Systematic elucidation of crystal structure of fluorinated gemini-type diamide derivatives having different lengths with thixotropic induced-ability to solvents

Article abstract of DOI:10.1016/j.jfluchem.2020.109505

Molecular packing structures for Gemini-type diamide derivatives with different linker and fluoroalkyl chain lengths were systematically determined using reciprocal lattice analysis. Diamide derivatives with two fluorocarbons, in which the linker was replaced with one hexamethylene chain and one pentamethylene chain, exhibited hydrogen bonding and crystallinity. Powder X-ray diffraction profiles displayed extremely sharp diffraction peaks like inorganic materials. Small-angle X-ray scattering analysis indicated extended chain crystals (ECCs) in these molecular groups. Reciprocal lattice analysis and high crystallinity allowed for the development of packing models for all compounds used in this study. Fifteen compounds were assigned to nearly orthorhombic and/or slightly distorted monoclinic systems, with one exception. All fluorinated Gemini-type diamides are characterized by a developed c-axis and have an ab-plane area that can accommodate a fluorocarbon chain. These fluorinated Gemini-type diamide derivatives are candidates for additive molecules to induce solvent thixotropy and form crystalline nanofibers through intermolecular hydrogen bonding. A correlation was found between molecular chain packing and crystal growth; a helical growth mode that permits gel formation by incorporating solvent molecules was also confirmed.

Full text of DOI:10.1016/j.jfluchem.2020.109505

Journal Pre-proof
Systematic Elucidation of Crystal Structure of Fluorinated Gemini-Type
Diamide Derivatives Having Different Lengths with Thixotropic
Induced-Ability to Solvents
Haruka Maruyama, Keito Fukushi, Rei Okano, Eiichi Satou, Tomoko
Yajima, Atsuhiro Fujimori
PII:
S0022-1139(20)30056-7
DOI:
https://doi.org/10.1016/j.jfluchem.2020.109505
FLUOR 109505
Reference:
To appear in:
Journal of Fluorine Chemistry
Received Date:
Revised Date:
Accepted Date:
27 November 2019
29 February 2020
3 March 2020
Please cite this article as: Maruyama H, Fukushi K, Okano R, Satou E, Yajima T, Fujimori A,
Systematic Elucidation of Crystal Structure of Fluorinated Gemini-Type Diamide Derivatives
Having Different Lengths with Thixotropic Induced-Ability to Solvents, Journal of Fluorine
Chemistry (2020), doi: https://doi.org/10.1016/j.jfluchem.2020.109505
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Systematic Elucidation of Crystal Structure of Fluorinated
Gemini-Type Diamide Derivatives Having Different
Lengths with Thixotropic Induced-Ability to Solvents
Haruka Maruyama,a Keito Fukushi,b Rei Okano,c Eiichi Satou,c Tomoko Yajima,d
Atsuhiro Fujimorib,*
a Faculty of Engineering, and b Graduate School of Science and Engineering, Saitama
University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan
c R & D Dept. Laboratory Additive Unit, Kusumoto Chemicals Ltd., 4-18-6, Benten, Soka-shi
Saitama, 340-0004, Japan
d Department of Chemistry, Faculty of Science, Ochanomizu Univ, Bunkyo-ku, Tokyo, 112-
8610, Japan
*Corresponding Author
1

Tel. and Fax: +81 48 858 3503
E-mail address: fujimori@apc.saitama-u.ac.jp
Graphical Abstract
H. Maruyama, et al
Highlight
 Fluorinated Gemini-type diamide derivatives with different length were systematically
synthesized.
 Crystal structure of fluorinated diamides were systematically analyzed.
 Fluorinated diamides used in this study formed extended chain crystals.
 Almost all fluorinated diamides formed monoclinic packing.
 Fluorinated diamides used in this study indicated gelation ability of solvents.
ABSTRACT
Molecular packing structures for Gemini-type diamide derivatives with different linker
and fluoroalkyl chain lengths were systematically determined using reciprocal lattice analysis.
Diamide derivatives with two fluorocarbons, in which the linker was replaced with one
2

hexamethylene chain and one pentamethylene chain, exhibited hydrogen bonding and
crystallinity. Powder X-ray diffraction profiles displayed extremely sharp diffraction peaks
like inorganic materials. Small-angle X-ray scattering analysis indicated extended chain
crystals (ECCs) in these molecular groups. Reciprocal lattice analysis and high crystallinity
allowed for the development of packing models for all compounds used in this study. Fifteen
compounds were assigned to nearly orthorhombic and/or slightly distorted monoclinic
systems, with one exception. All fluorinated Gemini-type diamides are characterized by a
developed c-axis and have an ab-plane area that can accommodate a fluorocarbon chain.
These fluorinated Gemini-type diamide derivatives are candidates for additive molecules to
induce solvent thixotropy and form crystalline nanofibers through intermolecular hydrogen
bonding. A correlation was found between molecular chain packing and crystal growth; a
helical growth mode that permits gel formation by incorporating solvent molecules was also
confirmed.
Keywords: Gemini-type diamides; fluorocarbons; crystalline packing; reciprocal lattice
analysis; thixotropic molecules
3

