Size-Selective Binding of Sodium and Potassium Ions in Nanoporous Thin Films of Polymerized Liquid Crystals

Size-Selective Binding of Sodium and Potassium Ions in

Nanoporous Thin Films of Polymerized Liquid Crystals

Gerardus M. Bögels, Jody A. M. Lugger, Olga J. G. M. Goor, and Rint P. Sijbesma*

liquid crystals.^[12–14]Within this ﬁeld, the

The development of a nanoporous material from a columnar liquid crystalline

complex between a polymerizable benzoic acid derivative and a 1,3,5-tris(1H-

benzo[d]imidazol-2-yl)benzene template molecule is described. The mor-

phology of the liquid crystalline complex is retained upon polymerization and

quantitative removal of the template molecule affords a nanoporous material

with the same lattice parameters. The nanoporous material selectively binds

cations from aqueous solution, with selectivity for sodium and potassium

ions over lithium and barium ions, as shown with FT-IR. Binding is also

quantiﬁed gravimetrically with a quartz crystal microbalance with dissipation

monitoring, a technique that is used for this purpose for the ﬁrst time here.

development of organic materials with

molecular sieving properties is an area

with very high relevance for applications.

Tschierske and co-workers have demon-

strated the ﬁrst examples of liquid crys-

talline superstructures that resemble the

structure of some zeolites.^[15,16]The ﬁrst

development of an organic nanoporous

material with 1D-aligned nanochannels

was reported by Gin and co-workers.^[17–20]

They demonstrated that lyotropic liquid

crystals (LCs) could be aligned on a mac-

roscopic scale to form a well-deﬁned

nanoporous material for water ﬁltration

applications. Feringan et al.,^[21,22]Kraft et al.,^[23]Kishikawa

et al.,^[24]and Lee et al.^[25]have shown examples of columnar

LC complexes between benzoic acid derivatives and different

kinds of template molecules that form multiple mesophases

depending on the length of the alkyl tails applied to the ben-

zoic acid derivatives. The latter two papers (Kishikawa et al. and

Lee et al.) used acrylate-functionalized benzoic acids to obtain a

cross-linked matrix from which the template molecule could be

removed. Both demonstrated >90% template removal, but the

polymer nanostructure was not fully retained.

Here, we use the self-assembly of a hydrogen-bonded

columnar LC complex to develop a nanoporous thin ﬁlm

with high retention of the nanostructure after cross-linking

and quantitative removal of the template. The nanopores

thus obtained bind metal cations in a size-selective manner.

(Figure 1). The nanoporous material was obtained using

1. Introduction

The use of self-assembling organic building blocks is a promi-

sing but challenging approach to develop nanostructured

porous materials.^[1–4]A promising approach to nanoporous

materials is based on the self-assembly of block copolymers.^[5–9]

Utilizing the nanosegregation of two covalently-connected,

incompatible polymer blocks, nanoporous materials can be

obtained with pore diameters down to 10 nm after selective

phase removal. Inorganic nanoporous materials, like alumi-

nosilicate structures known as zeolites, have pore sizes below

1 nm and are robust materials. However, processing of these

inorganic materials is difﬁcult and costly.^[10,11]Over the last

couple of years, much progress has also been made on the

development of synthetic organic nanostructured materials

with smaller features by using the self-assembly properties of

complex of 1,3,5-tris(1H-benzo[d]imidazol-2-yl)benzene

(BTB)^[26]with a polymerizable benzoic acid derivative to form

a columnar hexagonal (Col_hex) mesophase, polymerizing via

acyclic diene metathesis (ADMET)^[27,28]followed by quantita-

tive template removal. Finally, size-selective binding studies

were performed and quantiﬁed with Fourier-transform infrared

spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS),

and a quartz crystal microbalance with dissipation monitoring

(QCM-D), with QCM-D as a new characterization tool.

G. M. Bögels, J. A. M. Lugger, O. J. G. M. Goor,

Prof. R. P. Sijbesma

Laboratory of Molecular Science and Technology

Department of Chemical Engineering and Chemistry

Eindhoven University of Technology

PO Box 513, 5600 MB, Eindhoven, The Netherlands

E-mail: r.p.sijbesma@tue.nl

G. M. Bögels, J. A. M. Lugger, O. J. G. M. Goor,

Prof. R. P. Sijbesma

Institute for Complex Molecular Systems

Eindhoven University of Technology

PO Box 513, 5600 MB, Eindhoven, The Netherlands

2. Thermotropic Liquid Crystalline Properties of the

3:1 Complex between Polymerizable Benzoic Acid

and 1,3,5-tris(1H-benzo[d]imidazol-2-yl)benzene

This is an open access article under the terms of the Creative Commons

Attribution-NonCommercial License, which permits use, distribution

and reproduction in any medium, provided the original work is properly

cited and is not used for commercial purposes.

