N. V. Girbasova

Hydrodynamic and conformational properties of poly(acrylate) molecules with side dendrons based on L-aspartic acid

The conformational properties of poly(acrylate) with L-aspartic acid-based side dendrons of the first and second generations with hexyloxycarbonyl end groups have been studied by the methods of molecular hydrodynamics. Regularly branched dendrons are separated from the main chain by a benzamide fragment. The degree of polymerization of the main chain varies within 30-and 50-fold intervals for the dendrons of first and second generations, respectively. Mark-Kuhn-Houwink equations have been derived for poly(acrylate) in bromoform and dichloroacetic acid containing lithium chloride additives. The experimental results are discussed in terms of the models of the wormlike chain, weakly bent cylinder, and solid ellipsoid of revolution. On the basis of translational and rotational friction data, the persistent length of poly(acrylate) in bromoform and dichloroacetic acid containing small amounts of lithium chloride has been estimated.

Properties of dendronized acrylic polymers: Effect of composition and structure of peripheral groups

Two series of new acrylic polymers carrying L-aspartic acid-based dendrons in side chains with terminal hexyloxycarbonyl groups that are both directly and indirectly, via a rigid spacer, attached to polymer chains have been synthesized by the free-radical polymerization of monomers. The polymerization ability of the monomers has been studied. The properties of new polymers are compared with the properties of polymer analogs containing terminal methoxycarbonyl groups of dendrons. Upon incorporation of the rigid spacer, the shielding of reactive centers decreases and the polymerizability of the monomers increases. The replacement of terminal methyl groups in dendrons with hexyl groups in spacer-free polymers leads to a reduction in the degree of polymerization, while in the case of polymers containing spacers, high-molecular-mass products arise. This phenomenon is facilitated by the amphiphilic nature of the polymers and the additional enhancement in the rigidity of chains. A polymer carrying a third-generation dendron has been synthesized only for the latter series.

Hydrodynamic, conformational, and electrooptical properties of cylindrical dendrimers with dendron ionic addition in solutions

Cylindrical dendrimers of first, second, and third generations with side dendrons based on L-aspartic acid which are attached to poly(styrenesulfonic acid) chains via ionic bonds are studied by molecular hydrodynamic, optical, and electrooptical measurements. Macromolecules of the said dendrimers demonstrate significant kinetic rigidity in external electric and hydrodynamic fields simultaneously with moderate equilibrium chain rigidity. The comparative analysis of the experimental data on various cylindrical dendrimers with the polyvinyl backbone and L-aspartic acid-based dendrons is performed. It has been shown that, in solvents not disturbing intramolecular hydrogen bonds between side dendrons, the conformational and dynamic properties of various cylindrical dendrimers are similar. The molecular characteristics of cylindrical dendrimers in non-dissociating solvents are insignificantly affected by the mode of dendron attachment to the backbone (covalent or ionic binding).

Structure and properties of macromolecules with side dendrons based on L-aspartic acid

The molecular characteristics of cylindrical first-third generation dendrimers carrying dendrons based on L-aspartic acid are compared. It is shown that both the generation number of side dendrons and their structure determine the conformational, hydrodynamic, optical, and dipole characteristics of dendrite macromolecules. It is found that the studied class of cylindrical dendrimers is distinguished by a marked amount of intramolecular hydrogen bonds between side dendrite substituents. These bonds ensure the unusual combination of high kinetic rigidity and a compact conformation (low equilibrium rigidity) of macromolecules. The rupture of hydrogen bonds leads to an enlargement of molecular coils (an increase in equilibrium rigidity) that is accompanied by a sharp drop in kinetic rigidity.

Photoinitiated Polymerization of Acryloyl Chloride

Polymerization of acryloyl chloride in the bulk and in solution, induced by 300-nm UV radiation, was performed. The conditions were determined under which the polymer does not precipitate from the solution and is formed in a nearly quantitative yield, which allows its use in polymer-analogous transformations without isolation.

