Vincent J. McBrierty

Bio: Vincent J. McBrierty is an academic researcher from Bell Labs. The author has contributed to research in topics: (Hydroxyethyl)methacrylate & Self-healing hydrogels. The author has an hindex of 7, co-authored 8 publications receiving 647 citations. Previous affiliations of Vincent J. McBrierty include Trinity College, Dublin.

Water in hydrogels. Part 3. Poly(hydroxyethyl methacrylate)/saline solution systems

Abstract: High-resolution 23 Na NMR is used in conjunction with broad-line 1 H resonance and DSC to investigate the nature of water in PHEMA/saline systems. The introduction of sodium ions into the hydrated polymer system increases the nonfreezable water content and depresses devitrification. The Na + ions also decrease water mobility below 250 K, confirming sodium as a water-coordinating ion. A phase transition in hydrated PHEMA at 250 K is indicated

Interfacial effects on the NMR of composite polymers

Abstract: Several NMR experiments can provide estimates of the scale of spatial inhomogeneity in solid materials in the range of nanometers to microns. The effects underlying these experiments their interpretation, and models used in their interpretation are discussed and illustrated with applications to polymers. Examples chosen from the literature include semicrystalline polymers (polyethylene, polyvinylidene fluoride, polychlorotrifluoroethylene), filled elastomers (carbon-filled butadiene), copolymers (styrene: butadiene, dimethylsiloxane: bisphenol-A polycarbonate, polyurethane) and blends (polymethylmethacrylate-polystyreneacrylonitrile, polyvinylidene fluoride-polymethylmethacrylate). Comparison of examples directs attention to the similarity in anisotropic motional behavior of highly constrained interfacial material in semicrystalline and filled polymers. While no one experiment is applicable to all dimensions, or all systems, NMR has proven especially useful for dimensions in the range of tens of nanometers, where other techniques are often less revealing.

Ferroelectric properties of vinylidene fluoride copolymers

Abstract: Ferroelectric properties of copolymers of vinylidene fluoride with trifluoroethylene and tetrafluoroethylene are described with special interest in their polarization reversal and phase transition behavior. The ferroelectric phase consists of all-trans molecules packed in a parallel fashion while molecules adopt irregular TT, TG, T[Gbar] conformations in the paraelectric phase. In the ferroelectric phase, polarization reversal occurs at very high fields (> 100 MV/m) as a result of eventual 180° rotations of individual chain molecules around their axes. The switching time ranges from sec to nsec depending upon the strength of the applied field according to an exponential law with a particularly large activation field (∼ 1 GV/m). The value of the observed remnant polarization is consistent with prediction from a simple dipole sum implying a minor contribution from the Coulomb interaction. The ferroelectric-to-paraelectric transition appears most clearly for copolymers containing 50-80 mol% vinylide...

Molecular dynamics of solid polymers as revealed by deuteron NMR

Abstract: Pulsed deuteron NMR spectroscopy is described, which has recently been developed to become a powerful tool for studying molecular dynamics in solid polymers. It is shown that by analyzing the line shapes of2H absorption spectra and spectra obtained via solid echo and spin alignment, respectively, both type and timescale of rotational motions can be determined over an extraordinary wide range of characteristic frequencies, approximately 10 MHz to 1 Hz. By applying these techniques to selectively deuterated polymers, motional mechanisms involving different segments of the monomer unit can be monitored. In addition, motional heterogeneities in glassy polymers can be detected. The information about polymer dynamics available now is illustrated by a number of experimental examples. The chain motion in the amorphous regions of linearpolyethylene is discussed in detail and it is shown that it can clearly be distinguished from the chain motion of an amorphous polymer above the glass transition, wherepolystyrene is used as an example. Localized motions in the glassy state are illustrated through the jump motion phenyl groups exhibit both in the main chain (polycarbonate) and as a side group (polystyrene). The latter polymers also serve as examples for detecting motional heterogeneity. Finally, the mobility in novel classes of systems,liquid crystalline polymers andpolymer model membranes as revealed by2H NMR are described.