1. Introduction
Recently, the behavior exceeding the hierarchy, from the microscopic molecular level to
beyond the mesoscopic form to the macroscopic physical properties, is called the "cooperative
phenomenon" [1]. These phenomena are not easily predicted by technology. On the sub-
nanometer level, molecular groups can aggregate [2], orient [3], and integrate [4], in specific
patterns to create micrometer-scaled morphologies with physical properties that can be
studied at the millimeter-to-meter scale. However, the physical properties and functionality
measured on this scale may not account for factors other than molecular characteristics.
Supramolecular chemistry [5] represents one approach to studying higher-order structures [6]
and physical properties of molecular groups exceeding hierarchy by organizing/assembling
molecules [7, 8].
“Host-guest” compounds [9], such as crown ethers [10] and cyclodextrins [11], are well-
known in classical supramolecular chemistry for their ability to contain molecules and ions
via intermolecular interactions. Liquid crystals [12], organic crystals [13], Langmuir-Blodgett
(LB) films [14-17], self-assembled films [18], and biomolecular structures [19], are also
regarded as supramolecules. In addition, liposomes [20] and micelles [21], used in drug
delivery systems [22], are considered to be supramolecules. Supramolecules can form from
various forces, including van der Waals interactions (which are enhanced by molecular
4

arrangements) [23], hydrogen bonding [24], π-π interactions [25], and CH-π interactions [26],
all of which are capable of long-range interactions [27].
Multiple molecular functions can be induced using the supramolecular super-hierarchical
[28] cooperative effect. These attractive effects, such as liquid crystallinity [29], chirality
[30], light emission properties [31], magnetism [32], polarization [33], mechanical properties
[34], water/oil repellency [35, 36], and transparency/light propagation properties [37, 38],
stem from the properties of molecular groups. The phenomenon of gelation [39] often results
from hydrogen bond networks formed between solvated molecules [40]. Thixotropy can result
from similar forces [41]. Thixotropy can be defined as an increase in viscosity over time [42].
Using molecular technology, sponge-like gel structures trap solvent molecules, mainly
through fiber entangling via hydrogen-bond-induced molecular organization [43]. Because
hydrogen bonds are easily broken by applied external forces, the morphological structure
disintegrates and the solvent can flow freely [44]. When this behavior is reproduced under
static conditions, thixotropy is achieved by the additive molecule [45].
When used for industrial applications, this technology will not only increase viscosity,
but will require the surrounding solvent to be gelled or solidified. Additional applications may
be possible for gelation and thixotropy as well. For example, it may be possible to create
multitasking thixotropic additive molecules by introducing functional sites that induce
hydrogen bonding. Importantly, all molecular functions are derived from structure. However,
5

the unique function of a multifunctional molecule is difficult to predict unless the aggregate
structure spontaneously formed by the molecular group can be analyzed. We studied diamide-
based Gemini-type thixotropic additive molecules that are also used as anti-drip agents for
automotive paints. The corresponding molecule is modified with fluorocarbon to ensure that
the paint has thixotropic properties and is water- and oil-repellent (to promote a clean painted
surface). Since fluorocarbons are dispersible in nonpolar solvents [46], new thixotropic agents
have been developed with a wide choice of solvents. Moreover, the use of such paints on
watercraft could prevent the adherence of barnacles, which stick firmly to the hull and
promote pollution. Conventionally, a 2:1 condensed diamide derivative comprising 12-
hydroxystearic acid and a hexamethylenediamine that contains an asymmetric carbon has
been used as a thixotropic agent. Entanglement of the helical nanofibers via hydrogen
bonding controls the incorporation of solvent molecules. Over-developed fibers induce
contamination on the paint surface and lead to a nonuniform appearance due to visible light
scattering. Thus, it is important to control the physical properties derived from the structures
formed by thixotropic molecules [47-50].
In this study, we performed reciprocal lattice analysis [51] of wide-angle X-ray
diffraction data for precise analysis of the structure responsible for this function. This
technique can effectively obtain molecular packing using a powder or thin film sample
without requiring a single crystal [52]. As there are few examples of detailed structures of
6

