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The aim of this work was the synthesis of starch macroinitiators for cationic polymer grafted starches that: (i) are free of cationic homopolymer, and (ii) display a high degree of conversion of the cationic monomer. We show that this can be achieved by a free-radical polymerization reaction using the cationic monomer N-methacryloyloxyethyl-N,N-dimethyl-N-benzylammonium chloride (MADAM-BQ) and a new starch-based macroazoinitiator. For this purpose, the acid chloride of 4-tert-butylazo-4-cyanovaleric acid was synthesized and bound covalently to starch (predominantly in the C6 position) to form a nonsymmetrically substituted macroinitiator that was used to polymerize MADAM-BQ in aqueous media. Essentially no MADAM-BQ homopolymer was formed. The initiator decomposes thermally to starch radicals of high reactivity and low-molar mass radicals that do not initiate polymerization. The reason for the different reactivities of the radicals is presumably due to the nonsymmetric constitution of the starch-bound azo groups. The graft polymerization of MADAM-BQ in aqueous solution performs according to an ideal overall kinetic. The structure of the synthesized starch-graft-poly(MADAM-BQ) products is similar to that of block copolymers because of the low radical efficiency of the starch initiators in aqueous solution. Especially, starch substrates with a higher content of azo groups did not lead to graft products with shorter graft distances because the state of solution of these macroinitiators becomes worse and aggregation occurs with an increasing degree of substitution.

Micelles of ABC block copolymers with varying degrees of polymerization of the B block (n) and constant lengths of the A and C blocks were investigated by small-angle X-ray scattering (SAXS), analytical ultracentrifugation (AUC), surface tension measurements, and isothermal titration calorimetry. The copolymers consisting of hydrophilic poly(N-acylethylene imine)s, end-capped with a hydrophobic fluorocarbon and a hydrocarbon block, are polymeric surfactants (γ = 35 mN/m). They form cylindrical micelles with radii of 3.0 nm (n = 35), 3.8 nm (n = 57), and 4.0 nm (n = 72). Their lengths are about 20 nm. The micelles can be doped with 1,4-diiodoperfluorobutane for the polymers with n = 57 and 72 but not for n = 35. We assume that the doped micelles form distinct fluorocarbon domains, which are able to incorporate selectively the fluorocarbon dopant. The work presented here is a contribution to the development of multicompartment micelles.

The aim of this work is to investigate the stabilization of the conformation of adsorbed human serum albumin (HSA) on surfaces containing CF3 and/or OH groups. These groups are structural characteristics (mimics) of trifluoroethanol, which is known to stabilize the secondary structure of several proteins. We focused on three different types of organic surfaces: (i) self-assembled monolayers (SAMs) prepared from mixtures of thiols with CF3 and OH end groups, (ii) polymer surfaces of a poly(vinyl methyl ketone) (PVMKCF3/OH), which was modified with OH and CF3 groups, and (iii) surfaces of polymer fluorosurfactant complexes containing CF3 groups. It was revealed that the secondary structure of HSA in contact with the SAMs depends on the thiol composition. SAMs of mixed monolayers displayed the highest HSA recognition measured by antibody binding. CD measurements showed that PVMKCF3/OH surfaces retain the secondary structures of adsorbed HSA. Examples of polymer fluorosurfactant complexes are given that retain the secondary structure of adsorbed HSA and a complex that increase the content of α-helices. A combination of CF3 and OH groups is proposed as a new approach to prepare biocompatible surfaces.

We present here the preparation and the structures of thin films of an amphiphilic hexa-peri-hexabenzocoronene (HBC) containing 1, 5, 9, and 15 layers of columns. These films were prepared by the Langmuir−Blodgett technique on poly(ethylene imine) functionalized silicon wafers and investigated by X-ray reflectivity measurements using synchrotron radiation. Columns of HBC cores were aligned parallel to the silicon wafer surface. The thicknesses of the films, which were composed of stacks of highly coherent HBC layers plus a polymer layer, were 3.70−34.6 nm. Each HBC layer has a thickness of 2.4 nm. The transfer rate of the HBC monolayers from the water/air surface to the silicon wafer surface is close to 100%. A macroscopic in-plane orientation of the columns with their main axis parallel to the dipping direction was determined by polarized UV−vis spectroscopy.