Mixing the polymerizable benzoic acid 1 and BTB in a 3:1

ratio afforded a complex that demonstrated thermotropic

DOI: 10.1002/adfm.201603408

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Figure 1. Self-assembly approach for the template-assisted development of a nanoporous material and size-selective ion binding. The 3:1 complex

between benzoic acid 1 and BTB assembles in a Col_hexmesophase cross-linked by ADMET polymerization and the BTB template is quantitatively

removed, after which metal ion studies were conducted.

LC behavior. Comparison of the FT-IR spectra of the indi-

vidual components with the complex showed that a hydrogen-

bonded complex was formed (Figure 2A). The carbonyl

stretching vibration of the benzoic acid shifts from 1686 to

1676 cm⁻¹in the complex, which demonstrated the formation

lattice parameters correspond to a density of 1.13 g cm⁻³at

150 °C. The BTB molecule has a diameter of 1.6 nm (Figure S3,

Supporting Information), and when this template molecule is

removed from a polymerized benzoic acid matrix, formation of

pores similar in size to the diameter of BTB can be expected.



of a carboxylate salt. Furthermore, an N H stretching vibra-

tion around 3200 cm⁻¹was absent in the complex, while a pro-

nounced band arose in the complex at 3264 cm⁻¹, typical for the

formation of an imidazolium salt. These changes conﬁrmed

that an acid–base reaction had taken place between the tem-

plate (pK_aof the protonated 2-phenylbenzimidazolium is 5.23)

and the benzoic acid (pK_aof gallic acid is 4.41).^[29]

3. Polymerization of the 3:1 Complex between

Benzoic Acid and BTB

ADMET was used to cross-link the alkene functionalities of

benzoic acid 1.^[27,28]ADMET is a polycondensation reaction and

therefore only leads to cross-linking when more than two of the

three double bonds on each molecule react with neighboring

molecules. An LC mixture of BTB with 3 equivalents of ben-

zoic acid 1 was heated under vacuum at 100 °C with 2 mol% of

Grubbs’ 2nd generation metathesis catalyst (3) to achieve high

conversion of the terminal double bonds via ADMET. Network

formation was ﬁnished after 3 h according to FT-IR analysis.

The thermotropic LC properties of the complex were further

assessed by differential scanning calorimetry (DSC), X-ray dif-

fraction (XRD), and polarized optical microscopy (POM). The

DSC showed two phase transitions: a crystalline-to-LC phase

transition at 45 °C and isotropization at 230 °C (Figure 2B).

Upon annealing of the 3:1 complex in the isotropic state at

240 °C, phase separation of needle-shaped crystals was observed

by POM (Figure S1, Supporting Information). Most likely these

crystals consist of solid template or a 1:2 or 1:1 complex with

benzoic acid 1. Utilizing 3.3 equivalents of benzoic acid 1

made it possible to prevent phase separation at 100 °C with a

focal conical texture typical for a discotic columnar mesophase

(Figure 2C). With variable-temperature X-ray diffraction (VT–

XRD), the mesosphere was characterized in detail (Figure S2,

Supporting Information). Diffraction peaks with q-ratios of

1:√3:√4:√7, characteristic for a Col_hexphase, were observed.

An intercolumnar distance of 3.25 nm and an interdisc dis-

tance of 0.37 nm at 150 °C were calculated (Figure 2D). The

 

From the decrease of the end-terminal C H bending vibra-

tion at 908 cm⁻¹, depicted in Figure 3A, a conversion of 82%

was determined. The product was an insoluble polymer ﬁlm,

indicating enough cross-linking to ﬁxate the morphology.

Comparison of the XRD diffraction patterns of the complex

before and after polymerization of a bulk sample showed no

change in the lattice parameters of the Col_hexphase (Figure 3B).

Slight broadening of the peaks was observed, which is common

for polymerized materials.^[30–33]Shear-induced alignment was

also retained after polymerization, as can be seen in the 2D XRD

image of Figure 3C. In this diffractogram, the interdisc reﬂection

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

Figure 2. A) FT-IR of complex formation at a 3:1 ratio of carboxylic acid and template. B) DSC of the ﬁrst cooling and second heating run from the 3:1

complex. C) XRD of the 3:1 complex at 150 °C, Col_hophase with unit cell parameters: a = 3.25 nm and c = 0.37 nm. D) POM image of the template

and 3.3 equivalents of carboxylic acid at 100 °C.

Figure 3. A) FT-IR of ADMET polymerization of the complex with 2 mol% catalyst at 100 °C with application of vacuum for 3 h. B) Comparison of XRD

before and after ADMET polymerization of the complex and after template removal. C) 2D image of XRD after ADMET polymerization of shear-aligned

3:1 complex. D) UV–vis and ﬂuorescence measurements on extraction of the template with DMSO.

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Table 1. QCM-D results on template removal.

is perpendicular to the intercolumnar reﬂection, showing that

the disc-shaped complexes stack with their plane perpendicular

to the column axis, as well as the ﬂexible alkyl tails.

