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Karl F Freed - One of the best experts on this subject based on the ideXlab platform.
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self assembly and glass formation in a lattice model of Telechelic Polymer melts influence of stiffness of the sticky bonds
Journal of Chemical Physics, 2016Co-Authors: Karl F FreedAbstract:Telechelic Polymers are chain macromolecules that may self-assemble through the association of their two mono-functional end groups (called "stickers"). A deep understanding of the relation between microscopic molecular details and the macroscopic physical properties of Telechelic Polymers is important in guiding the rational design of Telechelic Polymer materials with desired properties. The lattice cluster theory (LCT) for strongly interacting, self-assembling Telechelic Polymers provides a theoretical tool that enables establishing the connections between important microscopic molecular details of self-assembling Polymers and their bulk thermodynamics. The original LCT for self-assembly of Telechelic Polymers considers a model of fully flexible linear chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)], while our recent work introduces a significant improvement to the LCT by including a description of chain semiflexibility for the bonds within each individual Telechelic chain [W.-S. Xu and K. F. Freed, J. Chem. Phys. 143, 024901 (2015)], but the physically associative (or called "sticky") bonds between the ends of the Telechelics are left as fully flexible. Motivated by the ubiquitous presence of steric constraints on the association of real Telechelic Polymers that impart an additional degree of bond stiffness (or rigidity), the present paper further extends the LCT to permit the sticky bonds to be semiflexible but to have a stiffness differing from that within each Telechelic chain. An analytical expression for the Helmholtz free energy is provided for this model of linear Telechelic Polymer melts, and illustrative calculations demonstrate the significant influence of the stiffness of the sticky bonds on the self-assembly and thermodynamics of Telechelic Polymers. A brief discussion is also provided for the impact of self-assembly on glass-formation by combining the LCT description for this extended model of Telechelic Polymers with the Adam-Gibbs relation between the structural relaxation time and the configurational entropy.
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self assembly and glass formation in a lattice model of Telechelic Polymer melts influence of stiffness of the sticky bonds
Journal of Chemical Physics, 2016Co-Authors: Wensheng Xu, Karl F FreedAbstract:Telechelic Polymers are chain macromolecules that may self-assemble through the association of their two mono-functional end groups (called “stickers”). A deep understanding of the relation between microscopic molecular details and the macroscopic physical properties of Telechelic Polymers is important in guiding the rational design of Telechelic Polymer materials with desired properties. The lattice cluster theory (LCT) for strongly interacting, self-assembling Telechelic Polymers provides a theoretical tool that enables establishing the connections between important microscopic molecular details of self-assembling Polymers and their bulk thermodynamics. The original LCT for self-assembly of Telechelic Polymers considers a model of fully flexible linear chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)], while our recent work introduces a significant improvement to the LCT by including a description of chain semiflexibility for the bonds within each individual Telechelic chain [W.-S....
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self assembly and glass formation in a lattice model of Telechelic Polymer melts influence of stiffness of the sticky bonds
arXiv: Soft Condensed Matter, 2016Co-Authors: Wensheng Xu, Karl F FreedAbstract:The lattice cluster theory (LCT) for strongly interacting, self-assembling Telechelic Polymers provides a theoretical tool that enables establishing the connections between important microscopic molecular details of self-assembling Polymers and their bulk thermodynamics. The original LCT for self-assembly of Telechelic Polymers considers a model of fully flexible linear chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. \textbf{136}, 064902 (2012)], while our recent work introduces a significant improvement to the LCT by including a description of chain semiflexibility for the bonds within each individual telecheic chain [W.-S. Xu and K. F. Freed, J. Chem. Phys. \textbf{143}, 024901 (2015)], but the physically associative (or called "sticky") bonds between the ends of the Telechelics are left as fully flexible. Motivated by the ubiquitous presence of steric constraints on the association of real Telechelic Polymers that impart an additional degree of bond stiffness (or rigidity), the present paper further extends the LCT to permit the sticky bonds to be semiflexible but to have a stiffness differing from that within each Telechelic chain. An analytical expression for the Helmholtz free energy is provided for this model of linear Telechelic Polymer melts, and illustrative calculations demonstrate the significant influence of the stiffness of the sticky bonds on the self-assembly and thermodynamics of Telechelic Polymers. A brief discussion is also provided for the impact of self-assembly on glass-formation by combining the LCT description for this extended model of Telechelic Polymers with the Adam-Gibbs relation between the structural relaxation time and the configurational entropy.