Colloidal properties of polymerizable counterion surfmers solutions based on alkylamino 2-acrylamido-2-methylpropanesulfonates in different solvents

Abstract Three polymerizable surfactants (surfmers) bearing 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as polymerizable group in the counterion have been designed, synthesized, and their micelle-forming properties have been investigated in different solvents. Solutions of dodecylammonium (DDA-AMPS), cetylammonium (CA-AMPS), and cetyltrimethylammonium (CTA-AMPS) 2-acrylamido-2-methylpropanesulfonates were studied in water, water–dioxane mixtures in a whole range of components ratios, and xylene. The solutions were investigated by capillary and rotational viscometry, conductometry, and small-angle neutron scattering; aggregates adsorbed from the solutions on as-split mica were studied by atomic force microscopy (AFM). The surfmers follow general regularities of surfactant behavior in aqueous solutions. Decrease in polarity of the media with an increase in dioxane content in water–dioxane mixtures leads to disappearance of direct micelles. At low water content (below 5%) the surfmers form reverse micelles in the mixtures. The surfmers form reverse micelles in low polarity solvents, such as xylene, which should affect the polymerization results.

Hydrodynamic, optical, and electrooptical properties of macromolecules of third-generation cylindrical dendrimers in chloroform and dichloroacetic acid

Acrylic polymers containing side dendrons of the third generation based on L-aspartic acid have been studied via the methods of molecular hydrodynamics, dynamic and static light-scattering, optics, and electrooptics. There are marked differences in hydrodynamic and optical properties of the macromolecules under study and previously examined polymers with side dendrons of first and second generations. In the range of degrees of polymerization from 10 to 40, these macromolecules possess an extremely low shape asymmetry. Experiments demonstrate the predominant orientation of end side dendrons along the main molecular chain. In chloroform solutions, the orientation of macromolecules in hydrodynamic and electric fields occurs according to the large-scale mechanism. In dichloroacetic acid, the hydrodynamic dimensions of macromolecules decrease, an effect that is accompanied by an increase in the kinetic flexibility of polymer chains.

Correlation of the thermal properties of main‐chain liquid crystalline polymers with the symmetry and anisometry of their mesogens

Several series of liquid crystalline poly[aroyl-bis(oxyarylates)] with oligomethylene (n = 6 and 10) and oligooxyethylene (n = 2; 3; 4 and -) spacers were synthesized. The structure of their mesogenic groups was varied by replacement of central or terminal units by those with reduced symmetry. The polymers were invetigated by methods, such as differential scanning calorimetry, polarizing optical microscopy and in some selected cases by X-ray diffraction methods using synchrotron radiation. An absence of transesterification during measurements at elevated temperatures was proved by 13 C NMR spectroscopy. The formation of smectic melts was demonstrated for all the polymers with high symmetry of the mesogenic group. A lower symmetry leads to a decrease of crystallinity of the polymers and to the appearance of a nematic phase in their melts. Comparative analyses of their thermal properties were made in order to determine the contribution of each single unit of the mesogenic groups on the thermal properties of the polymers.

Synthesis and molecular properties of polymers with asymmetrically substituted side dendrons based on L-aspartic acid

Various acrylic polymers in which an aspartic acid fragment with different end groups (the firstgeneration dendron) is attached to the main chain either via the amide group or the 4-aminobenzoic acid residue are studied. The synthesis of monomers and polymers with the asymmetric substitution of the aspartic fragment, in which a long hexadecyl group is situated only at the α-carboxyl group, is described. The molecular, optical, electrooptical, and conformational properties of the polymer containing the long hexadecyl group at the α-carboxyl bond and the hydrolyzed β-ester bond in the aspartic acid fragment are examined in detail. In the range M = (23−508) × 103, the Mark-Kuhn-Houwink equations [η] ∼ M0.53 and D ∼ M−0.53 are obtained for the intrinsic viscosity and diffusion of the polymers under study in octyl alcohol. The length of the statistical Kuhn segment (120 A), the hydrodynamic diameter of a chain (50 A), the shear optical coefficient, and the anisotropies of the segment and monomer unit are determined. An analysis of the experimental data shows that the main optical axis of the side hexadecyl chain makes an angle of ∼54.5° with the direction of the main chain.

Different approaches to synthesis of N-carboxyanhydrides of amides of trifunctional amino acids

Original method for synthesis of N-carboxyanhydrides of trifunctional α-amino acids containing substituents attached by amide bonds at the ω-functional group is suggested.