G. M. Pavlov

Design and synthesis of new anionic “polymeric ionic liquids” with high charge delocalization

Three novel ionic monomers having highly delocalized anions and electrochemically stable mobile cations, namely, 1-butyl-1-methylpyrrolidinium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethane-sulfonyl)imide, 1-butyl-1-methylpyrrolidinium 1,1-dicyano-1-[(3-(methacryloyloxy)propylsulfonyl)]methanide and 1-butyl-1-methylpyrrolidinium 1-cyano-1-[(3-(methacryloyloxy)propylsulfonyl)]imide were synthesized and characterized. The structure of these monomers was designed to be a mimic of the most highly conductive bis(trifluoromethylsulfonyl)imide, tricyanomethanide and dicyanamide anions. By radical polymerization procedure a series of new anionic “polymeric ionic liquids” (PILs) were prepared. The solubility of these linear PILs, thermal stability, glass transition temperatures, molar masses and ionic conductivities were estimated. An advantage of the novel PILs was demonstrated by the comparison of their ionic conductivity at 25 °C (2.0 × 10−8 ÷ 1.6 × 10−7 S cm−1) with the unmodified poly(1-ethyl-1-methylpyrrolidinium 3-(methacryloyloxy)propane-1-sulfonate) analog. The increase in ionic conductivity is as high as three orders of magnitude and was found to depend on the size of the attached anion. The new ionic monomers were subsequently copolymerized with poly(ethylene glycol) dimethacrylate and poly(ethylene glycol) methyl ether methacrylate. The investigation of the copolymers properties revealed further improvement of the conductivity in approximately two orders of magnitude and the achievement of σ = 4.8 ÷ 6.8 × 10−6 S cm−1) at 40 °C.

Polyelectrolyte Complexes of DNA and Linear PEI: Formation, Composition and Properties

In the present study, the complexation between linear 13.4 kDa poly(ethylene imine) (LPEI) and plasmid DNA was investigated. Analytical ultracentrifugation (AUC) was used for size and molar mass determination. Additionally, the morphology was studied by scanning force microscopy. The polyplex formation was investigated in a wide range of PEI nitrogen to DNA phosphate ratios (N/P). At N/P ratios below 1, the PEI/DNA complex formation is characterized by an incomplete DNA condensation and the formation of the primary DNA/PEI complexes. The merging of the initially formed polyplexes occurs at N/P ~2, resulting in the formation of polyplexes with much larger size and high aggregation rate. Stable and uniform polyplexes were formed at N/P > 10, with average sizes of the polyplexes of about 170 ± 65 nm. The content of uncomplexed PEI chains in the polyplex dispersion was estimated at four different N/P ratios, 6.2, 11.6, 28.6, and 57.8, by combining preparative centrifugation with a copper complex assay and by sedimentation velocity analysis as an alternative method. It is demonstrated that virtually all added PEI binds to the DNA at N/P < 2.5; further addition of PEI results in the appearance of a large amount of free PEI in solution. Nevertheless, PEI is able to bind in the whole range of N/P ratios tested. According to the data collected by sedimentation velocity analysis and scanning force microscopy, the single PEI/DNA complexes are composed on average of 8 to 32 single condensed DNA plasmids and 70 ± 25 PEI molecules.

Conformation zoning of large molecules using the analytical ultracentrifuge

A substantial proportion of large molecules made naturally or by artificial means exist as linear chains. In biology this includes DNA, mRNA, many important classes of sugar polymers (polysaccharides) and denatured proteins. In physical science this includes polyethylene, Polyvinylchloride and many important polymers used in plastics and also the many new ones being explored for use in drug delivery. Crucial to how many of these large molecules function is their conformation in solution (either aqueous or organic), a realm unfortunately outside the grasp of high-resolution techniques such as X-ray crystallography. We have now however devised a quick and accessible method for identifying the conformation type or “Zone” of a molecule: Zone A (extra rigid rod type); Zone B (rigid rod type); Zone C (semi-flexible type), Zone D (completely random coil) and Zone E (compact or highly branched particle). To perform this “Conformation Zoning” requires a few milligrams of material and access to one of the new types of high-speed Centrifuge which are now proliferating in academic and industrial establishments.

Hydrodynamic characteristics and equilibrium rigidity of pullulan molecules.

The hydrodynamic characteristics of the polysaccharide pullulan (polymaltotriose) in water have been investigated and its molecular characteristics have been determined. Experimental values varied over the following ranges: velocity sedimentation coefficient (S): 0.9 < S < 11.2, translational diffusion coefficient (10(7) cm2 s-1): 1.1 < D < 14.7 and intrinsic velocity (cm3 g-1): 6.7 < [eta] < 164, which corresponds to a change in molecular weight (x 10(3)) in the range 3.9 < MSD < 644. On the basis of analysis of the literature and our experimental data, excluded volume effects have been shown to have a prevailing influence on the chain length of these polysaccharides. The equilibrium rigidity and hydrodynamic chain diameter of pullulan were evaluated on the basis of the theory of hydrodynamic properties of a wormlike necklace, taking into account excluded volume effects. At low M (< 30 x 10(3)) the translation friction data (in contrast to viscometric data) cannot be described in the framework of the theory of linear molecules.

