Nuclear magnetic resonance thermal transitions

The glass-transition temperatures for solution-polymerized SBR as well as ESBR are routinely determined by nuclear magnetic resonance (nmr), differential thermal analysis (dta), or differential scanning calonme-... 

Thermal analysis is capable of providing accurate information on the phase transition temperatures, degradation temperatures, heat capacity, and enthalpy of transition of polymers using comparatively simple DTA, DSC, and TG instruments. The measurement time is short compared with other techniques, such as viscoelastic measurement and nuclear magnetic resonance spectroscopy. Moreover, any kind of material, e.g., powders, flakes, films, fibers, and liquids, may be used. The required amount of sample is small, normally in the range of several milligrams. 

Solid-state nuclear magnetic resonance (NMR) has been extensively used to assess structural properties, electronic parameters and diffusion behavior of the hydride phases of numerous metals and alloys using mostly transient NMR techniques or low-resolution spectroscopy [3]. The NMR relaxation times are extremely useful to assess various diffusion processes over very wide ranges of hydrogen mobility in crystalline and amorphous phases [3]. In addition, several borohydrides [4-6] and alanates [7-11] have also been characterized by these conventional solid-state NMR methods over the years where most attention was on rotation dynamics of the BHT, A1H4, and AlHe anions detection of order-disorder phase transitions or thermal decomposition. There has been little indication of fast long-range diffusion behavior in any complex hydride studied by NMR to date [4-11]. 

Well logging Electrical surveys resistivity conductivity shale formation factor salinity variations Interval transit time Bulk density Hydrogen index Thermal neutron capture cross section Nuclear magnetic resonance Downhole gravity data After drilling... 

The most important experimental techniques in this field are structural analyses by both X-ray and neutron diffraction methods, and infrared and Raman spectroscopic measurements. Less frequently used techniques are nuclear magnetic resonance, both broad band NMR spectroscopy and magic angle spinning methods (MAS), nuclear quadrupole resonance (NQR), inelastic and quasielastic neutron scattering, conductivity and permittivity measurements as well as thermal analyses such as difference thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetry (TG and DTG) for phase transition studies. 

The modest pressures of 5 kbar (0.5 GPa) necessary to cause transitions to columnar phases in polymers make the design of apparatus using large specimens relatively straightforward and it is easy to accommodate associated characterization techniques such as thermal conductivity or nuclear magnetic resonance (NMR) probes. Much of the author s early work was with a piston-cylinder apparatus with a working length of 5 cm and a diameter of... 

In the majority of cases the compatibility of the polymers is characterized by the glass-transition temperature Tg, determined by methods such as dilatometry, differential scanning calorimetry (DSC), reversed-phase gas chromatography (RGC), radiation thermal luminescence (RTL), dynamic mechanical spectroscopy (DMS), nuclear magnetic resonance (NMR), or dielectric loss. The existence of two... 

The obtained polymer (Ma, 351 D) was confirmed to be the intended substance by infrared spectroscopy and nuclear magnetic-resonance spectroscopy and found to have a liquid crystal transition temperature of 135°C by thermal analysis. 

The numerical value of the glass-transition temperature depends on the rate of measurement (see Section 10.1.2). The techniques are therefore subdivided into static and dynamic measurements. The static methods include determinations of heat capacities (including differential thermal analysis), volume change, and, as a consequence of the Lorentz-Lorenz volume-refractive index relationship, the change in refractive index as a function of temperature. Dynamic methods are represented by techniques such as broad-line nuclear magnetic resonance, mechanical loss, and dielectric-loss measurements. Static and dynamic glass transition temperatures can be interconverted. The probability p of segmental mobility increases as the free volume fraction / Lp increases (see also Section 5.5.1). For /wlf = of necessity, p = 0. For / Lp oo, it follows that p = 1. The functionality is consequently... 

---