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This chapter provides a brief overview of the principles as well as the potential applications of photoresponsive hydrogel films, which change surface topography. It discusses the operating mechanisms that lead to topographical changes. Changes in topography can affect the wettability of a surface, which is an interesting characteristic for making self‐cleaning coatings. The chapter also discusses polymer films that are useful for the development of self‐cleaning films. It then discusses responsive materials, for cell culturing and microfluidics applications. The chapter further shows that appealing photoresponsive polymer hydrogel coatings that change topography can be fabricated, which holds great promise in a variety of fields ranging from microfluidic devices to biomedical applications. When the structures of the topography are in the micrometer size regime, they influence the wettability of the surface. Two types of wetting can be defined: Wenzel and Cassie‐Baxter.

In the past decade, chiral nematic liquid crystals (LCs) have emerged as an attractive material for the development of stimuli-responsive systems (White et al. 2010; Ge and Yin 2011; Fenzl et al. 2014; Mulder et al. 2014; Stumpel et al. 2014). Due to the periodic alteration of their refractive indices, they act as one-dimensional photonic structures and reect circularly polarized light of same handedness. The reection of light is governed by Bragg’s law: λ θb = nP cos where λb is the wavelength of Bragg reection, n is the average refractive index, and P is the length of the helical pitch. The pitch of a chiral nematic is dened as the length traversed by the molecular director nˆ on 360° rotation (Figure 4.1a). It is inversely proportional to the concentration [C] as well as the helical twisting power β

Exciton dynamics in chiral helixes of an oligo-p-phenylenevinylene deriv. monofunctionalized with a ureido-s-triazine (MOPV) were studied. The latter functional group leads to oligomer dimerization by hydrogen bonding in dodecane soln., resulting in reversible supramol. assembly by solvophobic and p-p interactions. MOPV is a model system to study exciton transfer dynamics as it is possible to study the effect of intermol. interactions by comparing optical properties in the dissolved phase (above the transition temp.) and the supramol. assemblies. The model allows to ext. microscopic informations such as the av. exciton hopping annihilation rates. It is believed that this model also allows the quant. description of the exciton dynamics on supramol. architectures from subpicosecond to nanosecond timescales.

Stimuli-responsive materials which respond to triggers from the environment by changing their properties are one of the focal points in materials science. For precise functional properties, well-defined hierarchically ordered supramolecular materials are crucial. The self-assembly of liquid crystals has proven to be an extremely useful tool in the development of well-defined nanostructured materials. Liquid crystalline materials are appealing for making responsive materials since microscopic changes in the molecular order and orientation can lead to macroscopic changes in shape, optical properties, or porosity. By using photopolymerizable liquid crystals a wide variety of stimuli-responsive materials can be made from a relatively simple set of building blocks. Upon mixing different (reactive) mesogens, nematic, chiral nematic, and smectic liquid crystalline phases can be formed that can be applied as soft actuators, responsive optical materials and tunable nanoporous materials, respectively.

The challenge of the future is to minimize the energy consumption of buildings while maintaining an optimal comfort level in the interior. Controlling the energy streams in and out of the building , and especially daylight management, plays an important role. It deals with many, sometimes conflicting functions of the building: Generally a maximum of natural lighting is desired to reduce the need for lighting energy which in today’s buildings accounts for approximately 30% of the total electricity demand. But daylight contains a lot of energy. We need to block sun radiation in summer to prevent overheating, whereas in winter this incoming energy is desired to reduce the need for heating energy. By means of the PolyArch project we aim at clarifying the energy savings potential as well as identifying the technological challenges that need to be tackled in order to get PolyArch market ready. Prototypes of the product will be displayed and tested in the LightVan, a mobile light laboratory., SPOOL, Vol. 2 No. 2: Energy Innovation #3