Polyampholytes with alternating cationic and anionic monomers were synthesized and complexed with fatty acids (dodecanoic acid and perfluorododecanoic acid). The formation of the polyelectrolyte−fatty acid complexes is self-assembled and generates nanoparticles with sizes in the range of 3−5 nm that were named dressed micelles. A defined arrangement of the ionic charges of three polyampholytes was achieved by the copolymerization of a cationic vinyl monomer (N,N‘-diallyl-N,N‘-dimethylammonium chloride) and anionic vinyl monomers (maleamic acid, phenylmaleamic acid, and 4-butylphenylmaleamic acid). The zeta potentials of the polyampholyte dressed micelles were adjusted in the range of −56 to 25 mV. They increase when replacing the alkylated dodecanoic acid by its perfluorinated counterpart, and they also increase when enhancing the hydrophilicity of the polyampholyte. Analytical ultracentrifugation, dynamic light scattering, and isothermal titration calorimetry were used for the characterization of the fluorinated and the hydrogenated complexes.

Polyampholytes were synthesized and complexed with perfluorododecanoic acid. This produces highly fluorinated water-soluble nanoparticles, which are long-term stable. The polyampholytes are copolymers of styrylmethyl(trimethyl)ammonium chloride, methacrylic acid, and methyl methacrylate having more cationic monomers (28−100 mol %) than anionic monomers (0−16%). The cationic monomers form a complex with perfluorododecanoate ions to create neutral entities that aggregate while the negatively charged methacrylic monomers prevent a macroscopic precipitation such as normally observed in fluorinated complexes. Negatively charged nanoparticles, which have ζ potentials of about −40 mV, are formed as a result of the combined complexation and stabilization. Small-angle X-ray scattering investigations reveal that the particles are anisotropic. For example, disk-shaped particles with a diameter of D  30 nm and a height of 2.2 nm were formed for a high number of complexing groups (79 mol %). Cylindrical-shaped particles with lengths of H  25 nm and radii of 1.5 nm were produced for a medium number of complexing groups (57 mol %). Fluorescence spectroscopy with pyrene as the probe was used to determine the critical aggregation concentrations of the particles which are in the range 0.01−0.06 g L^-1.

The complexes formed between poly(ethylene oxide)-b-poly(ethylene imine)s and dodecanoic acid were studied in the solid state and as nanoparticles. The poly(ethylene imine) blocks had different architectures, cyclic, linear, and branched, while the poly(ethylene oxide) blocks were held constant. Self-organized lamellar-within-lamellar structures were obtained with two different length scales, which are, for example, 15 and 3 nm. Small-angle X-ray scattering methods were used to quantify the morphological differences between noncomplexed and complexed diblock copolymers. Core−shell nanoparticles were prepared from the complexes in aqueous solution with sizes around 200 nm. Their cores are formed by poly(ethylene imine) dodecanoate while their shells consist of poly(ethylene oxide). It was found that the shapes of the nanoparticles depend on the PEI block. They are, for example, prolate if the PEI is linear and spherical if the PEI is branched. The nanoparticles are block ionomer complexes and supposed to be potentially useful as drug carrier systems.

Polyelectrolyte complexes of poly(1,4-phenyleneethynylene carboxylate) (PPE) with 10 different cationic counterions were prepared. The counterions differed in their amphiphilicity, their headgroups (ammonium, pyridinium and sulfonium), and their alkyl chain lengths. It is shown that the optical properties of the PPE complexes depend on the nature of their counterions:  The peak wavelength of the electroluminescence shifts from 430 to 515 nm for single-layer light-emitting diodes (LEDs) when the counterions were changed from tetraethylammonium to sulfonium ions. All the PPE complexes with amphiphile counterions displayed ordered mesophases. They are smectic A or smectic B-like in the solid state at room temperature with long periods of 2.38−4.27 nm. By contrast, no mesomorphous structures were found for the PPE complexes with nonamphiphilic counterions. All complexes were investigated by using differential thermal analysis, small- and wide-angle X-ray scattering techniques, and fluorescence spectroscopy.

Polyelectrolyte complexes of high-molecular-weight poly(ethylene imine) (PEI) and n-alkyl carboxylic acids were prepared. They were investigated with the use of differential thermal analysis, small- and wide-angle X-ray scattering techniques, and fluorescence spectroscopy. The chain lengths of the carboxylic acids varied from decanoic acid (C10) to hexacosanoic acid (C26). Order−order transitions from smectic C to smectic A structures were found, whose enthalpies increase with 3 kJ/mol per CH2 group. The transitions result from the melting of n-alkyl side chains, which are packed into a two-dimensional hexagonal lattice. The transition temperatures, Tm, increased from −2 to 83 °C when the chain lengths were increased from C12 to C26. Thomson's rule was used to arrive at a quantitative description of the dependency of Tm on the chain length. Pyrene was incorporated into the complexes, and the apparent dielectric constant of its surroundings was determined to decrease stepwise with the increasing length of the side chains.

