Supplementary Information
1. Removal of Liquid Crystals from sample cells:
The homogeneous Mixture 1, which consisted of ZLI-2293, CB15,
BAHB, and photoinitiator at weight ratios of 53.3%, 13.3%, 33.3%, and
0.1%, respectively, was prepared to form a CLC phase with helical
molecular orientations at room temperature. A glass cell (10 μm thick)
was filled with Mixture 1 at room temperature by capillarity. The
PVA-coated inner surfaces of the cell had been rubbed to induce a planar
orientation. The cell containing Mixture 1 (called Cell A) was irradiated
with UV light (254 nm) for 1 hr to perform the photopolymerization that
leads to the formation of polymer dispersed cholesteric liquid crystal
(PDCLC cells). After UV irradiation, the cell was extracted with acetone
and then with CHCl3 for two days to remove any LC, chiral dopant, and
unreacted monomer thoroughly from the cell. Next, the cell was dried at
40°C in vacuo for 6 hr (Cell C). Thus, the imprinted cross-linked polymer
network was fabricated inside the cell. Finally, Cell C was refilled (by
capillary action) with each of nematic LCs ZLI-2293 and E7 without any
chiral dopant.
Organic solvent
Prepared LC cell
Grill stand
Magnetic stirring bar
Magnetic stirrer
Figure 1
After UV irradiation, the polymerized cell was extracted in solvent with
gentle stirring. After evaporating the solvent from the initially extracted
LC mixture, the residual LC was checked using FTIR. No residual
monomer was found in the LC mixture.
1
2. Fabrication of sample cells:
Spacer
(Side view)
(Top view)
Figure 2
A glass cell (20 μm thick) was filled, by capillarity, with Mixture 1 at
room temperature. The PVA-coated inner surfaces of the cell had been
rubbed to induce a planar orientation.
3. Photo-Polymerization:
UV lamp (254 nm, 6 Watt)
3 cm
Sample cell
Figure 3
Photo-polymerization was carried out using a 254 nm UV-lamp for 1
hour. The distance between UV-lamp and sample cell is 3 cm.
4. Measurement of reflection spectra:
Optical fiber (Ocean Optics R400-7-SR)
Light source
(Ocean Optics LS-1)
Detector
Sample cell
Data processor and
Recorder
Figure 4
An optical fiber system was used to measure the reflection spectrum
of the sample cells. Stander plates were used for both zero and complete
reflection calibrations.
After polymerization, the cross-linked polymer matrix could not be
further dissolved in liquid crystals. Consequently, the imprinted helical
2
pitch was considered to be fixed. The pitch of cholesteric liquid crystals
was estimated using Equation (1). Theoretically, from UV-vis spectra (λ0),
the approximate pitch of cholesteric liquid crystals can be calculated.
λ0 = navg P
(1)
5. Molecular structure of difunctional photopolymerizable monomer
BAHB, 4,4’-Bis(6-acryloyxy-hexyloxy)biphenyl, which was
synthesized in our lab. The detailed process has been previously
described in the following article.
Title: Fabrication and characterization of polymer stabilized cholesteric
liquid crystal cells with chiral monomers derived from borneol
Authors: Liu, Jui-Hsiang; Hung, Hsien-Jung
Source: Liquid Crystals, Volume 32, Number 1, January 2005 , pp.
133-142(10)
(C30H38O6)
3