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The behavior of single linear chains on a substrate is a well-studied area of polymer science. Herein, one of the most essential issues is the interaction of the chains with the substrate, which determines both macromolecular conformations near the substrate and adhesive properties of polymer materials. However, very little is known about the effect of macromolecular architecture on adhesion. In particular, there was no assessment of the effect of chain branching on the adhesion force. On the other hand, an essential progress in macromolecular chemistry allows the synthesis of various macromolecular architectures, including star-, comb-like, etc., in a very precise way. They are widely used in numerous applications. In particular, synthetic peptides are currently an integral part of many systems for biomedical purposes including bioglues, for which the adhesion force is a fundamental property. In this study, we conducted force experiments on the desorption of star-like pentapeptide chains from a solid substrate using an atomistic model of computer simulations. The cases of a linear chain and four- and eight-armed stars were considered. We have shown that the presence of branching enhances the adsorption strength under a fixed mass of the macromolecules. The force needed for chain desorption was shown to be linearly dependent on the branching degree.

The progress of the pillar[5]arene chemistry allowed us to set out a new concept on application of the supramolecular assemblies to create antimicrobial films with variable surface morphologies and biological activities. Antibacterial films were derived from the substituted pillar[5]arenes containing nine pharmacophoric guanidine fragments and one thioalkyl substituent. Changing the only thioalkyl fragment in the macrocycle structure made it possible to control the biological activity of the resulting antibacterial coating. Pretreatment of the surface with aqueous solution of the amphiphilic pillar[5]arenes reduced the biofilm thickness by 56 ± 10% of Gram-positive Staphylococcus aureusin the case of the pillar[5]arene containing a thiooctyl fragment and by 52 ± 7% for the biofilm of Gram-negative Klebsiella pneumoniaein the case of pillar[5]arene containing a thiooctadecyl fragment. Meanwhile, the cytotoxicity of the synthesized macrocycles was examined at a concentration of 50 μg/mL, which was significantly lower than that of bis-guanidine-based antimicrobial preparations.

Surface-active polymers have important applications as effective and responsive emulsifiers, foaming agents, and coatings. In this contribution, we explore the impact of the polymer architecture on the behavior at oil–water interfaces by comparing different poly(N-isopropylacrylamide) (pNIPAM)-based systems, namely, monolayers of linear and star-shaped macromolecules, ultralow cross-linked, regular cross-linked, and hollow microgels. Compression isotherms were determined experimentally as well as by computer simulations. The latter provides information about the conformational changes of the individual macromolecules as well as the interfacial properties of the monolayer, including the surface structure and the density distribution of an ensemble of interacting macromolecules near an interface. Surprisingly, the isotherms of the linear polymer, of the star polymer, and of the ultralow cross-linked microgel have an identical shape that differs from the isotherms of regular and hollow microgels. We introduced the mass fraction of adsorbed polymer, which gives a measure of the polymer segments contributing to the isotherm in relation to the most flexible architecture, i.e., the linear polymer, and allows a comparison of polymers with different architectures. The data demonstrate that increasing the number of cross-links leads to a significantly lower amount of polymer in the proximity of the interface as the increase in cross-linker reduces the deformability or softness of the polymers at the interface. The volume fraction profiles along the normal to the interface are essentially different in the microgel monolayers as compared to those in the linear and star polymer. The profiles through the microgel contact line and their growth upon initial compression are similar to those of the linear chains. Herewith, the profiles through the center of mass practically do not change upon compression. Therefore, the initial growth in the microgel surface pressure reveals the polymer-like behavior and is related to the deformation of the peripheral part of the microgel. Further compression of the microgel monolayer leads to 3D interactions of the microgels within the aqueous side of the interface and soft colloid-like behavior.

We have studied conformations of a single tethered chain, chains in a planar brush, and corona-forming blocks in diblock copolymer micelles using dissipative particle dynamics. Interactions of all components of the systems were considered explicitly. In addition to the conventionally studied normal elongation of the chains in the brush and micellar corona, we detect regimes of partial or full adsorption of the tethered chains. They are realized for compatible with the substrate (interface) chains (blocks) and solvophobic surfaces (strongly selective solvent for the copolymer). The physical reason for the adsorption is shielding of unfavorable solvent–substrate (or micellar core–solvent) contacts by polymers. In the case of block copolymer micelles, adsorption–desorption of the corona-forming blocks can induce morphology transformation which cannot be predicted/described by traditional theories.

