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The influence of controlled-pore glass (CPG) confinement on the phase behavior of octylcyanobiphenyl liquid crystal (LC) is studied by means of x-ray scattering and high precision calorimetry. For CPG samples with pore diameter 2R>24 nm, the smectic order parameter temperature dependence η(T) reveals apparent presmectic ordering far above the bulk smectic A–nematic (SmA-N) phase transition for both nontreated and silane-treated CPG matrices. The behavior of η(T) is qualitatively similar in all samples, well obeying the mean field approach (MFA) in which the surface wetting tendency plays the dominant role. In contrast, the critical fluctuations remain important in the specific heat data, which cannot be described within the MFA. We show experimentally that randomness and surface wetting become dominant over finite-size effects for 2R≤=10 nm, in agreement with theoretical analysis. In nontreated samples, the noncritical character of the static disorder and the interfacial LC-CPG coupling almost completely suppress the quasi-SmA-N and nematic-isotropic phase transitions at 2R∼15.1 and ∼7.5 nm, respectively. [ABSTRACT FROM AUTHOR]

We study the temperature evolution of smectic ordering of 8CB liquid crystal confined to various CPG matrices. The characteristic diameters of matrices ranged from 24 nm to 128 nm. The CPG voids were either left non-treated or were treated with silane. A weakly 1st order N-SmA transition in bulk 8CB, which could be attributed to the Halperin-Lubensky-Ma (HLM) effect, is broadened in confined samples. In confined samples substantial pretransitional anchoring was also observed, particularly in the silane-treated samples. [ABSTRACT FROM AUTHOR]