Film thickness

[nm]

Mass polymer with

template [mg cm⁻³

Mass polymer without

template [mg cm⁻³

Template

]

removed [%]

The morphology of unpolymerized thin ﬁlms was studied

with grazing incidence wide-angle X-ray scattering. Thin ﬁlms

(≈50 nm) of the complex without catalyst were prepared by

spin-coating from MeOH/CHCl₃solution (1:9 v/v) on clean

glass substrates. The diffraction pattern of the Col_hexphase

was observed when the spin-coated samples were heated above

50 °C (Figure S4, Supporting Information). Polymerized ﬁlms

were prepared by addition of 2 mol% catalyst and heating at

100 °C under vacuum. The hexagonal morphology of the unpo-

lymerized complex was retained in the polymer matrix. In line-

cuts of the multidomain planar samples, reﬂections were at an

angle of 60°, characteristic for a hexagonal lattice with planar

orientation of columns.^[34,35]Varying the angle of the incidence

beam probed the morphology of the surface and the bulk of the

material (Figure S5, Supporting Information). At low angles of

0.14°, mainly the surface is probed, while at higher incident

angles, more of the bulk material is probed. Both the lower and

the higher angles showed the same diffraction pattern, there-

fore the structure was uniform throughout the entire material.

181

1131

972

sensor and polymerized by heating to 100 °C for 3 h under

vacuum. The results of the QCM-D measurements before and

after template removal are summarized in Table 1. The amount

of adsorbed mass of the ﬁlm after spin-coating and poly-

merization on an empty gold sensor was 1131 1 mg cm⁻³.

This corresponds to a ﬁlm thickness of 181 7 nm. After three

extractions with DMSO, the sensors were washed with MilliQ

water and dried at 40 °C in a vacuum oven containing (P₂O₅)

for 1 h. The sensor showed a decrease in mass equal to the

removal of 98 1% of the BTB template. An example of the

QCM-D measurements is depicted in Figure 4A. Quantitative

template removal was also conﬁrmed by FT-IR analysis on the



bulk of the ﬁlm by the disappearance of the N H stretching

vibration at 3241 cm⁻¹and the presence of free carboxylic



acid groups with a carbonyl C O stretching vibration at 1676

cm⁻¹compared to 1685 cm⁻¹in the complex (Figure 4B). After

removal of the template, the structural properties were inves-

tigated with GISAXS (Figure 4C) and XRD (Figure 4D). The

presence of peaks at 60° intervals at 30°, 90°, and 150°, and full

retention of the diffraction signals with q-ratios of 1:√3:√4:√7,

demonstrated retention of the hexagonal structure after

removal of the template.

4. Preparation of Nanoporous Films by

Removal of Template

Nanoporous ﬁlms were prepared by extraction of BTB from

cross-linked thin ﬁlms on glass (thickness 50–200 nm) with

DMSO (a good solvent for BTB). The samples were shaken

three times for 1 h in 15 mL of solvent. The amount of

remaining template in the ﬁlm after each extraction was deter-

mined by ﬂuorescence spectroscopy (Figure 3D). Fluorescence

measurements on the thin ﬁlms were performed by excitation

at 330 nm and recording the emission spectra after every sub-

sequent extraction (Figure S6, Supporting Information). The

emission spectra were normalized and the emission band of

BTB at 522 nm was set to 100% before the extractions. After

three extractions, the template had been removed quantitatively

from the thin ﬁlm.

Another method to quantify the template removal is gravim-

etry using a QCM-D, which has been used frequently for bio-

logical binding studies^[36,37]and is rapidly ﬁnding applications

in materials science.^[38–40]In QCM-D, the change in frequency

of a quartz crystal resonator is monitored upon mass changes.

The adsorbed mass, M_f, and the frequency-shift, Δf_n, are related

by the Sauerbrey Equation (1)

5. Size-Selective Binding of Salt Ions from

Aqueous Solutions

The FT-IR analysis after BTB template removal showed that

the pore walls of the nanostructured materials were function-

alized with free carboxylic acid groups due to the presence

of the carbonyl stretching vibration at 1676 cm⁻¹(vide supra,

Figure 4B). Cross-linked ﬁlms of the complex, from which the

template had been removed, were soaked in aqueous solu-

tions of hydroxide salts to deprotonate the carboxylic acid

groups and form the corresponding metal carboxylate salts.

After soaking for 3 h in 100 × 10⁻³m solutions of the hydrox-

ides of Li⁺, Na⁺, K⁺, Cs⁺, and NH₄, the ﬁlms were dried and

analyzed with FT-IR spectroscopy (Figure 5A). Depending

on the cation, the FT-IR spectrum showed a shift in the sym-

metric and asymmetric C O stretching vibration from 1684



to 1558 cm⁻¹(asymmetric stretching) and 1585 to 1376 cm⁻¹

(symmetric stretching), indicative of the formation of the metal

carboxylate salt. None of the divalent cations were bound as

carboxylate salts. Of the monovalent cations, only Na⁺and K⁺

ions were capable of forming the corresponding carboxylate

salt. Even the smaller Li⁺ion was not bound, showing that

selectivity was not determined by ionic radius alone. A poten-

tial explanation for the observed selectivity can be found in the

size of the hydrated radii of the cations (Figure 5B). Divalent

cations have larger hydrated radii than monovalent ions, and

for monovalent cations the hydrated radius is smallest for Na⁺

M_f

∆f_n= −2nf_q²

(1)