Monolayers of polymer microgels with a spherical cavity adsorbed at the liquid–liquid interface were studied using mesoscopic computer simulations. One liquid, named water, was always considered as a good solvent, while the microgel solubility in the second liquid, named oil, was varied. The symmetric and asymmetric cases of vanishing and the strong differences in solubility between the network particles and the liquids were considered. The simulations provided us with an insight into the shape and volume changes of the microgels upon compression, making it possible to relate the response of the individual network with the collective order and structure of the monolayer. Similar to regular microgels, the compression of the monolayer of hollow particles led to a decrease in lateral sizes accompanied by shape transformation from a flattened to a nearly spherical shape. However, the presence of a cavity filled with solvent caused some unique differences in the behavior of the system. The adsorption pathway of hollow microgels at the liquid interface predefines: (a) the position of the particles with respect to the interface and (b) the structure of the monolayer. A striking discovery is that in the symmetric case of similar solubility of the microgel in both liquids, it is possible to produce a monolayer in which one part of the network faces the aqueous phase and the other part faces the oil phase. The polymer concentration profiles plotted along the normal to the interface reveal a redistribution of polymeric mass of the microgels relative to the interface, distinguishing between the microgels whose cavities are filled with water and oil, respectively. Moreover, the ratio between the microgels faced in water and oil does not change upon compression and predetermines the response and order of the monolayer.

The copolymer sequence can be considered as a new tool to shape the resulting system properties on demand. This perspective is devoted to copolymers with “partially segregated” (or nonblocky) sequences. Such copolymers include gradient copolymers and copolymers with random sequences as well as copolymers with precisely controlled sequences. We overview recent developments in the synthesis of these systems as well as new findings regarding their properties, in particular, self-assembly in solutions and in melts. An emphasis is put on how the microscopic behavior of polymer chains is influenced by the chain sequences. In addition to that, a novel class of approaches allowing one to efficiently tackle the problem of copolymer chain sequence design─data driven methods (artificial intelligence and machine learning)─is discussed.

Polymer hydrogels are known to be efficient absorbents of various aqueous solutions. Along with the hydrophilicity of the polymer network, the presence of specific functional groups is required for the absorption of respective solutes. Alternatively, a selective uptake can be realized without any specific attraction of solutes to the network, which is shown in this paper. By combining experimental and simulation approaches, we demonstrated that thermoresponsive poly(N-isopropylacrylamide) gels and microgels in compositionally strongly asymmetric water/1-octanol mixtures selectively uptake the minor (1-octanol) component. Initially swollen in water, the gels substitute water by the organic solvent upon the addition of its small fraction into aqueous solution. In turn, for microgels, it was shown that the single particles could absorb the amount of the organic liquid more than two times higher than their mass while preserving the colloidal stability. At the same time, the accumulation of 1-octanol in the networks “switches off” the temperature response. The mesoscopic computer simulations revealed a physical reason and molecular picture of the phenomenon. Absorption of the minor component by the gels is caused by the decrease in water/1-octanol interfacial tension due to the formation of the dense polymer layer at the interface. The simulations allowed tracking the evolution of the size and the internal structure of the single microgels with changing 1-octanol concentration.

Molecular brushes having alternating AB copolymer side chains composed of soluble (A) and responsive (B) monomer units were studied using dissipative particle dynamics simulations. As for thermoresponsive polymers, responsiveness means a variation of solubility of monomer units upon changing external conditions, leading to a variation of solvent quality. In other words, the solvent has a variable selectivity changing from non-selective to strongly selective for the side chains of the brush. The collapse of single brushes (regime of infinite dilution) and their self-assembly in the solution were examined. The effects of grafting density, backbone length and its solubility, as well as the sequence of monomer units in the side chains (alternating and random) were considered. The results demonstrated a similar behavior in the collapse of single brushes regardless of the considered comonomer sequences. Meanwhile, macromolecular aggregation in the solution showed the presence of a gel phase in a particular range of the solvent selectivity, and for strong selectivities, precipitation occurs. This range mainly depends on the grafting density of the side chains: the higher it is, the lower is the solvophobicity of the responsive segments needed for gelation. At the same time, this effect diminishes in the case when the backbone is sufficiently long. Conversely, for brushes with a short or solvophobic backbone, no gelation was observed, neither for the linear copolymers of the same composition as the side chains.