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lattice model of linear Telechelic Polymer melts i inclusion of chain semiflexibility in the lattice cluster theory
Journal of Chemical Physics, 2015Co-Authors: Karl F FreedAbstract:The lattice cluster theory (LCT) for the thermodynamics of Polymer systems has recently been reformulated to treat strongly interacting self-assembling Polymers composed of fully flexible linear Telechelic chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)]. Here, we further extend the LCT for linear Telechelic Polymer melts to include a description of chain semiflexibility, which is treated by introducing a bending energy penalty whenever a pair of consecutive bonds from a single chain lies along orthogonal directions. An analytical expression for the Helmholtz free energy is derived for the model of semiflexible linear Telechelic Polymer melts. The extension provides a theoretical tool for investigating the influence of chain stiffness on the thermodynamics of self-assembling Telechelic Polymers, and for further exploring the influence of self-assembly on glass formation in such systems.
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lattice model of linear Telechelic Polymer melts ii influence of chain stiffness on basic thermodynamic properties
arXiv: Soft Condensed Matter, 2015Co-Authors: Karl F FreedAbstract:The lattice cluster theory (LCT) for semiflexible linear Telechelic melts, developed in paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear Telechelic Polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear Telechelic Polymer melts that assemble on cooling when either Polymer volume fraction $\phi$ or temperature $T$ is high, but opposes self-assembly when both $\phi$ and $T$ are sufficiently low. This allows us to identify a boundary line in the $\phi$-$T$ plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of Polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear Telechelic Polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear Telechelic Polymer melts.
Jack F Douglas - One of the best experts on this subject based on the ideXlab platform.
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lattice cluster theory of associating Polymers iv phase behavior of Telechelic Polymer solutions
Journal of Chemical Physics, 2012Co-Authors: Jacek Dudowicz, Karl F Freed, Jack F DouglasAbstract:The newly developed lattice cluster theory (in Paper I) for the thermodynamics of solutions of Telechelic Polymers is used to examine the phase behavior of these complex fluids when effective Polymer-solvent interactions are unfavorable. The Telechelics are modeled as linear, fully flexible, Polymer chains with mono-functional stickers at the two chain ends, and these chains are assumed to self-assemble upon cooling. Phase separation is generated through the interplay of self-assembly and Polymer/solvent interactions that leads to an upper critical solution temperature phase separation. The variations of the boundaries for phase stability and the critical temperature and composition are analyzed in detail as functions of the number M of united atom groups in a Telechelic chain and the microscopic nearest neighbor interaction energy e(s) driving the self-assembly. The coupling between self-assembly and unfavorable Polymer/solvent interactions produces a wide variety of nontrivial patterns of phase behavior, including an enhancement of miscibility accompanying the increase of the molar mass of the Telechelics under certain circumstances. Special attention is devoted to understanding this unusual trend in miscibility.
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lattice cluster theory of associating Polymers ii enthalpy and entropy of self assembly and flory huggins interaction parameter χ for solutions of Telechelic molecules
Journal of Chemical Physics, 2012Co-Authors: Jacek Dudowicz, Karl F Freed, Jack F DouglasAbstract:The lattice cluster theory for solutions of Telechelic Polymer chains, developed in paper I, is applied to determine the enthalpy Δh(p) and entropy Δs(p) of self-assembly of linear Telechelics and to evaluate the Flory-Huggins (FH) interaction parameter χ governing the phase behavior of these systems. Particular focus is placed on examining how these interaction variables depend on the composition of the solution, temperature, van der Waals and local "sticky" interaction energies, and the length of the individual Telechelic chains. The FH interaction parameter χ is found to exhibit an entropy-enthalpy compensation effect between the "entropic" and "enthalpic" portions as either the composition or mass of the Telechelic species is varied, providing unique theoretical insights into this commonly reported, yet, enigmatic phenomenon.
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can the miscibility of Telechelic Polymer solutions increase with Polymer chain length
ACS Macro Letters, 2012Co-Authors: Jacek Dudowicz, Karl F Freed, Jack F DouglasAbstract:Increasing the molar mass of the Polymers in blends and in solutions tends to decrease miscibility, but application of the lattice cluster theory for strongly interactiong Polymer systems to Telechelic Polymer solutions explains why this usual trend can be inverted, a situation actually observed in some Telechelic Polymer solutions and blends.
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structural and dynamic heterogeneity in a Telechelic Polymer solution
Polymer, 2004Co-Authors: Dmitry Bedrov, Grant D Smith, Jack F DouglasAbstract:We utilize molecular dynamics simulations to investigate the implications of micelle formation on structural relaxation and Polymer bead displacement dynamics in a model Telechelic Polymer solution. The transient structural heterogeneity associated with incipient micelle formation is found to lead to a ‘caging’ of the Telechelic chain end-groups within dynamic clusters on times shorter than the structural relaxation time governing the cluster (micelle) lifetime. This dynamical regime is followed by ordinary diffusion on spatial scales larger than the inter-micelle separation at long times. As with associating Polymers, glass-forming liquids and other complex heterogeneous fluids, the structural ts relaxation time increases sharply upon a lowering temperature T; but the usual measures of dynamic heterogeneity in glassforming liquids (non-Gaussian parameter a2ðtÞ; product of diffusion coefficient D and shear viscosity h; non-Arrhenius T-dependence of tsÞ all indicate a return to homogeneity at low T that is not normally observed in simulations of these other complex fluids. The greatest increase in dynamic heterogeneity is found on a length scale that lies intermediate to the micellar radius of gyration and intermicellar spacing. We suggest that the limited size of the clusters that form in our (low concentration) system limit the relaxation time growth and thus allows the fluid to remain in equilibrium at low T: q 2004 Published by Elsevier Ltd.