ρ_qι

where n denotes the overtone order, f_qis the frequency

of the quartz crystal (f_q= 5 MHz), ρ_qis the density of the

quartz crystal (ρ_q= 2.65 g cm⁻³), and ν is the speed of light

(ν = 3.00 × 10⁸m s⁻¹). The Sauerbrey Equation (1) is only

valid for sufﬁciently rigid thin ﬁlms, i.e., with low dissipation

changes during mass adsorption measurements.^[41]

For the QCM-D measurements, thin ﬁlms of the BTB with

benzoic acid 1 complex were spin-coated on an empty gold

and K⁺ions, while the hydrated radii of Li⁺and NH₄ions are

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

Figure 4. A) Static QCM-D measurements of an empty gold sensor, after spin-coating and polymerization of the complex and after template removal.

B) FT-IR before and after template removal. C) Linecuts of GISAXS measurements before and after template removal. D) XRD of the polymer material

with and without the BTB template.

comparable in size to hydrated Cs⁺ions. The exclusive binding

of Na⁺and K⁺and rejection of the other tested monovalent and

divalent inorganic ions and organic cations^[42]demonstrate the

high size selectivity of this system.

QCM-D was used to quantify the amount of bound cations

and to determine the speciﬁcity of the binding with static, ex

situ measurements. The measurements were performed on

spin-coated and polymerized ﬁlms. QCM-D was performed

before and after deposition of a thin ﬁlm to the sensor, after

template removal and after exposure to 10 × 10⁻³m NaOH/

LiOH/Ba(OH)₂aqueous solution. Figure 6A shows an example

of a set of ex situ static measurements for a single sample after

drying of the sensor at every processing step (more examples in

Figure S7, Supporting Information). The ﬁgure shows a series

of steps, corresponding to mass changes when the polymer

ﬁlm with the template was deposited, followed by mass loss

when the BTB template was removed and a mass increase

when Na⁺ions were bound. The ﬁrst mass change allowed for

the determination of the number of carboxylic acid binding

sites, which was 25.72 nmol. The next step in the graph cor-

responded to removal of 8.48 nmol of template (99%). Finally,

the mass change after exposure to NaOH corresponded to

24.88 nmol of Na⁺ions, occupying 98% of the available car-

boxylic acid binding sites. The same experiment was also

performed without template removal, from which the nonspe-

ciﬁc interaction of Na⁺ions with the surface was calculated

Figure 5. A) Comparison of FT-IR spectra after exposure to different hydroxide salts (0.1 m (aq.). B) The hydrated radius of several cations, taken from

the literature.^[42]

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Figure 6. A) Static QCM-D measurements after template removal and exposure to 10 × 10⁻³m NaOH (aq). Time-dependent measurements where

each measurement takes approximately ≈1–2 min after stabilization of the signal for 20 min. B) Bar diagram of QCM-D results on binding or removal:

a) template removal as percentage of amount of polymer complex applied per area; b) percentage of total amount of carboxylic acid groups occupied;

c) percentage of total amount of carboxylic acids occupied, with template still present.

to be 7 2% (Figure 6B). It was found that Li⁺and Ba²⁺ions

occupy 3 7% and 5 2% of the carboxylic acid sites, respec-

tively, less than the nonspeciﬁc binding of the Na⁺ions. Finally,

exposing a sodium-saturated ﬁlm to deionized water partially

removed the bound Na⁺ions by 45 7% of the binding sites.

Angle-resolved XPS (AR-XPS) was performed to establish

whether binding of the Na⁺ions takes place throughout the bulk

of the material or only at the surface of the thin ﬁlms (Figure 7).

At 0° is the highest penetration depth but lowest surface expo-

sure; by increasing the angle to 60°, less of the bulk material

is probed but more of the surface is exposed. The nitrogen-to-

carbon ratio (N/C) before template removal demonstrated that

the density of nitrogen is constant throughout the thickness of

a 175-nm ﬁlm (Figure 7A). After template removal, nitrogen

was no longer detectable (Figure S8, Supporting Information).

Finally, the ratio of alkali metal (i.e., Na, Li or Ba) to carbon (M/C)

was determined from these measurements, before and after

exposure to the corresponding hydroxide solutions (Figure 7B).

The samples with BTB, without BTB, and the sample exposed

to LiOH did not contain a measurable amount of metal. The

absence of Li⁺conﬁrms that this ion is not absorbed by the nano-

porous material. The amount of sodium was constant over all

the angles, which shows a homogeneous distribution of sodium

throughout the material. Moreover, in nanoporous ﬁlms treated

with Ba(OH)₂, the barium signal increased with increasing tilt

angle, indicating nonspeciﬁc binding at the surface. This is due

to an inhomogeneous distribution of the barium at the surface.