Microgels, cross-linked polymers with submicrometer size, are ideal soft model systems. While spherical microgels have been studied extensively, anisotropic microgels have hardly been investigated. In this study, we compare the interfacial deformation and assembly of anisotropic core–shell and hollow microgels. The core–shell microgel consists of an elliptical core of hematite covered with a thin silica layer and a thin shell made of poly(N-isopropylacrylamide). The hollow microgels were obtained after a two-step etching procedure of the inorganic core. The behavior of these microgels at the oil–water interface was investigated in a Langmuir–Blodgett trough combined with ex situ atomic force microscopy. First, the influence of the architecture of anisotropic microgels on their spreading at the interface was investigated experimentally and by dissipative particle dynamic simulations. Hereby, the importance of the local shell thickness on the lateral and longitudinal interfacial deformation was highlighted as well as the differences between the core–shell and hollow architectures. The shape of the compression isotherms as well as the dimensions, ordering, and orientation of the microgels at the different compressions were analyzed. Due to their anisotropic shape and stiffness, both anisotropic microgels were found to exhibit significant capillary interactions with a preferential side-to-side assembly leading to stable microgel clusters at low interfacial coverage. Such capillary interactions were found to decrease in the case of the more deformable hollow anisotropic microgels. Consequently, anisotropic hollow microgels were found to distribute more evenly at high surface pressure compared to stiffer core–shell microgels. Our findings emphasize the complex interplay between the colloid design, anisotropy, and softness on the interfacial assembly and the opportunities it therefore offers to create more complex ordered interfaces.

Functional properties of macromolecules arise out of their chemical composition and their 3D conformation, exemplarily demonstrated by the secondary and tertiary structures of biomacromolecules. In synthetic macromolecules, precise introduction of branching and amphiphilicity are essential concepts to introduce shape-controlled functionality. Here, we report on the advancement of the concept of arborescent or graft-on-graft macromolecules from hydrophobic to hydrophilic polymers and the topologically controlled interfacial activity of such polymers. We synthesized hydrophilic arborescent polymers up to generation three (G3) in a grafting-fromprocedure. These are globular polymers with a high conformational flexibility, a feature otherwise found for biomacromolecules. Copper-wire catalyzed single electron transfer living radical polymerization (SET-LRP) of ethylene glycol methyl ether acrylate (EGMEA) and hydroxyethyl acrylate (HEA) allowed quantitative grafting initiation and end-group functionality. Degrees of polymerization of the grafts were adjusted around 25, and the total molecular weights varied from 35 × 103g·mol–1for G0 to a maximum of 3 × 106g·mol–1for G3 at polydispersities Đ≤ 1.2. In agreement with the sizes determined by dynamic light scattering (DLS) in a tetrahydrofuran solution, dissipative particle dynamics (DPD) simulations demonstrated that the molecules approached a globular conformation with increasingly more flat density profiles. At the same time, the molecules preserved a high conformational flexibility. This unique combination contributed to a strong interfacial activity in toluene-in-water suspensions. The molecules spread at the liquid–liquid boundary and adopt a disc-like conformation. Interfacial activity and molecular spreading were demonstrated by spinning drop tensiometer measurements (SDT) and scanning force microscopy (SFM) imaging of single molecules.

We propose computer simulations revealing the internal structure of liquid droplets formed by polymer solutions. Both suspended and droplets placed on a solid surface are simulated. In the case of droplets, which are in equilibrium with the solvent vapor (nonvolatile droplets), distribution of polymer chains is studied versus thermodynamic quality of the solvent (good and bad) and interactions of the polymer and the solvent with the surface. Both swollen and collapsed states of the chains within the droplet, their localization at the liquid–vapor interface, and adsorption on the solid surface are predicted. We construct various diagrams of states of the droplets. Then, we simulate a fast solvent evaporation from the droplet placed on a solid surface and study nonequilibrium polymer structures. The conditions for the appearance of a coffee ring (a ring-wise distribution of polymer after solvent evaporation) and homogeneous polymer layer are predicted.

Arborescent copolymers with a core–shell–corona (CSC) architecture were synthesized and the topology of the molecules was challenged (constrained) through intramolecular interactions, resulting in phase separation breaking the symmetry of radial density. The inner poly(2-vinylpyridine) shell of these arborescent polystyrene-g-[poly(2-vinylpyridine)-b-polystyrene] molecules can self-assemble by binding metallic salts and acids in apolar and intermediate-polarity solvents. Upon loading with HAuCl4, the characteristics of the polymer templates govern the “loading sites” of the metal within the molecules. Unique morphologies were observed for the metal-loaded G0–G4 arborescent copolymers investigated, namely, spherical, toroidal, raspberry-like, spherical nanocage, and a new worm-in-sphere morphology. The reason for the emergence of such morphologies is the interplay among intramolecular interactions of unlike polymer segments, solvent selectivity, the entropic elasticity of the arborescent substrate, and phase segregation induced by coordination with the charged metallic species. Meanwhile, the stability of the arborescent molecules against aggregation provides intramolecular phase segregation with imposed “confined” geometry and thus leads to nonconventional morphologies. Furthermore, the size of the arborescent molecules is much smaller than that of other known particles (droplets) serving as confined geometries. Computer simulations were used to model the mesostructure of the arborescent copolymers, to demonstrate the influence of solvent selectivity, together with HAuCl4loading, on the evolution of the morphology of the macromolecules.

