Time- and temperature-resolved in situ birefringence measurements were applied to analyze the effect of nanoparticles on the electric field-induced alignment of a microphase separated solution of poly(styrene)-block-poly(isoprene) in toluene. Through the incorporation of isoprene-confined CdSe quantum dots the reorientation behavior is altered. Particle loading lowers the order-disorder transition temperature, and increases the defect density, favoring nucleation and growth as an alignment mechanism over rotation of grains. The temperature dependent alteration in the reorientation mechanism is analyzed via a combination of birefringence and synchrotron SAXS. The detailed understanding of the effect of nanoparticles on the reorientation mechanism is an important prerequisite for optimization of electric-field-induced alignment of block copolymer/nanoparticle composites where the block copolymer guides the nanoparticle self-assembly into anisotropic structures.

The structural versatility of block copolymers on the nanometer scale make them highly promising candidates for many applications in soft matter nanotechnology, including optics, electronics, and acoustics. In order to harvest the full potential of nanostructured block copolymer materials and achieve widespread use outside of academia, adaptable strategies are required to control and manipulate their spatial orientation, periodicity, connectivity, and long-range order. Over the past two decades the use of an external electric field has been well established as a viable tool to control a wide variety of structural parameters of nanostructured block copolymers on both mesoscopic and nanoscopic length scales. Covering a wide range of experimental and theoretical work, this review aims to illustrate major scientific advances of the past years, focusing in particular on the underlying physics that governs the fundamental interactions between an external electric field and block copolymer mesophases and its impact on phase behaviour and orientational order in bulk, solution, and thin films.

Block copolymers form a variety of microphase morphologies due to their ability to phase separate. The hexagonally perforated lamellar (HPL) morphology represents an unusually long-lived, nonequilibrium transient structure between lamellar and cylindrical phases. We present a detailed study of a concentrated, HPL-forming poly(styrene-b-isoprene) diblock copolymer solution in toluene in the presence of an electric field. We will show that this phase is readily aligned by a moderate electric field and provide experimental evidence for an electric-field-induced order–order transition toward the lamellar phase under sufficiently strong fields. This process is shown to be fully reversible as lamellar perforations reconnect immediately upon secession of the external stimulus, recovering highly aligned perforated lamellae.

Polystyrene nanoparticles, cross-linked with divinylbenzene (PS-(DVB)(x)) and having radii, R-p <= 10 nm, have been synthesized using batch and semi-batch radical microemulsion polymerizations. The nanoparticles were characterized thoroughly using H-1 NMR, size exclusion chromatography, differential scanning calorimety, and various small-angle scattering techniques (light, X-rays, and neutrons). Control over network and interface morphologies of the PS-(DVB)(x), nanoparticles is readily achieved by varying the concentration of divinylbenzene and the polymerization technique (batch vs. semi-batch). Small-angle neutron scattering (SANS) allowed us to identify three distinct nanoparticle morphologies: (i) fuzzy soft gels with flexible chain-segments tethered/looped at the interface of a homogeneous core, (ii) smooth soft gels without a fuzzy interfacial layer, and (iii) dendritic glassy gels exhibiting an inhomogeneous core with an ill-defined interface. Atomic force microscopy imaging supports the morphologies and the softness of the nanoparticles as indicated by SANS. (C) 2013 Elsevier Ltd. All rights reserved.

External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the orderdisorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented paralleltotheapplied fieldprevail.Thepresentstudyaddsanadditionalmechanismtotheexperimentallycorroboratedsuiteofmechanisticpathways,by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the orderdisorder transition and well below it.

Electric fields have been shown to stabilize the disordered phase of near-critical block copolymer solutions. Here, we use in situ synchrotron small-angle X-ray scattering to examine how the initial orientation of lamellar domains with respect to the external field (phi) affects the shift in the order-disorder transition temperature (T-ODT) of lyotropic solutions of poly(styrene-b-isoprene) in toluene. We find a downward shift of the transition temperature, which scales with lamellar orientation as Delta T-ODT similar to cos(2) phi, in accordance with theory.

External electric fields readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-field-induced alignment of a lamellae-forming polystyrene-block-poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-field-assisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such films under benign experimental conditions.