6. Conclusion

A successful strategy was developed to obtain a nanoporous

material using self-assembly of a hydrogen-bonded com-

plex, combined with a cross-linking reaction based on alkene

metathesis. The approach provided ﬁlms with a high density

of nanopores, selective for the binding of Na⁺and K⁺ions over

a number of other metal cations. The ﬁrst example of quanti-

tative gravimetric analysis on ion binding in organic nanopo-

rous materials was demonstrated by QCM-D. Moreover, since

all divalent cations and large (hydrated) monovalent salt ions

tested were rejected by the ﬁlm, the selectivity of binding of Na⁺

and K⁺ions raises the question of whether these ﬁlms are can-

didates for selective ion transport in nanoﬁltration applications.

Future work will be focused on obtaining homeotropically

aligned ﬁlms and on integrating thin ﬁlms with aligned pores

on support materials for ﬂow-trough experiments.

Figure 7. AR-XPS plot of nanoporous materials with or without BTB template or exposed to different hydroxide salts: A) the nitrogen-to-carbon ratio

and B) the salt-to-carbon ratio.

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

1 equivalent) (35 mg mL⁻¹, ﬁnal concentration). Prior to use, a solution

of Grubbs catalyst (2nd generation, 2 mol%) in CHCl3 was added.

Clean glass substrates (30 × 30 mm) were obtained by dipping the

glass substrates in piranha solution (aqueous hydrogen peroxide 35%

and concentrated sulfuric acid, 1:3 v/v) for 10 s, rinsing thoroughly

with deionized water and drying. The liquid-crystal solution was spin-

coated on the clean substrate, placed in a preheated oven at 100 °C, and

vacuum was applied for 3 h. Subsequently, the sample was placed in

15 mL DMSO (3×) and extracted by careful shaking for 1 h each.

Methods—Fluorescence Spectroscopy: Fluorescence measurements

on the thin ﬁlms were performed by excitation at 330 nm and recording

the emission spectra after every subsequent extraction with DMSO (1 h

each). The emission spectra were normalized, and the emission band of

BTB at 522 nm before the extractions at 522 nm was set to 100%.

Methods—UV–Vis Spectroscopy: Concentrations were calculated

using the extinction coefﬁcient determined separately in DMSO at

λ_max= 316 nm. The initial amount of template was calculated according

to the thickness of the layer and the density of the polymerized complex

of the XRD measurements. Layer thickness was determined by a Veeco

Dektak 150 Surface Proﬁler.

Methods—Quartz Crystal Microbalance with Dissipation Experiments:

Sensors were prepared by ﬁrst cleaning them with piranha solution

(H₂SO₄/H₂O₂, 3:1, v/v) and extensive washing with MilliQ water,

followed by acetone and drying by air ﬂow. Subsequently, a ≈50 mg mL⁻¹

of the complex (benzoic acid:template:catalyst, 3:1:0.06 mol/mol/mol)

in CHCl₃/MeOH (9:1) was spin-coated on the sensors at 3000 rpm

for 30 s to obtain layer thicknesses of 100–200 nm. The sensors were

polymerized in a vacuum oven at 100 °C held under vacuum for 3 h.

The sample was measured dry to determine the layer thickness and

the amount of material on the sensor according to the Sauerbrey

equation. The sensors were extracted three times with 15 mL DMSO

for 1 h by careful shaking and ﬁnally rinsed with MilliQ water and dried

in a vacuum oven at 40 °C containing P₂O₅in vacuo for at least 1 h.

Subsequently, the dry sensors were measured again to determine the

amount of template that was removed. Subsequently, the sensors were

equilibrated in MilliQ water for 3 h with a ﬂow rate of 50 μL min⁻¹at

20 °C. The MilliQ water was exchanged for the NaOH (aq.) solution and

measured for an additional 3 h with a ﬂow rate of 50 μL min⁻¹at 20 °C.

Finally, the sensors were quickly rinsed with MilliQ water and dried in

a vacuum oven at 40 °C under vacuum and P₂O₅before quantifying

adsorbed sodium ions. All measurements were at least performed in

triplicate. Errors are given as standard deviations.

7. Experimental Section

Materials and Instrumentation: Chemicals and solvents were

purchased from Sigma-Aldrich or Biosolve, respectively, and used

as received, unless stated otherwise. FT-IR spectra were recorded at

room temperature on a Perkin Elmer Spectrum One spectrometer

equipped with a universal attenuated total reﬂectance (ATR) sampling

accessory. NMR spectra were recorded at room temperature on a Varian

Mercury 400 (400 MHz) spectrometer. Chemical shifts are given in

ppm with respect to tetramethylsilane (0 ppm) as internal standard.

Coupling constants are reported as J values in Hz. Column or ﬂash

chromatography was carried out using silica gel (0.035–0.070 mm,

≈6 nm pore diameter). Matrix-assisted laser desportion ionization

time-of-ﬂight (MALDI-TOF) mass spectra were obtained on

PerSeptive Biosystems Voyager-DE PRO spectrometer with α-cyano-

4-hydroxycinnamic acid as a matrix. POM images were recorded by a

Jeneval microscope equipped with crossed polarizers and Polaroid

DMC Ie CCD camera, equipped with a Linkam THMS 600 hot stage.

