Morphological Control of Coil-rod-coil Molecules ... - ACS Publications

Subscriber access provided by University of Winnipeg Library

Interface Components: Nanoparticles, Colloids, Emulsions, Surfactants, Proteins, Polymers

Morphological Control of Coil-rod-coil Molecules Containing m-terphenyl Group: Construction of Helical Fibers and Helical Nano-rings in Aqueous Solution Yuntian Yang, Keli Zhong, Tie Chen, and Longyi Jin Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.8b01904 • Publication Date (Web): 14 Aug 2018 Downloaded from http://pubs.acs.org on August 17, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Morphological Control of Coil-rod-coil Molecules Containing m-terphenyl Group: Construction of Helical Fibers and Helical Nano-rings in Aqueous Solution Yuntian Yanga†, Keli Zhongb†, Tie Chena, Long Yi Jina*

a

Key Laboratory for Organism Resources of the Changbai Mountain and Functional Molecules, Ministry of Education, and Department of Chemistry, College of Science,Yanbian University, Yanji 133002, China

b

College of Chemistry, Chemical Engineering and Food Safety, Bohai University, Jinzhou 121013, China

*Corresponding author. E-mail address: [email protected] (L. Y. Jin)

† Equally contribution to this work.

ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 26

ABSTRACT: Rod-coil molecules, composed of rigid segments and flexible coil chains, have a strong intrinsic ability to self-assemble into diverse supramolecular nanostructures. Herein, we report the synthesis and the morphological control of a new series of amphiphilic coil-rod-coil molecular isomers 1−2 containing flexible oligoether chains. These molecules are comprised of m-terphenyl and biphenyl groups, along with triple bonds, and possess lateral methyl or butyl groups at the coil or rod segments. The results of this study suggest that the morphology of supramolecular aggregates is significantly influenced by the lateral alkyl groups, and by the sequence of the rigid fragments in the bulk and in aqueous solution. The molecules with different coils self-assemble into lamellar or oblique columnar structures in the bulk state. In aqueous solution, molecule 1a, with a lack of lateral groups, self-assembled into large strips of sheets, whereas exquisite nanostructures of helical fibers were obtained from molecule 1b, which incorporated lateral methyl groups between the rod and coil segments. Interestingly, molecule 1c with lateral butyl and methyl groups exhibited a strong self-organizing capacity to form helical nano-rings. Nanoribbons, helical fibers, and small nano-rings were simultaneously formed from the 2a-2c, which are structural isomers of 1a, 1b, and 1c. Accurate control of these supramolecular nanostructures can be achieved by tuning

the

synergistic

interactions

of

the

non-covalent

driving

force

hydrophilic-hydrophobic interactions in aqueous solution.

KEYWORDS: Self-assembly; SAXS; rod-coil; nano-ribbons; helical fibers; nano-rings.


with

Page 3 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

INTRODUCTION Supramolecular architectures constructed by the self-assembly of organic molecular building blocks are of great interest owing to their electro-optical properties and potential applications for new discoveries in materials science.1-11 Self-assembly of π-conjugated units holds

high

utility

in

the

development of supramolecular

structures

with

novel

dimensionalities and morphologies.12-13 The highly ordered π-conjugated units are crucial for further applications in areas such as molecular electronics, biomimetic chemistry, and drug delivery systems.14-16 Rod-coil systems are proven to be one of the most promising candidates due to their considerable ability to spontaneously self-organize for the fabrication of various supramolecular nanostructures.17-22 Lee and other research groups systematically investigated a variety of rod-coil molecules, including H-shaped, k-shaped, dumbbell-shaped, and macrocycle rod-coil molecules.23-27 These molecules self-assembled into various well-defined nano-assemblies, including lamellar, columnar, and three-dimensional tetragonal and hexagonal structures in the bulk state, depending on the molecular shape, length of the coil or rod segments, external stimuli, and temperature of the system. Rod-coil molecules with polyethylene oxide (PEO) chains exhibit good solubility and biocompatibility in aqueous solution and facilitate the formation of various supramolecular aggregates with well-defined shapes and sizes, such as micelles, ribbons, planar networks, vesicles, helices, and tubules. The formation of these diversiform supramolecular nano-assemblies can be tuned through the parameters of the interactions between the rod building blocks, such as π-π stacking, metal ion complexation, electrostatic interactions, multiple hydrogen bonding, and van der Waals interactions.28-36 We previously reported the self-assembly of a rod-coil oligomer containing lateral methyl, ethoxymethyl, and other alkyl groups in the centre of the rod block into lamellar, bicontinuous cubic, hexagonal perforated layered, hexagonal close-packed, and tetragonal nano-structures in the bulk state through precisely controlled intermolecular interactions.37 Recently, we also reported the self-assembling behavior of n-shaped amphiphilic rod-coil molecules by introducing lateral alkyl groups at the centre of the anthracene building block and at the surface of the rod and coil segments. The molecule reversibly self-assembled into


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 26

helical nanostructures with helix-handedness inversion when the temperature of the aqueous system was increased, indicating that the lateral chains directly weaken the π–π stacking interaction within the aggregate structure. This effect in turn produces helical fibers with relatively loosely packed rigid segments.38 It is therefore a useful strategy to slightly modify the molecular structures in order to create ordered nanoaggregates. However, the self-assembly of isomers based on the sequence of the rod building blocks in rod-coil systems and the introduction of chiral groups or lateral alkyl units into the rod-coil molecules in the bulk and in aqueous solution have rarely been reported. In this report, we present the design and synthesis of coil-rod-coil molecules 1a−1c and their isomers, 2a−2c, consisting of one m-terphenyl and two biphenyl units linked together by acetylenyl bonds as the rod segments and an oligoether chain, with a degree of polymerization (DP) of 5, as the coil segments (Scheme 1). Molecules 1b and 2b contain lateral methyl groups between the rigid and flexible segments, whereas 1c and 2c incorporate both methyl and butyl groups at the surface of the rod-and-coil block and the middle of the rod block, respectively. The self-assembling behavior of the molecules is investigated using various techniques, including thermal polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), ultraviolet-visible and fluorescence (UV-Vis and FL, respectively) spectroscopy, atomic force microscopy (AFM), circular dichroism (CD), and transmission electron microscopy (TEM). EXPERIMENTAL SECTION Materials. Tetraethylene glycol, toluene-p-sulfonyl chloride (from acros), 2-methoxy ethanol, (-)-ethyl L-lact-ate, 2-methyl-3-butyn-2-ol, 3,4-dihydro-2H-pyran (from Aldrich), lithium aluminum hydride, 4-hydroxy-4’-iodobiphenyl, p-toluenesulfonic acid monohydrate, iodine monochloride in dichloromethane (1M) (from Alfa), tetrakis (triphenylphosphine) palladium(0),