aggregates of fluorine-based low-molecular compounds, this study contributes to our
understanding of solid structures for the molecular group (Fig. 1).
2. Materials and methods
2.1. Synthesis of fluorinated Gemini-type diamide derivatives with different chain
lengths
Figures 2 (a) and (b) show the compounds used in this study. Diamide derivatives
having one pentamethylene linker and two fluorocarbons with chain lengths CnF2n+1 (n = 1–7)
and having one hexamethylene linker and two fluorocarbons with chain length CnF2n+1 (n =
1–9), were used. The former and the latter are designated 2FnC5-diamides and 2FnC6-
diamides, according to their chain lengths, respectively. Schemes 1(a) and (b) describe the
synthesis of the compounds used in this study using linker starting materials
pentamethylenediamine and hexamethylenediamine, respectively. Three equivalents of
methyl fluorinated long chain carboxylate was added to tetrahydrofuran (THF) solvent at 0 °C
for 1 h to obtain the compound. After the reaction, compounds were purified by column
chromatography, and target compounds were obtained in 79–98% yield. Synthesis was
confirmed by nuclear magnetic resonance spectroscopy (NMR). Furthermore,
recrystallization was performed using THF and hexane, and high purity compounds were
obtained.
7

The reason for the comparative selection between the hexamethylene and the
pentamethylene linkers is to evaluate whether the orientation of the amide group has any
effect. Many of the diamide-based thixotropic additives that have been practically used
conventionally are those having a hexamethylene linker. Even from experimental facts,
molecules with short linkers are disadvantageous for expressing gelation ability. In this study,
in order to verify the odd-even effect of the linker length, we used a group of compounds with
different linker lengths. Detailed chemical structure analysis data including 1H NMR, C13
NMR, 19F NMR, etc. are shown in Supporting Information.
2.2. Hydrogen bonding and the solid-state structures of fluorinated Gemini-type diamide
derivatives
Infrared (IR) spectroscopy was performed with all synthesized compounds (Bruker AXS
Tensor II) to evaluate the formation of hydrogen bonding. For transmission measurements, 32
scans were accumulated using the KBr disk method. In addition, wide-angle X-ray diffraction
(WAXD) was measured to evaluate the crystal structure and crystallinity of each sample
(Bruker AXS D8 Advance, CuKα radiation, 40 kV, 100 mA). The apparatus was equipped
with a rotating anode source and a two-dimensional semiconductor detector for high power
measurement. Further, higher-order structural analysis was conducted using small-angle X-
ray scattering (SAXS, Rigaku Nanoviewer, CuKα radiation, 40 kV, 40 mA). Similarly, this
8

instrument was equipped with a rotating anode source and a two-dimensional semiconductor
detector. To elucidate molecular packing, reciprocal lattice analysis was performed with the
WAXD data. The lattice constant of stearic acid [53] or polytetrafluoroethylene [54] was used
as the initial value for calculations.
2.3. Gelation, thixotropy, and nanofiber morphology of fluorinated Gemini-type diamide
derivatives
Gelation tests were performed using ethanol, hexane and benzene solvents. For each
solvent, fluorinated Gemini-type diamide derivative was introduced as a thixotropic additive
at 1 wt%. The solution was warmed to 80 °C, then cooled to room temperature once the
additive was dissolved. The gelled sample was dried and the xerogel was observed using a
scanning electron microscope (SEM, Hitachi SU8030 ultrahigh resolution field emission
SEM). In addition, a spin-cast film was prepared from a 9:1 solvent mixture of
xylene/ethanol, and detailed morphological observations were made using an atomic force
microscopy (AFM, SII SPA300 with SPI3800 probe station, Dynamic Force Mode, Si tip
with spring constant 1.5 N / m).
3. Results and Discussion
9