DSC measurements were performed in hermetic T-zero aluminum

sample pans using a TA Instruments Q2000 – 1037 DSC equipped with

a RCS90 cooling accessory. All transition temperatures and enthalpies

were determined from the ﬁrst cooling and second heating run, with

heating and cooling rates of 10 K min⁻¹. XRD images were recorded on a

Ganesha lab instrument equipped with a Genix-Cu ultra-low divergence

source producing X-ray photons with a wavelength of 1.54 Å and a

ﬂux of 1 × 10⁸photons per second. Diffraction patterns were collected

on a Pilatus 300K detector with reversed-biased silicon diode array

sensor. The detector contains 487 × 619 pixels of 172 × 172 μm²and

consists out of three modules with an intermodule gap of 17 pixels in

between, resulting in two dark bands on the image. Grazing incidence

X-ray scattering measurements were performed on

a sample-to-

detector distance of 1080 mm for wide-angle X-ray scattering (WAXS)

or 1530 mm for small-angle X-ray scattering (SAXS). Temperature-

dependent measurements were executed with a Linkam HFSX350

heating stage and cooling unit. Azimuthal integration of the obtained

diffraction patterns was performed by utilizing the SAXSGUI software.

Equation (2) was used to convert the scattering vector into d-spacing,

where Bragg’s law (Equation (3)) is fulﬁlled (λ is the wavelength, n is

an integer, and θ is the angle of incidence). The beam center and the

q-range were calibrated using silver behenate (0.107 Å⁻¹; 58.43 Å)

2π

d =

q =

(2)

(3)

Synthetic Procedures: The synthesis of BTB was performed according

to literature.^[26]

4π

nλ

Synthesis of Polymerizable Benzoic Acid 1:

sinθ

To a stirred solution of methyl

gallate (2.1 g; 11.5 mmol;

UV–vis experiments on solutions were performed on a Cary 300 UV–

1.0 equiv.) in DMF (55 mL) was

added K₂CO₃(15.9 g; 115 mmol;

10.0 equiv.) and 11-bromo-1-

undecene (8.85 g; 37.95 mmol;

vis spectrophotometer equipped with a Peltier temperature controller.

All experiments were performed in 10 × 10 mm quartz cuvettes at 20 °C.

Unknown concentrations were obtained from a calibration curve of

known concentrations, according to Lambert–Beer’s law. Fluorescence

data were recorded on a Varian Eclipse ﬂuorescence spectrometer

equipped with a solid-state sample holder. QCM-D measurements

were performed in a Q-Sense E4 4-channel quartz crystal microbalance

with a peristaltic pump of Biolin Scientiﬁc. The AR-XPS measurements

were carried out with a Thermo Scientiﬁc K-Alpha equipped with a

monochromatic small-spot X-ray source and a 180° double-focusing

3.3 equiv.). The resulting suspension was heated to reﬂux (110 °C) for

overnight and after completion of the reaction, cooled to ambient

temperature, ﬁltered, and evaporated to dryness. The residue was

redissolved in EtOAc (17 mL)/water (22 mL), extracted with EtOAc

(2 × 17 mL), dried with Na₂SO₄, and ﬁltered. After removal of the

solvent, the crude compound was puriﬁed by ﬂash column

chromatography (heptane/ethyl acetate, 7:3 to 1:1) to obtain a white

hemispherical analyzer with

a 128-channel detector. Spectra were

solid (6.0 g, 82%). H-NMR (CDCl₃, 400 MHz): δ = 7.25 (s, 2H, 2x CH

obtained every 15° (starting close to 0°) using an aluminum anode

(Al Kα = 1486.6 eV) operating at 72 W and a spot size of 400 μm. Survey

scans were measured at a constant pass energy of 200 eV and region

scans at 50 eV. The background pressure was 2 × 10⁻⁹mbar and during

measurement 3 × 10⁻⁷mbar argon because of the charge compensation

for the dual beam source.

Methods—Sample Preparations: The fabrication of porous materials

was performed by making a stock solution of gallic acid alkene

(3 equivalents) in MeOH/CHCl₃(1:9 v/v) and adding this solution to

the required amount of solid benzene-1,3,5-trisbenzimidazole (BTB,

arom.), 5.80 (ddt, 3 H, J = 7 Hz, 10 Hz and 17 Hz, 3x CH₂= CH-CH₂),

4.97 (dd, 6H, J = 10 Hz and 17 Hz, 3x CH₂= CH), 4.01 (t, 6H, 7 Hz, 3x

CH₂-CH₂-O), 3.88 (s, 3H, CH₃O), 2.03 (dt, 6H, J = 8 Hz and 7 Hz,

3x CH₂= CH-CH₂), 1.81 (m, 6H, 3x CH₂-CH₂-O), 1.36 (m, 36H, 18x CH₂-

CH₂-CH₂). ¹³C-NMR (CDCl₃, 100 MHz): δ = 167.0, 152.9, 142.4, 139.3,

124.8, 114.2, 108.0, 73.6, 69.2, 52.2, 34.0, 30.4, 29.8, 29.7, 29.7, 29.6,

29.5, 29.4, 29.3, 29.3, 29.1, 29.1, 26.2, 26.2. ATR FT-IR: 3076, 2924, 2853,

1721, 1641, 1587, 1500, 1465, 1430, 1386, 1334, 1216, 1115, 1014, 993,

908, 863, 812, 765, 722, 671, 636, 577, 554 cm⁻¹. MALDI-TOF MS: m/z

Adv. Funct. Mater. 2016,

DOI: 10.1002/adfm.201603408

2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

calculated for C₄₁H₆₈O₅(M+H)⁺: 640.51, found: 640.50, (M+Na)⁺:

663.50, found: 663.49.