Liquid crystals (LCs) combine properties of both liquids and crystals and can be organized in a variety of nanostructured polymer films with a monolithic structure. Therefore, polymer-based LCs are ultimately suited as membrane with an accurately controlled nanoporosity. Nanoporous membranes that have a large surface area to volume ratio are of great current interest for their potential application in filtration, separation, ion conductivity, drug delivery, and catalysis. The small pore size in these materials (less than 1 nm) makes discrimination between molecules and ions based on size and shape possible.LCs can self-assemble in a variety of phases that have orientation order and, in some cases, positional order. For the construction of nanoporous membranes, various phases have been used. Well-known examples are hexagonal or columnar, lamellar or smectic, and cubic phases

Here, we report on the strong amplification of chirality observed in supramolecular polymers consisting of benzene-1,3,5-tricarboxamide monomers and study the chiral amplification phenomena as a function of temperature. To quantify the two chiral amplification phenomena, i.e., the sergeants-and-soldiers principle and the majority-rules principle, we adapted the previously reported sergeants-and-soldiers model, which allowed us to describe both amplification phenomena in terms of two energy penalties: the helix reversal penalty and the mismatch penalty. The former was ascribed to the formation of intermolecular hydrogen bonds and was the larger of the two. The latter was related to steric interactions in the alkyl side chains due to the stereogenic center. With increasing temperature, the helix reversal penalty was little affected and remained rather constant, showing that the intermolecular hydrogen bonds remain intact and are directing the helicity in the stack. The mismatch penalty, however, was found to decrease when the temperature was increased, which resulted in opposite effects on the degree of chiral amplification when comparing the sergeants-and-soldiers and the majority-rules phenomena. While for the former a reduction in mismatch penalty resulted in a decrease in degree of chiral amplification, for the latter it resulted in a stronger chiral amplification effect. By combining the sergeants-and-soldiers and majority-rules phenomena in a diluted majority-rules experiment, we could further determine the effect of temperature on the degree of chiral amplification. Extending the experiments to different concentrations revealed that the relative temperature, i.e., the temperature relative to the critical temperature of elongation, controls the degree of chiral amplification. On the basis of these results, it was possible to generate a general "master curve" independent of concentration to describe the temperature-dependent majority-rules principle. As a result, unprecedented expressions of amplification of chirality are recorded.

Materials showing rapid intramolecular energy transfer and polarization switching are of interest for both their fundamental photophysics and potential for use in real-world applications. Here, we report two donor-acceptor-donor triad dyes based on perylene-bisimide subunits, with the long axis of the donors arranged either parallel or perpendicular to that of the central acceptor. We observe rapid energy transfer (

In this review, we show the important role of supramolecular chemistry in the fabrication of stimuli responsive and hierarchically structured liquid crystalline polymer networks. Supramolecular interactions can be used to create three dimensional order or as molecular triggers in materials that can be applied as actuators, sensors and nanoporous materials.

Book review

Self-assembled amphiphiles are more common in the realm of aqueous systems than in organic solvents. Their scope has now been expanded with the advent of 'hydrophobic amphiphiles' of p-conjugated–alkyl systems, which show various self-assembled phases similar to classical amphiphiles.

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Trabajo presentado al "Emerging Liquid Crystal Technologies VIII" celebrado en California (US) del 2 al 5 de marzo de 2013., Defects in liquid crystals have been studied over decades to disclose information and knowledge on the structure of LC phases. More recently, LC defects have been identified as a tool to implement new physical functions useful in optical films for polarization conversion or mechanical actuators able to adopt novel exotic shapes. In the present paper we describe a general methodology to engineer different defect patterns by combining the use of linear photopolymerizable polymers and liquid crystals., We thank the Dutch NWO (VICI grant), the Spanish MINECO project MAT2011-27978-C02-02, CSIC project i-LINK0394, Gobierno de Aragón, and FEDER funding (EU) for their financial support.