Figure 3 shows IR spectra of fluorinated Gemini-type diamide derivatives with different
lengths and linkers. In these spectra, C-F stretching vibrations are observed equally at
approximately 1000–1200 cm–1, and a carbonyl band is observed at 1700 cm–1. The broad
band around 2350 cm–1 is derived from carbon dioxide, though to a varying degree. One
critical feature in the spectra of these derivatives is the presence of an amide band around
3200–3300 cm–1. This absorption band is isolated: there is no hydrogen bonding band for a
free amide around 3700 cm–1. Thus, the spectra indicate that hydrogen bonding networks lead
to the structure observed for each derivative.
Figure 4 shows WAXD profiles of fluorinated Gemini-type diamide derivatives with
different lengths and linkers. What can be seen at a glance is that all compounds display high
crystallinity based on the occurrence of very sharp diffraction peaks. Many of the compounds
display periodic structure developed on the low-angle side. For example, compounds other
than 2F9C6 and 2F5C5-diamides etc. show sharp, high-intensity diffraction peaks at low
angles. This indicates that it has a structure developed in the c-axis direction. 2F9C6 and
2F5C5-diamides have relatively low intensity diffraction peaks and are wide, but all
diffraction lines can be indexed. In this case, d100, d111, d120 (2F9C6-diamide), or d010, d110, d111
(2F5C5-diamide) strongly reflects the order of crystal planes existing relatively in the ab-
plane. On the other hand, the d002 planes, which are weak but corresponds to the order in the
c-axis direction, is confirmed in both profiles. Since long-chain compounds are easy to orient,
10

many compounds show a structure developed in the c-axis direction, but some substances
may remain relatively isotropic. By the way, in general, amphiphiles and/or polymers having
long fluorocarbons tend to exhibit strong diffraction peaks derived from the distance between
two-dimensional fluorocarbons (around 5.0 Å ). Here, clear diffraction peaks were observed
from approximately d = 4.4 to 4.7 Å . For hydrocarbon compounds, this spacing narrows to
around 4.1 to 4.2 Å . In low molecular weight compounds composed of light elements, the
diffraction peak is clearly visible because the X-ray scattering factor for fluorine atoms is
relatively large. However, the half-width of the peak indicates that these compounds are
highly ordered. IR measurements suggest that regulated structure is likely based on highly
developed hydrogen bonding. Due to the abundant number of sharp diffraction peaks, we
used reciprocal lattice analysis to determine the systematic crystal structures and molecular
packing for these fluorinated molecular groups. An accurate understanding of long-period
structures is required to proceed with this analysis reliably. Therefore, higher-order structure
analysis was performed for these compounds via SAXS measurements.
Figure 5 shows the SAXS patterns and profiles of excerpted fluorinated Gemini-type
diamide derivatives with different lengths and linkers. All SAXS patterns are circular and
show isotropic structures. Profiles obtained by integrating this pattern in the equatorial
direction show clear long-period values. In fact, almost all of these values correspond to the
extended chain length of each molecule. Thus, these fluorinated Gemini-type diamide
11

derivatives are extended chain crystals (ECCs). Based on this hypothesis, we have drawn a
packing model by indexing the WAXD diffraction peaks and applying reflection to the
reciprocal space. All the samples used in this study had a single melting point and were
analyzed as single-phase crystals at a measurement temperature 23 °C. This assumption is the
premise of the structural analysis in this study.
Figures 6, 7, and 8 show packing models for fluorinated Gemini-type diamide
derivatives by reciprocal lattice analysis. In particular, Figure 6 shows the crystal structure of
compounds with a pentamethylene linker and a fluorocarbon chain 1–6 carbon atoms long. Of
the 15 compounds used in this study, only 2F1C5-diamide could not be assigned using the
initial value referred to lattice constant for amphiphilic low molecular weight compounds. In
this case, the most appropriate initial value was the hexagonal packing of
polytetrafluoroethylene before a phase transition at room temperature. As a result, this
compound alone has a lattice structure comprising a rhombus-shaped unit cell composed of
two isosceles triangles. The a- and b-axes lengths are 5 Å , and the lattice constant is close to
that of a Teflon polymer. Since the molecular chain is short, we propose that a lattice structure
is formed in which the degree of rotation freedom of molecular chains is allowed at isotropic
molecular chain packing positions. On the other hand, the c-axis length is extremely
developed.
12

