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Two novel nanomaterials based on hybrid organic−inorganic polymers have been prepared via free radical polymerization of (I) dimethacrylate oligomers and (II) 2-hydroxyethyl methacrylate (HEMA) in the presence of different contents of organically modified titanium−oxo-clusters Ti16O16(OEt)24(OC2H4Mc)8 (OMc = methacrylate). Investigations, combining small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and energy-filtering transmission electron microscopy (EFTEM) lead to consistent structural and morphological characteristics for both grades of hybrid materials. Structural features, such as the subunit size and fractal dimensions are extracted from SAXS profiles. For the first grade of nanomaterials, i.e., for different content of titanium−oxo-clusters (2.5, 5 and 7.5 wt %) incorporated into a dimethacrylate-based matrix, aggregates with ramified mass fractal structures were found. Semiquantitative studies of TEM and EFTEM images revealed the presence of a uniform size distribution in the case of 2.5 wt % titanium cluster content with a typical size of 30 nm. A larger size distribution has been found for the 5 wt % and 7.5 wt % between 30 and 180 nm. For the second grade of nanomaterials, i.e., the 19.2 wt % of organically modified titanium clusters incorporated into poly(HEMA), compact and highly dense aggregates with a size distribution from a few nm up to 50 nm were found from TEM and EFTEM images. A significant increase of the storage modulus for the first grade of nanomaterials was revealed by dynamic mechanical analysis (DMA). The incorporation of Ti nanoclusters in the matrix lead to a significant alteration of the system's hardness as indicated through nano-indentation measurements. Thermogravimetric analysis also indicated a significant enhancement of the thermal stability compared to the neat matrix, probably because of the antioxidant effect of the titanium−oxo-clusters.

The fine structure of thin films of poly(styrene-block-4-vinylpyridine) copolymer−2-(4‘-hydroxybenzeneazo)benzoic acid (PS-PVP+HABA) assembly has been studied using the combination of atomic force microscopy, ellipsometry, X-ray reflectivity, GISAXS, XPS, and XPEEM. The films consist of cylindrical nanodomains formed by PVP+HABA associates surrounded by PS matrix. Alignment of the domains can be switched upon exposure to vapors of different solvents from the parallel to perpendicular orientation and vice versa with respect to the surface plane. Swelling in 1,4-dioxane leads the system from the cylindrical to the spherical morphology. Solvent evaporation results in a shrinkage of the matrix in the vertical direction and subsequent merging of the spheres into the perpendicularly aligned cylinders. The cylinders form a regular hexagonal lattice with a spatial period of 25.5 nm. On the other hand, vapors of chloroform induce in-plane alignment. The films consist of parallel layers of the cylinders separated by PS matrix and demonstrate the fingerprint-like structure. The nanocylinders of PVP+HABA are packed into a distorted hexagonal lattice exhibiting 31 nm in plane and 17 nm vertical periodicity. In both cases a thin wetting layer is found at the polymer−substrate interface. The free surface is enriched with PS.

We developed the simple contrasting procedure to improve AFM visualization of single positively charged polymer chains via counterion exchange between Cl^- anions and bulky hexacyanoferrate anions or negatively charged nanoclusters of Prussian Blue. This method allowed us to increase thickness of the resulting structures up to 10 nm and, consequently, to provide visualization of isolated polymer chains deposited on a glass surface (root-mean-square roughness about 1 nm). In contrast, the contrasting with relatively large PB clusters (more than 10 nm in size) distorts conformations of the molecules and even eventually leads to a fragmentation of polymer chains.

We report on the phase behavior and micellization phenomena of a poly(2-vinylpyridine-b-poly(methyl methacrylate)-b-(poly(acrylic acid) block terpolymer (P2VP−PMMA−PAA) in aqueous dilute solutions. This double hydrophilic terpolymer exhibits different self-assemblies depending on the pH of the solution. At low pH (1−2) heteroarm starlike micelles are formed bearing interactive P2VP and PAA arms in the corona. Aging phenomena due to intramicelleral interactions lead to morphology changes from Janus (segregated arms) to shell cross-linked micelles (mixed arms). As the pH increases from 2 to 3, electrostatic intermicellar attractive interactions rise leading to the formation of nonregular aggregates. An insoluble two-phase region around the isoelectric point of the ampholitic chains was observed between pH 3.2 and 5.8. Finally, at higher pH, an unexpected probably out-of-equilibrium morphology of aggregated amphiphilic heteroarm starlike micelles was observed after deposition on the mica substrate.

Single molecule conformations and associate morphologies for polystyrene/poly(2-vinylpyridine) (PS7−P2VP7) heteroarm star copolymer, formed in controlled environment and deposited onto mica or Si wafers, have been studied by atomic force microscopy (AFM) with molecular resolution. At concentrations below 0.01 mg/mL PS7−P2VP7 exists in the molecularly dissolved state in both selective (acidic water, toluene) and common good (chloroform, tetrahydrofuran) solvents. In acid conditions PS7−P2VP7 forms either unimolecular or multimolecular micelles depending on concentration and pH. The core of the micelles is constituted of the collapsed PS arms surrounded by protonated P2VP shell. PS7−P2VP7 undergoes inverse intramolecular segregation upon addition of toluene. In this case, P2VP arms form the dense core of the micelles embedded in the swollen PS shell. The transition between those two inverse types of micelles is strongly modified by interaction with the mica substrate. The micelles deposited onto mica from acidic water are trapped via P2VP extended arms. Upon treatment of the trapped micelles with toluene the PS core is swollen and PS arms gradually adapt an extended conformation whereas P2VP trapped arms retain their extended conformation due to the strong interaction with the mica substrate. The obtained “squash” structures exhibit a unique conformation that does not exist in any solvent and could not be obtained upon a simple adsorption procedure. Surface-supported metallization of the PS7−P2VP7 on Si wafers improves AFM resolution due to the selective deposition of the Pd clusters along the P2VP chains. Thus, the number of P2VP arms of the unimers as well as the aggregation number of the multimolecular micelles and morphological details of the structures were directly analyzed.

We prepare a series of mixed brushes of two incompatible polymers, polystyrene (PS) and poly(2-vinylpyridine) (P2VP) grafted by end groups to Si wafers from carboxyl-terminated P2VP (MW(P2VP) 42 kg/mol) and carboxyl-terminated PS. The molecular mass of PS ranged from 2.98 to 75 kg/mol. The mixed brushes are bidisperse (asymmetric) with respect to the difference of molecular mass of P2VP and PS while the polydispersity of PS and P2VP is narrow. We expose the mixed brushes to selective solvents (toluene for PS and ethanol for P2VP). The morphology and surface chemical composition are investigated using scanning probe microscopy and contact angle measurements. For small chain length asymmetry, the brushes exhibit lateral and perpendicular segregation, and the structure depends on the solvent quality. Upon increasing the molecular weight asymmetry, we encounter the transition from a morphology of laterally segregated domains to a layered (sandwich-like) structure. The location of this transition can be tuned by changing the solvent selectivity. We find qualitative agreement between experiments and self-consistent-field calculations.

In this work we present the orientational behavior of comb copolymer-like supramolecules P4VP(PDP)1.0, obtained by hydrogen bonding between poly(4-vinylpyridine) and pentadecylphenol, during large-amplitude oscillatory shear flow experiments over a broad range of frequencies (0.001−10 Hz). The alignment diagram, presenting the macroscopic alignment in T/TODT vs ω/ωc, contains three regions of parallel alignment separated by a region of perpendicular alignment. For our material, the order−disorder temperature TODT = 67 °C and ωc, the frequency above which the distortion of the chain conformation dominates the materials' viscoelasticity, is around 0.1 Hz at 61 °C. For the first time flipping from a pure transverse alignment via biaxial transverse/perpendicular alignment to a perpendicular alignment as a function of the strain amplitude was found.

The stretching-induced alpha−beta polymorphic transition in the crystalline regions of poly(butylene terephthalate) (PBT) is studied by small-angle X-ray scattering (SAXS), instead of by the wide-angle X-ray scattering (WAXS) usually used for this purpose. An expression for the increase of the long spacing upon the transition is derived from a simple model of oriented PBT as a set of microfibrils, each consisting of alternating crystalline and amorphous regions. This increase is calculated on the basis of the c unit cell parameter of both alpha and beta phases and the degree of crystallinity as obtained from differential scanning calorimetry. There is a fairly good agreement between this value and the experimentally measured one. The affine deformation model holds for both the alpha and beta phases in the whole interval of the strain, from zero up to the strain at break. Without external stress the microfibrils are in the fully relaxed state, as concluded from the values of the corresponding long spacing (from SAXS) comprising exclusively the alpha modification (from WAXS). Both the polymorphic transition and the change in the long spacing with strain are completely reversible in the deformation range investigated.

The associating behavior of a series of monodisperse poly(2-(dimethylamino)ethyl methacrylate)-b-poly(methacrylic acid) (PDMAEMA-b-PMAA) ampholytic diblock copolymers has been studied in water in the dilute regime as a function of pH and salt concentration. Dynamic light scattering (DLS) has been used to monitor the association behavior and transmission electron microscopy (TEM) to visualize the morphology of the aggregates. At and around the isoelectric point (IEP) of the ampholytic diblocks, strong electrostatic interactions occur and lead to the formation of insoluble complexes between negatively and positively charged blocks. These electrostatic interactions can be screened by the addition of salt, which leads to the partial dissolution of the material, according to Debye screening. For samples containing a major PDMAEMA block, spherical micelles are observed below the IEP. These micelles consist of a PMAA core surrounded by a water-soluble protonated PDMAEMA corona. At and above the IEP, these samples are insoluble. Spherical micelles are also formed below the IEP for samples containing a minor PDMAEMA block. These copolymers are insoluble at and around the IEP, whereas solubility is observed above the IEP with formation of aggregates of remarkable morphologies, including hollow spheres and complex compartmentalized aggregates. This aggregation is most favorable at high pH, and it cannot be accounted for only by electrostatic interaction between oppositely charged blocks. Indeed, short-range hydrophobic interaction between uncharged PDMAEMA blocks seems to play a key role in the association process. This is emphasized by quaternized poly(2-(dimethylamino)ethyl methacrylate)-b-poly(methacrylic acid) ampholytic copolymers which are carrying a permanent positive charge on the aminated monomeric units and do not form these particular aggregates.

The compatibility of d8-poly(methyl methacrylate) (d8-PMMA) and a series of poly(n-alkyl methacrylate)s (PnAlkMA) is studied by systematic variation of the length of the n-alkyl group from ethyl (EMA) to n-pentyl (nPenMA). Simultaneously, a series of symmetric diblock copolymers comprised of d8-PMMA and of PnAlkMA ranging from ethyl to n-hexyl (nHMA) is synthesized. Small-angle X-ray data of bulk samples of d8-PMMA-b-PEMA show that this block copolymer is in the disordered state. A change in the χ over 1/T plot occurs between 120 and 130 °C owing to fluctuations. All other block copolymers are in the ordered state at any temperature. The neutron reflection data of d8-PMMA-b-PEMA show a damped cosine concentration depth profile characteristic for thin films of block copolymers in the disordered state. In contrast, the bilayer film of the respective homopolymer pair indicates immiscibility. Neutron reflection measurements on thin films of diblock copolymers ranging from d8-PMMA-b-PnPrMA to d8-PMMA-b-PnHMA and of bilayer films of d8-PMMA and the respective PnAlkMAs show a decreasing apparent interfacial width with increasing length of the n-alkyl group. Taking into account the contributions of capillary waves leads to the inherent interfacial width. By use of the theoretical approach of Matsen and Bates, it is possible to extract the Flory−Huggins χ-parameter between the blocks and the average segment length.

Thermotropic main-chain liquid-crystalline polymers (LCPs) composed of azobenzene or azoxybenzene mesogens and flexible spacers with and without a phenyl side group have been characterized by gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction. The polymers exhibit smectic phases in the well-accessible temperature range from room temperature up to 160 °C. The morphology of thin films on a solid substrate was studied by X-ray reflectometry and scanning force microscopy (SFM). The smectic layers are mainly oriented parallel to the film surface. On the basis of X-ray reflectometry and SFM investigations, it is concluded that, at least in thin films, the polymer main chains are not extended like in the common model for main-chain LCPs, but almost regularly folded.