The role of electrostatics on the interfacial properties of polyelectrolyte microgels has been discussed controversially in the literature. It is not yet clear if, or how, Coulomb interactions affect their behavior under interfacial confinement. In this work, we combine compression isotherms, atomic force microscopy imaging, and computer simulations to further investigate the behavior of pH-responsive microgels at oil–water interfaces. At low compression, charged microgels can be compressed more than uncharged microgels. The in-plane effective area of charged microgels is found to be smaller in comparison to uncharged ones. Thus, the compressibility is governed by in-plane interactions of the microgels with the interface. At high compression, however, charged microgels are less compressible than uncharged microgels. Microgel fractions located in the aqueous phase interact earlier for charged than for uncharged microgels because of their different swelling perpendicular to the interface. Therefore, the compressibility at high compression is controlled by out-of-plane interactions. In addition, the size of the investigated microgels plays a pivotal role. The charge-dependent difference in compressibility at low compression is only observed for small but not for large microgels, while the behavior at high compression does not depend on the size. Our results highlight the complex nature of soft polymer microgels as compared to rigid colloidal particles. We clearly demonstrate that electrostatic interactions affect the interfacial properties of polyelectrolyte microgels.

Monolayers of polymer microgels adsorbed at the liquid interfaces were studied by dissipative particle dynamics simulations. The results demonstrated that the compressibility of the monolayers can be widely tuned by varying the cross-linking density of the microgels and their (in)compatibility with the immiscible liquids. In particular, the compression of the monolayers (increase of 2D concentration of the microgels) leads to the decrease of their lateral size. Herewith, the shape of the individual soft particles gradually changes from oblate (diluted 2D system) to nearly spherical (compressed monolayer). The polymer concentration profiles plotted along the normal to the interface reveal a nonmonotonous shape with a sharp maximum at the interface. This is a consequence of the shielding effect: saturation of the interface by monomer units of the subchains is driven by minimization of unfavorable contacts between the immiscible liquids and is opposed by elasticity of the network. The decrease of the interfacial tension upon concentration (compression) of the monolayer is quantified. It has been demonstrated that the interfacial tension significantly differs if the solubility of the polymer chains of the microgel network in the liquids changes. These results correlate well with experimental data. The examination of the microgels’ crystalline ordering in monolayers demonstrated a nonmonotonous dependency on the compression degree (microgel concentration). Finally, the worsening of the solvent quality leads to the collapse of the microgels in monolayer and nonmonotonous behavior of the interfacial tension.

The structure of complexes formed by oppositely charged polyelectrolytes and adsorbed layers on charged surfaces is sensitive to low-molecular-weight salt. Furthermore, if the concentration exceeds some threshold value, the complexes and adsorbed chains can be “dissolved”. This is due to the screening of the electrostatic interactions between charged units. In the current paper, we perform a comparative analysis of “dissolution” (dissociation) of complexes and layers upon addition of salt. For this, the conventional Brownian dynamics of computer simulations is used. We demonstrate that the complex based on linear chains dissociates at lower salt concentration than that required for desorption of equivalent chains from an oppositely charged surface. The physical reason is the difference in the symmetry of the electric field, which binds the chains into the complex (layer). In the salt-free regime, the intensity of the electric field (and attractive force) between two linear chains decays with the distance Rbetween them, like for two spherical objects, ∼R–2, if Ris bigger than the characteristic size of the chain. On the contrary, the attractive force of the chain to the infinite surface does not depend on the distance to the surface (the electric field is constant). Therefore, if attractive forces in the condensed states of the two systems are equal, one needs to add more salt to screen the constant force than the decaying one. The computer simulation results on the adsorption of the chains were compared with the experimental data obtained for adsorption of cationic poly(4-vinylpyridine) on the surface of anionic liposomes. Good quantitative agreement was achieved.

