Camille Bishop, a 5th-year graduate student working in Mark Ediger’s group as part of the MRSEC IRG 1, presented her work on liquid crystal-like order in vapor-deposited glasses at the Gordon Conference on Liquid Crystals in New London, NH that took place from July 7th-12th, 2019. The poster shows a wide range of different organic glasses created using physical vapor deposition, a thin film fabrication technique. How to control and tune the molecular organization in these structured glasses is discussed. Control of the structure in these sorts of materials should enable them to be applied to novel organic electronics.

1. Vapor-deposited glasses with tunable liquid crystal-like order
Camille Bishop1, A. Gujral1, M.F. Toney2, H. Bock3, L. Yu1,4, M.D. Ediger1
Conclusions and Outlook
• Glasses with varying liquid crystal-like order
and alignment can be created by physical
vapor deposition
• Vapor-deposited glass structure is
determined by deposition rate and substrate
temperature
• The effects of deposition rate and substrate
temperature can be related by a “Rate-
Temperature Superposition”
• Future work will optimize molecular packing
in columnar systems, with eventual focus on
anisotropic mechanical, optical, and
electronic properties
2D X-ray Scattering
Grazing-incidence X-ray scattering
measurements are used to probe anisotropic
translational order
1. Department of Chemistry, University of Wisconsin-Madison, 2. Stanford Synchrotron Radiation
Lightsource, 3. Centre de Recherche Paul Pascal, Université de Bordeaux & CNRS, 4. School of
Pharmacy, University of Wisconsin-Madison
Physical Vapor Deposition
• Organic molecules are evaporated and
deposited on bare Si in a high vacuum (10-6
Torr) chamber
• Highly mobile and structured free surface of
growing thin film results in anisotropic glasses
• Both the deposition rate
and the temperature of the
substrate during deposition
are varied to modify film
structure
L. Berthier, M.D. Ediger. Physics Today 69 (2016).
Rate-Temperature Superposition controls glassy structure in
Itraconazole and Posaconazole
Right: To tune the degree of molecular orientation
in vapor-deposited itraconazole glasses, both the
deposition rate and substrate temperature during
deposition can be changed. Depositing more
slowly is equivalent to depositing at a higher
substrate temperature – a 5.1 K increase in
substrate temperature produces an orientation
equivalent to depositing 10 times more slowly.2
Right: Posaconazole also obeys a Rate -
Temperature Superposition for molecular
orientation similar to that of its structural analog,
itraconazole – raising the substrate temperature
during deposition by 5.1 K produces an orientation
equivalent to depositing 10 times more slowly.
Below: The degree of orientational and smectic-
like order in posaconazole (despite it having no
equilibrium LC phases) can be tuned by either
substrate temperature or deposition rate.3
320K, 2 Å/s 325K, 2 Å/s 325K, 0.2 Å/s
0.2 0.4 0.6 0.8 1.0
Intensity(a.u.)
q (Å-1
)
320K, 2 Å s-1
325K, 2 Å s-1
325K, 0.2 Å s-1
Liquid-cooled
Decreasing effective rate
Decreasing
effective rate
Introduction
Physical vapor deposition
is used to create glasses
with high levels of tunable
liquid crystal-like order.
Three molecules – two
with equilibrium liquid
crystal phases, and one
By U.S. Army RDECOM -
https://www.flickr.com/photos/rdecom/4146880795/, CC BY
2.0,
https://commons.wikimedia.org/w/index.php?curid=9475694
without – were vapor deposited at various
deposition rates and temperatures to create
glasses with smectic-like and hexagonal
columnar order. Notably, the alignment of the
liquid crystal-like phases can be altered
without using any alignment layers. We find a
“deposition rate/substrate temperature
superposition principle” for which raising the
substrate temperature produces an equivalent
molecular orientation to depositing more
slowly. The superposition principle facilitates
the design of glasses with unique structural
properties by varying only two deposition
parameters, which should expand the range of
flexible, anisotropic materials for new organic
Preparing glasses with frozen liquid crystal-like order
Glassy solids with various degrees of liquid crystal-
like order and alignment can be produced by
physical vapor deposition. Top left: A)
Itraconazole, a smectic liquid crystal, can be vapor
deposited to produce glasses with varying degrees
of smectic-like order1,2. Bottom left: B)
Posaconazole has no known equilibrium LC
phases, yet forms a smectic-like glass when vapor
deposited.3 Top right: C) Phenanthroperylene, a
columnar liquid crystal, can be vapor-deposited to
create glasses with aligned columnar order.4
A) Itraconazole
High Tsub/
Low rate
Low Tsub/
High rate
B) Posaconazole
High Tsub/
Low rate
Low Tsub/
High rate
C) Phenanthroperylene
High Tsub
Low Tsub
Rate-Temperature superposition
of columnar structure
Preliminary data suggests that vapor-deposited
phenanthroperylene, a system with equilibrium
hexagonal columnar order, may obey a Rate-
Temperature superposition similar to those
seen for smectic-like systems. Both raising the
substrate temperature and decreasing the
deposition rate appear to increase the
hexagonal columnar order in the vapor-
deposited glass.
Tsub = 380K
Rate = 6 Å s-1
Tsub = 380K
Rate = 0.1 Å s-1
Tsub = 392K
Rate = 6 Å s-1
Raise TsubDecrease
rate
qxy
qz
References & Acknowledgements
1. A. Gujral et. al. Chem. Mater. 29 (2017) 849-
858.
2. C. Bishop et. al. J. Phys. Chem. Lett. 10 (2019)
3536-3542.
3. C. Bishop et. al. Submitted.
4. A. Gujral et. al. Chem. Mater. 29 (2017) 9110-
9119.
DMR-1720415 DE-AC02-76SF00515
electronics. Glasses
are ideal for
applications which
require
homogeneity,
processability, and
compositional
flexibility.