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).     

Hydrodynamic and electrooptical properties of star-shaped heteroarm fullerene (C60)-containing polymers in solutions

Star-shaped heteroarm polymers with a C₆₀ branching center and polystyrene and poly(2-vinylpyridine) arms of equal molecular masses have been studied by the methods of molecular hydrodynamics (translational diffusion and viscometry) and electrooptics (the Kerr effect). The experimental hydrodynamic data are interpreted in terms of the regular star model. The molecular masses and hydrodynamic sizes of star-shaped heteroarm polymers in solutions are estimated. A comparison of these values with the corresponding parameters of linear polymer-analogs (polystyrene and poly(2-vinylpyridine)) makes it possible to characterize the branching degree of macromolecules. The study of the electrooptical properties of the heteroarm polymer in benzene demonstrates the tendency of macromolecules toward aggregation.     

Protonated member of poly(diallylammonium) family: Hydrodynamic and conformational properties

Secondary polyamine in protonated salt form – poly(diallylammonium trifluoro-acetate) is characterized as representative of polymer series based on N,N-diallyl-ammonium. Its hydrodynamic behavior in 1 M NaCl has been compared with the other series members – quaternary poly(diallyldimethylammonium chloride) and tertiary poly(diallylmethylammonium trifluoroacetate). It was shown that these polymers belong to semirigid class whose Kuhn segment length ～4?nm just slightly depends on chemical structure at high ionic strength. As specific for secondary polyamine, the sensitivity to proton equilibrium in solution and counter ion type was detected resulting in great difference of its Mark–Kuhn–Houwink equations from the quaternary analogue at the same conditions.     

Hydrodynamic properties of rigid pyridine-containing poly(phenylene) dendrimers in solutions

The hydrodynamic properties of pyridine-containing polyphenylene dendrimers of the third and fourth generations in chloroform are studied by photon correlation spectroscopy and viscometry. It has been demonstrated that the hydrodynamic characteristics of these macromolecules in dilute solutions are similar to those of nondraining spheres. The hydrodynamic radius of these dendrimers is shown to be proportional to their molecular mass to a power of 1/3. It has been established that the macromolecules of the dendrimers under examination in solutions conserve the conformation and size over a wide temperature range. The detailed analysis of hydrodynamic data allowed a conclusion concerning an extremely low content of the polymer inside the equivalent sphere for the above dendrimers in solutions. The compounds of interest may be referred to as rigid dendritic systems.     

Hydrodynamic, conformational, and optical properties of cellulose tridecanoate molecules in solutions

Cellulose tridecanoates of various molecular weights were synthesized, and their characteristics in chloroform and tetrachloroethane solutions were studied by methods of translational diffusion, velocity sedimentation, flow birefringence (Maxwell’s method), and viscometry. The effects of solvent and temperature on the conformational characteristics of the macromolecules under consideration were examined. The anisotropy of the monomeric unit of cellulose tridecanoates was studied, and the contribution of pendant chains to the optical anisotropy of macromolecules of cellulose esters with aliphatic substituents was analyzed.     

Hydrodynamic and conformational properties of a hyperbranched polymethylallylcarbosilane in dilute solutions

The hydrodynamic and conformational properties of a hyperbranched polymethylallylcarbosilane in hexane solutions have been studied by light scattering, sedimentation, translational diffusion, and viscometry. Fractions with M = (1–75) × 10³ have been used in experiments. The solution behavior of the hyperbranched polymer significantly differs from the properties of both spherical particles and linear polymers. The shape of hyperbranched polymethylallylcarbosilane macromolecules differs from spherical—the asymmetry factor is p ≤ 1.5. Polymethylallylcarbosilane macromolecules in solutions are characterized by compact structure—the hydrodynamic radius is not higher than 4 nm at M = 75 × 10³.     

Dynamooptical and electrooptical properties of poly(methylphenylsiloxane) in solution and bulk

The dynamooptical, electrooptical, and hydrodynamic properties of a low-molecular-mass poly(methylphenylsiloxane) containing 33% phenyl radicals (with respect to the total amount of side groups) in dilute solutions and in bulk are studied. The size of macromolecules, as well as the molecular mass of the polymer, its shear optical coefficients Δn/Δτ = (0.29 ± 0.3) × 10^?10 (in decalin) and (0.43 ± 0.03) × 10^?10 cm s²/g (in bulk), and the specific Kerr constants K = (2.30 ± 0.02) × 10^?12 (in benzene), (2.23 ± 0.02) × 10^?12 (in decalin), and (2.24 ± 0.09) × 10^?12 cm⁵/[g (300 V)²] (in bulk), are estimated and compared with the corresponding characteristics of poly(dimethylsiloxane). The effect of solvents on the intramolecular mobility, optical anisotropy, and dipole structure of polymer macromolecules is considered.     