Although 2F2C5- and 2F3C5-diamides are both assigned to orthorhombic systems,
packing similar to the hexagonal crystal assignment for 2F1C5-diamide results when different
initial values are used in the calculations. The unit cell is rectangular, but the difference in
lattice distortion is small and the shape is anisotropic. In both cases, the b-axis is relatively
long, but the a-axis is about 5 Å . The a-axis had similar values for all compounds used in this
study. In addition, these materials are converged to an extreme developed structure along the
c-axis. The 2F4C5-, 2F5C5- and 2F6C5-diamides are attributed to monoclinic packing with
slightly reduced symmetry. Many of the packing structures of the compounds analyzed this
time were attributed to monoclinic packing. For the initial value, we used the lattice constant
for the polymorphic structure of stearic acid. Regardless of chain length, there is no
significant difference in the a-axis, and the b-axis is relatively long. Both have a developed
structure along the c-axis. Since angle β is not a right angle, the packing structure can be
drawn with inclination. As the chain length increases, in-plane interactions between the
helical fluorocarbon chains slightly increases, and a tilted molecular chain array forms.
Figure 7 shows the crystal structure of 2F7C5-diamide, and 2FnC6-diamide at n=1–4 with
hexamethylene linker. 2F7C5-diamide has the shortest a-axis length among pentamethylene
linker compounds and the anisotropy of unit cell is high. The c-axis becomes longer as the
molecular chain length increases and is the longest among the pentamethylene linker
compounds. The above seven compounds show relatively similar packing even if their crystal
13

systems are different, and the unit cell changes from isotropic to anisotropic arrangement as
the chain length increases, and lattice symmetry decrease. On the other hand, almost all
packing model of compounds with hexamethylene linkers assign to the monoclinic system. In
this figure, 2F1C6-, 2F3C6- and 2F4C5-diamides are assign ed to monoclinic packing. Since
exceptionally only 2F2C5-diamide forms orthorhombic packing, slightly high symmetric
packing appears to be achieved with relatively short chain lengths in these like materials. The
systematic resemblance of the a-axis length, the extension of the b-axis length to the a-axis
one, and the structure that is highly developed in the c-axis direction, including 2F5C6- to
2F9C6-diamides, show similar trends (Fig. 8).
The above results are summarized in Fig. S1 in the Supporting Information. It can be
seen that most of the structures are described by monoclinic packing, except for those of some
of the short-chain compounds. This lattice forms mainly from hydrogen bonds between amide
groups. However, since the extended chain-like packed structure has aligned molecular
phases, it is expected that the relatively weak van der Waals forces between fluorocarbons
will be enhanced. This enhancement of van der Waals interactions between fluorocarbons
likely distorts the lattice, leading to packing with vertical conformation and high symmetry
for the short chain compounds. Interestingly, this tendency tends to be higher for
pentamethylene compounds than for hexamethylene compounds. Since relatively strong van
der Waals forces exist between hydrocarbon chains, the lateral affinity is stronger for
14

hexamethylene compounds, thus they are more likely to produce more distorted lattices [55,
56]. As a result, the lattice packing of fluorinated Gemini-type diamide derivatives is
predicted to be hexagonal or orthorhombic with vertical chain conformation if intermolecular
hydrogen bonding alone is observed. As the hydrocarbon chain length increases, the strength
of the two-dimensional affinity slightly distorts the lattice and tends to converge to
monoclinic packing. In addition, these compounds form ECCs and develop periodic structures
along the c-axis, while the ab-plane creates a wide, anisotropic in-plane structure that can
easily accommodate thicker fluorocarbon chains of about 5 Å or more.
Table 1 shows the results of representative gelling tests with these compounds. The
thixotropic additives used in this study are intended to be applied and commercialized to
paints for private vehicles. The types of paints include aqueous solvents, phenyl solvents,
alcohol solvents, and normal alkane solvents. Ethanol, hexane, and benzene used in this study
are limited in their use due to their volatility and toxicity, but can be regarded as standard
solvents for the above paint-based solvents. Comparing compounds with the same
fluorocarbon length but different linker lengths, it can be seen that gelation ability with
phenyl solvents is high. This tendency was observed for toluene and xylene, as well as
benzene. On the other hand, pentamethylene compounds were able to gel hexane, a nonpolar
solvent. Hexamethylene compounds did not gel hexane but were able to gel alcohol. As the
chain length increases, solvent gelation ability is difficult to observe. Perhaps the pore size in
15

