AA-co-BA) used to modify CSP reached 30%, the tensile strength, elongation at break, and water-swelling ratio of WSR exhibited maximum value, and percentage loss of CSP exhibited minimum value. When the content of CSP in WSR was 30 phr, the tensile strength, elongation at break, and water-swelling ratio and percentage loss of CSP of the WSR containing CSP modified were 7.7 MPa, 1530, 438, and 2.5%, respectively.