Solid–liquid interfaces play an important role for functional devices. Hence, a detailed understanding of the interaction of soft matter objects with solid supports and of the often concomitant structural deformations is of great importance. We address this topic in a combined experimental and simulation approach. We investigated thermoresponsive poly(N-isopropylmethacrylamide) microgels (μGs) at different surfaces in an aqueous environment. As super-resolution fluorescence imaging method, three-dimensional direct stochastical optical reconstruction microscopy (dSTORM) allowed for visualizing μGs in their three-dimensional (3D) shape, for example, in a “fried-egg” conformation depending on the hydrophilicity of the surface (strength of adsorption). The 3D shape, as defined by point clouds obtained from single-molecule localizations, was analyzed. A new fitting algorithm yielded an isosurface of constant density which defines the deformation of μGs at the different surfaces. The presented methodology quantifies deformation of objects with fuzzy surfaces and allows for comparison of their structures, whereby it is completely independent from the data acquisition method. Finally, the experimental data are complemented with mesoscopic computer simulations in order to (i) rationalize the experimental results and (ii) to track the evolution of the shape with changing surface hydrophilicity; a good correlation of the shapes obtained experimentally and with computer simulations was found.

We investigate soft, temperature-sensitive microgels at fluid interfaces. Though having an isotropic, spherical shape in bulk solution, the microgels become anisotropic upon adsorption. The structure of microgels at interfaces is described by a core–corona morphology. Here, we investigate how changing temperature across the microgel volume phase transition temperature, which leads to swelling/deswelling of the microgels in the aqueous phase, affects the phase behavior within the monolayer. We combine compression isotherms, atomic force microscopy imaging, multiwavelength ellipsometry, and computer simulations. At low compression, the interaction between adsorbed microgels is dominated by their highly stretched corona and the phase behavior of the microgel monolayers is the same. The polymer segments within the interface lose their temperature-sensitivity because of the strong adsorption to the interface. At high compression, however, the portions of the microgels that are located in the aqueous side of the interface become relevant and prevail in the microgel interactions. These portions are able to collapse and, consequently, the isostructural phase transition is altered. Thus, the temperature-dependent swelling perpendicular to the interface (“3D”) affects the compressibility parallel to the interface (“2D”). Our results highlight the distinctly different behavior of soft, stimuli-sensitive microgels as compared to rigid nanoparticles.

In this work, we studied the behavior of charged microgels at a liquid–liquid interface by means of dissipative particle dynamics simulations with explicit electrostatic interactions; the liquids represent polar and nonpolar solvents like water and oil. The effect of the fraction of charged groups and both solvents qualities on the microgel size, shape, degree of immersion into different liquids, and 2D ordering of the microgels at the interface is studied. For the case of both athermal solvents, we demonstrated that increasing the fraction of charged units results in significant swelling of the microgel inside the polar liquid and a dramatic drop in the number of adsorbed monomer units. For the case of a bad nonpolar solvent for the polyelectrolyte microgels, they easily get detached from the surface into the polar solvent. When the opposite case of a bad polar solvent is considered (like high temperatures for thermosensitive PNIPAM- or PVCL-based microgels), the microgels demonstrate a decrease of the swelling perpendicular to the interface at low χ-values, and they start to swell into the nonpolar liquid at high χ-values. Two approaches for accounting for different dielectric permittivity of the liquids were considered: implicit and explicit ones; we obtained that the results of the two approaches were always in qualitative agreement. However, the explicit model is necessary to correctly reproduce the physics of the phenomena in certain regimes, in particular, when the charged molecules move through the interface of two liquids. Finally, the microgels ordering was studied at the liquid–liquid interface. We found that even at rather low fraction of charged monomer units the microgels exhibit an almost ideal hexagonal packing even though the average distance between the microgels centers is significantly larger than the microgel diameter, while uncharged microgels positions were completely random. This implies that the interfacial ordering can be controlled by using pH-sensitive monomer units in the microgel structure.

Microgels are nanometer-to-micrometer-sized cross-linked polymer networks that swell when dispersed in a good solvent. These soft colloids have emerged as versatile building blocks of smart materials, which are distinguished by their unique ability to adapt their behavior to changes in external stimuli. Using X-ray and neutron scattering and molecular simulation methods, we systematically measured and modeled the response to crowding of compressible, deformable microgels with varying cross-link densities and internal architectures. Our experiments and simulations demonstrate that incorporating a solvent-filled cavity during chemical synthesis provides an independent means of controlling microgel swelling that complements the influence of changing cross-link density. In other words, knowledge of the content of cross-links alone cannot be used to define microgel softness, but microgel architecture is another key property that affects softness. These results are potentially important for biomedical applications, such as drug delivery and biosensing.