A fluorinated polyelectrolyte−surfactant complex is shown to form highly ordered lamellar structures in the bulk material and in spin-cast films with a long period of 3.75 nm consisting of alternating fluorinated and polymer-rich layers. The smectic B-like structure was found to be stable up to temperatures of 185 °C. The wetting behavior of complex films with thicknesses in the range of 5.7−370 nm were investigated by using axis-symmetric drop shape analysis of contact angle measurements. Surface energies were calculated using the equation derived by Neumann and Li (ca. 11 mN/m), the Zisman critical surface tension (7 mN/m), and the Girifalco−Good−Fowkes dispersive surface energy (10 mN/m). The surface energies were found to be independent of the thickness of the films. By use of X-ray reflectivity it was found that up to 100 double layers were oriented macroscopically on silicon wafers when prepared by the spin-coat technique.

In this paper we discuss the preparation of complexes formed by polyethylenimine (PEI) and retinoic acid. The molecular weights of the PEIs were 600, 2000, 25 000, and 750 000 g/mol. All complexes form smectic A-like structures whose orders decrease with increasing molecular weight. The complexes in the bulk material obey Porod's law. Macroscopically oriented multilayer films of the complexes were prepared in a single-step procedure by spin coating and were characterized by X-ray reflectivity. The release of retinoic acid from the films was investigated by FTIR and surface tension measurements. It was found that the release from the complexes with the high molecular weight PEIs is faster than that from the complexes with low molecular weight. Steric stabilized nanoparticles of the complexes were prepared with sizes ranging from 170 to 580 nm by using Poloxamer 188 as the dispersing agent in aqueous media. Their characterization was carried out using dynamic light scattering and atomic force microscopy. It was found that the particle sizes decreased with the increasing molecular weight of the PEIs. Further, the particle structure became more compact with the increasing molecular weight of the PEIs. The particles of the complexes with the lowest molecular weight were assumed to be doughnut-shaped (toroids).

Polymeric complexes were prepared by using acrylate based copolymers, which contained 20, 30, 50, and 100 mol % diazosulfonate groups and a commercially available fluorinated surfactant (Fluorad FC135). The glass transition temperatures of the complexes were determined to be 71 ± 3 °C, this was independent of the amount of diazogroups. All these complexes are stable up to temperatures of about 200 °C. As determined by wide- and small-angle X-ray diffraction, the solid states of the complexes in the bulk material were determined to be smectic A-like structures with long periods of 3.8−4.4 nm. Ultrathin films with thicknesses in the range 4−40 nm were prepared by spin coating. The wetting behavior of the films was found to be independent of their thickness. As determined by automatic drop shape analysis of the contact angle measurements, the surface energies of complex films were in the range 10−14 mN/m.

The formation of lamellar structures in polyacrylonitrile (PAN) fibers was investigated in the temperature range from 25 to 500 °C using synchrotron small-angle X-ray scattering. It was found that, in addition to a first lamellar mesophase showing up at about 200−300 °C, a second lamellar mesophase appears in an inert atmosphere at temperatures higher than about 350 °C. The former was attributed to the cyclization, the latter to the aromatization reaction of PAN. The periods of the first (α) and the second (β) lamellar phase are about 13 and 5 nm, respectively. Both the α and the β phase show preferred orientation. The average angle between the fiber axis and the normals of the lamellae is about 15°. Homopolymer and copolymer fibers differ considerably in the kinetics of developing the α phase.

Multilayer structures of an optically active ionic polymer complex, which are formed by poly(1,4-phenyleneethynylenecarboxylic acid) and dimethylditetradecylammonium bromide, were prepared. The complex as bulk material was investigated by small-angle X-ray scattering and found to be lamellar in structure with a repeat unit of 3.2 nm. This mesomorphous structure consists of alternating ionic layers (1.3 nm) and nonionic layers (1.9 nm) with periodic undulations of a hexagonal symmetry and a maximum-to-maximum distance of 7.5 nm. The positions of the undulations in adjacent layers are not correlated; this results in typical asymmetric random-layer peak profiles. By contrast, the lamellae of thin complex films (the film thicknesses were in the range of 14−140 nm) show no undulations. X-ray reflectivity and atomic force microscopy (AFM) were used for the film characterization. As revealed by AFM the multilayer films show dewetting instabilities at elevated temperatures. Symmetric complex droplets are the final stage of the dewetting process. The absorptive and emissive behaviors of complex solutions and complex films were examined by UV−vis and fluorescence spectroscopy. It was shown that the supramolecular structuring of the complex has a substantial influence on the optical properties.

