Alexander V. Yakimansky

Methods of controlled radical polymerization for the synthesis of polymer brushes

Methods for the synthesis of polymer (molecular) brushes via various controlled-radical-polymerization approaches are considered, and their properties are analyzed. Special attention is paid to atomtransfer radical polymerization, which is most frequently used for these purposes. The potential of the synthesis of molecular brushes with various chemical structures, including amphiphilic brushes, is demonstrated in many examples.

Effective delivery of porphyrazine photosensitizers to cancer cells by polymer brush nanocontainers

Efficient drug delivery can be assigned to tasks that attract the most acute attention of researchers in the field of anticancer drug design. We have reported the first case of using amphiphilic polymer brushes as nanocontainers for photosensitizer delivery to cancer cells. Regular graft-copolymers of hydrophobic polyimides with hydrophilic polymethacrylic acid side chains were loaded with photosensitive dye tetra(4-fluorophenyl)tetracyanoporphyrazine (Pz) providing a sufficiently stable homogeneous fraction of fluorescent Pz-loaded nanoparticles with a size of 100-150 nm. Pz-loaded polymer brushes were substantially more efficient for Pz delivery into cells compared with other types of particles examined, Pz-polyethyleneglycol and Pz-methylcellulose. In vivo, an efficient Pz delivery to tumor can also be expected since the Pz-PB particle size is in the optimal range for passive targeting. Pz-PB showed pronounced photodynamic activity, while, that is important, in the absence of irradiation the PB carrier itself was significantly less toxic than the dye itself. Summing up, water-soluble polymer brushes with polyimide backbones and polymethacrylic acid side chains can be regarded as a novel type of nanocontainers providing efficient intracellular drug delivery for photodynamic therapy of cancers.

Modern Methods for Studying Polymer Complexes in Aqueous and Organic Solutions

This review summarizes published data concerning modern physicochemical methods used to study complexation processes of polymers in solutions. Some of them—dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, cryotransmission electron microscopy, atomic force microscopy, small-angle neutron scattering, analytical-velocity sedimentation, and luminescence methods—make it possible to gain insight into the structure of polymer complexes, while the other methods, such as isothermal titration calorimetry and surface plasmon resonance, provide an opportunity to assess the intensity of specific interactions between complex components.

Diphilic Macromolecular Brushes with a Polyimide Backbone and Poly(methacrylic acid) Blocks in Side Chains

Novel macromolecular brushes with a polyimide backbone and diphilic diblock copolymer side chains consisting of a hydrophilic block of poly(methacrylic acid) adjacent to the backbone and the outer hydrophobic block of poly(methyl methacrylate) are synthesized. The synthesis includes the grafting of poly(tert-butyl methacrylate) to the polyimide chain followed by the polymerization of methyl methacrylate on the graft copolyimide as a branched multicenter macroinitiator. Brushes with diphilic side chains are obtained via the acidic hydrolysis of ester groups in the first block of side chains. The grafting polymerization of methacrylates is performed according to the “grafting from” approach by the method of pseudoliving atom transfer radical polymerization using two methodologies of polymerization activated by either copper- or iron-containing complexes. Conditions providing the controlled regime of the polymerization processes under study are found, and pathways for the targeted regulation of the degree of polymerization of methacrylate blocks and their grafting density are determined. As is shown by dynamic light scattering and transmission electron microscopy, the macromolecules of brushes with diphilic side chains form in ethanol homotypic, obviously spherical, supramolecular micellar structures with hydrodynamic radii in the range from 40 to 120 nm depending on the length and grafting density of the two blocks in diphilic side chains.

Study of formation of metal–polymer complexes between copper (I) and polyamic acids by HPLC

ABSTRACT Structural, molecular, and hydrodynamic characteristics of thermostable functionalized polymers [polyamic acids (PAAs) with biquinoline chelate groups in the main chain] were studied by high-performance liquid chromatography. Size exclusion mechanism of chromatography in conditions including suppression of polyelectrolyte swelling and ion-exclusion effects was proved. The influence of molecular and structural characteristics of PAAs on their ability to form metal–polymer complexes (MPCs) with copper(I) chloride was studied. The critical polymer concentration at which binding of two PAA macromolecules with Cu+ ion takes place to form MPCs was estimated.

Manifestation of side-chain interactions in solution properties of “loose” PI-graft-PMMA molecular brushes

ABSTRACT The molecular properties of polymer brushes composed of polyimide with polymerization degree 50 and loosely grafted poly(methyl methacrylate) chains of variable length (PI-graft-PMMA) were studied by viscometry, dynamic light scattering, and equilibrium electro-optical Kerr effect methods in a diluted solution. It was established that the intrinsic viscosity and hydrodynamic dimension of PI-graft-PMMA copolymers increase when the electro-optical Kerr constant decreases with the elongation of PMMA side chains in the range of 40–110 monomer units. The observed difference in the solution properties of the copolymers was explained by their side-chain interactions in spite of a large distance between the neighboring grafting points typical of “loose brushes.” A strong effect of the chain rigidity and dipole structure on solution properties of the studied samples was demonstrated. The Kuhn segment lengths for PI-graft-PMMA copolymers were estimated to vary in the range 3.8–12.1 nm.