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We have followed the reorientation kinetics of various block copolymer solutions exposed to an external electric DC field. The characteristic time constants follow a power law indicating that the reorientation is driven by a decrease in electrostatic energy. Moreover, the observed exponent suggests an activated process in line with the expectations for a nucleation and growth process. When properly scaled, the data collapse onto a single master curve spanning several orders of magnitude both in reduced time and in reduced energy. The power law dependence of the rate of reorientation derived from computer simulations based on dynamic density functional theory agrees well with the experimental observations. First experiments in AC electric fields at sufficiently high frequencies confirm the notion that the reorientation process is dominated by differences in the dielectric constants rather than by mobile ions.

We studied the morphology of micelles formed by a well-defined poly(1,2-butadiene)-block-poly(ethylene oxide) diblock copolymer (PB-b-PEO). Dissolved in n-heptane at 70 °C, that is, above the melting point of PEO, spherical micelles are formed due to the selectivity of the solvent for the PB-block. If the solutions are cooled down to low temperatures, the liquid PEO-block crystallizes within the cores of the spherical micelles that remain stable. If, however, the solutions are quenched to 30 °C, the spherical micelles aggregate to a novel meander-like structure within several minutes. In its final state, the meander-like super-structure is crystalline, as revealed by time-resolved wide-angle X-ray scattering. The super-structure is shown to result from crystallization-induced aggregation of spherical micelles. Moreover, crystallization leads to well-defined angles between subsequent aggregating units. A quantitative Avrami-type analysis of the crystallization kinetics demonstrates that the formation of the meander-type structure resembles a 2D growth process combined with a breakout crystallization, showing an Avrami-exponent of 2.5. In contrast to this, crystallization at low temperatures resembles a confined crystallization with a low Avrami-exponent of 0.7. All data demonstrate that the morphology of block copolymers having a crystallizable block can be switched by the competition of aggregation and crystallization.

Atomically flat mica surfaces were chemically modified with an alkyl trifluoromethyl ketone, a covalent inhibitor of esterase 2 from Alicyclobacillus acidocaldarius, which served as a tag for ligand-directed immobilization of esterase-linked proteins. Purified NADH oxidase from Thermus thermophilus and human exportin-t from cell lysates were anchored on the modified surfaces. The immobilization effectiveness of the proteins was studied by atomic force microscopy (AFM). It was shown that ligand-esterase interaction allowed specific attachment of exportin-t and resulted in high-resolution images and coverage patterns that were comparable with immobilized purified protein. Moreover, the biological functionality of immobilized human exportin-t in forming a quaternary complex with tRNA and the GTPase Ran-GTP, and the dimension changes before and after complex formation were also determined by AFM.

Block copolymers consisting of incompatible components self-assemble into microphase-separated domains yielding highly regular structures with characteristic length scales of the order of several tens of nanometres. Therefore, in the past decades, block copolymers have gained considerable potential for nanotechnological applications, such as in nanostructured networks and membranes, nanoparticle templates and high-density data storage media. However, the characteristic size of the resulting structures is usually determined by molecular parameters of the constituent polymer molecules and cannot easily be adjusted on demand. Here, we show that electric d.c. fields can be used to tune the characteristic spacing of a block-copolymer nanostructure with high accuracy by as much as 6% in a fully reversible way on a timescale in the range of several milliseconds. We discuss the influence of various physical parameters on the tuning process and study the time response of the nanostructure to the applied field. A tentative explanation of the observed effect is given on the basis of anisotropic polarizabilities and permanent dipole moments of the monomeric constituents. This electric-field-induced effect further enhances the high technological potential of block-copolymer-based soft-lithography applications.

The dynamics of early stage of terrace formation in thin supported films of cylinder forming triblock copolymers was studied both theoretically using self-consistent-field theory (DSCFT) and experimentally by insitu scanning force microscopy (SFM). In experiment, an initially flat film of incommensurable thickness was imaged continuously, and the evolution of a vertical orientation of cylinders into a parallel one as well as the respective development of thickness gradient (terrace formation) was captured in detail. On the grounds of these experimental observations, the parameters of the computational model A3B12A3 were determined to match the structures in experiment. Both systems show excellent agreement in details of structural phase transitions and in the dynamics of the step development, suggesting that the underlying transport mechanisms are governed by diffusion. The early stage of terrace formation is characterized by the development of the step height up to 80 of its equilibrium value and associated reorientation of cylindrical domains. © 2007 American Chemical Society.