The complexation of a cationic poly(p-phenylene) with tetraethylammonium perfluoro-1-octanesulfonate results in a highly fluorescent polymeric complex which forms cylindrical aggregates in solution and a columnar mesomorphous structure in the solid state. Two columns per unit cell are arranged in a rectangular two-dimensional lattice with lattice constants of 5.2 and 3.3 nm. A remarkably large phase width which varies from −50 to 300 °C, as determined by small-angle X-ray scattering and differential calorimetry, was found. The optical properties of the complex in solution and in the solid state were investigated using UV−vis and fluorescence spectroscopy.

The formation of microvoids in polyacrylonitrile (PAN) fibers was studied as a function of temperature by synchrotron small-angle X-ray scattering (SAXS). The microvoids show preferred orientation and have elongated shapes with lengths in the range of 30 to 100 nm and diameters in the range of 0.5 to 3.0 nm. In the pristine fibers, the microvoid content is of the order of one volume percent, the length is 30−40 nm, and the diameter 2−3 nm. It was found that varying numbers of additional microvoids are formed in a temperature range of 190 °C to 470 °C. In the final stage, the content of microvoids is of the order of 10−20 volume percent, and their lengths and diameters are 40 and 0.5 nm, respectively. The formation of the microvoids is correlated with the cyclization and aromatization reactions of the fibers, which are important steps in the formation of the carbon fiber structure. A detailed SAXS evaluation procedure was used for the quantitative description of orientation, length, diameter, and relative volume of microvoids. The procedure may be of interest for the characterization of microvoid systems in other types of fibers.

The dielectric behavior of polyacrylonitrile (PAN) in its pristine and cyclized stages was investigated. A PAN homopolymer displays a strong secondary relaxation at an activation energy of Ea = 111 kJ/mol in the pristine stage and a weak relaxation at Ea = 48 kJ/mol in the cyclized stage. By contrast, a PAN copolymer with itaconic acid, which is used in carbon fiber production, displays a strong secondary relaxation at Ea = 134 kJ/mol in the pristine stage and two relaxations with activation energies of Ea = 24 kJ/mol for the lower frequency relaxation and Ea = 9 kJ/mol for the higher frequency relaxation. No relaxations were found for either polymer in the aromatized stage. The relaxation spectra were interpretated in terms of the Havriliak−Negami (HN) function.

Structures of water-insoluble complexes of polyethyleneimine (PEI) and fluorinated acids, varying in chain length from 4 to 16, were examined via contact angle measurements, X-ray diffraction, and infrared spectroscopy. The wettability of complex surfaces was shown to decrease with increasing chain length. The surface energy of the complexes can be adjusted in the range from about 19 to 9 mN/m. Complexes of PEI with perfluorobutanoic acid and perfluoropentanoic acid are amorphous. Complexes with perfluoroheptanoic acid, perfluorodecanoic acid, and perfluorododecoanoic acid are mesomorphous, while the complex with perfluorohexadecanoic acid is partially crystalline.

We discuss the preparation, the X-ray spectra and their theory, and electron microscopy of nanoparticles showing a lamellar internal structure. Retinoic acid was immobilized by complexation with poly(l-arginine), poly(l-histidine), and poly(l-lysine). The resulting solid-state complexes were prepared as nanoparticles with diameters of 320−380 nm, and with internal structures, which are smectic A-like. By small-angle X-ray scattering the unit cell was determined to be in the range of 3.10−3.62 nm, thus depending linearly on the monomer mass. The X-ray scattering of finite lamellar structures of “onion”- and “tart”-type spherical nanoparticles were determined theoretically. The uniform boundary of the onion-type particles results in secondary maxima near the Bragg reflections. Further, the highest degree of polydispersity to find these secondary maxima in scattering experiments was determined to be about 1% if the particle size is 300 nm. When electron microscopy was used, it was shown that the particles consist of a complex-containing core surrounded by a dispersing agent-containing shell. The core was revealed to be more of the tart- than the onion-type. When circular dichroism was used, the conformation of poly(l-arginine) and poly(l-lysine) within the complexes was determined to be an α-helix, whereas that of poly(l-histidine) was predominantly of the coil-type.

The structures of the water-insoluble complexes of acrylate-based copolymers containing diazosulfonate groups and a fluorinated cationic surfactant (Hoe L-3658-1) were examined by X-ray diffraction, contact angle measurements, differential scanning calorimetry, and spectroscopic methods (IR, UV−vis, fluorescence). The structures of the complexes were shown to be lamellar and determined by using Ruland's interface distribution function procedure. Remarkably low critical surface tensions were found, indicating the formation of ordered layers of fluorocarbon segments at the surfaces of the complexes. Fine-tuning of the complex structures was achieved by varying the composition of the copolymers as well as the pH value present at the time of preparation. The formation of excimers was found to be strongly influenced by the complex structure.

The complexation of poly[(acrylamidopropyl)trimethylammonium chloride] with sodium [bis(perfluorohexylethyl)-2-sulfosuccinate] (Fluowet SB) in aqueous solution results in a highly ordered mesomorphous polyelectrolyte−surfactant complex. Films prepared from the complex exhibited a remarkably low critical surface tension of 6 mN/m, which was determined by dynamic contact angle data. Small-angle X-ray scattering data revealed the structure to be lamellar with repeat units in the range 3.48−3.90 nm, depending on the water content. Atomic force microscopy (AFM) allowed the film surface to be visually represented. It consists of characteristic elevations and depressions. The distance between the elevations ranges from 100 to 300 nm, and the elevations have a uniform height of about 3.4 nm, which confirms their lamellar structure. A detailed investigation of the viscoelastic properties was carried out using dynamic mechanical measurements. Master curves of the storage moduli of dry and wet samples were calculated.

Five solid complexes of poly[(diallyldimethylammonium chloride)-co-(N-methyl-N-vinylacetamide)] with perfluorooctadecanoic acid were prepared at 1:1 stoichiometry. Remarkably low surface energies, as determined by contact angle measurements, were attributed to a strong enrichment of complex surfaces with CF3 groups. By increasing of the charge density of the polyelectrolyte, the surface energy decreased from 14 to 9 mN/m. As determined by small-angle X-ray scattering, the solid complexes show a mesomorphic structure. A columnar liquid crystalline-like structure with columns consisting of stacks of disklike micelles, two-dimensionally ordered in hexagonal arrays, is suggested. The thermal stability of the structures is explained by Coulomb interactions between diallyldimethylammonium groups and carboxylate ions

Two solid complexes of surfactants with a pendant trimethylsilyl moiety and a cationic polyelectrolyte are prepared. These complexes form smectic A-like lamellar mesophases and low-energy surfaces (20 and 36 mN/m). The lamellar structures are characterized in detail by small-angle X-ray scattering using the interface distribution function concept. Both complexes are fabricated as highly transparent, flexible films with tensile moduli of 12 and 30 MPa and low glass transition temperatures (−10 and −56 °C). The application of the complexes as new coating materials is discussed.

Solid complexes of poly[diallyldimethylammonium chloride)-co-(N-methyl-N-vinylactetamide)] with perfluorodecanoate were prepared with a 1:1 stoichiometry. The surface energies of the fluorinated complexes were in the range of 13 to 15 mN/m independent of the fluorine amount present. This result was attributed to the formation of a surface of closely packed trifluoromethyl groups. All of the complexes form thermally stable, self-organized mesophases with body-centered cubic or body-centered tetragonal symmetry. The unit cell volume shrinks from 100 to 40 nm³ with increasing charge density of the polyelectrolyte. This shrinkage is accompanied by an increase in the bulk density from 1.44 to 1.87 g/cm³. From wide-angle X-ray scattering it was derived that the packing order of the perfluoroalkyl chains strongly depends on the charge density and increases in a stepwise manner from amorphous to crystalline.

The solid-state organization of a liquid crystalline metallosupramolecular polyelectrolyte−amphiphile complex at the nanoscopic level is decoded by a combination of X-ray scattering and molecular modeling. The nanostructured material, which self-assembles from transition metal ions, ditopic ligands, and amphiphiles, has a hierarchical architecture consisting of alternating strata of metallo units and interdigitated amphiphiles.