Nanogels and microgels are soft, deformable, and penetrable objects with an internal gel-like structure that is swollen by the dispersing solvent. Their softness and the potential to respond to external stimuli like temperature, pressure, pH, ionic strength, and different analytes make them interesting as soft model systems in fundamental research as well as for a broad range of applications, in particular in the field of biological applications. Recent tremendous developments in their synthesis open access to systems with complex architectures and compositions allowing for tailoring microgels with specific properties. At the same time state-of-the-art theoretical and simulation approaches offer deeper understanding of the behavior and structure of nano- and microgels under external influences and confinement at interfaces or at high volume fractions. Developments in the experimental analysis of nano- and microgels have become particularly important for structural investigations covering a broad range of length scales relevant to the internal structure, the overall size and shape, and interparticle interactions in concentrated samples. Here we provide an overview of the state-of-the-art, recent developments as well as emerging trends in the field of nano- and microgels. The following aspects build the focus of our discussion: tailoring (multi)functionality through synthesis; the role in biological and biomedical applications; the structure and properties as a model system, e.g., for densely packed arrangements in bulk and at interfaces; as well as the theory and computer simulation.

A striking discovery in our work is that the distribution of ionizable groups in polyampholyte microgels (random and core–shell) controls the interactions with the captured proteins. Polyampholyte microgels are capable to switch reversibly their charges from positive to negative depending on pH. In this work, we synthesized differently structured polyampholyte microgels with controlled amounts and different distribution of acidic and basic moieties as colloidal carriers to study the loading and release of the model protein cytochrome c (cyt-c). Polyampholyte microgels were first loaded with cyt-c using the electrostatic attraction under pH 8 when the microgels were oppositely charged with respect to the protein. Then the protein release was investigated under different pH (3, 6, and 8) both with experimental methods and molecular dynamics simulations. For microgels with a random distribution of ionizable groups complete and accelerated (compared to polyelectrolyte counterpart) release of cyt-c was observed due to electrostatic repulsive interactions. For core–shell structured microgels with defined ionizable groups, it was possible to entrap the protein inside the neutral core through the formation of a positively charged shell, which acts as an electrostatic potential barrier. We postulate that this discovery allows the design of functional colloidal carriers with programmed release kinetics for applications in drug delivery, catalysis, and biomaterials.

Micelle formation of amphiphilic block copolymers of various architectures comprising both flexible and rodlike blocks were studied in a selective solvent via dissipative particle dynamics (DPD) simulations. Peculiarities of self-assembly of Y-shaped (insoluble rigid block and two flexible soluble arms) and comblike (soluble flexible backbone with insoluble rigid side chains) copolymers are compared with those of equivalent rod–coil diblock copolymers. We have shown that aggregation of the rigid blocks into the dense core of the micelles is accompanied by their nematic ordering. However, the orientation order parameter and aggregation number of the micelles are strongly dependent on macromolecular architecture. Relatively small micelles of pretty high nematic order parameter, S2≈ 0.5–0.8, are the features of the Y-shaped and rod–coil copolymer micelles. They are characterized by different responses to the solvent quality worsening. The aggregation number of the rod–coil diblock copolymer micelles increases and that of the Y-shaped copolymer micelles decreases at the solvent quality worsening. However, the order parameter grows in both cases, achieving a maximum value for the Y-shaped copolymer micelles. Herewith, the core elongates. On the contrary, comblike copolymers self-assemble into bigger spherical micelles whose core possesses a lower nematic order of the rods, S2≈ 0.3–0.4. The aggregation number is shown to depend on the length of the combs (on the number of repeating elements in the architecture). Possible physical reasons for such behavior of the systems are discussed.

Using a combination of a mean-field theoretical method and the numerical Scheutjens–Fleer self-consistent field approach, we predict that it is possible to have re-entrant morphological transitions in nanostructures of diblock copolymers upon variation in temperature-mediated solubility of the associating blocks. This peculiar effect is explained by the different rates in variation of the density of the collapsed core domains and the corresponding interfacial energy as a function of the temperature. The theoretical findings are supported by existing experimental observations of reversed sequences of the morphological transitions occurring upon temperature variation in solutions of amphiphilic block copolymers.