Local surface potential measurements on alkoxy-substituted poly (p-phenylene ethynylene), poly (EHO-OPPE), as an electron transport material (ETM) and poly (triphenyl diamine), poly (TPD), as a hole transport material (HTM) and their blends in three different compositions (1 : 3, 1 : 1, 3 : 1) were performed by using scanning Kelvin force microscopy (SKFM). Simultaneously the topography of all surfaces was obtained using atomic force microscopy (AFM). In this paper, we propose a new principle for mapping out the local surface potential distributions of macrophase separated segments in the model polymer blend systems through the combined mode of intermittent contact AFM–SKFM techniques. The energetics and kinetics involved are also discussed in terms of potential distributions in the different phases of surface morphologies in the single-layered pristine as well as single-layered two component polymer blend systems. The experimental results provide considerable insight into the electrical/electronic properties of these ETM and HTM materials and reveal highly qualitative information for the first time to show a direct conformation of apparent work function difference between the ETM rich and HTM rich components. Finally, an attempt has been made to perform the combined approaches of valuable and high resolution complementary techniques such as scanning electron microscopy, absorption and photoluminescence spectra in order to correlate the observed contact potential difference/surface potential difference between the two rich ETM and HTM components obtained from microscopic and macroscopic scans.

The interactions between the anionic surfactant sodium dodecyl sulfate (SDS) and a hydrophobically modified nonionic polymer, methyl cellulose (MC), have been investigated in aqueous solution by fluorescence correlation spectroscopy (FCS) and rheology. FCS is used to follow the dynamics of different populations of single aggregates. We are able to follow the solution properties over a wide concentration range of both polymer and surfactant. At constant MC concentration the diffusion time of single aggregates increases gradually up to a certain SDS concentration and decreases to a minimum when the SDS concentration is further increased. This behavior coincides with the behavior of the zero shear viscosity. A model is proposed to explain the effect of surfactant concentration on polymer conformation and aggregation size.

We study the details of the defect dynamics in thin films of a cylinder-forming polystyrene-block-polybutadiene (SB) diblock copolymer melt. The high temporal resolution of in-situ scanning force microscopy (SFM) uncovers elementary dynamic processes of structural rearrangements on time scales not accessible so far. Short-term interfacial undulations and the formation of transient phases (spheres, perforated lamellae, and lamellae) are observed. We demonstrate that the well-known structural defects are annihilated by short-term phase transitions into what may be considered excited states. These temporary phase transitions are reproduced in simulations based on dynamic self-consistent field theory. We discuss the role of the observed structural evolution in the context of the equilibrium phase behavior in SB thin films.

Terrace formation and morphological behavior in thin films of polystyrene-block-polybutadiene block copolymer have been studied on two chemically different substrates by means of scanning force microscopy. Cylinders parallel to the film plane (C∥) are found on weakly interacting substrates in up to five-layer-thick films. A bottom layer of half cylinders is stabilized at the substrate. On strongly interacting substrates, the development of the C∥ microdomains and nonbulk perforated lamella (PL) and lamella (L) phases depends on the local film thickness. The sequence of structures at transition thickness (in between the steps) suggests a few percent increase of the characteristic microdomain spacing in the order C∥−PL−L. Comparison of the interlayer distances on the two types of substrates points to lamella-like structures in bulk of the films on strongly interacting surfaces.

We have devised a novel route towards a nanoscopically striped surface pattern with long range order via the self-assembly of an ABC triblock terpolymer thin film exposed to an in-plane electric field. Via the interplay between surface interactions and the effect of the electric field the lamellae were oriented both perpendicular to the plane of the film and parallel to the electric field. Moreover, quasi in-situ scanning force microscopy measurements were used to follow the reorientation process as a function of time and to yield insight into the microscopic steps eventually leading to the ordered microdomain structure.