[10] H. Awala, J.-P. Gilson, R. Retoux, P. Boullay, J.-M. Goupil,

V. Valtchev, S. Mintova, Nat. Mater. 2015, 14, 447.

[11] X. Meng, F.-S. Xiao, Chem. Rev. 2014, 114, 1521.

[12] L. T. de Haan, J. M. N. Verjans, D. J. Broer, C. W. M. Bastiaansen,

A. P. H. J. Schenning, J. Am. Chem. Soc. 2014, 136, 10585.

[13] T. P. J. Knowles, T. W. Oppenheim, A. K. Buell, D. Y. Chirgadze,

M. E. Welland, Nat. Nanotechnol. 2010, 5, 204.

[14] T. H. Ware, M. E. McConney, J. J. Wie, V. P. Tondiglia, T. J. White,

Science 2015, 347, 982.

[15] S. Poppe, A. Lehmann, A. Scholte, M. Prehm, X. Zeng, G. Ungar,

C. Tschierske, Nat. Commun. 2015, 6, 8637.

A solution of methyl gallate alkene

(3.0 g; 4.68 mmol; 1.0 equiv.) in

MeOH/H₂O (3:1 v/v, 26 mL) was

treated with KOH (2.13 g,

37.91 mmol; 8.1 equiv.) and

heated at reﬂux overnight. The

reaction mixture was cooled to ambient temperature after completion of

the reaction, neutralized to pH ≈ 3.0 with 3.0 ^mHCl, and extracted with

EtOAc (3 × 20 mL). The organic phase was dried with Na₂SO₄, ﬁltered,

and evaporated to dryness to obtain the desired product as a white solid

in quantitative yield (2.9 g). ¹H-NMR (CDCl₃, 100 MHz): δ = 11.37 (br. s,

1H, OH), 7.30 (s, 2H, 2 x CH arom.), 5.83 (ddt, 3H, J = 12 Hz, 21 Hz

and 34 Hz, 3 x CH₂= CH-CH₂), 4.95 (dd, 6H, J = 21 Hz and 34 Hz,

[16] Y. Ishida, Materials 2011, 4, 183.

[17] X. Feng, M. E. Tousley, M. G. Cowan, B. R. Wiesenauer, S. Nejati,

Y. Choo, R. D. Noble, M. Elimelech, D. L. Gin, C. O. Osuji, ACS

Nano 2014, 8, 11977.

[18] D. L. Gin, W. Gu, B. A. Pindzola, W.-J. Zhou, Acc. Chem. Res. 2001,

34, 973.

[19] B. P. Hoag, D. L. Gin, Macromolecules 2000, 33, 8549.

[20] X. Feng, S. Nejati, M. G. Cowan, M. E. Tousley, B. R. Wiesenauer,

R. D. Noble, M. Elimelech, D. L. Gin, C. O. Osuji, ACS Nano 2016,

10, 150.

[21] B.Feringán,P.Romero,J.L.Serrano,R.Giménez,T.Sierra,Chem.-Eur.

J. 2015,

3 x CH₂= CH), 4.02 (m, 6H, 3 x CH₂-CH₂-O), 2.05 (m, 6H, 3 x CH₂

CH-CH₂), 1.78 (m, 6H, 3 x CH₂-CH₂-O), 1.31 (m, 36H, 18 x CH₂-

CH₂-CH₂). ¹³C-NMR (CDCL₃, 100 MHz): δ = 177.9, 172.2, 153.0, 143.2,

139.3, 123.8, 114.3, 108.6, 73.7, 69.3, 34.0, 30.5, 29.8, 29.7, 29.6, 29.6,

29.6, 29.6, 29.5, 29.4, 29.3, 29.3, 29.1, 29.1, 26.2, 26.2, 21.0. ATR FT-IR:

3078, 2976, 2922, 2851, 2636, 1686, 1641, 1586, 1504, 1464, 1431, 1390,

1328, 1275, 1228, 119, 1068, 991, 948, 908, 866, 767, 750, 724, 681, 626,

584, 543, 496, 479 cm⁻¹. Maldi-ToF MS: m/z calculated for C₄₀H₆₆O₅

(M+Na)⁺: 649.48, found: 649.48.

[22] A. A. Vieira, E. Cavero, P. Romero, H. Gallardo, J. L. Serrano,

T. Sierra, J. Mater. Chem. C 2014, 2, 7029.

[23] A. Kraft, A. Reichert, R. Kleppinger, Chem. Commun. 2000, 1015.