cuprous

iodide,

4-(trimethylsilyl)

phenylboronic

acid,

3-(trimethylsilyl)phenylboronic acid 1,3-diiodobenzene, 4-butylaniline, N-bromosuccinimide, sodium nitrite, sodium carbonate anhydrous (from TCI) and the conventional reagents were used as received.


Page 5 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Techniques. Proton nuclear magnetic resonance (1H NMR, 300 MHz) spectra were recorded in CDCl3 on a Bruker AM-300 instrument. The thermal transitions of the molecules were determined by using a PerkinElmer Pyris Diamond differential scanning calorimeter. Small angle X-ray scattering (SAXS) measurements were performed using an Anton Paar SAXS system and synchrotron radiation at the 1W2A X-ray beam line at the Beijing Accelerator Laboratory.39 The anisotropic texture was analyzed with a Zeiss polarized optical microscope with a Mettler FP82 hot-stage and a Mettler FP90 central processor. Matrix-assisted desorption/ionization time-of-flight mass spectrometric (MALDI- TOF-MS) analysis was performed

on

a

PerSeptive

Biosystems

Voyager-DESTR

instrument

using

2-cyano-3-(4-hydroxyphenyl)acrylic acid (CHCA) as the matrix. The UV-vis and FL spectra were obtained with JASCO UV-V650 UV-vis and JASCO FP-8200 FL spectrometers, respectively. CD spectra were obtained with a CS30088 Applied Photophysics Chirascan Spectrometer. Atomic force microscope (AFM) images were produced by an Agilent 5500 Atomic Force Microscope. The transmission electron microscope (TEM) experiments were performed with a Hitachi HT7700 microscope. Synthesis of molecules 1−2. Molecules 1−2 were synthesized by following a similar procedure. A representative example

is

presented

for

compound

1a

as

follows.

16-((4'-Iodo-[1,1'-biphenyl]-4-yl)oxy)-2,5,8,11,14-pentaoxahexadecane (0.46 g, 0.87 mmol), 4,4''-diethynyl-1,1':3',1''-terphenyl (0.11 g, 0.40 mmol), CuI (6.0 mg, 0.032 mmol), and Pd(PPh3)4 (18.3 mg, 0.016 mmol) were dissolved in absolute tetrahydrofuran (THF; 30 ml) and Et3N (20 ml). The mixture was refluxed for 36 h under Ar atmosphere, concentrated by evaporation, and washed with water. The mixture was extracted with dichloromethane three times, and the collected organic layers were dried over anhydrous magnesium sulfate and filtered. After complete removal of the volatiles using a rotary evaporator, the crude product was purified by silica gel chromatography (EtOAc:MeOH, 30:1 to 10:1). The pure product was obtained as a yellow solid in 47% yield (200 mg). 1H NMR (300 MHz, CDCl3, δ, ppm):


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

7.85 (s, 1H), 7.54-7.71 (m, 23H), 7.01 (d, J=9 Hz, 4H), 4.19 (t, J=3 Hz, 4H), 3.89 (t, J=3Hz, 4H), 3.53-3.78 (m, 32H), 3.38 (s, 6H). MALDI-TOF-MS m/z (M+Na)+ 1106. Molecule 1b. Yield: 52%. 1H NMR (300 MHz, CDCl3, δ, ppm): 7.84 (s, 1H), 7.53-7.66 (m, 23H), 7.02 (d, J=9 Hz, 4H), 4.59-4.65 (m, 2H), 3.52-3.75 (m, 36H), 3.38 (s, 6H), 1.35 (d, J=6 Hz, 6H). MALDI-TOF-MS m/z (M+Na)+ 1134, (M+K)+ 1150. Molecule 1c. Yield: 55%. 1H NMR (300 MHz, CDCl3, δ, ppm): 7.53-7.68 (m, 21H), 7.44 (s, 2H), 7.02 (d, J=9 Hz, 4H), 4.57-4.67 (m, 2H), 3.53-3.75 (m, 36H), 3.38 (s, 6H), 2.76 (t, J=6 Hz, 2H), 1.72-1.77 (m, 2H), 1.40-1.48 (m, 2H), 1.35 (d, J=6 Hz, 6H), 0.98 (t, J=6 Hz, 3H). MALDI-TOF-MS m/z (M+Na)+ 1190. Molecule 2a. Yield: 51%. 1H NMR (300 MHz, CDCl3, δ, ppm): 7.86 (s, 2H), 7.44-7.65 (m, 22H), 7.00 (d, J=9 Hz, 4H), 4.18 (t, J=3 Hz, 4H), 3.89 (t, J=3 Hz, 4H), 3.53-3.77 (m, 32H), 3.37 (s, 6H). MALDI-TOF-MS m/z (M+Na)+ 1106. Molecule 2b. Yield: 52%. 1H NMR (300 MHz, CDCl3, δ, ppm): 7.85 (s, 2H), 7.44-7.65 (m, 22H), 7.01 (d, J=9 Hz, 4H), 4.56-4.65 (m, 2H), 3.52-3.71 (m, 36H), 3.37 (s, 6H). 1.35 (d, J=9 Hz, 6H). MALDI-TOF-MS m/z (M+Na)+ 1134. Molecule 2c. Yield: 55%. 1H NMR (300 MHz, CDCl3, δ, ppm): 7.84 (s, 2H), 7.43-7.66 (m, 21H), 7.01 (d, J=9 Hz, 4H), 4.56-4.66 (m, 2H), 3.52-3.74 (m, 36H), 3.37 (s, 6H), 2.77 (t, J=6 Hz, 2H), 1.70-1.78 (m, 2H), 1.40-1.48(m, 2H), 1.35 (d, J=9 Hz, 6H), 0.98 (t, J=6 Hz, 3H). MALDI-TOF-MS m/z (M+Na)+ 1190, (M+K)+ 1206.


Page 6 of 26

Page 7 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Scheme 1. Synthetic route of rod-coil molecules 1a-1c and 2a-2c.

RESULTS AND DISCUSSION Synthesis. The amphiphilic molecules 1a−1c and 2a−2c were synthesized according to Schemes 1 and S1, using 4-hydroxy-4-iodobiphenyl, 2-methyl-3-butyn-2-ol, tetraethylene glycol, 4-(trimethylsilyl)phenylboronic

acid,

3-(trimethylsilyl)-

phenylboronic

acid,

1,3-diiodobenzene, and 4-butylaniline as the starting materials, through a stepwise procedure involving a Suzuki-Miyaura coupling step, a demethylation step, two steps of Sonogashira coupling, and nucleophilic substitutions. The structures of 1a−1c and 2a−2c were characterized by 1H-NMR spectroscopy and MALDI-TOF MS; the results were in full agreement with the chemical structures presented in Figures S1 and S2. Structure analysis in bulk state. The supramolecular nanostructures of molecules 1a−1c and 2a in the bulk state were investigated by means of POM, DSC, and SAXS techniques. Figure 1 shows the DSC heating and cooling traces of the molecules, and the transition temperatures obtained from the DSC measurements are summarized in Table S1. The phase transition temperatures decreased as side groups were introduced into the molecules, suggesting that the presence of lateral alkyl groups weakens the π-π stacking, which is the main driving force for molecular assembly.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Thereafter, loosely packed molecular assemblies were formed from these molecules. Notably, molecules 2b and 2c exhibited viscous liquid states, which means that the rod-coil molecules were more loosely arranged than the bent-shaped molecules owing to the steric hindrance of the neighboring rod domains. Therefore, we can infer that the main driving forces (π-π stacking) of 1 are stronger than those of the isomers 2.

Figure 1. DSC traces (10 °C/ min) recorded during the second heating scan and first cooling scan of 1a-1c and 2a.

For the assemblies of molecule 1a, using POM, a focal conic spherulitic fan-like texture was observed during the liquid state to liquid crystalline phase transition, indicating the presence of a columnar structure at 245°C (Figure 2).40-43 In order to investigate the assembly structure of 1a in detail, SAXS experiments were performed. The SAXS pattern of 1a acquired at 265 °C showed four reflections in the liquid crystalline phase. The peaks can be assigned to the (100), (010), (210), and (300) reflections of a two-dimensional oblique columnar structure with a characteristic angle γ = 64° (Figure 3a), and lattice constants a = 5.13 nm and b = 2.97 nm (Table S2). In addition, three peaks of 1a corresponding to the equidistant q-spacings in the small-angle region can be assigned to the (001), (002), and (003)


Page 8 of 26

Page 9 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

reflections, indicating a lamellar structure in the crystalline phase.44-48 The measured layer spacing of 4.7 nm is close to the estimated molecular length (the estimated lengths of the rod segment and coil chain are ~3.1 nm and ~4.1 nm from the Corey-Pauling-Koltun (CPK) molecular model, respectively). This suggests that a typical monomolecular layer structure was formed in which the rod segments are fully interdigitated with each other (Figure 3b).

Figure 2. Representative optical polarized micrographs (40×) of the oblique columnar structures of molecule 1a measured at 245 °C.

However, molecule 1b only exhibited a crystalline phase, as confirmed by DSC and POM analyses. As shown in Figure S3a, small spherulitic textures corresponding to a typical columnar mesophase (140 °C) were observed by POM. The SAXS peaks shown in Figure 3c can be characterized as the (100), (010), (210), (120), (200), and (310) reflections, corresponding to a 2D oblique columnar structure with a characteristic angle γ = 41° (Figure 3c), and lattice constants a = 6.66 nm and b = 5.70 nm (Table S3). Notably, the results show that the layer structure of 1a was transformed to the 2D columnar structure of 1b in the crystalline phase via slight modification of the molecular structure. It can be deduced that the methyl groups located at the rigid and flexible segments can weaken the stacking interactions


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

of the bent-shaped rod segments to form the columnar structure.38,49-50 Molecule 1c, containing an alkyl group at the center of the rod and methyl groups in the coils, also exhibited only a crystalline phase at lower temperature, suggesting that the molecular packing of 1c is looser than that of 1a and 1b (Figure S3b). The SAXS pattern of 1c showed (100), (010), (200), and (120) reflections of a 2D oblique columnar structure with lattice parameters a = 7.40 nm, c = 4.69 nm, and γ = 37° (Figure 3d, Table S4). Similarly, molecule 2a (an isomer of 1a) exhibited an oblique columnar structure with lattice parameters a = 3.86 nm, b = 2.70 nm, and γ = 65° in the crystalline phase (Figure S4, Table S5).

Figure 3. Small-angle X-ray diffraction patterns of 1a, 1b and 1c measured in solid state and melt state plotted against q (= 4πsinθ/λ): (a) oblique columnar phase for 1a at 265 oC; (b) lamellar phase for 1a at 200 oC; (c) oblique columnar phase for 1b at 150 oC; (b) oblique columnar phase for 1c at 35 oC.

Notably, molecules 1a, 1b, and 1c, incorporating the same rigid segment but with different lateral chains, can self-organize into a lamellar or an oblique columnar structure by accurately tuning the molecular interactions in the bulk state. The formation of various


Page 10 of 26

Page 11 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

supramolecular nanostructures is governed by the steric repulsion between the aromatic rod domains and the flexible oligoether chains. When the rod segments self-assemble into anisotropic nanoassemblies, the lateral alkyl groups incorporated into the rod or at the surface of the rod and coil segments can enhance the repulsive forces compared to non-lateral groups. Therefore, the preferred assemblies of rod segments could be balanced by these steric repulsions and produce thermodynamically stable nanostructures. In addition, the isomer of 1a, molecule 2a self-assembles into oblique columnar structures instead of a lamellar structure. This indicates that the looser packing of 2a relative to that of 1a, confirmed by DSC, tends to form a more stable columnar structure than the lamellar structure in the solid state. Compared to 1a, the weaker π-π stacking of 2a serves to decrease the interfacial area of dissimilar parts of the molecules to form more thermodynamically stable supramolecular nanostructures.44 Hence, it is evident that the sequence of the rod segments plays an important role in the construction of different supramolecular nanostructures by affecting the driving force for molecular assembly. It is worth emphasizing that we have synthesized n-shaped rod-coil molecules comprising of anthracene rigid block and oligoether chains and investigated their self-assembling behavior in bulk state.38 The experimental results revealed that these molecules self-assemble into lamellar, hexagonal perforated lamellar and oblique columnar structures in liquid crystalline phase and in solid state. Compared to 2a-2c containing m-terphenyl groups, the n-shaped molecules which have similar molecular structures of 2a-2c, have a strong tendency of rigid blocks to be assembled into ordered supramolecular nanostructures. This means that the π-π stacking interactions of the n-shaped molecules with conjugated anthracene units are more enhanced than 2a-2c with m-terphenyl units. Thus, molecules 2a-2c display the oblique columnar phases in liquid crystalline phase, while the n-shaped molecules exhibit hexagonal perforated lamellar structure. According to the above analysis, we concluded that various supramolecular nanostructures are able to be produced by accurate controlling the intermolecular interactions such as π-π stacking, through slightly modifying molecular building block, as well as change of the sequence of the rod block. Aggregation behavior in aqueous solution.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The rigid–flexible molecules 1−2 combined with hydrophilic oligoether chains can produce various nanostructures with a rigid hydrophobic core surrounded by oligoether chains in aqueous solution. The aggregation behavior of these molecules was studied using UV-Vis and FL spectroscopy, CD, TEM, and AFM in aqueous solution. The UV-Vis spectra of the molecules (Figure 4) in dichloromethane showed a sharp absorption peak at 314−328 nm, which is attributed to the π-π* transition of the rod moiety in the molecule. However, these absorption peaks were noticeably broadened and red-shifted, accompanying strong hypochromic effects, in aqueous solution. This is attributed to molecular aggregation. In addition, molecules 1−2 fluoresced strongly in dichloromethane, whereas significantly diminished fluorescence was observed in aqueous solutions (Figure S5). We therefore deduced that aggregation took place in the aqueous solution, where the close arrangement of the rod segments reduces the fluorescence emission.

Figure 4. Absorption and emission spectra of 1b (a) and 1c (b) in dichloromethane and in aqueous solution (0.002 wt%).

The detailed formation of the supramolecular nanoaggregates of 1a−1c was initially investigated by AFM and TEM experiments. The AFM image of a sample of 1a (0.01 wt%) on hydrophilic mica clearly revealed rectangular sheets with widths in the 450−800 nm range and lengths up to 10−20 µm (Figure 6a). The thickness of the sheet (~3.3 nm) observed using AFM was nearly consistent with the rod length of 1a (3.1 nm as estimated by CPK modeling), suggesting that the molecules arrange into sheets as monolayers (Figure 8a).


Page 12 of 26

Page 13 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 5. CD spectra of 1a-1c for (a) and 2a-2c for (b) (0.01 wt%) in aqueous solutions.

Interestingly, the AFM image of molecule 1b, with a lateral methyl group in the coil, showed helical nanofibers with mean widths ranging from ~8 to ~9 nm and lengths of up to several µm (Figure 6b). The CD spectra of 1b also showed a positive Cotton signal at 309 nm, which is nearly consistent with the UV-Vis spectra. These results suggest that the adjacent aromatic bent-shaped rods are mutually rotated in the same direction to minimize the energy balance of microphase separation (Figure 5a). To ease the steric constraints imposed by the coil segment with the methyl groups at the surface of the rod and coil segment, the chiral coil segment tilts the stack of the repeating rod units along the fibril axis on top of each other (Figure 8b). This dynamic assembly process ultimately produces thermodynamically favored helical nanofibers.51-56


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 6. (a) AFM image of 1a 0.01 wt% in aqueous solution. (b) AFM image of 1b. (c) TEM image of 1c (obtained from 0.01 wt% in aqueous solution and negatively stained with uranyl acetate). (d) AFM image of 1c.

Modifying the fundamental structure of 1b by introducing a butyl chain at the rod centre produced 1c, with both lateral methyl and butyl groups. Unexpectedly, the TEM image of 1c shows predominantly ring-shaped aggregated structures with a cross-sectional diameter of ~8.5 nm and nano-ring diameters ranging from ~30−120 nm (Figure 6c). The CD spectrum of molecule 1c exhibited the Cotton effect in the spectral range of the aromatic segment (Figure 5a). From the CD data, we deduce that the supramolecular handedness is derived from the chiral centers located in the coil domains. To probe the handedness of the self-assembled 1c molecules, AFM experiments were performed. The AFM image of 1c clearly displays helical nano-rings, with sizes consistent with the TEM results (Figure 6d). The formation of the nano-rings is attributed to the change of the surface curvature of the rod and coil domains (Figure 8c). Compared to 1b with the lateral methyl group, 1c incorporates methyl and butyl alkyl groups in the rod-coil molecules. This slight modification of the molecular structure


Page 14 of 26

Page 15 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

induces weaker intermolecular interaction, as evidenced by the DSC and SAXS data for the bulk state. The loose packing of the rod block of 1c, as well as its hydrophilic-hydrophobic interactions, leads to a tendency to self-assemble into thermostable nanoaggregates with increasing surface curvature in aqueous solution. Considering that chiral oligoethers induce handedness in the aggregates, the relatively looser, tilted rod segments stack closely side by side with mutual rotation along a certain angle to minimize the steric hindrance, resulting in the formation of helical toroids through microphase separation and hydrophobic interactions.57-58 In contrast with the bent-shaped molecules 1a−1c, the AFM and TEM images of their isomers, molecules 2a−2c incorporating the triple bonds at the 3,3`` position of the terphenyl unit, display supramolecular nanobelts, helical fibers, self-assembles into nanoribbons with diameters of ~80−100 nm and lengths of more between the rigid and flexible segments also exhibits helical fibers with a uniform diameter of ~7 nm and lengths of up to several µm, as illustrated by TEM and AFM (Figure 7b and 7c). Molecule 2c, containing a butyl group at the middle of the rods, self-assembles into nano-ring aggregates with a cross-sectional diameter of ~8 nm and ring diameter of ~18−25 nm (Figure 7d and S6), where these values are smaller than that of nano-rings formed by 1c. These results imply that the sequence of the rigid segments, as well as the lateral alkyl groups at the surface of the rod and coil segments or at the center of the rod block, significantly impact the molecular arrangement in creating various morphologies of rod-coil molecules by affecting the assembling driving force.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 7. (a) AFM image of 2a. (b) AFM image of 2b. (c) TEM image of 2b. (d) TEM image of 2c (0.01 wt% in aqueous solution and negatively stained with uranyl acetate).

Notably, the two series of isomers described here, which have different configurational sequences of rod building blocks but the same molecular weight and coil chains, exhibit different self-organizing behavior in dilute aqueous solution. Molecule 1a, with a bent-shaped rod segment, self-assembles into sheets, whereas its isomer, 2a, self-organizes into nanoribbons (Figure 8d). Although molecules 1a and 2a have the same hydrophilic chains, the driving force of assembly for 1a is stronger than that of 2a, as demonstrated by SAXS analysis in the bulk state, due to the difference in the configurational sequence of the rods. The variation in the driving forces can directly affect the molecular self-organization to produce sheet-like and ribbon-like assemblies in aqueous solutions. Molecules 1b and 2b with lateral chiral groups both self-organize into helical fibers in aqueous environment. No noticeable changes in the morphology were observed in this case, either by AFM or TEM, which means that the self-organization of 1b and 2b is mainly controlled by hydrophilic-hydrophobic effects rather than intermolecular interactions for the construction of helical fibers, although there are synergistic effects between these parameters in the creation of nano-objects. Interestingly, when a butyl group was introduced at the rod center for


Page 16 of 26

Page 17 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

molecules 1b and 2b, large and small supramolecular helical nano-rings were obtained. As mentioned above, molecules 1c and 2c tend to exhibit looser packing than 1a−1b and 2a−2b due to the microphase separation between the coil and rod domains. The reduced driving force for self-assembly leads to supramolecular nano-rings with a larger interface curvature than that of the other molecules, which lowers the total free energy of these molecular systems.59 Notably, control of the size of the nano-rings formed by 1c and 2c in aqueous solution was achieved by tuning the rod sequences of these molecules. Molecule 2c self-assembled into smaller helical nano-rings than 1c, given that the intermolecular interactions of the rigid rod aromatic regions of 1c are weaker than those of 2c. To minimize the energy balance, compared to 1c, 2c self-assembles into relatively thermodynamically stable smaller nano-rings with higher curvature than that of 1c. For molecules 1a and 2a with stronger intermolecular interactions than those of 1a and 1c, the effect of the sequence of rod blocks directly influences the formation of sheets and nanoribbons, instead of inducing size control with the same morphology. These results further verify that tuning the synergistic effect between the sequence of the rod and the hydrophilic-hydrophobic interaction can successfully create a variety of nano-objects from amphiphilic molecules in aqueous solution. It should be noted that we have previously reported self-assembling behavior of the bent-shaped molecules with benzene unit at the center of the rod block, connected by an acetylene bond.60 The bent-shaped molecules self-assemble into nanoribbons, helical fibers and nanoparticles in aqueous solution. While, 1a-1c with similar molecular structure of bent-shaped molecules incorporating benzene unit self-assemble into sheets, helical nanofibers and helical nano-rings through controlling intermolecular interactions. The results of the assembly of the bent-shaped molecules reveal that the driving force of the rod building block significantly influences the shape of the molecular nano-assemblies in aqueous solutions. Compared to molecules 1a-1c with m-terphenyl group at the center of the rod block, the bent-shaped molecules with benzene unit at the middle of the rod segment have relatively loose packing of rod segments due to the short rod length of the building block in bulk state and in aqueous solution. This point has been demonstrated by SAXS analyses of 1a-1c and the bent-shaped molecules with benzene unit. For example, 1a self-organizes into lamellar


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

and oblique columnar structures in the crystalline phase and liquid crystalline phase, but the bent-shaped molecule with benzene unit only self-assembles into hexagonal structure in the solid state. In addition, we have reported that n-shaped molecule with anthracene unit incorporating lateral butyl and methyl groups at the center of rod and at the surface of the rod and coil segments, respectively, self-assembles into thermal-responsive reversible helical nanofibers. While, molecule 1c with similar molecular structure of above mentioned molecule, spontaneously self-organizes into helical nanorings. In contrast to the n-shaped molecule with butyl group, the intermolecular interaction of 1c with m-terphenyl group is more weakened, because 1c incorporates m-terphenyl group instead of the planar anthracene unit. Therefore, the reduced driving force for self-assembly of 1c induces larger interface curvature than that of the bent-shape molecule with anthracene unit, subsequently, to produce thermodynamically stable supramolecular nano-rings.


Page 18 of 26

Page 19 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 8. Schematic representation of the proposed self-assembly of molecules in aqueous solution: (a) sheets for 1a. (b) helical fibers for 1b. (c) helical nano-rings for 1c. (d) nano-ribbons for 2a.

CONCLUSIONS A new class of isomers, 1 and 2, consisting of m-terphenyl and biphenyl units as the rod segments and oligoether with lateral alkyl groups as the coil segments, were successfully synthesized. Molecules 1a−1c were observed to self-assemble into lamellar and oblique columnar structures in the crystalline and liquid crystalline phases, respectively, whereas the isomer of 1a self-assembles into an oblique columnar structure in the crystalline phase. In aqueous solutions, molecule 1a self-assembles into sheets, whereas its isomer, 2a, self-organizes into long nanoribbons. The self-organization of 1b and 2b with lateral methyl groups between the rod and coil segments produces helical nanofibers. Furthermore, incorporating butyl groups at the center of the rod block causes the molecules to self-assemble into large and small helical nano-rings. From these observations, it is concluded that modulations of the molecular configuration of the rod building blocks and/or


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

π–π stacking and hydrophobic-hydrophilic interactions allow accurate control of the aggregation behavior of amphiphilic rod-coil molecular systems in an aqueous environment. The various morphologies of supramolecular aggregates created by the rod-coil molecular isomers may have potential applications for photo-electronic and biomimetic materials.


Page 20 of 26

Page 21 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: XXXXX. Additional scheme, figures, and tables (PDF).

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (grant number: 21562043, 21564016, 21304009, 21164013). The Natural Science Foundation of Liaoning Province (20170540019). We are grateful to Bejing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences for help with the X-ray scattering measurements of molecular structures.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

REFERENCES [1] Deshmukh, S.; Solomon, L.; Kamath, G.; Christopher Fry, H.; San karanarayanan, S. Water Ordering Controls the Dynamic Equilibrium of Micelle–Fibre Formation in Self-Assembly of Peptide Amphiphiles. Nat. Commun. 2016, 7, 12367. [2] Zhang, Q.; Wang, W.; Kong, X.; Mendes, R.; Fang, L.; Xue, Y.; Xiao, Y.; Rümmeli, M.; Chen, S.; Fu, L. Edge-to-Edge Oriented Self-Assembly of ReS2 Nanoflakes. J. Am. Chem. Soc. 2016, 138, 11101–11104. [3] Dong, Q.; Qu, W.; Wang, P.; Wong, W-Y. A Novel Supramolecular System with Multiple Fluorescent States Constructed by Orthogonal Self-Assembly. Polym. Chem. 2016, 7, 3827−3831. [4] Wang, X.; Han, Y.; Liu, Y.; Zou, G.; Gao, Z.; Wang, F. Cooperative Supramolecul ar Polymerization of Fluorescent Platinum Acetylides for Optical Waveguide Applications. Angew. Chem. Int. Ed. 2017, 56, 12466−12470. [5] Cohen, E.; Weissman, H.; Pinkas, I.; Shimoni, E.; Rehak, P.; Král, P.; Rybtchinsk i, B. Controlled Self-Assembly of Photofunctional Supramolecular Nanotubes. ACS Nano, 2018, 12, 317–326. [6] Huang, M.; Hsu, C.; Wang, J.; Mei, S.; Dong, X.; Li, Y.; Li, M.; Liu, H.; Zhang, W.; Aida, T.; Zhang, W.; Yue, K.; Cheng, S. Selective Assemblies of Giant Tetrahedra via Precisely Controlled Positional Interactions. Science 2015, 348, 424–428. [7] Xia, D.; Wei, P.; Shi, B.; Huang, F. A Pillar[6]arene-based [2]pseudorotaxane in Solution and in the Solid State and Its Photo-Responsive Self-Assembly Behavior in Solution. Chem. Commun. 2016, 52, 513−516. [8] Zhou, J.; Yu, G.; Huang, F. Supramolecular Chemotherapy Based on Host–Guest Molecular Recognition: A Novel Strategy in the Battle against Cancer with a Bright Future. Chem. Soc. Rev. 2017, 46, 7021−7053. [9] Huang, T.; Zhu, Z.; Xue, R.; Wu, T.; Liao, P.; Liu, Z.; Xiao, Y.; Huang, J. B.; Yan, Y. Allosteric Self-A ssembly of Coordinating Terthiophene Amphiphile for Triggere d Light Harvesting. Langmuir 2018, 34, 5935–5942. [10] Liu, W.; Chen, J.; Zhou, D.; Liao, X.; Xie, M.; Sun, R. A High-performance Dielectric Block Copolymer with a Self-Assembled Superhelical Nanotube Morphology. Polym. Chem. 2017, 8, 725−734. [11] Chen, M.; Zhu, H.; Zhou, S.; Xu, W.; Dong, S.; Li, H.; Hao, J. C. Self-Organization and Vesicle Formation of Amphiphilic Fulleromonodendrons Bearing Oligo(poly(ethylene oxide)) Chains. Langmuir 2016, 32, 2338−2347. [12] Takai, A.; Chen, Z.; Yu, X.; Zhou, N.; Marks, T.; Facchetti, A. Annulated Thienyl-Vinylene-Thienyl Building Blocks for π-Conjugated Copolymers: Ring Dimensions and Isomeric Structure Effects on π-Conjugation Length and Charge Transport. Chem. Mater. 2016, 28, 5772–5783. [13] Albert, S.; Thelu, H.; Golla, M.; Krishnan, N.; Varghese, R. Modular Synthesis of Supramolecular DNA Amphiphiles through Host–Guest Interactions and Their Self-Assembly into DNA-decorated Nanovesicles. Nanoscale 2017, 9, 5425−5432. [14]Wang, L.; Wang, Y.; Hao, J. C.; Dong, S. Magnetic Fullerene-DNA /Hyaluronic Acid Nanovehicles with Magnetism/Reduction Dual-Responsive Triggered Release. Biomacromolecules 2017, 18, 1029−1038.