In the present paper we investigate the behavior of polyrotaxanes under bad solvent conditions by means of computer simulations. Polyrotaxanes can be viewed as amphiphilic macromolecules with annealed sequences because the rings can freely move along the backbone. We showed that, depending on the ring inclusion ratio and the rings radius, one can observe various structures. If the rings radius is small (i.e., enough to fit only one monomer unit), in bad solvent we observed the formation of a collapsed core surrounded by long loose tails and loops with an increased ring density. Upon increasing of the backbone–solvent incompatibility, the core grows as well as the number of rings located on its surface; the latter leads to a partial screening of the backbone–solvent interactions. When the rings are large enough to fit several monomer units, the backbone packs inside the rings, which allows for complete isolation from the solvent. If the number of rings (i.e., the inclusion ratio) is large enough to fit all the monomer units, unimolecular cylindrical micelles are formed in bad solvent. Such micelles are formed by the backbone packed inside the rings that are stacked on “top” of each other. We showed that the transition from the coil to the unimolecular micelle is sensitive to the solubility of the rings: if the rings tend to distribute along the backbone, higher incompatibilities are required for the unimolecular micelles formation compared to the case when the rings tend to form aggregates. In the state of unimolecular micelles the backbone is completely isolated from the solvent, which makes the micelles soluble even at rather high concentrations.

We demonstrate that a microgel can enter and exit a narrow cylindrical pore under external stimuli leading to collapse and swelling of the microgel. Attractive interactions between the microgel and the pore surface stimulate the microgel entering upon its collapse. The entering is driven by a gain in the surface energy: the area of the microgel–pore contacts is maximized within the pore. Swelling of the microgel within the pore of a finite size is thermodynamically favorable if the pore thickness exceeds a certain threshold value. Otherwise, the swelling leads to the microgel exit. The physical reason for this is a gain in the elastic free energy of the subchains which are less stretched outside the pore. We systematically study swelling and collapse of the microgel within the pore. Both longitudinal size and radial concentration profiles are calculated for different strength of interactions of the beads with each other and the pore surface. We predict an intramicrogel “phase” coexistence leading to the formation of a dense adsorbed layer near the pore surface and highly swollen central part of the microgel. Furthermore, the permeation of nanoparticles, whose size is smaller than the mesh size of the microgels, was simulated under different swelling and adsorption degrees. It is demonstrated that the microgel can slow down and completely stop the permeation of nanoparticles through the pore.

We describe a facile method for the synthesis of microgels with covalent and noncovalent ionic cross-links. Microgels were synthesized by copolymerization of various N-vinyllactams with zwitterionic monomer (methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide in the presence of a cross-linking agent (bis(acrylamide)) in water-in-oil emulsion. Monodisperse colloidally stable microgels with a high amount (>30 mol %) of zwitterionic groups were synthesized. High contents of zwitterionic groups in microgels led to the formation of reversible ionic cross-links along with permanent covalent cross-links generated by bis(acrylamide). The obtained microgels exhibit interesting temperature-triggered swelling/deswelling behavior in aqueous solution. With an increase of the temperature above 10 °C, the microgels swell due to the destruction of the zwitterionic cross-links. Above the lower critical solution temperature of poly(N-vinyllactam) chains at T> 32 °C, the microgels shrink due to the destruction of the hydrogen bonds and enhanced hydrophobic interactions. The variation of zwitterionic groups and cross-linker concentrations influenced the extent of swelling/deswelling at different temperatures. New doubly thermoresponsive microgels were synthesized using three homologues: N-vinylcaprolactam (VCL), N-vinylpiperidone (VPi), and N-vinylpyrrolidone (VPy). It was shown that the temperature-triggered deswelling of microgels is strongly dependent on the size of the lactam ring.

Amphiphilic arborescent block copolymers of two generations (G2 and G3) and polymer microgels, obtained via cross-linking of diblock copolymers, were studied in a selective solvent and at liquid interface via dissipative particle dynamics (DPD) simulations. Depending on the primary structure, single arborescent macromolecules in selective solvent can have both core–corona and multicore structures. Self-assembly of the G2, G3, and microgels in the selective solvent is compared with equivalent linear diblock copolymers. The latter self-assemble into spherical micelles of large enough aggregation number. On the contrary, stability of unimolecular micelles is a feature of the arborescent copolymers and microgels, whereas their ability to aggregate is very low. Adsorption of the single molecules at liquid (oil–water) interface leads to their flattening and segregation of the amphiphilic blocks: hydrophilic and hydrophobic blocks are exposed toward water and oil, respectively. Depending on the character of interactions between monomer units, which can be controlled by temperature or solvent(s) quality, Janus, patchy, and nanosegregated structures can be formed within the macromolecules. Their self-assembly at the interface can lead to the formation of both loose and dense monolayers, which can be homogeneous and nanostructured. The pretty fast adsorption kinetics of G2 macromolecules make them efficient stabilizers of emulsions.