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influence of self assembly on dynamical and viscoelastic properties of Telechelic Polymer solutions
EPL, 2002Co-Authors: Dmitry Bedrov, Grant D Smith, Jack F DouglasAbstract:Incipient micellization in a model self-associating Telechelic Polymer solution results in a network with a transient elastic response that decays by a two-step relaxation: the first is due to a heterogeneous jump-diffusion process involving entrapment of end-groups within well-defined clusters and this is followed by rapid diffusion to neighboring clusters and a decay (terminal relaxation) due to cluster disintegration. The viscoelastic response of the solution manifests characteristics of both a glass transition and an entangled Polymer network.
Craig J Hawker - One of the best experts on this subject based on the ideXlab platform.
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Development of thermal and photochemical strategies for thiol-ene click Polymer functionalization
Macromolecules, 2008Co-Authors: Luis M. Campos, Benjamin W. Messmore, Kato L. Killops, Jos M. J. Paulusse, Denis Damiron, Eric Drockenmuller, Ryosuke Sakai, Craig J HawkerAbstract:A series of alkene-functional Polymers were synthesized by controlled Polymerization techniques in order to investigate and compare the efficiency and orthogonality of both photochemically and thermally initiated thiol−ene click coupling reactions. The coPolymers were designed to have single or multiple alkene-functional groups along the backbone, and to evaluate the robustness of these procedures, functionalization reactions with a library of mercaptans were studied. In comparing the photoinitiated reaction to its thermal counterpart, the thiol−ene photocoupling was found to proceed with higher efficiency, require shorter reaction times for complete conversion, and displayed a higher tolerance to various backbones and functional groups. To examine the orthogonality of the thiol−ene click reaction, an asymmetric Telechelic Polymer based on PS was designed with alkene functionality at one end and an azide at the other. The thermally initiated thiol−ene coupling was found to be completely orthogonal with th...
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Development of thermal and photochemical strategies for thiol-ene click Polymer functionalization
International Journal of Biological Macromolecules, 2008Co-Authors: Luis M. Campos, Benjamin W. Messmore, Kato L. Killops, Jos M. J. Paulusse, Denis Damiron, Eric Drockenmuller, Ryosuke Sakai, Craig J HawkerAbstract:A series of alkene-functional Polymers were synthesized by controlled Polymerization techniques in order to investigate and compare the efficiency and orthogonality of both photochemically and thermally initiated thiol−ene click coupling reactions. The coPolymers were designed to have single or multiple alkene-functional groups along the backbone, and to evaluate the robustness of these procedures, functionalization reactions with a library of mercaptans were studied. In comparing the photoinitiated reaction to its thermal counterpart, the thiol−ene photocoupling was found to proceed with higher efficiency, require shorter reaction times for complete conversion, and displayed a higher tolerance to various backbones and functional groups. To examine the orthogonality of the thiol−ene click reaction, an asymmetric Telechelic Polymer based on PS was designed with alkene functionality at one end and an azide at the other. The thermally initiated thiol−ene coupling was found to be completely orthogonal with the traditional azide/alkyne click reaction allowing the individual chain ends to be quantitatively functionalized without the need for protection/deprotection strategies. From these studies, the demonstrated efficiency and orthogonality of thiol−ene chemistry shows it to be a practical addition to the family of click reactions that are suitable for Polymer functionalization.
Jacek Dudowicz - One of the best experts on this subject based on the ideXlab platform.
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lattice cluster theory of associating Polymers iv phase behavior of Telechelic Polymer solutions
Journal of Chemical Physics, 2012Co-Authors: Jacek Dudowicz, Karl F Freed, Jack F DouglasAbstract:The newly developed lattice cluster theory (in Paper I) for the thermodynamics of solutions of Telechelic Polymers is used to examine the phase behavior of these complex fluids when effective Polymer-solvent interactions are unfavorable. The Telechelics are modeled as linear, fully flexible, Polymer chains with mono-functional stickers at the two chain ends, and these chains are assumed to self-assemble upon cooling. Phase separation is generated through the interplay of self-assembly and Polymer/solvent interactions that leads to an upper critical solution temperature phase separation. The variations of the boundaries for phase stability and the critical temperature and composition are analyzed in detail as functions of the number M of united atom groups in a Telechelic chain and the microscopic nearest neighbor interaction energy e(s) driving the self-assembly. The coupling between self-assembly and unfavorable Polymer/solvent interactions produces a wide variety of nontrivial patterns of phase behavior, including an enhancement of miscibility accompanying the increase of the molar mass of the Telechelics under certain circumstances. Special attention is devoted to understanding this unusual trend in miscibility.
