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  • 1
    Electronic Resource
    Electronic Resource
    Simple one-particle diffusional model to mimic some properties of the glass transition (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4214-4222 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new simplified model is proposed to mimic some properties of the glass transition. The physical system undergoing glass transition is modeled as Brownian particle diffusing in one- or two-dimensional space with obstacles. In one dimension obstacles are points which cannot be crossed by Brownian particles, in two dimensions obstacles are randomly distributed sections of straight lines which are impenetrable for the diffusing particle. The obstacles have a finite lifetime τ. After time τ the obstacle disappears and reappears in some new random position. In another modification of the model the obstacle barrier can be opened for short time and then closed again. Both cases are studied for one-dimensional diffusion, while in two dimensions only the first modification of the model is considered. The main feature of the model is that the mean lifetime of obstacles τ is connected with the diffusion coefficient of the Brownian particle through the coupling equation Dτ=K, with K being the coupling constant. This idea is borrowed from the theory of reptations in polymer liquids. Both analytical calculations and results of computer simulations are presented. The model is shown to reflect some of the features of glass transition. It was found that a slight change in the model, i.e., opening and closing of a barrier in the same position versus transfer of a barrier to a new position, leads to a drastic change in the diffusion kinetics of the system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471158
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  • 2
    Electronic Resource
    Electronic Resource
    Statics and Dynamics of .omega.-Functionalized Block Copolymers of Styrene and Isoprene (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 5109-5118 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00118a045
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation study of adsorption of polymer chains with variable degree of rigidity. I. Static properties (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4806-4813 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption of a single polymer chain onto a solid surface is investigated by molecular dynamics simulations. The chain is composed of mass points interacting via a truncated Lennard-Jones potential, i.e., the excluded volume interaction is taken into account, and grafted to the surface with one end. The average adsorption degree is calculated for various chain lengths (N = 16, 32, 64, 128) and adsorption energies. In addition, the scaling behavior of the adsorption degree and the radius of gyration is investigated. The adsorption degree and the average length of loops and tails are obtained for chains of various stiffnesses. In this context, we find that stiffer chains adsorb more easily. Moreover, the distribution of the mass points perpendicular to the surface as well as the orientation of the bonds with respect to the surface is discussed for various adsorption energies and stiffnesses. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471175
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  • 4
    Electronic Resource
    Electronic Resource
    Collapse of single DNA molecule in poly(ethylene glycol) solutions (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6595-6602 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The compactization of a single DNA molecule in polyethylene glycol (PEG) solution was investigated both theoretically and experimentally. A theory is proposed taking into account the polyelectrolyte effect and redistribution of PEG within DNA coils. This approach makes it possible to describe the dependence of critical value, c, of PEG concentration at the point of DNA collapse on the degree of PEG polymerization, P, and on the concentration of low-molecular salt, ns. Observation of single DNA molecule in solution of PEG has been carried out by means of fluorescence microscopy which allows one to observe the conformation of individual DNA directly. Direct evidence that the coil–globule transition of DNA occurs as first order phase transition was obtained. It was confirmed that the critical concentration of PEG decreases with an increase of the degree of PEG polymerization and salt concentration. The width of the coexistence region of coil and globule was found to be dependent on salt concentration and degree of polymerization of PEG. It was found that DNA undergoes re-entrant globule–coil transition in concentrated solution of high-molecular weight PEG. These experimental results correspond well to the theoretical predictions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469375
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  • 5
    Electronic Resource
    Electronic Resource
    Associating polymers: Equilibrium and linear viscoelasticity (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 1066-1075 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00108a038
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  • 6
    Electronic Resource
    Electronic Resource
    Conformational Transitions in Polyelectrolyte Networks in Binary Solvents: Microheterogeneities in the Collapsed State (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 3925-3929 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00115a026
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  • 7
    Electronic Resource
    Electronic Resource
    Polymers with Strongly Interacting Groups: Theory for Nonspherical Multiplets (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 7491-7500 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00126a029
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  • 8
    Electronic Resource
    Electronic Resource
    Interaction between small colloidal particles and polymer chains in a semidilute solution: Monte Carlo simulation (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 753-768 
    Details
    ISSN: 1435-1536
    Keywords: Key words Colloids ; macromolecules ; solution ; interaction ; computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Interaction between flexible-chain polymers and small (nanometric) colloidal particles is studied by Monte Carlo simulation using two-dimensional and three-dimensional lattice models. Spatial distribution of colloidal particles and conformational characteristics of chains in a semidilute solution are considered as a function of the segment adsorption energy, ɛ. When adsorption is sufficiently strong, it induces effective attraction of polymer segments, which results in contraction of macromolecular coils. The strongly adsorbing polymer chains affect the equilibrium spatial distribution of the colloidal particles. The average size of colloidal aggregates 〈m〉 exhibits a nontrivial behavior: with ɛ increasing, the value of 〈m〉 first decreases and then begins to grow. The adsorption polycomplex formed at strong adsorption exhibits a mesoscopic scale of structural heterogeneity. The results of computer simulations are in a good agreement with predictions of the analytic theory [P.G. Khalatur, L.V. Zherenkova and A.R. Khokhlov (1997) J Phys II (France) 7:543] based on the integral RISM equation technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050308
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  • 9
    Electronic Resource
    Electronic Resource
    Computer simulation of polymer networks: mesoscopic heterogeneity of the structure and topological parameters (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 1180-1185 
    Details
    ISSN: 1573-9171
    Keywords: polymeric networks ; Monte Carlo method ; structural heterogeneity ; topological parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Samples of networks of reacting bi- and trifunctional monomers have been obtained by the dynamic Monte Carlo method for the two dimensional lattice model. Systems with various densities and numbers of chemical junctions have been studied. The steady-state structural factor, the number of the degree of conversion, and topological parameters of samples appear to depend strongly on the initial (random) spatial configuration and the size of the Monte Carlo base cell. Deviations of structural parameters calculated by ensemble and time averaging are statistically significant, which makes it possible to classify networks of this type as so-called non-ergodic fortuitous media that exhibit this property for scales of ∼102 nm. Newly developed facilities for topological analysis allow one to observe the kinetics of changes in individual components of the system: trees, circuits, and other more complex structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00700885
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  • 10
    Electronic Resource
    Electronic Resource
    Swelling behavior of polyelectrolyte gels in the presence of salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2665-2670 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling behavior of weakly crosslinked polyelectrolyte gels based on sodium methacrylate (PMA) and diallyldimethylammonium chloride (DADMAC) in aqueous medium was studied in the presence of different types of salts (NaCl, arginine hydrochloride, cetylpyridinium chloride (CPC), sodium dodecyl sulfate (SDS), and sodium dodecylbenzenesulfonate (SDBS)). It is shown that, starting from some characteristic concentration of a salt, a further increase of the salt concentration results in the shrinking of the gels. This characteristic concentration is defined by the gel parameters (polymer concentration in the gel that is a function of the monomer concentration at the conditions of hydrogel synthesis) and does not depend on the kind of salt used, except for the system polyelectrolyte gel/oppositely charged surfactant (PMA-CPC and DADMAC-SDS or SDBS). It is shown that the initial rate of gel shrinking for all studied systems, including the system gel/oppositely charged surfactant, is determined by the salt concentration and the gel parameters. For the systems PMA-CPC and DADMAC-SDS the gel collapse is a two-step process.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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