We have structurally characterized the liquid crystal (LC) phase that can appear as an intermediate state when a dielectric nematic, having polar disorder of its molecular dipoles, transitions to the almost perfectly polar-ordered ferroelectric nematic. This intermediate phase, which fills a 100-y-old void in the taxonomy of smectic LCs and which we term the “smectic Z _A ,” is antiferroelectric, with the nematic director and polarization oriented parallel to smectic layer planes, and the polarization alternating in sign from layer to layer with a 180 Å period. A Landau free energy, originally derived from the Ising model of ferromagnetic ordering of spins in the presence of dipole–dipole interactions, and applied to model incommensurate antiferroelectricity in crystals, describes the key features of the nematic–SmZ _A –ferroelectric nematic phase sequence.

We report the observation of the smectic A_F, a liquid crystal phase of the ferroelectric nematic realm. The smectic A_Fis a phase of small polar, rod-shaped molecules that form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the ∼10 Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field ∼2 × 10⁵V/m is observed. The SmA_Fphase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic (N)–smectic Z_A(SmZ_A)–ferroelectric nematic (N_F)–SmA_Fphase sequence, and 7N/DIO, exhibiting an N–SmZ_A–SmA_Fphase sequence. The latter presents an opportunity to study a transition between two smectic phases having orthogonal systems of layers.

Ambidirectionality, which is the ability of structural elements to move beyond a reference state in two opposite directions, is common in nature. However, conventional soft materials are typically limited to a single, unidirectional deformation unless complex hybrid constructs are used. We exploited the combination of mesogen self-assembly, polymer chain elasticity, and polymerization-induced stress to design liquid crystalline elastomers that exhibit two mesophases: chevron smectic C (cSmC) and smectic A (SmA). Inducing the cSmC-SmA–isotropic phase transition led to an unusual inversion of the strain field in the microstructure, resulting in opposite deformation modes (e.g., consecutive shrinkage or expansion and right-handed or left-handed twisting and tilting in opposite directions) and high-frequency nonmonotonic oscillations. This ambidirectional movement is scalable and can be used to generate Gaussian transformations at the macroscale.

Significance: Enhanced surface mobility enables rapid equilibration of vapor-deposited glasses toward the supercooled liquid (SCL). We demonstrate that thin films of N , N ′-bis(3-methylphenyl)- N , N ′-diphenylbenzidine molecular glass, when vapor deposited below a certain temperature, can access a high-density supercooled liquid (HD-SCL) state through a liquid–liquid phase transition ∼ 35 K below the nominal glass transition temperature of ordinary SCL. The HD-SCL phase transforms into the ordinary SCL when the thickness is increased above 60 nm, demonstrating that HD-SCL is only thermodynamically favored in thin films. These results provide a recipe for accessing kinetically inaccessible regions in the energy landscape, which are critical for understanding the glass transition phenomenon. High-density stable glass states that can resist crystallization and dewetting is also important in various applications.