We investigate the influence of incompatibility and dielectric contrast on the reorientation kinetics of concentrated solutions of lamellar block copolymers in the presence of an external DC electric field. We study solutions of AC diblock copolymer and ABC triblock terpolymers. The inclusion of a short, polar middle block B is used to tailor both the degree of incompatibility and the dielectric contrast between the two majority phases. In situ synchrotron radiation small-angle X-ray scattering is used to monitor the reorientation process. For the AC diblock copolymer sample only weak electric field induced reorientation could be achieved, following a very slow kinetics, whereas for the ABC triblock terpolymer, reorientation is observed above a threshold value of 0.3 kV/mm. The orientation kinetics is well described by a single exponential with characteristic time constants varying between a few seconds and several minutes depending on the polymer concentration and the electric field strength. We identify a narrow concentration window, in which the interplay between chain mobility and gain in free energy in the electric field allows the preparation of highly anisotropic bulk polymer samples by exposure to an electric field. The results are compared to free energy calculations revealing a distinct difference in the driving force for reorientation as a consequence of an increase in dielectric contrast and chain mobility upon introduction of the B middle block.

We present a novel route to prepare pH-dependent nanostructures from highly ordered thin films of poly(styrene)-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) triblock terpolymers. Using a polymer-analogous reaction, we modify the chemical nature of the block components without altering the overall microdomain structure. In particular, we perform an acid-catalyzed hydrolysis of the poly(tert-butyl methacrylate) block to poly(methacrylic acid) in a microphase-separated perforated lamella (PL) structure. Scanning force microscopy in an aqueous environment is used to follow structural changes of the PL phase as a function of the pH value. Due to the particular microdomain structure of the precursor triblock terpolymer, an almost perfect one-dimensional swelling of the films is observed with increasing pH.

We study the effect of a chemical pattern on the wetting and dewetting behaviour of thin polystyrene (PS) films on regularly corrugated silicon substrates. Our results reveal that the film preparation, annealing method, and confinement play a critical role in the final film structure. On evaporating gold on both sides of the facets (such that it covered the crests of the facets, and not the troughs), we observed dewetting, which proceeded to the gold, demonstrating an enthalpic effect contrary to the outcome previously observed when gold was only evaporated on one side of the facet. We also coated the substrate with octadecyltrichlorosilane (OTS); this led to a gold and OTS striped structure. PS films several nanometres thick dewet such substrates, with a preferential direction for dewetting in the direction of the stripes forming droplets of a considerably larger size than the stripes.

We report on the thin film phase behavior of poly(styrene)-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) triblock terpolymers with volume fractions φPS:φP2VP:φPtBMA scaling as 1:1.2:x, with x ranging from 3.05 to 4. On controlled annealing in the vapor of a nearly nonselective solvent the films form terraces of well-defined thickness with a highly ordered hexagonally perforated lamella structure. Using a gradient combinatorial technique we are able to systematically map the dependence of the morphology on the film thickness. By use of substrates with different surface energy we demonstrate that the perforated lamella is a stable phase, regardless of the chemical nature of the substrate, which makes the structure and methodology robust for application in nanotechnology.

Microphase separation and morphology of thin films of ABC triblock terpolymers are studied with a self-consistent-field theory. Thin films of poly(styrene)-block-poly(2-vinylpyridine)-block-poly(fertbutyl methacrylate) (SVT) triblock terpolymers are modeled as A3B4C 12 Gaussian chains confined in a slit. The bulk morphologies are found to be much more robust with respect to the interaction parameters when compared to the morphologies in the confined situation. By adjusting the interaction parameters between the polymer components and the surfaces, we can model the experimentally observed sequence of surface structures as a function of the film thickness. At well-defined film thicknesses a highly ordered perforated lamella structure is observed. We systematically explore the influence of film thickness, surface field, and the interaction parameters between the different polymer components on the phase behavior. © 2005 American Chemical Society.

Amylose-block-polystyrenes with various block copolymer compositions were investigated in water and in THF solution. Fluorescence correlation spectroscopy, dynamic light, scattering (DLS), and asymmetric flow field-flow fractionation with multiangle light scattering detection indicate the presence of unimers, oligomers, and large micellar species in THF. Up to four different species: were detectable by DLS with hydrodynamic radii ranging from a few nanometers to > 10 mum, indicating that the system is not in a thermodynamic equilibrium state. Collapsed aggregrates were monitored on a Silicon surface by scanning force microscopy and transmission electron microscopy. In water. crew-cut micelles were obtained from the same block copolymers by a single solvent approach, using elevated temperature and pressure. These crew-cut aggregates are much more uniform than the respective star aggregates in THF, and their radii scale with R-h proportional to N-core(1/4), R-h proportional to N-corona(1/6) in solution and with R proportional to N-core(1/4), R proportional to N-corona(1/2) on a silicon surface.

