The Mantid framework is a software solution developed for the analysis and visualization of neutron scattering and muon spin measurements. The framework is jointly developed by software engineers and scientists at the ISIS Neutron and Muon Facility and the Oak Ridge National Laboratory. The objectives, functionality and novel design aspects of Mantid are described.

The thermal stability of the electric field induced poled order in a new class of second-order optically nonlinear polymers, "donor-imbedded" side-chain polyimides containing no flexible connectors or tethers to the nonlinear optical (NLO) chromophore, is investigated. In these polymers, the electron-donor part of the chromophore is a diaryl-substituted amine that is incorporated as a part of the polymer backbone. The donorimbedded systems used in this study have exceptional chemical stabilities at elevated temperatures (350 degrees C) and impressive poled order stability at extremely high temperatures (300 degrees C). In both respects, they were significantly more stable than a true side-chain polyimide with a similar NLO-active chromophore covalently linked to the polymer backbone by a flexible tether group.

A series of symmetric and asymmetric poly(di-ra-alkylsilanes) have been investigated to assess their minimum-energy conformations, crystal packing, and, in the case of poly(di-n-tetradecylsilane) (PdnTDS), the conformation of the n-alkyl side chains. All of the polymers exhibit a thermochromic transition. X-ray diffraction measurements were made above and below the transition temperature to determine unit ceil parameters for both the ordered and disordered phases. A TGTG' silicon backbone conformation has been identified and found to occur routinely in symmetric poly (di-n-alkylsilanes) having side chain lengths between 9 and 14 carbon atoms. This unique conformation has previously been shown to be energetically feasible by molecular modeling calculations. Spectroscopic measurements on PdnTDS indicate that the side chains have predominantly an all-trans conformation. In all the polysilanes studied above their transition temperatures, it has been found that the backbone conformations become somewhat disordered, but the chains maintain a columnar arrangement on a hexagonal lattice. X-ray diffraction patterns from the disordered phases feature one strong and one or two weaker equatorial reflections. The d-spacing of the strongest reflection, which relates directly to the radius of the cylindrical molecular envelope, increases as the lengths of the n-alkyl side chains increase, apparently to accommodate the extra side chain length. The side chains themselves are disordered above the transition. Based on molecular models and the X-ray values of the cylindrical radii, the side chains are not extended but on average are shortened, presumably by the presence of one or more gauche bonds.

The orientational decay of chemically and thermally stable high-temperature chromophores doped into thin films made from polyimides and a variety of other polymeric hosts has been investigated. The chromophores are aligned using electric field poling and second-harmonic generation (SHG) is used to probe the decay of the electric field poling induced alignment. The decay rate of the SHG signal from films poled using both a corona discharge and side-by-side in-plane electrodes was measured. When electrodes are chosen so that the effects of charge injection are minimized, little difference has been observed between the orientational decays from films poled using the two methods for either an amorphous preimidized polyimide host or a highly anisotropic film poled during imidization. The films imidized during poling showed significant orientational stability at 250 °C for over 15 h after a fast initial partial decay. In addition, the decay of the SHG signal was measured as a function of temperature below the glass transition in a wide variety of different polymer host systems. The temperature dependence of the decay was found to be non-Arrhenius, but could be strongly correlated with the glass transition temperature of the guest-host system using an empirical relationship similar to the Williams–Landel–Ferry or Vogel–Tamann–Fulcher equation.

We describe here the preparation and characterization of the first processible nonlinear optical (NLO) polyimide where the chromophore is not incorporated using a flexible tether functionality. The polymer has a very high glass temperature and shows exceptional thermal and chemical stability. Poled samples also show outstanding orientational stability, consistent in part with the high glass transition temperature.