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To study the supramolecular polymerisation mechanisms of a self-assembling system, concentration- and temperature-dependent measurements can both be used to probe the transition from the molecular dissolved state to the aggregated state. In this report, both methods are evaluated to determine their effectiveness in identifying and quantifying the self-assembly mechanism for isodesmic and cooperative self-assembling systems. It was found that for a rapid and unambiguous determination of the self-assembly mechanism and its thermodynamic parameters, temperature-dependent measurements are more appropriate. These studies allow the acquisition of a large data set leading to an accurate determination of the self-assembly mechanism and quantification of the different thermodynamic parameters that describe the supramolecular polymerisation. For a comprehensive characterisation, additional concentration-dependent measurements can be performed.

Self-assembly is a promising approach for the construction of nano-sized objects with a specific function. Recently, we have reported on a star-shaped oligo(p-phenylene vinylene) (OPV) substituted hexaarylbenzene in which the no. of OPV segments is increased to six, and the propeller-like structure resulted in more stable stacks in alkane solvents. The stability of the assemblies enabled the use of size exclusion chromatog. (SEC) to study the monomer content in addn. to the normally applied temp. and concn. dependent optical techniques, which mainly probe the assembly characteristics. The formation of two types of assemblies, as visualized with CD spectroscopy, allowed for the visualization of a bimodal distribution in the SEC trace where the two peaks could be assigned to monomers and assemblies by UV/vis spectroscopy. The application of SEC showed for the first time the analogy of the cooperative nucleation-elongation self-assembly mechanism with chain-growth polymn. in covalent polymer chem.

We have determined the internal organization of elongated sexithiophene aggregates in solution by combining small-angle X-ray scattering and magnetic birefringence experiments. The different aggregate axes can be probed independently by performing the experiments on magnetically aligned aggregates.Wehave found multiwalled cylindrical aggregates consisting of radially oriented sexithiophene molecules with p-p-stacking in the tangential direction, a structure that is considerably different from those previously found in other solvents. The aggregate morphology of this semiconducting material can thus be tuned by using different solvents, which offers the attractive perspective to steer chemical self-assembly toward nanostructures with desired functionalities, especially in combination with the alignment in a magnetic field.

A new guest based on diphenylanthracene functionalized with glycinylurea was synthesized. The guest having trisdodecyloxyalkylic groups has been fully characterized by NMR spectroscopy (1H-NMR, 13C-NMR) and MALDI-TOF-MS. The resulting Guest was complexed with dendritic adamantyl urea Host of fifth generation and the association constant has been calculated. By size exclusion chromatography was proved that the multivalent host strongly binds 32 molecules of the DPA guests as a result of acid-base and hydrogen bonding interactions.

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Glycinylurea functionalized p-conjugated diphenylanthracene guests (DPA guests) that bind to adamantyl urea modified dendritic hosts were synthesized and fully characterized by NMR spectroscopy (1H-NMR, 13C-NMR) and MALDI-TOF-MS. The resulting supramolecular assemblies have been investigated with respect to their binding properties. DPA guests molecules were able to click into urea functionalized N,N-bis methyl amine host as a result of acid-base (between COOH of the guest and amines of the host) and hydrogen bonding interactions (between the urea linkages of dendrimer and the guest). The guest molecules were bound as 1:1 inclusion complexes and the association constants for both guests have been calculated. Subsequently, an adamantyl urea modified fifth generation poly(propylene imine) dendrimer was synthesized as a multivalent host which contains 32 N,Nbis amine binding sites. Size exclusion chromatography showed that 32 of the DPA guests strongly bind to the fifth generation adamantyl functionalized dendritic host.