Hydroxylated fullerenes and fullerene-containing poly(urethanes)

The methods of preparing hydroxylated fullerenes in which hydroxyl groups are attached either directly to the fullerene framework or via various linkers are generalized and analyzed. The methods of synthesis of poly(urethanes) based on hydroxyfullerenes of both types are considered. The syntheses afford linear, network, and star-shaped polymers containing a covalently bonded fullerene. The physical, physicochemical, and mechanical properties of fullerene-containing poly(urethanes) are described.     

Nanosponges as products of N-alkylation of 4-vinylpyridine and poly(4-vinylpyridines) in dilute solutions

Hydrophilic ionic nanosponges with quaternary pyridinium groups are synthesized on the basis of 4-vinylpyridine and its polymer. Their synthesis relies on the use of bior polyfunctional agents alkylating pyridine in dilute solutions in a thermodynamically good solvent. Individual intramolecularly crosslinked soluble macromolecules with molecular masses from 6000 to 400000 are prepared at various degrees of dilution. 1,4-Bis(halomethyl)benzenes, p-vinylbenzyl chloride, and poly(vinylbenzyl chloride) are used as N-alkylating agents. The shapes and sizes of macromolecules are determined via the methods of diffusion, sedimentation, viscometry, dynamic light scattering, atomic force microscopy, and transmission electron microscopy.     

Hydrodynamic properties and conformation of poly(3‐hexylthiophene) in dilute solutions

Conducting polymers demonstrate low solubility in organic solvents. Introducing aliphatic substituents into polymer chains improves their solubility, but may also lead to changes in conformational characteristics of macromolecules. In the present work, the studies of hydrodynamic properties and conformational characteristics of comb‐shaped poly(3‐hexylthiophene) with aliphatic side substituents were carried out in chloroform solutions. Conformational analysis of the studied macromolecules was performed for the first time using homologous series with a wide range of molecular weights of the polymers in dilute solutions. The hydrodynamic properties of these macromolecules were interpreted using the worm‐like spherocylinder model and the straight spherocylinder model. The projection of the monomer unit in the direction of the main polymer chain λ = 0.37 nm was determined experimentally. The following parameters of poly(3‐hexylthiophene) were characterized and quantified: equilibrium rigidity (Kuhn segment length) А = 6.7 nm and hydrodynamic diameter of a polymer chain d = 0.6 nm. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 875–883     

Conformational, optical, and electrooptical properties of cellulose pelargonates in solutions

Newly prepared cellulose pelargonate samples of various molecular weights were studied in dioxane and chloroform solutions by isothermal translation diffusion, high-speed sedimentation, flow birefringence (Maxwell effect), electric birefringence (Kerr effect), and viscometry. The conformational, hydrodynamic, optical, electrooptical, and dynamic characteristics of the polymer were determined.     

The conformational stability of tactic poly(2-hydroxyethyl methacrylate) in aqueous salt solutions

The conformational stability of tactic poly(2-hydroxyethyl methacrylate) (PHEMA) in aqueous salt solutions was investigated by measurements of swelling, surface-free energy, and differential scanning calorimetry, as this polymer in water is sensitive in various electrolytes. In the case of inorganic salts, the major role for the salt effect is played by the anions, and the exposure of hydrophobic components at the PHEMA surface can be correlated with the increase of the degree of swelling. The influence of cations is considerably weaker. In the case of organic salts, tetraalkylammonium halides cause the chain extension more effectively with the increase of alkyl chain length in the cations. This result indicates that the breakdown of the hydrophobic parts in PHEMA provides an important clue on conformational stability. The amount of water molecules bound with the hydrophilic sites of tactic-PHEMA mainly depends on the chain extension and the hydration of cations. Since the sites in tactic-PHEMA influenced by the cation and the anion are different, their effects cause the conformational transition at a specific range of salt concentration. © 1993 John Wiley & Sons, Inc.     

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.     

Hydrodynamic thickness and deformational properties of adsorption layers of poly(ethyleneoxides)

From the measurements of surface potentials of quartz capillaries before and after adsorption of poly(ethylene oxides) (PEO) of various molecular mass, an assessment of the equilibrium hydrodynamic thickness of the adsorption layers has been obtained. The results have been compared with those of independent measurements of . The flow of the polymer solution under increasing pressure drops at the ends of a capillary, which causes the corresponding shear stress () on the surface of adsorbed PEO layers, results in the deformation of the latter, which manifests itself in decreasing 5. The values decrease by several times when the shear stress rises to 2×10₂ N m^–2. Such values of have been obtained using thin capillaries (r = 5÷6 mm) and by application of the capillary electrokinetic method with pressure drops up to 5÷6 MPa.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 31–37, January, 1994.     