We propose a model of molecular motor based on diblock copolymer strongly adsorbed on a patterned surface. One of the blocks of the copolymer is modeled as field responsive. It is shown that time‐periodic collapse‐readsorption of the responsive block leads to the directed motion (reptation) of the molecule along the “track” provided by the surface pattern. Both the Langevin dynamics (LD) technique of computer simulation for the bead‐spring model and numerical solution of the Newton equations of a simplified (toy) model of the copolymer are used. The physical reason of directionality of the motion is shown to be an anisotropy of the friction of the molecule with the surface.

We propose a theoretical explanation of the parallel and perpendicular lamellar orientations in free surface films of symmetric polystyrene‐block‐polybutadiene diblock copolymers on silicon substrates (with a native SiOxlayer). Two approaches are developed: A correction to the strong segregation theory and a qualitative analysis of the intermediate segregation regime. We show that the perpendicular orientation of the lamellae formed by the molecules of high molecular weight is stabilized by A–B interfacial interactions. They are weaker in the case of the perpendicular orientation of the lamellae, whereas the surface tension coefficient of the A–B interface decreases with the increase of the molecular weight.

We synthesised P4VP bromides with octyl and dodecyl pendant groups; the bromide anions in these polymer salts were further substituted with dodecylsulfate or bis(2-ethylhexylsuccinate) anions. Direct SFM visualisation of the original P4VP chains, of the macromolecular salts and of their complexes, showed that the attachment of the pendant groups and especially the complexation with the surfactants promotes stretching of the macromolecules while adsorbing on mica substrate. On the other hand, viscosimetry showed that in solution (chloroform) the comb‐like chains and their complexes with dodecylsulfate had more compact conformations than those of the original P4VP. The scaling exponents describing the correlation between the contour length and the end‐to‐end distance of the adsorbed macromolecules were found to be ca. 3/4, which is indicative of 2D self‐avoiding walk statistics.

The structures of a molecular brush in a good solvent are investigated using synchrotron small-angle X-ray scattering in a wide range of concentrations. The brush under study, PiPOx239-g-PnPrOx14, features a relatively long poly(2-isopropenyl-2-oxazoline) (PiPOx) backbone and short poly(2-n-propyl-2-oxazoline) (PnPrOx) side chains. As a solvent, ethanol is used. By model fitting, the overall size and the persistence length as well as the interaction length and interaction strength are determined. At this, the interplay between form and structure factor is taken into account. The conformation of the molecular brush is traced upon increasing the solution concentration, and a rigid-to-flexible transition is found near the overlap concentration. Finally, the results of computer simulations of the molecular brush solutions confirm the experimental results.

Anisotropic, submicrometer-sized particles are versatile systems providing interesting features in creating ordering in two-dimensional systems. Combining hard ellipsoids with a soft shell further enhances the opportunities to trigger and control order and alignment. In this work, we report rich 2D phase behavior and show how softness affects the ordering of anisotropic particles at fluid oil–water interfaces. Three different core–shell systems were synthesized such that they have the same elliptical hematite–silica core but differ with respect to thickness and stiffness of the soft microgel shell. Compression isotherms, the shape of individual core–shell microgels, and their 2D order at a decane–water interface are investigated by means of the Langmuir–Blodgett technique combined with ex-situ atomic force microscopy (AFM) imaging as well as dissipative particle dynamics (DPD) simulations. We show how the softness, size, and anisotropy of the microgel shell affect the side-to-side vs tip-to-tip ordering of anisotropic hybrid microgels as well as the alignment with respect to the direction of compression in the Langmuir trough. A large, soft microgel shell leads to an ordered structure with tip-to-tip alignment directed perpendicular to the direction of compression. In contrast, a thin and harder microgel shell leads to side-to-side ordering orientated parallel to the compression direction. In addition, the thin and harder microgel shell induces clustering of the microgels in the dilute state, indicating the presence of strong capillary interactions. Our findings highlight the relevance of softness for the complex ordering of anisotropic hybrid microgels at interfaces.

Cover:The article by Potemkin and coworkers provides free‐energy considerations to explain the molar mass dependent morphology of lamellar diblock copolymer thin films of poly(styrene‐b‐butadiene). Atomic force microscopy (AFM) and grazing‐incidence small‐angle scattering (GISAXS) data were instrumental to establish the lamellar orientation as a function of the interaction parameter χNand the ratio of film thickness over lamellar thickness Dred. The relevant free‐energy contributions are discussed that determine the boundary between the observed orientational phases. Further details can be found in the article by I. I. Potemkin,*P. Busch, D.‐M. Smilgies, D. Posselt, and C. M. Papadakis on page 579.