The kinetics of phase transitions is essential for understanding pattern formation in structured fluids1,2. These fluids play a key role in the morphogenesis of biological cells1,3,4,5, and they are very common in pharmaceutical products and plastic materials2. Until now, it has not been possible to follow phase transitions in structured fluids experimentally in real time and with high spatial resolution. Previous work1,2 has relied on static images and indirect experimental evidence from spatially averaging scattering experiments. Simulating the processes with computer models is a further challenge because of the multiple time and length scales involved6,7,8,9,10,11,12,13,14. Our movies based on in situ scanning force microscopy show the time sequence of the elementary steps of a phase transition in a fluid film of block copolymer from the cylinder to the perforated lamella phase. The movies validate a versatile simulation model that gives physical insight into the nature of the process. Our approach provides a means of improving the study and understanding of pattern formation processes in nanostructured fluids. We expect a significant impact on nanotechnology where block copolymers serve as self-organized templates for the synthesis of inorganic nanostructured materials15,16,17,18,19,20,21,22,23,24.

The near-surface rheology of polystyrene films at temperatures around Tg was probed via the decay kinetics of shallow, nanoscale surface corrugation gratings. The gratings were created via hot embossing with a stepped silicon template. The wavelengths are distributed in a range between 25 and 60 nm and have a modulation depth of about 0.8 nm peak-to-peak. Upon heating, one observes a surface tension-driven decay of the surface corrugation at temperatures more than 30 deg below the bulk Tg. Such a fast decay is unexpected and indicates a strongly lowered glass temperature near the surface.

We have used spectroscopic ellipsometry to determine the Flory-Huggins parameters in thin films of polystyrene, poly(2vinyl pyridine), and poly(tert butyl methacrylate) swollen in controlled atmosphere of various common solvents. From the experimental data the concentration dependent Flory-Huggins interaction parameters between the homopolymers and the different solvents are revealed. Similar experiments were performed on binary copolymers of the three components. From the comparison between the degree of swelling of the homopolymers and the copolymers, respectively, the polymer/polymer Flory-Huggins interactions parameters are determined as a function of solvent content as well.

Decagonal Al–Ni–Co quasicrystals were cleaved in ultrahigh-vacuum and the resulting surfaces were investigated by dynamic scanning force microscopy. The samples were cleaved perpendicular to the tenfold axis and perpendicular to one of the twofold axes. Both surfaces show a rough structure with lateral features on the nanometer scale and height differences of angstroms to nanometers. While the corrugation of the tenfold surface does not show any correlation to the quasiperiodic bulk structure, the twofold surface exhibits row-like corrugations, which indicate the existence of columnar structure motifs along the direction of the tenfold axis as expected from structure models. Images from surface regions tilted with respect to the twofold plane strongly indicate the existence of inclined netplanes. In addition, we studied surfaces of an n 0 -(Al–Pd–Mn) quasicrystal approximant, which was cleaved perpendicular to the pseudo-tenfold b-axis. These surfaces show a corrugated structure as well, similar to the results obtained from the decagonal Al–Ni–Co surfaces. There is no indication of a correlation to the periodicity or other structural features of this orthorhombic, crystalline material. � 2004 Elsevier B.V. All rights reserved.

We discuss the use of fluorescence correlation spectroscopy (FCS) to study the diffusion of single dye-labeled polymer chains in organic solvents. Monodisperse batches of polystyrenes labeled with a single Rhodamine B molecule have been synthesized via anionic polymerization of styrene and ethylene oxide end-capping followed by a polymer analogous coupling reaction. MALDI-ToF mass spectrometry is used to characterize the resulting material. A commercial FCS system has been modified to permit FCS measurements in volatile organic solvents. FCS was used to determine the molecular weight dependence of the diffusion coefficient of 10 nM solutions of end-labeled polystyrenes in toluene. The data are utilized to establish a calibration procedure for FCS measurements in organic solvents.

