A. A. Lezov

Molecular Properties of the Copolymers of N,N-Diallyl-N,N-Dimethylammonium Chloride and Maleic Acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.

Synthesis, hydrodynamic, and conformational properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

Poly(N-acryloyl-11-aminoundecanoic acid) samples are synthesized in monomer solutions occurring in both micellar and nonmicellar states. It is shown that polymeric ionogenic surfactants of various molecular masses can be prepared through variation in the concentration of a polymerizable surfactant or in the ionic strength of a solution. The polymer of interest is investigated in detail via the methods of molecular hydrodynamics (viscometry, isothermal diffusion, and velocity sedimentation), dynamic light scattering, GPC, and scanning probe microscopy. The solubility of the polymer in various solvents is examined in detail, and the tendency of this polymer toward association in DMF solutions is discovered. The equilibrium rigidity of macromolecules, which is characterized by the Kuhn segment length A = 100 × 10−8 cm, and the effective hydrodynamic radius are determined in a dioxane-cyclohexanol mixed solvent.

Optical, dynamic, and electro-optical properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

The optical, electro-optical, and dynamic characteristics of poly(N-acryloyl-11-aminoundecanoic acid) in organic solvents and of the sodium salt of its monomer in water were studied via the methods of flow birefringence, equilibrium and nonequilibrium electric birefringence, and dynamic light scattering. It is shown that, in aqueous solutions, the monomer forms coarse particles of both symmetric and asymmetric shapes. The linear dimensions of these particles are estimated from the data of translational and rotational diffusion. Polymer macromolecules in organic solvents feature negative anisotropy of optical polarizability. Contributions of optical microform and macroform effects to the observed flow birefringence are analyzed in detail. The intrinsic optical anisotropy of the monomer unit of the polymer, which correlates well with the corresponding values for comb-shaped polymers of a similar structure, is estimated. It is shown that polymer molecules lack marked intrinsic permanent macromolecular dipoles and that electric birefringence in their solutions is associated with macroscopic induced dipole moments that appear during orientation of the dipole moments of polar groups in side chains of the polymer under application of an electric field.

Molecular properties of poly(carboxybetaine) in solutions with different ionic strengths and pH values

Viscometry and dynamic and static light scattering are employed to study the molecular properties of water-soluble poly(carboxybetaine), that is, poly(2-(diallyl(methyl)ammonium) acetate). It is shown that, in solutions with pH 1, the polymer behaves as a polyelectrolyte. In media with pH 6 and 13, an increase in the concentration of sodium chloride increases the intrinsic viscosity of the polymer and the hydrodynamic radius of its macromolecules, thereby indicating the antipolyelectrolyte effect typical of polymer zwitterions. In water and 0.1 M NaOH, the second virial coefficient of the polymer is close to zero, while exponent ν, which relates the sizes of macromolecules to their molecular masses, is 0.5. In 1 M NaCl, the second virial coefficient becomes positive, while exponent increases to 0.58. The Kuhn segment lengths of poly(carboxybetaine) molecules are 6.3 and 6.6 nm in water and 1 M NaCl, respectively. An increase in the hydrodynamic radius of macromolecules with the ionic strength of the solution is due to the shielding of attraction between zwitterions belonging to polybetaine monomer units located far apart along a macromolecular chain.

Conformational, optical, electro-optical, and dynamic characteristics of cross-linked poly(N-acryloyl-11-aminoundecanoic acid)

Polymerizable surfactants now attract a great interest due to high potential of their practical application as components of pseudostationary phase in micellar chromatography, drug carriers, and “building blocks” for molecular design of nanoparticles and nanostructured polymer materials, for encapsulation of various biological preparations. In the present work, we have studied poly(N-acryloyl-11-aminoundecanoic acid) (cross-linked comb-like polymer). Cross-linked polymers were obtained via copolymerization of the surfactant bearing double bond in hydrophobic tail with hydrophobic bifunctional cross-linker in micellar solution. Of special interest was the comparison between cross-linked and non-cross-linked polymers and influence of alkaline medium on characteristics of these samples. Non-cross-linked polymers were obtained by hydrolysis of the cross-linked product (treating with NaOH). The mixture of cyclohexanol and dioxane (1:1 volume ratio) was used as a solvent. Detailed studies of the obtained polymers by viscometry, dynamic light scattering, flow birefringence, and equilibrium and non-equilibrium electric birefringence were performed. It was established that during cross-linking process, two types of bonds are formed (the ones inside individual molecules and between several polymer chains). It was shown that cross-linked macromolecular nanoparticles can be transformed into comb-like polymers.

