Topological defects commonly emerge during phase transitions, with their topological charge ($s$) serving as a discrete invariant that dictates defect stability, dynamics, and ordering pathways. Liquid crystals across the nematic-smectic A (N-SmA) transition provide an ideal model for exploring how $s$ constraints govern defect evolution, yet the role of non +1 charges in mediating smectic order remains largely unexplored. Here, we systematically investigate the influence of $s$ on defect evolution during the N-SmA phase transition by combining photoalignment lattices with distinct topological charge distributions and a vertically aligned surface. For $s=+1/2$, cooling from the isotropic to the N phase generates disclination lines. During subsequent thermal cycling across the N-SmA transition, these lines reorient and induce the formation of previously unreported deformed semitoroidal focal conic domains (semi-TFCDs). Landau–de Gennes simulations reveal that the morphological transition in the N phase originates from a geometric transformation of the disclination lines, driven by constraints imposed by the emergence of layered structures. Further analysis indicates that splay deformation promotes TFCD generation. This is confirmed by the observation that reducing the distance between relatively oriented +1/2 alignment singularities diminishes the bending contribution and leads to ordered TFCD formation. In addition, as $s$ increases, the total director rotation within a unit region changes by 2πs, thereby altering the splay-to-bending deformation ratio. At $s=+1$, pure radial splay yields optimal ordered TFCDs. For $s=+3/2$, splay and bending coexist; the unsuppressed bending deformation disrupts layer continuity, resulting in frustrated TFCD arrays. For higher $s$, bending deformation dominates, causing fragmentation and disorder of SmA textures, and irregular TFCDs form at positions dominated by splay deformation. In this work, we advance the understanding of topological defect-mediated phase transitions by revealing the rich morphological diversity arising from the interplay between topological constraints and molecular deformations. We also offer broader insights into soft matter physics, where topological defects serve as fundamental building blocks for hierarchical self-assembly, pattern formation, and the design of functional materials.

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• Landau theory
• Order parameters
• Phase transitions
• Topological defects
• Liquid crystals
• Thermal techniques