We experimentally establish a phase diagram of thin films of concentrated solutions of a cylinder forming polystyrene-block-polybutadiene-block-polystyrene triblock copolymer in chloroform. During annealing the film forms islands and holes with energetically favored values of film thickness. The thin film structure depends on the local thickness of the film and the polymer concentration. Typically, at a thickness close to a favored film thickness parallel orientation of cylinders is observed, while perpendicular orientation is formed at an intermediate film thickness. At high polymer concentration the cylindrical microdomains reconstruct to a perforated lamella structure. Deviations from the bulk structure, such as the perforated lamella and a wetting layer are stabilized in films thinner than approximately 1.5 domain spacings.

Using sequential living anionic polymerization we synthesized well-defined linear ABC triblock terpolymers from polystyrene (PS), poly(2-vinylpyridine) (P2VP), and poly(tert-butyl methacrylate) (PtBMA). The length of the PtBMA block was systematically increased at constant block length ratios of the PS and P2VP blocks. The microdomain structures were characterized by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). With increasing PtBMA block size we observe a systematic change in the bulk structure of the block copolymers.

We investigate the microdomain orientation kinetics of concentrated block copolymer solutions exposed to a dc electric field by time-resolved synchrotron small-angle X-ray scattering. As a model system, we use a lamellar polystyrene-b-polyisoprene block copolymer dissolved in toluene. Our results indicate two different microscopic mechanisms, i.e., nucleation and growth of domains and grain rotation. The former dominates close to the order−disorder transition, while the latter prevails under more strongly segregated conditions. This conclusion is corroborated by computer simulations based on dynamic density functional theory. The orientation kinetics follows a single-exponential behavior with characteristic time constants varying from a few seconds to some minutes depending on polymer concentration, temperature, and electric field strength. From the experimental results we deduce optimum conditions for the preparation of highly anisotropic bulk polymer samples via solvent casting in the presence of an ele...

Thermal annealing of organic light-emitting diodes based on polymer composites prior to the metal deposition is found to substantially improve the devices' luminescence efficiency. Phase separation between the matrix polymer and the hole conducting low molecular weight component is shown to be the origin of this behavior. We use atomic force microscopy along with selective dissolution of one of the components to establish the domain morphology of the devices. The presence of the metal electrode is shown to significantly influence the phase separation process. Finally, a correlation between the domain morphology and the electrooptical properties is established.

We show that the near surface structure of lamellar ABC triblock copolymer mesostructures can deviate considerably from the “ideal” surface anticipated from the bulk structure of the material. Varying the molecular architecture and the surface energy difference between the respective blocks, we show that such surface reconstructions are caused by a complex balance of enthalpic and entropic contributions to the free energy of the system. The results are compared to the well-known surface behavior of classical crystals and experimental conditions for what may be called “block copolymer surface science” are discussed.

We study the self-assembly in thin films of a lamella-forming polystyrene-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) triblock terpolymer thin film on a polyimide substrate and compare it with the self-assembly of the same system on a native oxide silicon (SiOx) substrate. In addition to scanning force microscopy, we performed cross-sectional transmission electron microscopy. Both polyimide and SiOx substrates attract the polar P2VP middle block. However, significant differences between the two substrates were revealed: (i) the difference in the interaction strength between the substrate and the polymers caused a different configuration of P2VP chains adsorbed to the substrate and hence a different structure of the first layer, and (ii) the structure of the first layer influenced the self-assembly of the lamellae throughout the entire film. In contrast to SiOx substrates, on polyimide substrates the lamellae with the equilibrium thickness were formed in one step through a new intermed...

We describe the synthesis and the solution properties of Janus micelles containing a polybutadiene (PB) core and a compartmentalized corona consisting of a poly(methacrylic acid) (PMAA) and a polystyrene (PS) hemisphere. The Janus micelles were obtained via cross-linking the middle block of a microphase-separated PS-block-PB-block-PMMA triblock copolymer in the bulk state, followed by alkaline hydrolysis of the poly(methyl methacrylate) (PMMA) ester groups. Results of fluorescence correlation spectroscopy, field flow fractionation, light scattering, cryogenic transmission electron microscopy, scanning electron microscopy, and scanning force microscopy indicate that above a critical aggregation concentration of about 0.03 g/L spherical supermicelles are formed from about 30 PS-PMAA micelles in aqueous solution in the presence of NaCl. These supermicelles have radii of 40-60 nm, significantly increasing on ionization (pH >6). In addition, very large spherical objects are observed with radii of 100-250 nm.