Water-soluble polyelectrolyte complexes of pyridine-containing polyphenylene dendrimers

The sizes of soluble polyelectrolyte complexes formed through mixing of solutions of dimethyl sulfate-alkylated rigid pyridine-containing polyphenylene dendrimers of various generations with the solution of sodium polystyrenesulfonate are measured with the use of dynamic light scattering. Effects of the length of the polyanion chain of the dendrimer, the generation number of the dendrimer, and the charge ratio of polymer components on the sizes of the complexes are examined. The results of this study are in agreement with the theoretical analysis of interaction between the charged dendrimer and the polyelectrolyte of the opposite charge sign and suggest the spontaneous formation of nanosized particles of water-soluble complexes.

Conformational properties of biocompatible poly(2-ethyl-2-oxazoline)s in phosphate buffered saline

Inspired by the increasing popularity of poly(2-ethyl-2-oxazoline) (PEtOx) for biomedical applications, this study reports the complete and thorough solution analysis of the homologous series of biocompatible PEtOx samples in a very broad range of molecular weights ranging from 11.2 × 103 g mol−1 up to 260 × 103 g mol−1. The main focus of the research was on the determination of the conformational properties of PEtOx macromolecules at a temperature of 37 °C in phosphate buffered saline (PBS) simulating the parameters of physiological media. The polymers were studied in PBS solutions by analytical ultracentrifugation, dynamic light scattering (DLS), translational diffusion, and intrinsic viscosity measurements in a temperature range from 15 °C up to 72 °C. The complete set of Kuhn–Mark–Houwink–Sakurada scaling relationships revealed linear trends over the whole range of the studied molar masses, while the determined scaling indices at 37 °C correspond to the coil conformation in a thermodynamically good solvent ([η] = 0.045 × M0.62, s0 = 0.010 × M0.46 and D0 = 1750 × M−0.54). Based on the intrinsic viscosity values (most sensitive characteristic to the size variations of polymer coils, [η] ∼ r3), it was demonstrated that PEtOx macromolecules in PBS solutions undergo a transition from swollen polymer coils with gradual deterioration of thermodynamic quality of solutions within the temperature range of 15–45 °C, reaching θ-conditions at 55 °C with further precipitation at 62–72 °C. Also, to the best of our knowledge, the conformational parameters (equilibrium rigidity/the Kuhn segment length and the diameter of the polymer chain) of PEtOx macromolecules were evaluated under physiological conditions for the first time and constitute A = 1.8 ± 0.3 nm and d = 0.7 ± 0.4 nm. These equilibrium rigidity values classify PEtOx as a flexible macromolecule with rigidity similar to that of poly(ethylene glycol). For the first time, we were able to demonstrate a direct influence of thermosensitivity on the rigidity of the biocompatible polymer: PEtOx. The Kuhn segment length is undoubtedly decreasing when approaching the LCST.

Optical and hydrodynamic properties of solutions of copolymers of N,N-dimethylaminoethyl methacrylate and 2-deoxy-2-methacrylamido-D-glucose that contain silver particles

Ag0 nanoparticles are prepared via the reduction of silver ions by copolymers of N,N-dimethylaminoethyl methacrylate and 2-deoxy-2-methacrylamido-D-glucose of various compositions in water at room temperature. It is found that an insignificant part of the macromolecules is involved in the reduction of Ag+ to Ag0 and stabilization of the resulting nanoparticles. As shown by flow-birefringence studies, the optical properties of solutions of stabilized silver nanoparticles change abruptly relative to the optical properties of the solutions of the initial copolymers.

Formation of interpolyelectrolyte complexes with controlled hydrodynamic radii in solutions

Interpolyelectrolyte complexes (IPEC) of poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and comb-like amphiphilic polyelectrolyte poly(11-acryloyloxyundecyltrimethyl-ammonium) cation (PAUTA) were synthesized via polymerization of AUTA ionically bound to a PAMPS macromolecule. Nanoparticle dispersions with controlled hydrodynamic radii were prepared by varying molecular weight of the initial PAMPS. The morphology and sizes of IPEC dispersions were studied by atomic force microscopy (AFM). Nanoparticles dispersions stability under different salt conditions was assessed.

Molecular and conformational properties of comb-like polymers with ionically bound side chains studied in organic solvent

ABSTRACT Conformational and dynamo-optical properties of a homologous series of poly(cetyltrimethylammonium 2-acrylamido-2-methylpropane sulfonates) with molecular masses ranging from 80 to 700 kDa were studied in chloroform solutions by viscometry, dynamic light scattering, sedimentation, and flow birefringence. The Mark–Kuhn–Houwink Equations for this polymer in chloroform were obtained; the values of hydrodynamic diameter and the Kuhn segment length as well as the value of intrinsic anisotropy of polarizability of the monomer unit were defined.