The nucleotide-appended oligo(p-phenylenevinylene), {bis[2,5-bis(2-methoxyethoxy)-1,4-phenylene]bis(2,1-ethenediyl-1,4-phenylenemethylene)}bis(2'-deoxy-3'-thymidylic acid) (8), has been synthesized, and self-assembly of the single-component 8 and binary self-assembly of 8 with a complementary single-stranded 20-meric oligodeoxyadenylic acid (9) have been examined in aqueous solutions. Atomic force microscopy (AFM), UV-visible (UV-vis), and circular dichroism (CD) measurements revealed that right-handed helical stacks with 6.4- and 5.1-nm diameters self-assemble from the binary components of 8 and 9 as a template depending on the residual stoichiometry of the two components (thymine (T):adenine (A) = 1:1 and T:A = 2:1, respectively). The concentration of 9 was found to strongly influence the CD spectra of 8 in aqueous solutions. Consequently, we concluded that the one side of the thymine moieties in the stacked assemblies of 8 complexes with a single chain of 9. Complementary T-A base pairs thus formed and induced helical stack of the oligo(p-phenylenevinylene)s in the binary self-assembly. In contrast, self-assembly of the single-component 8 and binary self-assembly of 8 with the noncomplementary 20-meric oligothymidylic acid (10) produced no remarkable formation of fibrous structures like helical stacks.

Nine different a,v-phenyl-endcapped bithiophenes were synthesised, and the effect of the different side chains on the liquid crystalline properties, alignment ability and charge carrier mobility have been studied. An increase in chain length leads to a decrease in the liquid crystalline–isotropic phase (clearing) transition temperature. Remarkably, introduction of an asymmetric carbon centre close to the p-conjugated segment resulted in the loss of the liquid crystalline phase. Alignment on rubbed polyimide was obtained for the liquid crystalline thiophene derivatives lacking heteroatoms in the side chain and for the chiral a,v-phenyl-endcapped bithiophene. Some bithiophenes showed bipolar charge transport in time-of-flight (TOF) measurements, with mobilities up to 3 6 1023 cm2 V21 s21 in the liquid crystalline state. Field effect transistors revealed mobility for holes up to 1 6 1023 cm2 V21 s21 (crystalline state). From the data set obtained, it can be concluded that the use of linear hydrocarbon chains as solubilising tails in these types of p-conjugated building blocks gives the best overall electronic performance.

The liquid/solid interface provides an ideal environment to investigate self-assembly phenomena and scanning tunneling microscopy (SIM) is the preferred methodology to probe the structure and the properties of physisorbed monolayers on the nanoscale. Physisorbed monolayers are of relevance in areas such as lubrication, patterning of surfaces on the nanoscale, and thin film based organic electronic devices, to name a few. It's important to gain insight in the factors which control the ordering of molecules at the liquid/solid interface in view of the targeted properties. STM provides detailed insight into the importance of molecule-substrate (epitaxy) and molecule-molecule interactions to direct the ordering of both achiral and chiral molecules on the atomically flat surface. The electronic properties of the self-assembled physisorbed molecules can be probed by taking advantage of the operation principle of STM, revealing spatially resolved intramolecular differences within these physisorbed molecules.

Oligo(p-phenylene vinylene)s (OPVs) are ideal model compds. for studying electronic materials based on org. matter. By making use of non-covalent interactions, well-defined OPV aggregates are obtained in dodecane soln. These aggregates are helically organized and have a sharp melting temp., which increases upon elongating the conjugated backbone. The high interchromophoric order causes the exciton dynamics in the stacks to resemble those of polymer thin films. Blending OPVs of different length results in the formation of mixed aggregates, in which efficient energy transfer occurs from short to longer oligomers. At low doping levels, the longer oligomers are present as molecularly dissolved species inside the donor aggregates while they interact upon increasing the acceptor content. Using ethylene oxide in stead of dodecyl side chains enables the formation of OPV assemblies in an aq. environment. By incorporating cyano-substituted OPV acceptors into these aggregates, efficient energy transfer is obsd. to the trap mols.