Page 22 of 26

Page 23 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

[15] Jiang, H.; Zhang, L.; Chen, J.; Liu, M. Hierarchical Self-Assembly of a Porphyrin into Chiral Macroscopic Flowers with Superhydrophobic and Enantioselective Property. ACS Nano, 2017, 11, 12453–12460. [16] Zhang, S.; Zheng, Y.; Fu, D.; Li, W.; W u, Y.; Li, B.; Wu, L. X. Biocompatible Supramolecular Dendrimers Bearing a Gadolinium-substituted Polyanionic Core for MRI Contrast Agents. J. Mater. Chem. B. 2017, 5, 4035−4043. [17] Yu, S.; Yang, Y.; Chen, T.; Xu, J.; Jin, L. Donor–Acceptor Interaction-driven Self-Assembly of Amphiphilic Rod–Coil Molecules into Supramolecular Nanoassemblies. Nanoscale 2017, 9, 17975−17982. [18] Wei, J.; Sun, S.; Lu, Q.; Gao, P.; Wang, Y.; Li, X.; Jiang, Y. The Formation of Fibers via Complementary Base Pairing of DNA-conjugated Bovine Serum Albumin. Chin. Chem. Lett. 2018, 29, 461−463. [19] Xiao, T.; Wang, L. Recent Advances of Functional Gels Controlled by Pillar[n]arene-based Host–Guest Interactions. Tetrahedron Lett. 2018, 59, 1172−1182. [20] Li, W.; Kim, Y.; Lee, M. Intelligent Supramolecular Assembly of Aromatic Block Molecules in Aqueous Solution. Nanoscale 2013, 5, 7711−7723. [21] Guo, S.; Liu, X.; Yao, C.; Lu, C.; Chen, Q.; Hu, X.; Wang, L. Photolysis of a Bola-Type Supra-Amphiphile Promoted by Water-Soluble Pillar[5]arene-induced Assembly. Chem. Commun. 2016, 52, 10751-10754. [22] Chen, S.; An, Z.; Tong, X.; Chen, Y.; Ma, M.; Shi, Y.; Wang, X. Stronger Intermo lecular Forces or Closer Molecular Spacing? Key Impact Factor Research of Gelator Self-Assembly Mechanism. Langmuir 2017, 33, 14389–14395 [23] Shen, B.; He, Y.; Kim, Y.; Wang, Y.; Lee, M. Spontaneous Capture of Carbohydrate Guests through Folding and Zipping of Self‐Assembled Ribbons. Angew. Chem. Int. Ed. 2016, 55, 2382–2386. [24] Kim, Y.; Shin, S.; Kim, T.; Lee, D.; Seok, C.; Lee, M. Switchable Nanoporous Sheets by the Aqueous Self‐Assembly of Aromatic Macrobicycles. Angew. Chem. Int. Ed. 2013, 52, 6426–6429. [25] Kim, Y.; Lee, M. Supramolecular Capsules from Bilayer Membrane Scission Driven by Corannulene. Chem. Eur. J. 2015, 21, 5736 –5740. [26] Wang, Y.; Kim Y.; Lee, M. Static and Dynamic Nanosheets from Selective Assembly of Geometric Macrocycle Isomers. Angew. Chem. 2016, 128, 13316–13320. [27] Zhang, J.; Chen, X.; Wei, H.; Wan, X. Tunable Assembly of Amphiphilic Rod–Coil Block Copolymers in Solution. Chem. Soc. Rev. 2013, 42, 9127−9154. [28] Brassinne, J.; Fustin, C-A.; Gohy, J-F. Control Over the Assembly and Rheology of Supramolecular Networks via Multi-Responsive Double Hydrophilic Copolymers. Polym. Chem. 2017, 8, 1527−1539. [29] Shao, B.; Zhu, X.; Plunkett, K.; Vanden Bout, D. Controlling the Folding of Conjugated Polymers at the Single Molecule Level via Hydrogen Bonding. Polym. Chem. 2017, 8, 1188−1195. [30] Wu, Y.; Wang, K.; Tan, H.; Xu, J.; Zhu, J. Effect of Counterions on the Self-Assembly of Polystyrene-Polyphosphonium Block Copolymers Emulsion Solvent Evaporation-Induced Self-Assembly of Block Copolymers Containing pH-Sensitive Block. Langmuir 2017, 33, 9889–9896.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

[31] Tian, L.; Zhong, K.; Liu, Y.; Huang, Z.; Jin, L.; Hirst, L. Synthesis and Self-Assembly of Coil–Rod–Coil Molecules with Lateral Methyl and Ethyl Groups in the Center of the Rod Segment. Soft Matter, 2010, 6, 5993–5998. [32] Ji, X.; Liu, L.; Zhao, H. The Synthesis and Self-assembly of Bioconjugates Composed of Thermally-Responsive Polymer Chains and Pendant lysozyme Molecules. Polym. Chem. 2017, 8, 2815−2823. [33] Wu, H.; Chen, Y.; Liu, Y. Reversibly Photoswitchable Supramolecular Assembly and Its Application as a Photoerasable Fluorescent Ink. Adv. Mater. 2017, 29, 1605271. [34] Meng, L-B.; Zhang, W.; Li, D.; Li, Y.; Hu, X-Y.; Wang, L. Y.; Li, G. pH-Responsive Supramolecular Vesicles Assembled by Water-Soluble Pillar[5]arene and a BODIPY Photosensitizer for Chemo-Photodynamic Dual Therapy. Chem. Commun. 2015, 51, 14381−14384. [35] Cheng, M.; Zhang, J.; Ren, X.; Guo, S.; Xiao, T.; Hu, X-Y.; Jiang, J.; Wang, L. Y. Acid/Base-Controllable Fluorescent Molecular Switches based on Cryptands and Basic N-heteroaromatics. Chem. Commun. 2017, 53, 11838−11841. [36] Zhang, J.; Chen, X.; Li, W.; Li, B.; Wu, L. Solvent Dielectricity-Modulated Helical Assembly and Morphologic Transformation of Achiral Surfactant-Inorganic Cluster Ionic Complexes. Langmuir 2017, 33, 12750−12758. [37] Zhong, K.; Wang, Q.; Chen, T.; Huang, Z.; Yin, B.; Jin, L. Self‐Assembly of Rod‐Coil Molecules into Lateral Chain‐Length‐Dependent Supramolecular Organization. J. Appl. Polym. Sci. 2011, 123, 1007−1014. [38] Yang, Y.; Cui, J.; Li, Z.; Zhong, K.; Jin, L.; Lee, M. Self-Assembly of n‐Shaped Rod−Coil Molecules into Thermoresponsive Nanoassemblies: Construction of Reversible Helical Nanofibers in Aqueous Environment. Macromolecules 2016, 49, 5912–5920. [39] Li, Z.; Wu, Z.; Mo, G.; Xing, X.; Liu, P. A Small-Angle X-ray Scattering Station at Beijing Synchrotron Radiation Facility. Instrum. Sci. Technol. 2014, 42, 128−141. [40] Wang, Z.; Cui, J.; Liang, Y.; Chen, T.; Lee, M.; Yin, B.; Jin, L. Supramolecular Nanostructures from Self-Assembly of T-Shaped Rod Building Block Oligomers. J. Polym. Sci. Part A: Polym. Chem. 2013, 51, 5021–5028. [41] Jin, L.; Bae, J.; Ahn, J-H.; Lee, M. Structural Inversion in 3-D Hexagonal Organization of Coil–Rod–Coil Molecule. Chem. Commun. 2005, 1197−1199. [42] Wang, Z.; Zhong, K.; Liang, Y.; Chen, T.; Yin, B.; Lee, M.; Jin, L. Ordered Nanostructures from Self-Assembly of H-Shaped Coil–Rod–Coil Molecules. J. Polym. Sci. Part A: Polym. Chem. 2015, 53, 85–92. [43] Jin, L.; Bae, J.; Ryu, J-H.; Lee, M. Ordered Nanostructures from the Self-Asse mbly of Reactive Coil–Rod–Coil Molecules. Angew. Chem. Int. Ed. 2006, 45, 650–653. [44] Li, Z.; Yang, Y.; Wang, Y.; Chen, T.; Jin, L.; Lee, M. Construction of Supramolecular Assemblies from Self-Organization of Amphiphilic Molecular Isomers. Chem. Asian. J. 2016, 11, 2265–2270. [45] Lu, Z.; Zhong, K.; Liu, Y.; Li, Z.; Chen, T. and Jin L. Self-Organizing p-quinquephenyl Building Blocks incorporating Lateral Hydroxyl and Methoxyl Groups into Supramolecular Nano-assemblies. Soft Matter. 2016, 12, 3860−3867.


