M. A. Simonova

Synthesis and investigation of the solution behavior of graft block copolymers of polyimide and poly(methyl methacrylate)

Graft copolymers with a polyimide backbone and poly(methyl methacrylate) side chains are investigated in dilute chloroform and ethyl acetate solutions via the methods of molecular hydrodynamics and optics. Copolymer samples are prepared through the “grafting from” method via atom-transfer radical polymerization with a multicenter polyimide macroinitiator. In solutions of copolymers with low degrees of functionalization Z (40%), supermolecular structures are formed as a result of interactions between the polyimide backbones. In samples with Z → 100%, the backbone is well screened by side chains; therefore, molecular solutions are formed in both solvents. The hydrodynamic and conformational behavior of samples with high functionalization degrees changes after the transition from ethyl acetate to chloroform owing to the different thermodynamic qualities of the solvents with respect to the copolymer components. In both solvents, the backbone tends to avoid contact with a poor solvent. This effect is more pronounced in the case of ethyl acetate. Macromolecules of the studied graft copolymers are characterized by high equilibrium rigidities (>40 nm) that are 10 times higher than the corresponding characteristics of aromatic polyimides.

Development of xMAP assay for detection of six protein toxins.

xMAP technology was used for simultaneous identification of six protein toxins (staphylococcal enterotoxins A and B, cholera toxin, ricin, botulinum toxin A, and heat labile toxin of E. coli). Monoclonal antibody-conjugated xMAP microspheres and biotinilated monoclonal antibodies were used to detect the toxins in a sandwich immunoassay format. The detection limits were found to be 0.01 ng/mL for staphylococcal enterotoxin A, cholera toxin, botulinum toxin A, and ricin in model buffer (PBS-BSA) and 0.1 ng/mL for staphylococcal enterotoxin B and LT. In a complex matrix, such as cow milk, the limits of detection for staphylococcal enterotoxins A and B, cholera toxin, botulinum toxin A, and ricin increased 2- to 5-fold, while for LT the detection limit increased 30-fold in comparison with the same analysis in PBS-BSA. In the both PBS-BSA and milk samples, the xMAP test system was 3-200 times (depending on the toxin) more sensitive than ELISA systems with the same pairs of monoclonal antibodies used. The time required for a simultaneous analysis of six toxins using the xMAP system did not exceed the time required for ELISA to analyze one toxin. In the future, the assay may be used in clinical diagnostics and for food and environmental monitoring.

Synthesis and Investigation of Double Stimuli-Responsive Behavior of N-Isopropylacrylamide and Maleic Acid Copolymer in Solutions

Poly(N-isopropylacrylamide-co-maleic acid) [poly(NIPAAm-co-MA)] linear copolymer with comonomer molar ratio NIPAAm:MA = 94:6 was synthesized by free-radical copolymerization. The molar mass, MsD = 28,000 Da, of poly(NIPAAm-co-MA) was determined using hydrodynamic methods. The self-assembly of poly(NIPAAm-co-MA) in aqueous solution at a concentration of 0.015 g cm−3 within the pH interval from 1.8 to 10.6 and the temperature interval from 22 to 60°C was investigated by static and dynamic light scattering. The copolymer showed a double temperature and pH responsiveness. Three types of particles, namely, macromolecules (or unimers), micellar-like structures, and loose aggregates existed in the poly(NIPAAm-co-MA) aqueous solutions. The fraction of dissolved entities and the hydrodynamic radii of the micellar-like structures and loose aggregates depended considerably on temperature and pH. The temperature of the phase separation and the width of the phase separation interval increased with pH. An influence of pH on kinetic processes in poly(NIPAAm-co-MA) solutions was observed.

Conformations of Molecular Brushes Based on Polyimide and Poly(methyl methacrylate) in Selective Solvents: Experiment and Computer Simulation

The effect of solvent quality with respect to main and side chains on the conformations of molecular brushes is investigated by the methods of molecular hydrodynamics and optics as well as by computer simulation. Copolymers with a polyimide backbone and poly(methyl methacrylate) side chains are studied in solvents featuring strongly different thermodynamic qualities (chloroform, ethyl acetate, and 3-heptanone). The studied samples have close total molecular masses and backbone lengths but differ in grafting densities and lengths of side chains: a brush with densely grafted and relatively short side chains versus a brush with loosely grafted but very long side chains. For both types of brushes, similar changes in hydrodynamic behavior with improvement in the solvent quality are found experimentally. Computer simulation shows that these changes have different origins. In the former case, macromolecules are elongated, and their volumes grow simultaneously, while in the latter case, the shape of the macromolecules remains close to spherical and the changes in hydrodynamic parameters are mainly due to an increase in the volume of macromolecules.