π‐Conjugated Donor and Donor–Acceptor Metallo‐Polymers

Two zinc(II)- and two ruthenium(II) containing π-conjugated metallo-polymers were synthesized and characterized in detail. We could prove by SEC, analytical ultracentrifugation (AUC) and viscosimetry the ruthenium(II) metallo-polymers to be high molar mass materials (M(fs)  = 20 000 g · mol(-1) Ru1-2; M(fs)  = 34 000 g · mol(-1) Ru1) exhibiting intrinsic viscosities of up to [η] = 192 · cm(3)  · g(-1) . Applying spin-coating we produced homogeneous films of the polymers and could, subsequently, investigate the photophysical properties in the solid state. Introducing the Ru(II) metallo-polymers mixed with PCBM[60] as photoactive layer in bulk-heterojunction solar cells resulted in very low efficiencies due to morphology problems.

Amphiphilic star-shaped block copolymers as unimolecular drug delivery systems: investigations using a novel fungicide

Amphiphilic star-shaped poly(e-caprolactone)-block-poly(oligo(ethylene glycol)methacrylate) [PCLa-b-POEGMAb]4 block copolymers with four arms and varying degrees of polymerization for the core (PCL) and the shell (POEGMA) were used to investigate the solution behavior in dilute aqueous solution using a variety of techniques, including fluorescence and UV/Vis spectroscopy, dynamic light scattering, analytical ultracentrifugation, and isothermal titration calorimetry. Particular emphasis has been applied to prove that the systems form unimolecular micelles for different hydrophilic/lipophilic balances of the employed materials. In vitro cytotoxicity and hemocompatibility have further been investigated to probe the suitability of these structures for in vivo applications. A novel fungicide was included into the hydrophobic core in aqueous media to test their potential as drug delivery systems. After loading, the materials have been shown to release the drug and to provoke therewith an inhibition of the growth of different fungal strains.

Conformation parameters of linear macromolecules from velocity sedimentation and other hydrodynamic methods

Linear macromolecules constitute a broad class of synthetic and natural polymers which are highly useful in various technologies and represent the key molecular systems in living nature. The study of the molecular characteristics of these polymers represents an important problem in fundamental and applied science. The methods of molecular hydrodynamics have been and remain an important way of studying the molar mass, molar mass distribution, size and conformation of linear polymers. This paper discusses the approaches to the problems of hydrodynamic methods, in particular analytical velocity ultracentrifugation, in the study of various types of linear macromolecule. The velocity sedimentation data were processed with three different methods: Sedanal and Sedfit software, and the classical approach of evaluating the rate at which the sedimentation boundary moves. The Sedfit program also allows an evaluation of the frictional ratio values, i.e., the coefficient of translational diffusion. It will be discussed for which systems the estimation of the frictional ratio obtained by Sedfit is adequate and for which it is not. The applications of other hydrodynamic methods (intrinsic viscosity, translational diffusion) are also discussed with a view to obtaining the conformational characteristics of linear macromolecules.

Ruthenium(II) Metallo-Supramolecular Polymers of Click-Derived Tridentate Ditopic Ligands

New ditopic 2,6-bis(1,2,3-triazol-4-yl)pyridine ligands featuring a π-conjugated spacer and clicked-on solubilizing groups were employed in the synthesis of Ru(II) metallo-supramolecular polymers that exhibit an intense metal-to-ligand charge transfer absorption in the visible light region. The coordination polymers obtained were studied in solution by means of size exclusion chromatography and analytical ultracentrifugation, revealing a comparably high molar mass and moderate rigidity. Investigations in the solid state by atomic force and transmission electron microscopy confirmed the formation of rod-like polymers. Furthermore, film preparation by drop-casting showed good film-forming properties. Thus, the solution-processable, photoredoxactive polymers might be applicable in solar cells.

Examination and optimization of the self-assembly of biocompatible, polymeric nanoparticles by high-throughput nanoprecipitation

In recent years, the development of polymer nanoparticle suspensions by nanoprecipitation has gained increased attention both by industry and academia. However, the process by which such formulations are prepared is a highly empirically driven enterprise, whereby developing optimized formulations remains an iterative process. In this contribution, a new approach towards exploration of the materials space for these systems is reported, based on systematically varying processing and formulation to understand their influence on the characteristics of the resulting materials. Taking advantage of the tools and techniques that have already been standardized by informatics-driven life sciences disciplines, we have prepared libraries of nanoparticle formulations of poly(methyl methacrylate-stat-acrylate), poly(lactic-co-glycolic acid), and acetal-derivatized dextran by using a pipetting robot. They were subsequently characterized using a dynamic light scattering plate reader, analytical ultracentrifugation, and scanning electron microscopy. With this high-throughput nanoprecipitation approach, large numbers of materials can be prepared, screened, and the formulation rationally optimized.

Size and shape of inulin in dimethyl sulphoxide solution

A comparative hydrodynamic characterization of the solution properties of the fructan polysaccharide inulin extracted from two different sources and solubilized in dimethyl sulphoxide is described. For Jerusalem artichoke inulin a weight average molecular weight Mw of 3400 6 150 Da from sedimentation equilibrium in the analytical ultracentrifuge is obtained, together with an intrinsic viscosity [ h] of 9.1 6 0.2 ml g π1 and a sedimentation coefficient (corrected to a solvent density and viscosity of that at water at 208C) s 20,w of ,0.4 S. Chicory root inulin had somewhat similar properties, with an Mw of 6200 6 200 g mol π1 ,[ h] of 10.7 6 0.2 ml g π1 and s 20,w also of ,0.7 S. These results appear reasonably consistent with a rather compact model with a relatively large degree of solvent association. q 1999 Elsevier Science Ltd. All rights reserved.