which these thixotropic additive molecules are fibrillated and entangled by hydrogen bonding
must match the size of the solvent molecule [49]: it may be difficult to create a pore size that
can easily incorporate large solvent molecules. Phenyl-type solvents are likely to be taken into
the intertwined fiber structure, due to their relatively large molecular size. Results indicate
that hexamethylene compounds can grow fibers even in polar solvents, but that longer
fluorocarbon chain lengths seem to lower solubility and cause precipitation. Thus, the
molecular size and solubility of the solvent appear to be a factor in the selectivity of solvent
gelation. In addition, all of the solvents that showed gelation also displayed thixotropic
properties; they flowed again when stimulated by a magnetic stirrer and re-gelled after a lapse
of time. This suggests that relatively weak hydrogen bonds are responsible.
Figure 9 shows a SEM image of nanofibers formed by a fluorinated diamide derivative
gelled with a benzene solvent. In this sample, the obtained benzene gel was dried and
observed as a xerogel. Almost all molecules that caused gelation displayed fibrous forms as
xerogels, but 2F2C5- and 2F3C5-diamides, whose crystal structure was attributed to
orthorhombic crystals, were particularly mixed, with many helical fiber forms. A 2F3C5-
diamide film was prepared by spin-casting and AFM was also conducted. A straight fiber
containing a partly spiral shaped fiber was observed. Helical morphology tends to occur when
molecules are packed more densely. In this study, the analyzed crystal lattice and fiber sizes
are disparate, but they may be influenced by the hyper-hierarchical cooperation effect [57].
16

Fibers with spirals tend to entangle efficiently, and solvent gelation tends to be more efficient.
These results are summarized in Fig. 10. In this study, molecular packing in the crystal
structure of fluorinated diamide derivatives with solvent thixotropic ability was systematically
shown. In future studies, we plan to clarify the correlation between molecular packing and
gelation.
4. Conclusions
Reciprocal lattices of fluorinated Gemini-type diamide derivatives with different
fluorocarbon and linker lengths were systematically analyzed to evaluate their molecular
packing. Diamide derivatives with hexamethylene and pentamethylene linkers form hydrogen
bonding networks and display high crystallinity. The compounds form ECCs, which develop
along the c-axis. Reciprocal lattice analysis revealed packing arrangements for all 15
synthesized compounds. Except for some short-chain compounds, the majority of compounds
were assigned to the monoclinic system. Intermolecular hydrogen bonding is the main
interaction forming the crystal lattice, while van der Waals interactions between long
fluorocarbons likely cause the distortion that slightly reduces the lattice symmetry.
Fluorinated Gemini-type diamide derivatives demonstrated gelation ability similar to that of a
general-purpose solvent. Several fluorothixotropic agents were able to gel phenyl solvents
with large molecular sizes. Gelation results indicate solvent selectivity as well. Fluorinated
17

Gemini-type diamide derivatives with relatively dense packing tend to form helical fibers
when solvated. Since the helical form promotes gelation, future elucidation of molecular
packing and helical form is worthwhile.
Declaration of Interest Statement
There is no conflict of interest for this paper
Acknowledgements
This study was supported by JSPS KAKENHI Scientific Research on Innovative Areas
“MSF Materials Science (Grant Numbers JP 19H05118)”, and JSPS KAKENHI Grant
Numbers (C) JP 17K05988.
18

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[SCHEME and TABLE TITLES]
Scheme 1. Synthetic process for the compounds used in this study: (a) pentamethylene and
(b) hexamethylene derivatives.
[FIGURE CAPTIONS]
Figure 1. Research strategy of this study.
Figure 2. (a) Diamide derivatives having one pentamethylene linker and two fluorocarbons
with chain length CnF2n+1 (n = 1–7) and (b) diamide derivatives having one
hexamethylene linker and two fluorocarbons with chain length CnF2n+1 (n = 1–9).
Figure 3. IR spectra of fluorinated Gemini-type diamide derivatives with different lengths
and linkers.
Figure 4. WAXD profiles of fluorinated Gemini-type diamide derivatives with different
lengths and linkers.
Figure 5. SAXS patterns and profiles of excerpted fluorinated Gemini-type diamide
derivatives with different lengths and linkers.
Figure 6. Schematic illustration of packing models for fluorinated Gemini-type diamide
derivatives (compounds with a pentamethylene linker and a fluorocarbon chain of
length 1–6) by reciprocal lattice analysis.
Figure 7. Schematic illustration of packing models for fluorinated Gemini-type diamide
27

derivatives (2F7C5-diamide, and 2FnC6-diamide at n = 1–4 with hexamethylene
linker) by reciprocal lattice analysis.
Figure 8. Schematic illustration of packing models for fluorinated Gemini-type diamide
derivatives (2FnC6-diamide at n = 5–9 with hexamethylene linker) by reciprocal
lattice analysis.
Figure 9. SEM images of xerogels and AFM image of spin-cast film of fluorinated Gemini-
type diamide derivatives.
Figure 10. Schematic illustration of concluding remarks in this study.
28

Scheme 1
(a)
H. Maruyama, et al
n = 1~7
(b)
n = 1~7, 9
29