Studies of molecular dynamics and non-isothermal crystallization process of 4-n-butyloxybenzylidene-4′-n'-octylaniline (BBOA) liquid crystal under two dimensional nano-confinement Małgorzata Jasiurkowska-Delaporte a, ⁎, Ewa Juszyńska-Gałązka a , Piotr M. Zieliński a , Monika Marzec b a Institute of Nuclear Physics Polish Academy of Sciences, PL-31342 Krakow, Poland b Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków, Poland abstract article info Article history: Received 12 December 2019 Received in revised form 21 March 2020 Accepted 31 March 2020 Available online 02 April 2020 The impact of confinement imposed by cylindrical pores of alumina matrix on the molecular dynamics and phase behavior of BBOA liquid crystal was examined by a combination of Broadband Dielectric Spectroscopy (BDS), Dif- ferential Scanning Calorimetry (DSC) and Fourier-Transform Infrared Spectroscopy (FTIR) methods. The phase transition temperatures as a function of inverse pore diameter show linear dependence. The BDS studies revealed new relaxation processes related to gradual paranematic-to-nematic transition in nanopores. Special emphasis is given to the influence of spatial constraints on the non-isothermal crystallization process upon cooling. Further- more, the analysis of temperature dependent IR spectra of BBOA pointed out that the band ascribed to vibration of methylene group ν s (CH 2 ) changes abruptly at crystallization temperature in bulk whereas a continuous tem- perature evolution of the ν s (CH 2 ) band shift upon crystallization was observed under confinement. © 2020 Elsevier B.V. All rights reserved. Keywords: Confinement Liquid crystals Phase transition Inter- and intra-molecular dynamics Kinetics of crystallization process Broadband dielectric spectroscopy Differential scanning calorimetry Fourier-transform infrared spectroscopy 1. Introduction The understanding of self-organization phenomena in soft matter system is one of the challenges of present-day condensed matter phys- ics. Materials showing spontaneous order, such as liquid crystals (LCs) have attracted wide attention due to their interesting physical proper- ties and technological importance in various fields like electronics [1], photonics [2], telecommunications [3] and medicine [4–6]. In the con- text of current trend in device miniaturization and development of nanotechnology it is essential to elucidate behavior of liquid crystalline materials in spatial restriction. Araki et al. [7] demonstrated by Monte Carlo simulations that LCs in porous matrix offer promise for the design of low-power optical devices. These studies report that porous structure imposed a high density of topological defect lines in liquid crystalline phases. Moreover, such system shows the capability to keep memory about the molecular alignment forced by external electric field. Numerous scientific papers report different theoretical [8–10] and experimental [11–19] studies of liquid crystals confined in various host systems. New material properties originating from finite size of pores and interaction between molecules and pore surface have been found, including optical properties [20], dynamic peculiarities [21–29] and phase diagram different than in bulk [30,31]. It was concluded that a change in the transition temperature origins from two competing effects: orientational order locally imposed by pore surface that in- creases the transition temperature and disordering effect resulting from the elastic forces and rearrangement of defect lines which cause the reduction of the transition temperature. For example, 5CB liquid crystalline compound enclosed in a nanoporous aluminium oxide (AAO) matrix [32] demonstrates a linear reduction of nematic to isotro- pic (N/I) and nematic to crystal transition (Cr/N) temperatures with de- creasing reciprocal of pore diameter. Interestingly, the relatively large nanopores can increase the temperature of N/I transition. In the case of rode-like liquid crystalline molecules a surface potential within the pores plays a role of an ordering field [25,33–35]. It was proved that the chemical modification of the inner pore surface affects the thermo- dynamics [34] and dynamics properties of [11,36–38]. Our previous paper reports the impact of nanometric confinement on inter- and in- tramolecular dynamics of 4-heptyl-4′-isothiocyanatobiphenyl (7BT) [31]. It was found that the smectic E (SmE) phase occurring in bulk 7BT is replaced by surface induced molecular order. An analysis of the temperature dependencies of infrared absorption bands revealed the different influence of spatial constraint on flexible and rigid molecular units: i.e. the amorphous-like behavior of alkyl chains and the gradual ordering of molecular cores during cooling. Combined dielectric studies Journal of Molecular Liquids 308 (2020) 113039 ⁎ Corresponding author. E-mail address: Malgorzata.Jasiurkowska-Delaporte@ifj.edu.pl (M. Jasiurkowska-Delaporte). https://doi.org/10.1016/j.molliq.2020.113039 0167-7322/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq