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Zhao Y.,Tianjin University | Stejskal J.,Czech Institute of Macromolecular Chemical | Wang J.,Tianjin University
Nanoscale | Year: 2013

Hierarchical architectures attract a large number of scientists and engineers because of their unique physicochemical properties compared with bulk materials and their precursors. It is believed that intermolecular interactions play a key role in the formation of these hierarchical architectures. However, the principle of coordination of various intermolecular interactions in the self-assembly process is not clear. Here, an aniline oligomer is used as a model brick to study the formation process of well-defined hierarchical architectures, and the directional growth mechanism is proposed. It is assumed that aniline oligomer molecules are asymmetric, and driven by intermolecular attractive forces to aggregate in various manners. Combined with the interactions between the aniline oligomer and molecules from the medium, three-dimensional assemblies, flower-like and urchin-like microspheres, can be formed. The variability and complexity of morphologies produced in the process was analyzed according to the intermolecular interactions, which includes hydrogen bonding, π-π stacking, hydrophobic interaction, etc. The applicability of these special hierarchical architectures, such as in the preparation of superhydrophobic surfaces, is also discussed. © The Royal Society of Chemistry 2013.

Stejskal J.,Czech Institute of Macromolecular Chemical
Progress in Polymer Science | Year: 2015

The chemical or electrochemical oxidation of phenylenediamines in acidic aqueous media yields the corresponding oligomers or polymers. Their structures and properties are discussed in relation to a closely-related conducting polymer, polyaniline. Depending on the reaction conditions, polyphenylenediamines are produced as powders, colloidal dispersions, thin films, or composites. In contrast to polyaniline, polyphenylenediamines are rated as non-conductors and their conductivities are low. Similarly to polyaniline, these polymers display a salt-base transition and they are redox-active. They act as reductants of noble-metal compounds to the corresponding metals or as precursors in the carbonization to nitrogen-rich carbons. Applications proposed in the literature are outlined; they include the corrosion protection of metals, catalysis, electrorheology, sensors, energy-conversion devices, electrochromism, noble-metal recovery, and water treatment. © 2014 Elsevier Ltd. All rights reserved.

Netopilik M.,Czech Institute of Macromolecular Chemical
Journal of Chromatography A | Year: 2012

The SEC separation of a randomly branched polymer, in particular local dispersity due to branching, are theoretically examined. A model of the SEC separation of randomly branched polymer with tetrafunctional branch points enabling the estimation of local dispersity was developed. Measurable quantities (branching indices) were compared with real data. Local dispersity due to branching is demonstrated to depend on elution volume and degree of branching and in the area of the beginning of the elution curve it can reach non-negligible values. © 2012 Elsevier B.V.

Kriz J.,Czech Institute of Macromolecular Chemical
Journal of Physical Chemistry B | Year: 2012

According to 1H and 13C NMR spectra, relaxations, and PFG NMR self-diffusion measurements, partially hydrophobic additives methyl-ethyl ketone (MEK), methyl-isopropyl ketone (MIPK), and methyl-t-butyl ketone (MTBK) facilitate the conformation change and subsequent self-association of the copolymer Pluronic L64. The correlation time (4-9 ms) and activation energy (43-52 kJ/mol) of transition between its conformation states decrease with the increasing hydrophobicity and bulkiness of the additive. The temperature of the first PPO self-association decreases in the same order (by 4 K for MTBK). The interaction of the additives was indirectly proved by the decrease of their rotational and translational mobility in the presence of L64. The rotational correlation time τc is between 3 and 6 × 10-11 s, whereas that of the same molecules in the absence of L64 is lower than 6 × 10-12 s. The normalized self-diffusion coefficient decreases to about 0.7 of its original value in the presence of L64. The interaction of the additive with the PPO block is transient but effective enough to facilitate its conformational change and self-association. Its mediation by a water molecule bound to PPO as a possible mechanism is suggested. © 2012 American Chemical Society.

Pechar M.,Czech Institute of Macromolecular Chemical | Pola R.,Czech Institute of Macromolecular Chemical
Biotechnology Advances | Year: 2013

The coiled coil is a superhelical structural protein motif that has been thoroughly investigated in recent years. Because of the relatively well-understood principles that determine the properties of coiled coil peptides and proteins, macromolecular systems containing the coiled coil motif have been suggested for various applications. This short review focuses on hybrid polymer coiled coil systems designed for drug delivery purposes. After a short introduction, the most important features of the coiled coils (stability, association number, oligomerization selectivity and orientation of helices) are described, and the factors influencing these characteristics are discussed. Several examples of the most interesting biomedical applications of the polymer-coiled coil systems (according to the authors' opinion) are presented. © 2011 Elsevier Inc.

Spevacek J.,Czech Institute of Macromolecular Chemical
Macromolecular Symposia | Year: 2011

The different dynamics of polymer segments forming phase-separated globular structures in aqueous (D2O) solutions affects both the shape of NMR spectra and NMR relaxation times of polymer and solvent. Two types of the approach are discussed. The first one is based on the reduction of integrated intensities of polymer NMR lines in high-resolution NMR spectra in the system undergoing the coil-globule phase transition. The fraction p of phase-separated units (units with significantly reduced mobility) and subsequently, e.g., thermodynamic parameters ΔH and ΔS characterizing the coil-globule phase transition can be determined. The second approach is based on measurements of 1H NMR relaxation times of water (HDO) which provide information on behaviour of water during phase transition. The power of both approaches is demonstrated on results obtained with solutions of several thermoresponsive homopolymers and copolymers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stejskal J.,Czech Institute of Macromolecular Chemical
Chemical Papers | Year: 2013

Preparations of hybrid composites composed of two conducting components, a conducting polymer and silver, are reviewed. They are produced mainly by the oxidation of aniline or pyrrole with silver ions. In another approach, polyaniline or polypyrrole are used for the reduction of silver ions to metallic silver. Other synthetic approaches are also reviewed. Products of oxidation of aniline derivatives, including phenylenediamines, are considered. Morphology of both the conducting polymers and the silver in composites displays a rich variety. Conductivity of the composites seldom exceeds 1000 S cm-1 and seems to be controlled by percolation. Interfacial effects are also discussed. Potential applications of hybrid composites are outlined; they are likely to extend especially to conducting inks, printed electronics, noble-metal recovery, antimicrobial materials, catalysts, and sensors. © 2012 Institute of Chemistry, Slovak Academy of Sciences.

Stejskal J.,Czech Institute of Macromolecular Chemical | Trchova M.,Czech Institute of Macromolecular Chemical
Polymer International | Year: 2012

This paper deals with aniline oligomers produced by the oxidation of aniline with ammonium peroxydisulfate under alkaline conditions. Oligomers obtained in 1 mol L -1 ammonium hydroxide as microspheres have been analyzed. They are brown, non-conducting, and are composed of tens of aniline constitutional units. They contain oxygen in semiquinonoid and quinonoid constitutional units or both, and sulfur in sulfonic or sulfate groups. Phenazine-like units in the oligomers have been identified by UV-visible spectra and the IR spectra support them. IR spectroscopic analysis of fractions insoluble and soluble in chloroform suggests that aniline oligomers are not uniform and strong hydrogen bonding occurs in their structure. Aniline oligomers will be potentially useful in applications that do not require conductivity but use the redox or salt-base transitions typical of polyaniline. Their applicability is illustrated by the ability to reduce silver cations to silver, base-salt transitions and in the carbonization to nitrogen-containing carbons. © 2011 Society of Chemical Industry.

Trchova M.,Czech Institute of Macromolecular Chemical | Stejskal J.,Czech Institute of Macromolecular Chemical
Pure and Applied Chemistry | Year: 2011

Polyaniline (PANI), a conducting polymer, was prepared by the oxidation of aniline with ammonium peroxydisulfate in various aqueous media. When the polymerization was carried out in the solution of strong (sulfuric) acid, a granular morphology of PANI was obtained. In the solutions of weak (acetic or succinic) acids or in water, PANI nanotubes were produced. The oxidation of aniline under alkaline conditions yielded aniline oligomers. Fourier transform infrared (FTIR) spectra of the oxidation products differ. A group of participants from 11 institutions in different countries recorded the FTIR spectra of PANI bases prepared from the samples obtained in the solutions of strong and weak acids and in alkaline medium within the framework of an IUPAC project. The aim of the project was to identify the differences in molecular structure of PANI and aniline oligomers and to relate them to supramolecular morphology, viz. the nanotube formation. The assignment of FTIR bands of aniline oxidation products is reported. © 2011 IUPAC.

Ulbrich K.,Czech Institute of Macromolecular Chemical | Subr V.,Czech Institute of Macromolecular Chemical
Advanced Drug Delivery Reviews | Year: 2010

Synthetic strategies and chemical and structural aspects of the synthesis of HPMA copolymer conjugates with various drugs and other biologically active molecules are described and discussed in this chapter. The discussion is held from the viewpoint of design and structure of the polymer backbone and biodegradable spacer between a polymer and drug, structure and methods of attachment of the employed drugs to the carrier and structure and methods of conjugation with targeting moieties. Physicochemical properties of the water-soluble polymer-drug conjugates and polymer micelles including mechanisms of drug release are also discussed. Detailed description of biological behavior of the polymer-drug conjugates as well as application of the copolymers for surface modification and targeting of gene delivery vectors are not included, they are presented and discussed in separate chapters of this issue. © 2009 Elsevier B.V. All rights reserved.

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