Host-Guest Mesomorphism: Cooperative Stabilization of a Bowlic Columnar Phase.

TitleHost-Guest Mesomorphism: Cooperative Stabilization of a Bowlic Columnar Phase.
Publication TypeJournal Article
Year of Publication1995
AuthorsXu, B, Swager, TM
JournalJournal of the American Chemical Society
Keywordsbowlic columnar azo substituted calixarene formamidebutane, liq crystal azo substituted calixarene formamidebutane

The azo-substituted calix[4]arene I (R = N:N-C6H3-(O(CH2)10H)2-3,4) in pure form does not display a stable thermotropic mesophase. A novel method is reported for stabilization of mesomorphic behavior by making use of the calix[4]arene's receptor properties. In particular host-guest interactions between I and 1,4-(diformamide)butane (II) stabilize a bowlic hexagonal columnar phase (Bh) with very low clearing enthalpies and high fluidity. X-ray diffraction studies indicate that the Bh phase is the only mesophase present at I:II ratios of 2:1, but at ratios of 4:1 and 1:1 this phase coexists with small amts. of other unidentified phases. This system also displays the unusual properties that the range of mesomorphism is independent of the host/guest ratio and that only a fractional amt. of guest is required to stabilize the mesophase. The latter feature is indicative of a cooperative transition to the mesomorphic state. [on SciFinder(R)]