ABSTRACT Studies on critical behaviour associated with different phase transitions are of fundamental importance in condensed matter physics and may suitably be explored in the realm of soft materials. In this work, we report on high-resolution measurements of specific heat capacity (C p) from modulated differential scanning calorimetry (MDSC) to investigate the critical behaviour at the smectic A to nematic (SmA–N) phase transition in a binary system consisting of nonyloxy-cyanobiphenyl (9OCB) and heptylcyanobiphenyl (7CB). All the investigated mixtures exhibit detectable SmA–N heat capacity anomaly with gradually increasing peak height with enhancement in the concentration of 9OCB. Critical exponent α, obtained from the analysis of temperature dependence of the specific heat capacity data at the SmA–N phase transition, has been observed to assume values between those predicted for the 3D-XY and tricritical systems. The outcomes are also compared with those obtained from the high-resolution optical birefringence measurements.

中文翻译：

---

极性-极性二元体系中近晶 A 到向列相转变附近临界行为的量热研究

摘要 对与不同相变相关的临界行为的研究在凝聚态物理学中具有根本重要性，并且可以在软材料领域进行适当的探索。在这项工作中，我们报告了从调制差示扫描量热法 (MDSC) 中对比热容 (C p) 的高分辨率测量，以研究二元系统中近晶 A 到向列 (SmA-N) 相变的临界行为壬氧基-氰基联苯 (9OCB) 和庚基氰基联苯 (7CB)。所有研究的混合物都表现出可检测的 SmA-N 热容异常，峰高随着 9OCB 浓度的增加而逐渐增加。临界指数 α，从 SmA-N 相变比热容数据的温度依赖性分析中获得，已经观察到假设值介于 3D-XY 和三临界系统的预测值之间。结果还与从高分辨率光学双折射测量中获得的结果进行了比较。