TY - JOUR
T1 - Low temperature aging in a molecular glass
T2 - The case of: cis -methyl formate
AU - Cassidy, Andrew
AU - Jørgensen, Mads R.V.
AU - Glavic, Artur
AU - Lauter, Valeria
AU - Plekan, Oksana
AU - Field, David
N1 - Publisher Copyright:
© the Owner Societies.
PY - 2021/8
Y1 - 2021/8
N2 - Glassy films of cis-methyl formate show spontaneous dipole orientation on deposition from the vacuum, the so-called 'spontelectric effect', creating surface potentials and electric fields within the films. We follow the decay of these fields, and their accompanying dipole orientation, on the hours timescale at deposition temperatures between 40 K and 55 K. Our data trace the low temperature 'secondary decay' mechanism, at tens of degrees below the glass transition temperature of 90 K. We show that secondary decay is due to molecular rotation, with associated activation energies lying between 0.1 and 0.2 eV. Diffusion is absent, as established from published neutron reflectivity data. Using an analytical model for the spontelectric effect, data are placed on a quantitative footing, showing that angular motion in excess of 50° reproduces the observed values of activation energies. Exploitation of the spontelectric effect is new in the study of glass aging and is shown here to give insight into the elusive processes which take place far from the molecular glass transition temperature. This journal is
AB - Glassy films of cis-methyl formate show spontaneous dipole orientation on deposition from the vacuum, the so-called 'spontelectric effect', creating surface potentials and electric fields within the films. We follow the decay of these fields, and their accompanying dipole orientation, on the hours timescale at deposition temperatures between 40 K and 55 K. Our data trace the low temperature 'secondary decay' mechanism, at tens of degrees below the glass transition temperature of 90 K. We show that secondary decay is due to molecular rotation, with associated activation energies lying between 0.1 and 0.2 eV. Diffusion is absent, as established from published neutron reflectivity data. Using an analytical model for the spontelectric effect, data are placed on a quantitative footing, showing that angular motion in excess of 50° reproduces the observed values of activation energies. Exploitation of the spontelectric effect is new in the study of glass aging and is shown here to give insight into the elusive processes which take place far from the molecular glass transition temperature. This journal is
UR - http://www.scopus.com/inward/record.url?scp=85111636182&partnerID=8YFLogxK
U2 - 10.1039/d1cp01332g
DO - 10.1039/d1cp01332g
M3 - Journal article
C2 - 34279530
AN - SCOPUS:85111636182
SN - 1463-9076
VL - 23
SP - 15719
EP - 15726
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 29
ER -