Biomedical subjects

B J Say

Publications and source records attributed to B J Say.

4 recordsLinked to original sources

PubMed2000

Methods for correlating T1rho and FID components in wideline 1H NMR studies of motionally heterogeneous polymer systems.

We address the problem of correlating the observed FID and T1rho components in wideline 1H relaxation measurements of motionally heterogeneous polymers, and show that different methods of data treatment can highlight different aspects of the correlations present. For a sample of polypropylene we find that the T1rho relaxation behaviour is driven by relaxation associated with the intermediate FID component, which strongly suggests a motionally inhomogeneous amorphous region in the sample.

Magnetic Resonance Spectroscopy↗

PubMed1998

A method for analysing proton NMR relaxation data from motionally heterogenous polymer systems.

Historically, the results of studies of the motional processes present in polymers above the glass transition temperature (Tg) by proton NMR spin-lattice relaxation in either the laboratory or rotating frames (T1 or T1p) have shown poor agreement with the results from similar studies carried out using other techniques such as dielectric or mechanical relaxation. We believe that this is mainly because of the complication of the NMR results due to magnetisation transport, either by spin diffusion or by bulk diffusion of the polymer. We suggest a novel approach to the analysis of proton NMR relaxation data from a motionally heterogeneous polymer, and show that the results of such an analysis are intrinsically reasonable and of the form expected for dielectric or mechanical relaxation.

Electrochemistry↗

PubMed1997

Solid-state 19F NMR investigation of poly(vinylidene fluoride) with high-power proton decoupling.

The use of high-power proton decoupling has enabled highly-resolved spectra of fluorine polymers to be recorded, as is exemplified herein for semicrystalline poly(vinylidene fluoride) (PVDF). By means of high MAS speeds (up to 17 kHz), the spinning sidebands are removed from the whole of the relevant chemical shift range. For spectra of the crystalline regions of the polymer, the high-power decoupling is necessary, though its effect is not large. Various relaxation techniques have been used to examine the semicrystallinity and the polymorphism of PVDF, with special pulse sequences used to discriminate between the various domains. Different chemical shifts have been observed for the signals of the amorphous and crystalline phases. Those of the more immobile parts cover a substantial range.

Chemical Phenomena↗

PubMed1996

Analysis of spin-diffusion measurements by iterative optimisation of numerical models.

This work shows how information from a number of solid-state 1H NMR experiments can be combined in a numerical model of a heterogeneous polymer system, which can then be iteratively optimised by varying a small number of parameters to fully represent the spin-diffusion and relaxation behaviour of the system. In this way useful information can be obtained not only about the size of the heterogeneities present, but also about the intrinsic relaxation behavior of the different regions.

Butadienes↗