Search results for " Opera"

Polymer-polymer interaction parameters in solvent/polymer/polymer ternary systems

1981

Abstract Empirical equations defining the relationships between b23 and χ23 interaction parameters for the ternary systems toluene (1)/poly(dimethylsiloxane), PDMS, (2)/polystyrene, PS, (3) and benzene (1)/PDMS(2)/PS(3) have been determined. The dependences of both interaction parameters on the mean molecular weights of the macromolecular components have also been studied. A single dependence of b23 (or χ23) upon the mean molecular weight is found when both polymeric components have intermediate to high molecular weights. However, that single dependence is not found when the molecular size of polymer (2) is low.

Role of Solvent Compatibility in the Phase Behavior of Binary Solutions of Weakly Associating Multivalent Polymers

2021

AbstractCondensate formation of biopolymer solutions, prominently those of various intrinsically disordered proteins (IDPs), is determined by “sticky” interactions between associating residues, multivalently present along the polymer backbone. Using a ternary mean field “stickers-and-spacers” model, we demonstrate that if sticker association is of the order of a few times the thermal energy, a delicate balance between specific binding and non-specific polymer-solvent interactions gives rise to a particularly rich ternary phase behavior under physiological circumstances. For a generic system represented by a solution comprising multi-associative scaffold and client polymers, the difference i…

Biological evaluation of PLLA membranes, with different pore diameters, to stimulate cell adhesion and growth in vitro

2015

Polymeric membranes prepared via DIPS (Diffusion Induced Phase Separation) are widely studied and utilized as scaffolds for the regeneration of tissue. In this work, poly (L)-lactide membrane are prepared through a DIPS protocol starting from a ternary solution made of polymer, dioxane (solvent) and water (non-solvent). A three-dimensional, porous and mechanically stable membrane is desirable for ingrowth of human bronchial epithelial cells. Polymeric membranes prepared via DIPS (Diffusion Induced Phase Separation) are widely studied and utilized as scaffolds for the regeneration of tissue. In this work, poly (L)-lactide membrane are prepared through a DIPS protocol starting from a ternary …

Mapping onto ideal chains overestimates self-entanglements in polymer melts

2017

In polymer physics it is typically assumed that excluded volume interactions are effectively screened in polymer melts. Hence, chains could be described by an effective random walk without excluded volume interactions. In this letter, we show that this mapping is problematic by analyzing the occurrence of knots, their spectrum and sizes in polymer melts, corresponding random walks and chains in dilute solution. The effective random walk severely overrates the occurrence of knots and their complexity, particularly when compared to melts of flexible chains, indicating that non-trivial effects due to remnants of self-avoidance still play a significant role for the chain lengths considered in t…

1988

The unperturbed dimensions parameter KΘ is one of the most important characteristics of a polymer chain. For binary systems (polymer/solvent) and mostly for ternary systems (polymer/solvent(1)/solvent(2)) the KΘ values show large discrepancies with respect to those under thetaconditions in a single solvent. These discrepancies can be explained by considering that the interaction parameter χ (and consequently the coil dimensions or the number of intramolecular contacts between polymer segments) changes with molecular weight M. Assuming this dependency, a modified Stockmayer-Fixman equation is proposed from which a unique value of KΘ for a given polymer, independent of M, is obtained. The use…

A procedure for predicting sorption equilibrium in ternary polymer systems from Flory–Huggins binary interaction parameters and the inversion point o…

1989

A procedure has been developed, based on the Flory–Huggins theory as generalized by Pouchlý, which permits the calculation of preferential (λ) and total (Y) sorption coefficients from previous information on the binary interaction parameters, χ, χ, and g12(ϕ10) and on the mixture composition at which the sign of λ inverts. The expressions obtained were applied to 10 cosolvent polymer systems for which experimental values of λ and Y are known. Practically in all the studied systems, the theoretical predictions are in fair accordance with the experimental data.

A Flory–Huggins thermodynamic approach for predicting sorption equilibrium in ternary polymer systems

1989

The Flory–Huggins theory as modified by Pouchlý has been applied to calculate preferential (λ) and total (Y) sorption coefficients for a ternary polymer system. The ternary interaction function (ϕ1ϕ2ϕ3GT(u1, ϕ3)) is described as the product of three independent binary functions. This expression allows prediction of λ and Y from binary interaction parameters χ, χ, g, g, and g12(ϕ10). Three ternary polymer systems are used to check the validity of the expression. Moreover for polymer systems in which the parameters g and/or g are unknown, a procedure to evaluate them has been developed and verified on systems for which sufficient experimental information is available.

Evidence of ternary interaction parameters for polymer solutions in mixed solvents from headspace-gas chromatography

2000

Partial vapor pressures of the volatiles have been measured for four solvent/precipitant/polymer systems at different temperatures. The high molecular weight compounds were polysulfone or polyethersulfone and the mixed solvent was either DMF/acetone or DMF/water. Systems containing the very powerful precipitant water exhibit a special phenomenon: Upon the addition of polymer to a mixed solvent of constant composition the partial vapor pressure of water increases by a factor of more than two before it falls to zero as the volume fraction of the polymer approaches unity. This particular situation cannot be modeled using binary interaction parameters only, in contrast to the results obtained w…

Isobaric Vapor−Liquid Equilibria for Binary and Ternary Mixtures of Ethanol and 2-Propanol with 2-Butanone and Butyl Propionate at 101.3 kPa

2009

This paper presents vapor−liquid equilibrium (VLE) data at 101.3 kPa for the ternary systems ethanol + 2-butanone + butyl propionate and 2-propanol + 2-butanone + butyl propionate and some of their...

Unified Thermodynamic Modeling of Polymer Solutions: Polyelectrolytes, Proteins, and Chain Molecules

2013

The thermodynamic description of the systems specified in the title requires in general dissimilar theories. This contribution presents an approach that is capable of modeling all of them with a maximum of three adjustable parameters. The Ansatz starts from the Flory–Huggins theory and extends it in a 2-fold manner: The number of segments assigned to the solvent is no longer one but treated as an adjustable parameter to account for the differences in the molecular geometries and in the free volumes of the components. Furthermore, the modeling allows for effects resulting from ternary contacts of the solvent/polymer/polymer type. Examination of the acquired thermodynamic expressions by means…