[24] K. Kishikawa, A. Hirai, S. Kohmoto, Chem. Mater. 2008, 20, 1931.

[25] H.-K. Lee, H. Lee, Y. H. Ko, Y. J. Chang, N.-K. Oh, W.-C. Zin, K. Kim,

Angew. Chem. 2001, 113, 2741.

Supporting Information

Supporting Information is available from the Wiley Online Library or

from the author.

[26] J.-F. Xiong, S.-H. Luo, J.-P. Huo, J.-Y. Liu, S.-X. Chen, Z.-Y. Wang,

J. Org. Chem. 2014, 79, 8366.

[27] K. R. Villazor, T. M. Swager, Mol. Cryst. Liq. Cryst. 2004, 410, 247.

[28] K. B. Wagener, J. M. Boncella, J. G. Nel, Macromolecules 1991, 24, 2649.

[29] W. M. Haynes, CRC Handbook of Chemistry and Physics, 91st ed.,

CRC Press, Boca Raton, FL 2010.

[30] M. P. Patel, M. Braden, K. W. M. Davy, Biomaterials 1987, 8, 53.

[31] N. Satsangi, H. R. Rawls, B. K. Norling, J. Biomed. Mater. Res. B

Appl. Biomater. 2004, 71B, 153.

Acknowledgements

G.M.B. and J.A.M.L. contributed equally to this work. The authors

gratefully thank the animation studio of the Institute of Complex Molecular

Systems for the provided images. Also, Tiny Verhoeven is thankfully

acknowledged for performing the XPS measurements and Patricia

Dankers for providing the QCM-D equipment. This work was supported

by the Dutch Ministry of Education, Culture and Science (Gravity program

024.001.035) and NanoNextNL, a micro and nanotechnology consortium

of the Government of the Netherlands and 130 partners.

[32] N. Satsangi, H. R. Rawls, B. K. Norling, J. Biomed. Mater. Res. B

Appl. Biomater. 2005, 74B, 706.

[33] B. S. Forney, C. Baguenard, C. A. Guymon, Chem. Mater. 2013, 25, 2950.

[34] E. Pouzet, V. D. Cupere, C. Heintz, J. W. Andreasen, D. W. Breiby,

M. M. Nielsen, P. Viville, R. Lazzaroni, G. Gbabode, Y. H. Geerts,

J. Phys. Chem. C 2009, 113, 14398.

Received: July 7, 2016

Revised: August 2, 2016

Published online:

[35] J. Jung, J. Lee, H.-W. Park, T. Chang, H. Sugimori, H. Jinnai, Macro-

molecules 2014, 47, 8761.

[36] P. Neirynck, J. Schimer, P. Jonkheijm, L.-G. Milroy, P. Cigler,

L. Brunsveld, J. Mater. Chem. B 2014, 3, 539.

[37] R. P. G. Bosmans, W. E. Hendriksen, M. Verheijden, R. Eelkema,

P. Jonkheijm, J. H. van Esch, L. Brunsveld, Chem. - Eur. J. 2015, 21,

18466.

[1] G. M. Whitesides, B. Grzybowski, Science 2002, 295, 2418.

[2] T. Aida, E. W. Meijer, S. I. Stupp, Science 2012, 335, 813.

[3] D. J. Broer, C. M. W. Bastiaansen, M. G. Debije, A. P. H. J. Schenning,

Angew. Chem. Int. Ed. 2012, 51, 7102.

[38] O. Zybaylo, O. Shekhah, H. Wang, M. Taﬁpolsky, R. Schmid,

D. Johannsmann, C. Wöll, Phys. Chem. Chem. Phys. 2010, 12,

8093.

[4] T. Kato, T. Yasuda, Y. Kamikawa, M. Yoshio, Chem. Commun. 2009, 729.

[5] H. Ahn, S. Park, S.-W. Kim, P. J. Yoo, D. Y. Ryu, T. P. Russell, ACS

Nano 2014, 8, 11745.

[39] G. Findenig, R. Kargl, K. Stana-Kleinschek, V. Ribitsch, Langmuir

2013, 29, 8544.

[6] W. Chen, S. Park, J.-Y. Wang, T. P. Russell, Macromolecules 2009, 42,

7213.

[40] H. Deligöz, B. Tieke, Colloids Surf. A 2014, 441, 725.

[41] D. Johannsmann, The Quartz Crystal Microbalance in Soft Matter

Research, in Soft and Biological Matter, Springer International

Publishing, Cham, Switzerland 2015, pp. 191–204.

[42] B. Tansel, Sep. Purif. Technol. 2012, 86, 119.

[7] C. G. Gamys, J.-M. Schumers, C. Mugemana, C.-A. Fustin,

J.-F. Gohy, Macromol. Rapid Commun. 2013, 34, 962.

[8] C. G. Gamys, J.-M. Schumers, A. Vlad, C.-A. Fustin, J.-F. Gohy, Soft

Matter 2012, 8, 4486.

[9] D. A. Olson, L. Chen, M. A. Hillmyer, Chem. Mater. 2007, 20, 869.