Abstract
Infrared Transition Moment Orientational Analysis (IR-TMOA) and Broadband Dielectric Spectroscopy
(BDS) are combined to study molecular order and dynamics of the glass-forming liquid
Tris(2-ethylhexy)phosphate (TEHP) confined in uni-directional nanopores with diameters of 4, 8,
and 10.4 nm. The former method enables one to determine the molecular order parameter of
specific IR transition moments. It is observed that the central P=O moiety of TEHP has a weak
orientational effect (molecular order parameter Sz =−0.1±0.04) due the nanoporous confinement,
in contrast to the terminal C–H groups. BDS traces the dynamic glass transition of the guest
molecules in a broad spectral range and at widely varying temperature. An enhancement of
the mobility takes place when approaching the glass transition temperature and becomes more
pronounced with decreasing pore diameter. This is attributed to a slight reduction of the density of
the confined liquid caused by the 2-dimensional geometrical constraint.