Since the first report on electric field-induced alignment of block copolymers (BCPs) in 1991, electric fields have been shown not only to direct the orientation of BCP nanostructures in bulk, solution, and thin films, but also to reversibly induce orderorder transitions, affect the orderdisorder transition temperature, and control morphologies' dimensions with nanometer precision. Theoretical and experimental results of the past years in this very interesting field of research are summarized and future perspectives are outlined.

We investigate the kinetics of block copolymer/nanoparticle composite alignment in an electric field using in situ transmission small-angle X-ray scattering. As a model system, we employ a lamellae forming polystyrene-block-poly(2-vinyl pyridine) block copolymer with different contents of gold nanoparticles in thick films under solvent vapor annealing. While the alignment improves with increasing nanoparticle fraction, the kinetics slows down. This is explained by changes in the degree of phase separation and viscosity. Our findings provide extended insights into the basics of nanocomposite alignment.

Piezoelectric properties in non-polar block copolymers are a novelty in the field of electroactive polymers. The piezoelectric susceptibility of poly(styrene-b-isoprene) block copolymer lamellae is found to be up to an order of magnitude higher when compared to classic piezoelectric materials. The electroactive response increases with temperature and is found to be strongest in the disordered phase.

We have studied the interpolyelectrolyte complexation in chloroform between polystyrene-block-poly(cetyltrimethylammonium acrylate), (PA− CTA+), and poly(2-(methacryloyloxy)ethyldimethylethyl-ammonium dodecyl sulfate) (quaternized poly(2-(dimethylamino)ethyl methacrylate) complexed with sodium dodecyl sulfate), (PDMAEMAQ+ DS−). Turbidimetry, dynamic/static light scattering, and transmission electron microscopy show the formation of large aggregated interpolyelectrolyte complex species, which are colloidally stable in chloroform or even chloroform-soluble if the certain conditions are met. We suggest such co-assemblies to be micellar species with a core assembled from electrostatically coupled fragments of the polymeric components. The corona is built up either from a mixture of polystyrene blocks and excessive fragments of (PDMAEMAQ+ DS−) chains or from a mixture of polystyrene blocks and excessive fragments of (PA− CTA+) blocks, depending on which polymeric component was taken in excess for the interpolyelectrolyte complexation. However, their real structures may deviate from such idealized consideration because of the non-equilibrium character of interpolyelectrolyte complexation in organic media of low polarity.

Smart organic-inorganic nanohybrids are formed in aqueous solution by the interaction of amphiphilic block copolymer micelles of poly(n-butyl acrylate)-block-poly(acrylic acid) (PnBA(x)-b-PAA(y) with x = 90, 100 and y = 100, 150, 300) and diglycidylaminopropyl-functional silsesquioxane nanoparticles. We investigate the structure of the complex nanohybrids in dependence on pH and salinity. The complexation preserves the original size of the micelles according to dynamic light scattering (DLS) measurements. Cryogenic transmission electron microscopy (cryo-TEM) and Fourier-transform infrared spectroscopy (FT-IR) measurements unveil the formation of organic-inorganic nanohybrids. Furthermore, cryo-TEM micrographs provide evidence for the formation of a core-shell-corona structure of the nanohybrid system. Dialysis experiments with fluorescently labeled silsesquioxane nanoparticles clearly demonstrate the interaction between the micellar system and the silsesquioxane nanoparticles.

The formation of multicompartment micelles featuring a "spheres on sphere" core morphology in acetone as a selective solvent is presented. The polymers investigated are ABC triblock terpolymers, polybutadiene-b-poly(2-vinyl pyridine)-b-poly(tert-butyl methacrylate) (BVT), which were synthesized via living sequential anionic polymerization in THF. Two polymers with different block lengths of the methacrylate moiety were studied with respect to the formation of multicompartmental aggregates. The micelles were analyzed by static and dynamic light scattering as well as by transmission electron microscopy. Cross-linking of the polybutadiene compartment could be accomplished via two different methods, "cold vulcanization" and with photopolymerization after the addition of a multifunctional acrylate. In both cases, the multicompartmental character of the micellar core is fully preserved, and the micelles could be transformed into core-stabilized nanoparticles. The Successful cross-linking of the polybutadiene core is indicated by (1)H NMR and by the transfer of the aggregates into nonselective solvents Such as THF or dioxane.