Conformational properties of metathesis poly(trimethylsilylnorbornene) in solutions

The hydrodynamic and conformational properties of silicon-containing polynorbornene prepared by metathesis polymerization of 5-trimethylsilylnorbornene in the presence of Grubbs Ru carbene complex were studied by viscometry, isothermal translation diffusion, and centrifugal sedimentation. For the ten-sample homologous series of the polymer, Mark-Kuhn-Houwink relationships correlating the hydrodynamic characteristics of the molecules in toluene with their molecular weight were obtained. Original Russian Text ? N.P. Evlampieva, M.L. Gringol’ts, I.I. Zaitseva, O.V. Okatova, T.S. Dmitrieva, P.P. Khlyabich, E.I. Ryumtsev, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 11, pp. 1899–1905.     

Flow properties of poly(methyl methacrylate) solutions

Viscosity and normal stress behavior were measured for poly(methyl methacrylate) samples of various average molecular weights in diethyl phthalate solution at 30 and 60°C. All samples conformed approximately to the most probable distriution (M?_w/M?_n = 2). Concentrations ranged from 0.113 to 0.38 g/ml, and M?_w from 53,800 to 1,620,000. Despite considerable evidence in the literature of unusual linear viscoelastic behavior for this polymer, its nonlinear properties appear to be rather conventional. The viscosity–shear rate master curve was similar to that found earlier for concentrated solutions of polystyrene and poly(vinyl acetate) of comparable molecular-weight distribution. The viscosity time constant τ_o parallels τ_R, the characteristic time of the Rouse model, although the residual dependence of τ_o/τ_R on concentration and molecular weight appears to be slightly different from that for polystyrene and poly(vinyl acetate). Similar conclusions apply to the recoverable compliance J_e,^o estimated from the normal stress behavior of each solution, and its relationship to the Rouse model compliance J_R.     

Hydrodynamic and conformational properties of dendron-modified polystyrene molecules

The molecular characteristics of polystyrene modified by the Frechet type dendrons of 1–4 generations were studied in tetrahydrofuran by viscometry, isothermal diffusion, electric birefringence, and dynamic and static light scattering. It was shown that dendronized polystyrene molecules whose polymerization degree changes from 1640 to 930 with an increase in the generation number of dendrons occur in the coillike conformation. The equilibrium rigidity of macromolecules tends to increase with increasing the generation number of dendrons. The Kuhn segment length grows from 3.9 nm for polystyrene molecules modified by dendrons of the first generation to 23.3 nm for polystyrene molecules carrying dendrons of the fourth generation.     

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

Dynamic surface properties of poly(N-isopropylacrylamide) solutions

The dynamic surface elasticity of aqueous solutions of poly(N-isopropylacrylamide) (pNIPAM) has been measured by the oscillating barrier and capillary wave methods as a function of time and concentration. While the real and imaginary parts of the surface elasticity almost did not change with the concentration, their kinetic dependencies proved to be nonmonotonic. Simultaneous measurements of the film thickness and adsorbed amount by null-ellipsometry showed that the pNIPAM adsorption can be divided into two steps corresponding to the formation of a concentrated narrow region close to the air phase and a region of tails and loops protruding into the bulk liquid. The local maximum of the elasticity can be observed in the course of the first step when the adsorbed macromolecules do not form long loops and tails. The results are in agreement with recent data on the nonequilibrium surface properties of solutions of other nonionic homopolymers and the theory of dilational surface viscoelasticity.     

Rheological properties of anisotropic poly(para-benzamide) solutions

A study has been made of the viscous properties of poly(para-benzamide) (PBA) solutions in dimethyl acetamide, which undergo a transition from an isotopic to an anisotropic (liquid-crystal) state at a definite concentration C^*. The polymer solutions behave in many respects (as regards the concentration and temperature dependence of viscosity, etc.) like solutions of low molecular weight compounds forming a liquid crystal phase, although the transitions are less pronounced in the polymer solutions owing to their polydispersity. It is shown that the viscometric method, being extremely sensitive to C^*, is convenient for determining phase diagrams of anisotropic polymer solutions. The values of C^* as related to the molecular weight of PBA have been determined, and a general criterion for transition from isotropic to anisotropic solutions established; the latter has the form (CM?)^* ≈ 1.3 × 10⁵ at 20°C. This criterion is in line with the condition for the formation of the liquid-crystal structure in a dispersion of rodlike particles as proposed by Flory. Generalized concentration dependences of viscosity have been plotted by reducing concentration to C^* and viscosity, to the maximum viscosity at the phase transition point. In investigating the flow properties of PBA solutions we revealed the existence of a yield point in the range of low shear stresses, and an intersection of the flow curves of solutions of different concentration at high shear stresses, which excludes a generalized representation of the flow curves in reduced ordinary-type coordinates.