Stabilization of Bicontinuous Cubic Phase and Its Two‐Sided Nature Produced by Use of Siloxane Tails and Introduction of Molecular Nonsymmetry

Abstract

A recent intriguing finding that a helical network arrangement forms the bicontinuous cubic phase is attracting great attention for the possibility of new routes to asymmetric synthesis by achiral molecules. However, the design of the molecular structure for the cubic phase is still unrevealed. In this work, a nonsymmetric core molecule with larger naphthalene and smaller benzene moieties at each side of the central linkage and the same disiloxanyldecyloxy terminal at both terminals is shown to be the first example of molecule forming both single-layered and double-layered core assembly modes in the Ia3d phase as a single molecule system. The molecule forms the former mode at high temperatures as a thermodynamically stable phase, similarly to the symmetric naphthalene core system, whereas, on cooling below a temperature (~350 K), a metastable Ia3d phase forms a double-layered core state down to room temperature, which is common to the benzene core system. As another effect of the nonsymmetric core, the cubic phase is maintained at room temperature for more than 100 days with slight distortion. Infrared spectral studies and quantum chemical calculations suggested the easy transformation between the two core assembly modes. The core nonsymmetry can be a versatile fine-tuning of the core assembly mode and phase stability for the cubic phase molecules.

Room-temperature Ia3̄d phase obtained for the binary mixture containing different sizes of siloxanyl terminals

“…The electron density maps were reconstructed by the XRD intensity analyses, 13,25,27,39 and the selected two states at 323 K on cooling and after being aged at 296 K for 378 days are compared in Fig. 6.…”

“…A plausible origin is probably the mixing entropy effect which is likely to become a maximum at the M-50 mixture. Experimentally, this was also reflected in the frequency change in the IR methylene C-H asymmetric stretching (n as (C-H) CH 2 ) vibration during the room-temperature storage; the frequency is known to shift to higher frequencies as the gauche bond density in the chain is increased 17,18,26,27,41 and the highest frequency of B2924.5 cm À1 was most evidently maintained in the M-50 mixture, showing the highest flexibility of the alkyl spacer connecting the siloxanyl terminal and aromatic core portion among the three mixtures and Bis-B10Si2 (Fig. S20, ESI †).…”

“…[20][21][22][23][24] In view of the situation, we have developed several siloxane-containing Cub LC compounds and demonstrated that they could easily take antispindle-like molecular shapes around room temperature. [25][26][27] Two compounds shown in Fig. 1b are representative ones, having a bis(benzoyl)hydrazine core with disiloxanyldecyloxyl or trisiloxanyldecyloxyl terminals at both the 4-and 4 0 -positions, which we abbreviate as Bis-B10Si2 and Bis-B10Si3, respectively.…”

Control of the Organization of 4,4′-bis(carbazole)-1,1′-biphenyl (CBP) Molecular Materials through Siloxane Functionalization

“…Overall, ODMS possesses weak intermolecular forces entailing a very low surface tension, solubility parameter and dielectric constant, in particular [13]. In addition, ODMS is endowed with a propensity for microphase separation easily leading to the self-organization of siloxane-containing molecular systems [14][15][16]. Finally, with regard to geometrical parameters, siloxane chains are rather bulky, as illustrated by the larger molecular section of the linear ODMS chain (σ = 41 Å 2 ) as compared to the one of the linear alkyl chains (σ = 21.5 Å 2 ) [17].…”

Preparation and optimization of glyceryl monooleate-low molecular weight chitosan nanoparticles for delivery of morpholinopyrrolizine derivative

“…Gycerylmonooleate (GMO) forms a cubic phase in contact with an aqueous medium and has been investigated as an anticancer agent delivery system [8]. However, these nanocarriers are unstable at physiological pH [9]. Chitosan is a natural cationic polyamine polymer.…”