Behavior of thermo- and pH-responsive copolymer of N-isopropylacrylamide and maleic acid in aqueous solutions

ABSTRACT A thermo- and pH-responsive copolymer of N-isopropylacrylamide with maleic acid was studied using light scattering and turbidimetry methods. Aqueous solutions with pH values from 1.8 to 10.9 and in the concentration range from 0.001 to 0.015 g/cm3 were investigated. At all pH values and concentrations, phase separation was observed at temperatures T > 33°C. The temperatures of the start and the width of the phase separation interval increased with decrease of copolymer concentration and increase in pH. The redistribution of scattering entities, namely, macromolecular unimers, micelle-like structures, and loose aggregates, and growth of aggregate hydrodynamic radius took place during heating.

Model and Hybrid Polystyrenes Containing Trispentafluorophenylgermanium End Groups

Abstract The synthesis of the model functionalized polymers of various molecular weight–containing active pentafluorophenylgermanium end groups was performed through chain-transfer reaction to germanium organic compounds-tris(pentafluorophenyl)germane by a free-radical polymerization of styrene. Upon subsequent activated copolycondensation of the obtained polymers with tris(pentafluorophenyl)germane in methyl ethyl ketone environment in the presence of the activator triethylamine hybrid linear-dendritic the block copolymers of polystyrene and perfluorinated poly(phenylenegermane) were obtained. Molar mass and hydrodynamic characteristics of model and hybrid polymers were studied by the methods of size exclusion chromatography, static and dynamic light scattering, and viscometry.

Effect of Concentration on the Properties of Heat- and PH-Sensitive Copolymers of Poly(N-Isopropylacrylamide) with Maleic Acid in Aqueous Solutions

The behavior of a linear statistical copolymer poly(N-isopropylacrylamide) with maleic acid at a fixed pH value and two widely different concentrations (0.4 and 1.5 g/dL) is investigated by the methods of static and dynamic light scattering in dilute aqueous solutions. Studies were carried out in a wide temperature range – from 19 to 60°C. It is shown that at room temperature in the solutions of both concentrations there are three types of particles: unimolecular micelles, micelle-like structures, and aggregates. The fraction of micelle-like structures and aggregates increases when the concentration is decreased. The sizes of all the particles present in solution are independent of the concentration. It was found that dilution increases the starting temperature of the interval of phase separation and its width.

Conformation of the Linear-Dendritic Block Copolymers of Hyperbranched Polyphenylenegermane and Linear Poly(methylmethacrylate)

Dilute solutions of linear-dendritic block copolymers of linear poly(methylmethacrylate) with hyperbranched polyphenylenegermane were investigated by light scattering methods. The obtained results were compared with characteristics of functionalized poly(methylmethacrylate) with -Ge(C6F5)3 terminal groups, linear poly(methylmethacrylate), and hyperbranched polyphenylenegermane. The investigated samples differ by molar masses of the linear components. It was shown that molecules of functionalized poly(methylmethacrylate) in solution have a conformation that is typical for linear polymers in good solvent, while the linear-dendritic polymers in dilute chloroform solution have compact structure and high density in comparison with linear poly(methylmethacrylate).

Behaviorial Features of Aqueous Solutions of Thermoresponsive and pH-Sensitive Polymers with complicated architectures

Research on self-organization and aggregation in solutions of thermoresponsive and pH-sensitive polymers with complicated architectures such as star-shaped polyoxazolines and grafted copolymers with a polyimide spine and polydimethylaminoethylmethacrylate side chains was reviewed. A statistical N-isopropylacrylamide—maleic-acid copolymer was studied for comparison. Hydrophobic blocks in the macromolecules reduced the phase-stratification temperature and changed the set of scattering species by forming monomolecular micelles. An increased intramolecular density led to slower aggregate formation in solutions of polymers with complicated architectures.

Hydrodynamic and Molecular Properties of Hyperbranched Copolymers Formed by Pentafluorophenylgermane Hydrides

The hyperbranched copolymers of tris(pentafluorophenyl)germane (C6F5)3GeH and bis(pentafluorophenyl)germane (C6F5)2GeH2, synthesized by the method of activated copolycondensation, have been studied by means of dynamic and static light scattering methods, analytical ultracentrifugation, isothermal translational diffusion, and capillary viscometry in dilute chloroform solutions. It has been shown that the copolymer molar mass grows with increasing content of (C6F5)2GeH2. The molecules of polymer investigated have a compact dense structure, their shape being slightly different from the spherical one.