Experimental research on wetting in polymer films is a subject that is reaching maturity. We review progress from the past few years in research into the influence of a boundary in polymer blends, concentrating largely on the wetting transition, and the growth of wetting layers, where we pay particular attention to blends in which hydrodynamic flow plays a dominant role. A summary of work over the same period concerning the dewetting of polymer films is also included, along with a discussion of the role of pattern formation caused by dewetting and topographically and chemically patterned substrates. We conclude by summarising some experiments that we believe may inspire future research.

Thin films of incompatible block copolymers self-assemble into highly regular supramolecular structures with characteristic dimensions in the 10-100 nm regime. There is increasing interest in controlling the resulting structures and utilizing them, for instance in the area of nanotechnology. So far, research has concentrated mainly on exploiting the melt structure of diblock copolymers. Recent work on block copolymer solutions and more complex co- and terpolymer architectures has revealed a rich variety of novel thin-film structures, some of which exhibit high complexity and order. In addition, by use of mean field dynamic density functional theory along with well-controlled experiments, the fundamentals of thin film structure formation have been elucidated. We highlight some aspects of these studies and point to future directions in this lively field of materials science.

We have studied the thin film morphologies of polystyrene-b-poly(2-vinylpyridine) diblock copolymers and polystyrene-b-poly(2-vinylpyridine)-b-poly(tert-butyl methacrylate) triblock copolymers after “annealing” in the vapor of different solvents. We find distinct differences in the resulting thin film morphologies. The differences are explained qualitatively on the basis of concentration-dependent Flory−Huggins interaction parameters of the different components.

We study the self-assembly in thin films of a lamella-forming polystyrene-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) triblock copolymer by means of scanning force microscopy (SFM) and cross-sectional transmission electron microscopy (TEM). We follow the time development of the microdomain structure in the films during solvent vapor treatment. After preparation on a polar substrate preferentially attracting the middle block of poly(2-vinylpyridine), the films exhibit a spongelike microdomain morphology. With subsequent solvent vapor treatment, metastable lamellae with the spacing much smaller than the equilibrium value are first formed from free surface and grow toward the substrate and eventually establishes a multilayered structure throughout the film. As a result of this process, defects associated with the lamellar structure are annihilated from the free surface and accumulated close to the solid substrate. On an extended solvent vapor treatment, the lamellae thicken toward the equ...

We describe the synthesis, characterization, and properties of polystyrene-block-poly- (ethylene-alt-propylene)-block-polyethylene (PS-b-PEP-b-PE) and polystyrene-block-poly(ethylene-alt- propylene)-block-polystyrene (PS-b-PEP-b-PS) triblock copolymers. Morphological investigations using TEM, SEM, and SFM reveal for the PS-b-PEP-b-PE triblock copolymers a morphology consisting of PS cylinders and PE crystallites within a matrix of the PEP block, whereas the PS-b-PEP-b-PS triblock copolymer shows interconnected, distorted PS cylinders in the PEP matrix. Mechanical characterization of these triblock copolymers demonstrated that for small strains the PS-b-PEP-b-PE triblock copolymers exhibit the aimed smaller plastic deformations, i.e. better elastic properties, compared to the polystyrene- based ABA type thermoplastic elastomer. However, at high strains the PS-b-PEP-b-PS triblock copolymer shows a significantly better elastic recovery. The high plastic set at high elongations in PS-b-PEP-b-PE triblock copolymers is attributed to the weaker resistance of the PE crystallites compared to amorphous PS domains in the PS-b-PEP-b-PS triblock copolymer.

We synthesized analogous series of monodisperse ABC triblock copolymers with symmetrical end blocks A/C and different short middle blocks B (5−10 wt %) with varying polarities by sequential anionic polymerization, i.e., polystyrene-b-poly(2-vinylpyridine)-b-poly(methyl methacrylate) (PS-b-P2VP-b-PMMA) and polystyrene-b-poly(2-hydroxyethyl methacrylate)-b-poly(methyl methacrylate) (PS-b-PHEMA-b-PMMA). Thin (thickness ∼ 20 nm) and ultrathin films (thickness ≤ 7 nm) were prepared by either dip-coating or adsorption from solution onto silicon wafers. The copolymer films were investigated by scanning force microscopy. In thin films, the polar middle block adsorbs preferentially to the polar substrate, resulting in a polymer film surface that exclusively consists of PS and PMMA microdomains. In ultrathin films, the two polar B and C blocks behave like a single B block resulting in structures which can be described by recent scaling laws. The lateral spacing and the morphology of the structures can be controlled...