Page 24 of 26

Page 25 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

[46] Liu, Y.; Zhong, K.; Li, Z.; Wang, Y.; Chen, T.; Lee, M.; Jin, L. Synthesis and Self-Assembly of Amphiphilic Bent-Shaped Molecules based on Dibenzo[a,c]phenazine and Poly(ethylene oxide) Units. Polym. Chem. 2015, 6, 7395−7401. [47] Kim, H-J.; Kim, Y.; Cho, S.; M. Lee. Self-Assembly of a Tripod Aromatic Rod into Stacked Planar Networks. Chem. Eur. J. 2015, 21, 11836–11842. [48] Yu, S.; Yang, Y. ; Li, C.; Chen, T.; Jin, L. Three-Dimensional Crystalline Supramolecular Nanostructures from Self-Assembly of Rod–coil Molecules incorporating Lateral Carboxyl Group in the Middle of the Rod Segment. Polym. Int. 2015, 64, 1408−1414. [49] Zhong, K.; Wang, Q.; Chen, T.; Jin, L. Self-Assembly of Coil-Rod-Coil Molecules into Bicontinuous Cubic and Oblique Columnar Assemblies depending on Coil Chain Length. Eur. Polym. J. 2013, 49, 3244–3250. [50] Ryu, J-H.; Oh, N-K.; Zin, W-Z.; Lee, M. Self-Assembly of Rod-Coil Molecules into Molecular Length-Dependent Organization. J. Am. Chem. Soc. 2004, 126, 3551–3558. [51] Burnworth, M.; Tang, L. Kumpfer, J.; Duncan, A.; Beyer, F.; Fiore, G.; Rowan, S.; Weder, C. Optically Healable Supramolecular Polymers. Nature 2011, 472, 334–337. [52] Goel, M.; Narasimha, K.; Jayakannan, M. Helical Self-Assemblies of Segmented Poly(phenylenevinylene)s and Their Hierarchical Donor–Acceptor Complexes. Macromolecules 2014, 47, 2592−2603. [53] Han, M.; Cho, S.; Norikane,Y.; Shimizu, M.; Seki, T. Assembly of an Achiral Chromophore into Light-Responsive Helical Nanostructures in the Absence of Chiral Components. Chem. Eur. J. 2016, 22, 3971−3975. [54] Kumar, M.; George, S. Homotropic and Heterotropic Allosteric Regulation of Supramolecular Chirality. Chem. Sci. 2014, 5, 3025−3030. [55] Sun, R.; Xue, C.; Ma, X.; Gao, M.; Tian, H.; Li, Q. Light-Driven Linear Helical Supramolecular Polymer Formed by Molecular-Recognition-Directed Self-Assembly of Bis(p-s ulfonatocalix[4]arene) and Pseudorotaxane. J. Am. Chem. Soc. 2013, 135, 5990–5993. [56] Kim, H.; Kang, S.; Lee, Y.; Seok, C.; Lee, J.; Zin, W.; Lee, M. Self-Dissociating Tubules from Helical Stacking of Noncovalent Macrocycles. Angew. Chem. Int. Ed. 2010, 49, 8471−8475. [57] Yashima, E.; Maeda, K.; Iida, H.; Furusho, Y.; Nagai, K. Helical Polymers: Synthesis, Structures, and Functions. Chem. Rev. 2009, 109, 6102–6211. [58] Lee, C.; Grenier, C.; Meijer, E.; Schenning, A. Preparation and Characterization of Helical Self-Assembled Nanofibers. Chem. Soc. Rev. 2009, 38, 671–683. [59] Yu, S.; Shan, R.; Sun, G.; Chen, T.; Wu, L.; Jin, L. Construction of Various Supramolecular Assemblies from Rod-Coil Molecules Containing Biphenyl and Anthracene Groups Driven by Donor-Acceptor Interactions. ACS Appl. Mater. Interfaces 2018, DOI: 10.1021/acsami.8b01461. [60] You, S.; Zhong, K.; Jin, L. Control of Supramolecular Nanoassemblies by Tuning the Interactions of Bent-Shaped Rod–Coil Molecules. Soft Matter, 2017, 13, 3334–3340.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table of Content Graphics


Page 26 of 26

Morphological Control of Coil-rod-coil Molecules ... - ACS Publications

Recommend Documents