pH- and salinity-responsive organic–inorganic nanohybrid stars based on poly(acrylic acid) (PAA) stars and N,N-di(2,3-dihydroxypropyl)3-aminopropylfunctional silsesquioxane nanoparticles are readily formed by mixing of aqueous solutions of the components. The interaction between stars of two different arm lengths, (PAA100)21, (PAA200)24, with water-soluble silsesquioxane nanoparticles is studied according to changes in pH and salt concentration. The original size of the stars is conserved during complexation according to dynamic light scattering (DLS) measurements and light scattering (LS) titration experiments, which exclude star–star aggregation or crosslinking during the interaction. The proposed interaction mechanism is based on hydrogen-bonding and Coulomb interactions. Cryogenic transmission electron microscopy measurements demonstrate the formation of nanohybrid stars. Small-angle neutron scattering experiments enable a quantitative determination of the fraction of bound nanoparticles and indicate an equilibrium between free and bound nanoparticles.

We utilize inelastic incoherent neutron scattering (INS) to quantify how fullerenes affect the 'fast' molecular dynamics of a family of polystyrene related macromolecules. In particular, we prepared bulk nanocomposites of (hydrogenous and ring-deuterated) polystyrene and poly(4-methyl styrene) using a rapid precipitation method where the C-60 relative mass fraction ranged from 0% to 4%. Elastic window scan measurements, using a high resolution (0.9 mu eV) backscattering spectrometer, are reported over a wide temperature range (2-450 K). Apparent Debye-Waller (DW) factors < u(2)>, characterizing the mean-square amplitude of proton displacements, are determined as a function of temperature, T. We find that the addition of C-60 to these polymers leads to a progressive increase in < u(2)> relative to the pure polymer value over the entire temperature range investigated, where the effect is larger for larger nanoparticle concentration. This general trend seems to indicate that the C-60 nanoparticles plasticize the fast (approximate to 10(-15) s) local (approximate to 1 angstrom) dynamics of these polymer glasses. Generally, we expect nanoparticle additives to affect polymer dynamics in a similar fashion to thin films in the sense that the high interfacial area may cause both a speeding up and slowing down of the glass state dynamics depending on the polymer-surface interaction.

We report on interpolyelectrolyte complexes (IPECs) formed by micelles of ionic amphiphilic diblock copolymers with polyisobutylene (PIB) and poly(sodium methacrylate) (PMANa) blocks interacting with quaternized poly(4-vinylpyridine) (P4VPQ). The interpolyelectrolyte complexation was followed by turbidimetry and small angle neutron scattering (SANS). The data obtained by means of a combination of SANS, dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM) provide evidence on the core-shell-corona structure of the complex species with the shell assembled from fragments of electrostatically bound PMANa and quaternized P4VPQ fragments, original PIBx-b-PMAA(y) micelles apparently playing a lyophilizing part. The complex formation is followed by potentiometric titration as well. This process is initially kinetically controlled. In the second step larger aggregates rearrange in favor of smaller complexes with core-shell-corona structure, which are thermodynamically more stable. An increase in ionic strength of the solution results in dissociation of the complex species as proven by SANS and analytical ultracentrifugation (AUC). This process begins at the certain threshold ionic strength and proceeds via a salt-induced gradual release of chains of the cationic polyectrolyte from the complex species.

Layered1 Double Hydroxides (LDHs) represent a class of anion exchanging clays that are easily prepared under normal laboratory settings through a wide selection of divalent and trivalent metal cations. LDHs consists of mixed metal hydroxide layers that are bound together through electrostatic interactions, by charge balancing anions, and extensive hydrogen bonding with the interlayer anions and water [1, 2]. The size and anion exchange capacity (AEC) of LDHs can be systematically manipulated during the preparation process by post-precipitation treatments and by varying the divalent: trivalent metal ratios [3, 4]. This versatility offers a unique opportunity to systematically investigate synergistic effects that may occur when these two properties are varied along with changing levels of adhesion.For this study, LDH materials were prepared using a 2: 1 divalent: trivalent metal ratio, in which the overall crystallinity and particle sizes were modified by subsequent thermal aging of the newly formed LDH crystallites. The LDH materials were then intercalated with naphthalenecarboxylate anions, and then dispersed into a specific epoxy matrix. The mechanical properties of these nanocomposites were then measured.