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lattice cluster theory of associating Polymers ii enthalpy and entropy of self assembly and flory huggins interaction parameter χ for solutions of Telechelic molecules
Journal of Chemical Physics, 2012Co-Authors: Jacek Dudowicz, Karl F Freed, Jack F DouglasAbstract:The lattice cluster theory for solutions of Telechelic Polymer chains, developed in paper I, is applied to determine the enthalpy Δh(p) and entropy Δs(p) of self-assembly of linear Telechelics and to evaluate the Flory-Huggins (FH) interaction parameter χ governing the phase behavior of these systems. Particular focus is placed on examining how these interaction variables depend on the composition of the solution, temperature, van der Waals and local "sticky" interaction energies, and the length of the individual Telechelic chains. The FH interaction parameter χ is found to exhibit an entropy-enthalpy compensation effect between the "entropic" and "enthalpic" portions as either the composition or mass of the Telechelic species is varied, providing unique theoretical insights into this commonly reported, yet, enigmatic phenomenon.
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lattice cluster theory of associating Polymers i solutions of linear Telechelic Polymer chains
Journal of Chemical Physics, 2012Co-Authors: Jacek Dudowicz, Karl F FreedAbstract:The lattice cluster theory (LCT) for the thermodynamics of a wide array of Polymer systems has been developed by using an analogy to Mayer's virial expansions for non-ideal gases. However, the high-temperature expansion inherent to the LCT has heretofore precluded its application to systems exhibiting strong, specific "sticky" interactions. The present paper describes a reformulation of the LCT necessary to treat systems with both weak and strong, "sticky" interactions. This initial study concerns solutions of linear Telechelic chains (with stickers at the chain ends) as the self-assembling system. The main idea behind this extension of the LCT lies in the extraction of terms associated with the strong interactions from the cluster expansion. The generalized LCT for sticky systems reduces to the quasi-chemical theory of hydrogen bonding of Panyioutou and Sanchez when correlation corrections are neglected in the LCT. A diagrammatic representation is employed to facilitate the evaluation of the corrections to the zeroth-order approximation from short range correlations.
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can the miscibility of Telechelic Polymer solutions increase with Polymer chain length
ACS Macro Letters, 2012Co-Authors: Jacek Dudowicz, Karl F Freed, Jack F DouglasAbstract:Increasing the molar mass of the Polymers in blends and in solutions tends to decrease miscibility, but application of the lattice cluster theory for strongly interactiong Polymer systems to Telechelic Polymer solutions explains why this usual trend can be inverted, a situation actually observed in some Telechelic Polymer solutions and blends.
Etienne Schacht - One of the best experts on this subject based on the ideXlab platform.
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intramolecular excited state processes of a halato Telechelic Polymer evaluated by global compartmental analysis of the fluorescence decay surface with the use of model compounds
Macromolecules, 1997Co-Authors: Jan Van Stam, Noel Boens, Frans C De Schryver, Bart Hermans, Geert Trossaert, Erik Goethals, Robert Jerome, Etienne SchachtAbstract:The excited-state processes of the halato-Telechelic Polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are investigated by time-resolved fluorescence. The photophysical processes can be described by an intramolecular three-state excited-state model. Such a system is not identifiable in the absence of a priori information. It is possible to perform a global compartmental analysis of the fluorescence decay surface using the scanning technique, based on model compound data previously obtained [Hermans et al., J. Phys. Chem. 1994, 98, 13583 and Hermans et al. Macromolecules 1995, 28, 3380]. The value boundaries on the rate constant for ring closure of the chain ends show that this process is close to diffusion-controlled.
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Global compartmental analysis of the fluorescence decay surface of the halato Telechelic Polymer (n,n-dimethyl-n-[3-(1-pyrenyl)propyl]ammonio)-trifluoromethanesulfonate-end-capped poly(tetrahydrofuran)
Macromolecules, 1995Co-Authors: Bart Hermans, Noel Boens, Frans C De Schryver, Jan Van Stam, Geert Trossaert, Erik Goethals, Philippe Teyssie, Robert Jerome, Etienne SchachtAbstract:Global Compartmental Analysis of the Fluorescence Decay Surface of the Halato Telechelic Polymer (N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)-trifluoromethane-sulfonate-End-Capped Poly(tetrahydrofuran)