We have used optical microscopy and scanning force microscopy to study the dewetting of polystyrene from poly(methyl methacrylate) on silicon substrates as a function of film thickness. We have performed measurements for bilayers with a lower layer more viscous than the upper layer, as well as for the opposite situation. For a solidlike (highly viscous) lower layer, the dewetting speed is constant and independent of the thickness of the polystyrene film. However, for a liquidlike lower layer, the radius of the dewetted holes grows as t2/3, where t is the annealing time, and depends on the thickness of both layers. The absolute values of the dewetting speed are in reasonable agreement with theoretical predictions.

Atom transfer radical polymerization (ATRP) was applied to the synthesis of amphiphilic cylindrical polymer brushes by using the “grafting from” technique. The procedure included the following steps: (1) ATRP of 2-hydroxyethyl methacrylate (HEMA) gave well-defined poly(HEMA), (2) subsequent esterification of the pendant hydroxy groups of poly(HEMA) with 2-bromoisobutyryl bromide yielded a polyinitiator, poly(2-(2-bromoisobutyryloxy)ethyl methacrylate (PBIEM), (3) ATRP of various monomers (tert-butyl acrylate, or styrene) using PBIEM as polyinitiator yielded cylindrical brushes with homopolymer side chains, (4) addition of a second monomer (styrene or tert-butyl acrylate) formed the cylindrical brushes with diblock copolymer side chains (core−shell cylinders), and (5) hydrolysis of the poly(tert-butyl acrylate) (PtBA) block of the side chains to poly(acrylic acid) (PAA) formed amphiphilic core−shell polymer brushes. By using this technique, well-defined core−shell cylindrical polymer brushes with polystyr...

A novel synthetic concept for preparing hyperbranched polymers on a planar surface is described, in which a silicon wafer grafted with an initiator layer composed of an α-bromoester fragment is use...

We investigate in detail the processes involved when soft polymeric materials are imaged with TappingMode atomic force microscopy (TM-AFM). Measuring lateral arrays of amplitude/phase vs distance (APD) curves, we are able to determine quantitatively the amount of tip indentation and reconstruct the shape of the “real” surface of the sample. Moreover, contrast inversion in height and TappingMode phase images is explained on the basis of attractive and repulsive contributions to the tip−sample interaction. The experiments are performed on surfaces of poly(styrene-block-butadiene-block-styrene) (SBS) triblock copolymers acting as a model system.

We use scanning force microscopy and stepwise erosion in a radio-frequency (rf) plasma to obtain a three-dimensional volume image of an ultrathin poly(styrene-b-butadiene-b-styrene) triblock copolymer film. The free surface of the film exhibits domains of two distinctly different structures, i.e., hexagonal arrays of isolated dots and parallel stripes. A common forehand interpretation relates these surface morphologies to a cylindrical microdomain morphology with the cylinders oriented perpendicularly and parallel to the plane of the film, respectively. In contrast, our experiments show that the “dots” merge into parallel cylinders at some distance underneath the film surface. These results demonstrate that care has to be taken when the thin film morphology of block copolymers is inferred from their surface structure.

We investigate phase separation in a thin film of a binary polymer blend A/C in the presence of a solid substrate covered with immobilized nanoscopic domains of the respective polymers. The patterned substrate is realized by physisorbing a microphase separated brush of an ABC triblock copolymer. We observe a marked suppression of phase separation in the blend on the pattern as compared to a laterally homogeneous substrate. The effect is studied as a function of blend film thickness. The results are compared to a simple estimate of the interfacial energies.

We have studied the microdomain morphology of thin ABC triblock copolymer films supported by a solid substrate. The films were exposed to various solvent vapors, and the effect of the solvent removal speed on the resulting morphologies is investigated. Slow solvent extraction rates lead to a parallel alignment of lamellar microphases within the plane of the film. On fast drying, a perpendicular orientation of the lamellae is found. In the case of block copolymer samples with a highly anisotropic macroscopic shape, the microdomains can be aligned over large lateral areas. The results are discussed in view of the mechanical strain fields present during the drying process.