Cholesteric star-shaped liquid crystals induced by a maltose core: synthesis and characteristics

Abstract

Three esters of maltose (A1-A3) with 4-(4-(alkoxybenzoyloxy)phenoxy) -6-oxohexanoic acid (b1-b3) side-arms have been synthesised. All the maltose derivatives were laevo-rotationary, unlike their parent cores. The side arm b1 did not display liquid crystalline (LC) properties, and b2 and b3 displayed thermotropic nematic LC properties. The star-shaped compound (SSC) A1 with b1 side-arms did not display a mesomorphic phase. Unlike the nematic schlieren texture provided by side-arms b2 and b3, the star-shaped liquid crystals (SSLC) A2 and A3 displayed Grandjean and oily texture in the cholesteric phase. The results suggest that the LC properties of the side-arms have an important influence on the formation of LC properties in an SSC, and that the maltose core is important in determining the mesomorphic phase type. In other words, the SSC displayed LC properties only when the side-arms were also LC, and the maltose core induced a cholesteric phase in the SSLC with nematic side-arms. The mesomorphic regions for A2 and A3 were 39.1 and 53.7 • C during the heating cycle and 63.8 and 107.0 • C during the cooling cycle, respectively. The longer terminal chain rendered the mesomorphic region broader.

Effect of the Different Structure of the Chiral Core on Phase Behaviors of Cholesteric Star-Shaped Liquid Crystals

“…Over the past two years we have focused on whether a cholesteric SSLC might be generated by a chiral core. Glucose, sorbitol, maltose and melitose had previously been used as chiral cores in the synthesis of cholesteric SSLCs [9][10][11]. Our results now indicate for the first time that glucose, maltose, melitose and sorbitol are able to induce a cholesteric phase in SSLCs containing nematic LC side-arms.…”

“…These results indicate that a is cholesteric SSLC. b and c displayed typical grandjean, oily and fingerprint textures of cholestical phase, too ( reported in reference [10,11]). The above results indicate that glucose core, just like maltose and melitose cores, can also induce a cholesteric phase in the SSLC with the same nematic side-arms, and the number of sugar ring of the chiral core did not affect the mesomorphic type and texture of a, b and c.…”

“…According to results reported previously, b and c are cholesteric SSLCs. The data of b and c refered from reference [10,11] are summarised in Table 1. a was investigated by DSC, POM and XRD.…”

“…The results of FT-IR, 1 H NMR spectroscopy and elementary analysis confirmed that the target star-shaped liquid crystal, a had been produced. The synthesis and properties of b and c were reported previously [10,11].…”

“…One type of unconventional liquid crystal, those possessing a star-shaped molecular structure, usually comprise a core and a small number of mesomorphic units as side-arms [1][2][3][4][5][6][7][8][9][10][11]. The common mesophase of star-shaped liquid crystals (SSLC) is columnar.…”