Search results for "Flor"

Neutron reflectometry studies on the interfacial width between polystyrene and various poly(alkylmethacrylates)

1999

From neutron reflectometry we have obtained the interfacial width (typically 2-8 nm) between incompatible polymers above the glass transition temperatures. The investigated polymer bilayers consist of a deuterated polystyrene top layer and various poly(alkylmethacrylates) as a bottom layer. We obtained interesting effects of the length of the alkyl group on the interfacial width. Using mean-field theory we calculate Flory-Huggins-Stavermann interaction parameters X from the interfacial width a I data. These results are compared with investigations of the interfacial width between deuterated poly(methylmethacrylate) and respective polyalkyl-methacrylates.

Relative strength of H-bonding groups on biodegradable polymer-based blends in solution

2006

The intermolecular hydrogen bonding interactions between poly(3-hydroxybutyrate) and poly(styrene-co-vinyl phenol) copolymers with mutual solvent epichlorohydrin were thoroughly investigated by steady-state fluorescence and viscosity techniques. Fluorescence spectroscopy along with viscosity technique was used to asses the intermolecular hydrogen bonding between poly-(3-hydroxybutyrate) and its blends with five copolymer samples of styrene–vinyl phenol, containing different proportions of vinyl phenol but similar average molecular weight and polydispersity index. In the case of very low OH contents (2–4 mol %), as expected, both components of poly(3-hydroxybutyrate) and poly(styrene-co-4-vi…

Intrinsic Viscosities of Polymer Blends and Polymer Compatibility: Self-Organization and Flory-Huggins Interaction Parameters

2018

Preparation and determination of the structure of high-performance polymer blends by small-angle neutron scattering

1995

Amorphous blends from a deuterated polyaryletherketone and a polyetherimide have been prepared and investigated by neutron scattering. The used components differ remarkably in their structure antheir solution properties. The blends on the other hand are combinatorial mixtures : the scattering quantity Φ 1 Φ 2 /S(q) is independent of the composition of the blends if the polymer chains have the same length

Polymer-polymer interaction, in the presence of a solvent as measured by viscometry

2001

Dilute solution viscometry experiments have been carried out in five ternary polymer systems solvent(1)/polymer(2)/polymer(3). Values of the specific viscosity of polymer (3) in a ‘binary solvent’ formed by polymer(2) + solvent(1) have been used to determine the compatibility of the polymer blends. Krigbaum and Wall formalism has been used to predict compatibility which relies on an interaction parameter that depends on the concentration, weight fraction and molar mass of each polymer. To reduce the dependences and to clarify the criterion of compatibility, a parameter independent of polymer (3) composition and molar mass has been deduced. This parameter shows the same behaviour with polyme…

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…

Intrinsic viscosities of polyelectrolytes in the absence and in the presence of extra salt: Consequences of the stepwise conversion of dextran into a…

2011

Abstract Viscosities of dilute polymer solutions were measured in capillary viscometers for samples varying in their fraction f of charged units from 0.00 to 0.90. The dependence of the logarithm of the relative viscosity on polymer concentration c is in all cases reproduced quantitatively by three characteristic parameters: [ η ], the intrinsic viscosity; B , a viscometric interaction parameter (related to the Huggins constant); [ η ] , a parameter required only for polyelectrolytes at low concentrations of extra salt. In pure water [ η ] increases more than 80 times as the fraction f rises from zero to 0.90 and [ η ] starts from zero and goes up to ≈71 mL/g. Upon the addition of NaCl [ η …

Stimuli-responsive brushes with active minority components: Monte Carlo study and analytical theory

2015

Using a combination of analytical theory, Monte Carlo simulations, and three dimensional self-consistent field calculations, we study the equilibrium properties and the switching behavior of adsorption-active polymer chains included in a homopolymer brush. The switching transition is driven by a conformational change of a small fraction of minority chains, which are attracted by the substrate. Depending on the strength of the attractive interaction, the minority chains assume one of two states: An exposed state characterized by a stem-crown-like conformation, and an adsorbed state characterized by a flat two-dimensional structure. Comparing the Monte Carlo simulations, which use an Edwards-…

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.