Diffusion in Model Networks as Studied by NMR and Fluorescence Correlation Spectroscopy

We have studied the diffusion of small solvent molecules (octane) and larger hydrophobic dye probes in octane-swollen poly(dimethyl siloxane) linear-chain solutions and end-linked model networks, using pulsed-gradient nuclear magnetic resonance (NMR) and fluorescence correlation spectroscopy (FCS), respectively, focusing on diffusion in the bulk polymer up to the equilibrium degree of swelling of the networks, that is, 4.8 at most. The combination of these results allows for new conclusions on the feasibility of different theories describing probe diffusion in concentrated polymer systems. While octane diffusion shows no cross-link dependence, the larger dyes are increasingly restricted by fixed chemical meshes. The simple Fujita free-volume theory proved most feasible to describe probe diffusion in linear long-chain solutions with realistic parameters, while better fits were obtained assuming a stretched exponential dependence on concentration. Importantly, we have analyzed the cross-link specific effect on probe diffusion independently of any specific model by comparing the best-fit interpolation of the solution data with the diffusion in the networks. The most reasonable description is obtained by assuming that the cross-link effect is additive in the effective friction coefficient of the probes. The concentration dependences as well as the data compared at the equilibrium degrees of swelling indicate that swelling heterogeneities and diffusant shape have a substantial influence on small-molecule diffusion in networks.

A fortran program for routine analysis of magnetic susceptibility data

Title of program: SUSCEPT2 Catalogue Id: ABNA_v1_0 Nature of problem Faraday susceptibility data in the form of balance readings are converted to susceptibilities, and optionally interpreted in terms of a Curie-Weiss temperature dependence. Versions of this program held in the CPC repository in Mendeley Data ABNA_v1_0; SUSCEPT2; 10.1016/0010-4655(78)90094-2 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019

A general-purpose routine for the analysis of spectroscopic peak shapes

Title of program: SPEC3 Catalogue Id: ABMM_v1_0 Nature of problem The program analyzes spectroscopic peak shapes parametrically (eleven parameters). A simulated spectrum may be juxtaposed, adjusted variously, and similarly analyzed. Plotting is provided. Versions of this program held in the CPC repository in Mendeley Data ABMM_v1_0; SPEC3; 10.1016/0010-4655(75)90002-8 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019

A fortran code for automatic spectrum analysis on medium-scale computers

Abstract Title of program: PEAK2 Catalogue number: ABML Program obtainable from: CPC Program Library, Queen's University of Belfast, Northern Ireland (see application form in this issue) Computer: IBM 370/155 and 370/158; Installation: The University of Akron, Akron, Ohio, USA Operating system: OS/MVT Programming language used: FORTRAN IV (G) High-speed store required: 14,000 words (56 kbt) at execution time Number of bits in a word: 32 Overlay structure: None Number of magnetic tapes required: None O... Title of program: PEAK2 Catalogue Id: ABML_v1_0 Nature of problem The program performs fully automatic detection, description, and fitting of peaks (including doublets) in digital X-Y spectra of various kinds, given only an approximate width, and the choice of positive or negative (absorption) height, of the peaks. Versions of this program held in the CPC repository in Mendeley Data ABML_v1_0; PEAK2; 10.1016/0010-4655(75)90015-6 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019

Pulsed and Steady Field Gradient NMR Diffusion Measurements in Polymers

Abstract Some twenty years after the development of the steady and pulsed gradient spin-echo NMR methods of measuring self-diffusion, these techniques are now maturing and experiencing a surge of interest, much of it concentrated on polymer systems. The methods are briefly reviewed here, together with the most important results in polymers, with particular concentration on work described within the last few years. The research is divisible into three categories: diffusion of diluent and penetrant molecules in rubbery high polymers, diffusion of polymer molecules in dilute and semidilute solutions with liquid solvents, and diffusion of macromolecules dissolved in concentrated solutions or melts of equivalent or different polymers of arbitrary molecular weight. The review includes the main theoretical interpretations of the experiments, particularly the free-volume theory in its various forms and power-law behaviors postulated by recent refinements of tube/reptation and scaling theory. This article represents an updated elaboration of an earlier review.</jats:p

A Fortran program to collect histograms of microscopic scalar interactions

Title of program: INTHIST2 Catalogue Id: ABMX_v1_0 Nature of problem The effects of scalar interactions among members of a host lattice, and/or between these and an interstitial or substituted species, are simulated. Versions of this program held in the CPC repository in Mendeley Data ABMX_v1_0; INTHIST2; 10.1016/0010-4655(78)90039-5 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018

A flexible, all-purpose curve-fitting program

Title of program: UNIFIT2 Catalogue Id: ABMR_v1_0 Nature of problem The program fits theoretical models of arbitrary form (up to 20 parameters) to experimental data (x, y, delta y), calculates chi- square, and plots data, error bars, and fit. Versions of this program held in the CPC repository in Mendeley Data ABMR_v1_0; UNIFIT2; 10.1016/0010-4655(76)90053-9 ABMR_v2_0; UNIFIT4; 10.1016/0010-4655(79)90010-9 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019