A series of perylene bisimide mols. contg. aliph., arom. or ethyleneoxide side chains were synthesized and fully characterized. They form supramol. stacks in apolar methylcyclohexane (MCH) soln. as demonstrated by concn. and temp. dependent absorption, CD and fluorescence studies. Among the four perylene bisimides, P4 was chosen to be investigated in more detail in the solid state. It was found to orthogonal self assembly with p-type OPV derivs. into sep. nano-sized p-and n-type stacks in MCH. In contrast, in toluene only molecularly dissolved species were present. In films deposited from MCH as well as from toluene photo-induced electron transfer takes place from the p-type material to the n-type material. As a result of the orthogonal self-assembly process, in films from MCH an ordered network of fibers was formed whereas in films from toluene no ordering was obsd.

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Vorig jaar werd door NWO een VIDI-voorstel gehonoreerd om op nanometergrootte elektrische componenten te maken. Bij dit voorstel was niet voor een moleculaire, maar voor een zogenaamde supramoleculaire aanpak gekozen. Bij deze strategie worden organische halfgeleiders zodanig ontworpen dat ze eendimensionale kristallen vormen met een lengte van honderd nanometer. Het idee is om deze draden tussen elektrodes te brengen om zo miniatuur elektro-optische apparatuur te construeren.

Self-organizing molecules can form structures with useful electronic properties. These supramolecular materials combine the benefits of polymers with those of organic crystalline systems.

The self-assembly of alpha,alpha'-linked sexithiophenes with chiral and achiral penta(ethylene glycol) chains attached at the alpha- positions of the terminal rings, that is, 2,2':5',2":5",2'''',2'''':5'''',2'''''- sexithiophene-5,5'''''-dicarboxylic acid- (2S)-2-methyl-3,6,9,12,15-pentaoxahexadecyl ester (1) and 2,2':5',2":5",2''':5"',2'''':5''''m2'''''-sexithiophene-5,5'''''-dicarboxylic acid-3,6,9,1 2,15-pentaoxahexadecyl ester (2), respectively is described. Analysis of the UV/vis, fluorescence, circular dichroism, and circular polarization of luminescence spectroscopic data shows that these compounds form chiral aggregates in polar solvents and in the solid state. In n-butanol aggregation occurs at temperatures below 30 degreesC, while above this threshold temperature the aggregates break up without an intermediate disordered state of aggregation, and the compounds are molecularly dissolved. The "melting temperature" of the aggregates depends on the concentration of sexithiophene, indicating that the optical changes observed are a result of intermolecular processes. Mass spectrometric measurements reveal that 1 and 2 can form mixed aggregates. Analysis of the optical spectra reveals that in these mixed aggregates, chiral 1 molecules act as "sergeants" to direct the packing of the "soldiers" 2, illustrating cooperativity within the columns. In water, the same type of chiral aggregates are formed as in n-butanol below 30 degreesC; however, these aggregates are still present, but the chirality is lost above 30 degreesC. In spin-coated films of 1 chiral aggregates are present. AFM studies show that 1 self-organizes into chiral fiberlike structures in the solid state. Furthermore both 1 and 2 display thermotropic liquid crystalline behavior between 180 and 200 degreesC

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There has been a huge increase in the global demand of energy over the last few years. One of the main contributors to energy consumption in buildings, cars, greenhouses and indoor spaces is the cooling devices needed to maintain the indoor temperature at comfortable levels. To reduce the energy used by cooling devices, we need improved light control in transparent building elements, such as windows. Infrared (IR) reflectors applied to the windows for rejection of infrared light would be very attractive, especially if they do not affect light in the visible region. A method to selectively and precisely control infrared transmission is via the use of cholesteric liquid crystal (Ch-LC) polymer reflectors. Ch-LCs, also known as chiral-nematic LCs, reflect circularly polarized light as a result of their self-organizing molecular helices. The pitch of the helix in these networks determines the wavelength of reflection. In contrast to existing alternatives, they are characterized by a very sharp cut-off between the transmissive and the reflective state enabling exact tailoring of the heat reflection. In this article we have focused on fabrication of infrared reflectors using Ch-LCs and a computational model was used to predict the energy savings of this IR-reflector in an office building in Abu Dhabi which indicated that 6 % energy savings can be realized.