Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

A Landau-de Gennes model that integrates the nematic quadrupolar tensor order parameter and complex smectic-A order parameters is used to simulate the two-dimensional growth of an initially homogeneous smectic-A spherulite in an isotropic matrix. These simulations are performed in the shape-dynamic (nano-scale) regime of growth under two material conditions: isotropic nematic elasticity and equal splay-bend nematic elasticity. A comparison of the growth kinetics, spherulite morphology, interfacial/bulk energy landscapes between both cases is made showing that equal nematic splay-bend elasticity is required to reproduce past experimental and theoretical observations. Additionally, a previously unknown undulation instability during spherulite growth is found which, in conjunction with preferred planar anchoring and defect shedding mechanisms at micron length scales, could explain the formation mechanism of focal conic curvature defects and ultimately smectic-A "batonnet" structures observed experimentally.