Microstructure studies nuclear magnetic resonance

Nuclear magnetic resonance (NMR) spectroscopy is another physical technique which is especially useful for microstructure studies. Because of the sensitivity of this technique to an atom s environment in a molecule, NMR is useful for a variety of microstructural investigations We shall consider the application to copolymers now and to questions of stereoregularity in Sec. 7.11... 

Since about 1960 nuclear magnetic resonance (NMR) spectroscopy has become an important tool for the study of chain configuration, sequence distribution and microstructure of polymers. Its use started from early broad-line studies of the one-set of molecular motion in solid polymers and passed through the solution studies of proton NMR, to the application of the more difficult but more powerful carbon-13 NMR methods to both liquids and solids. 

Carbon-13 nuclear magnetic resonance has become an in ortant tool with which to study the microstructure and molecular dynamics... 

Oguni.N., Komoda,T., Nomura,M., Tani,H. Studies on microstructure of polystyrene oxide and its a-deuterated derivatives with high resolution nuclear magnetic resonance spectroscopy (in preparation). 

Freeze-fracture TEM combined with nuclear magnetic resonance and quasielastic light scattering was used to study the microstructure of surfactant-water systems and dynamics of o/w and bicontinuous ME systems [41], The authors reported a rather abrupt transition from a discontinuous droplet (o/w) to bicontinuous (oil-and-water) microstructure occurring at low surfactant concentration, close to a three-phase region in the constructed phase diagram of pentaethylene glycol dodecyl ether, water, and octane [41],... 

In terms of characterizing the microstrac-ture of polymer chains, the two most useful techniques are infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy. Commercial infrared spectrometers were introduced after the end of the second world war and quickly became the workhorse of all polymer synthesis laboratories, providing a routine tool for identification and, to a certain degree, the characterization of microstructure (e.g., the detection of short chain branches in polyethylene). In this regard it can no longer compete with the level of detail provided by modem NMR methods. Nevertheless, IR remains useful or more convenient for certain analytical tasks (and a powerful tool for studying other types of problems). So here we will first describe both techniques and then move on to consider how they can be applied to specific problems in the determination of microstructure. 

Petiaud, R., Pham, Q.T., 1985. Polychloroprenes 1. Study of the microstructure using H-1 nuclear magnetic resonance. J. Polym. Sci. Part A Polym. Chem. 23 (5), 1333-1342. 

Herein we present a detailed study on the influence of the chemical and physical properties of the polymers used to prepare the c/p coating formulation on hydration of the cement inside the coating. The water ingress into the c/p phase is followed by nuclear magnetic resonance, while the cement hydration and phase composition is monitored by X-ray diffraction. These results are compared to those of the microstructural analyses using scanning electron microscopy. The combination of the three methods allows a more detailed interpretation of the mechanical performance of the coated rovings. 

Schaefer et al. (19) studied the interphase microstructure of ternary polymer composites consisting of polypropylene, ethylene-propylene-diene-terpolymer (EPDM), and different types of inorganic fillers (e.g., kaolin clay and barium sulfate). They used extraction and dynamic mechanical methods to relate the thickness of absorbed polymer coatings on filler particles to mechanical properties. The extraction of composite samples with xylene solvent for prolonged periods of time indicated that the bound polymer around filler particles increased from 3 to 12 nm thick between kaolin to barium sulfate filler types. Solid-state Nuclear Magnetic Resonance (NMR) analyses of the bound polymer layers indicated that EPDM was the main constituent adsorbed to the filler particles. Without doubt, the existence of an interphase microstructure was shown to exist and have a rather sizable thickness. They proceeded to use this interphase model to fit a modified van der Poel equation to compute the storage modulus G (T) and loss modulus G"(T) properties. 

Gaze and Loucheux, ° using the vinyl acetate-MA pair, have also attempted to look at the influence of a CTC between comonomers on the microstructure of the products. Nuclear magnetic resonance spectra showed no differences in configuration between two MA-vinly acetate copolymers prepared in such a manner that a CTC would form in one system but not the other. Thermogravimetric studies did show some dilference, postulated to result from differences in the conformation of the ester group. Attempts were made to explain the differences by discussing a mechanism for the participation of the CTC formation in the copolymerization. 

Py-GC Fourier-transform (FT) nuclear magnetic resonance (NMR) spectroscopy is another complementary technique that provides more detailed information on the structure of polymers than does Py-GC alone. As an example of the application of this technique Leibman and co-workers [2] applied it to a study of short-chain branching in polyethylene (PE) and polyvinylchloride (PVC). The nature and relative quantities of the short branches along the polymer chains were determined, providing detailed microstructural information. Down to 0.1 methyl, ethyl, or w-butyl branches per 1000 methylene groups can be determined by this procedure. Other structural defects can also be determined, thus providing significant information on polymer microstructure that is not otherwise readily obtained. 

Now that all levels of the structural hierarchy within a fat crystal network are quantifiable (to various extents), as well as the amounts of solid fat within the network (by use mainly of pulsed nuclear magnetic resonance), it is important to relate these quantifiable parameters to rheological indicators such as the shear elastic modulus. One model to relate the microstructure to the shear elastic modulus was developed in colloidal physics by Shih et al. [57]. A brief chronology of the adaptation of this theory to the study of fat networks follows. 

A Nuclear Magnetic Resonance Study of the Microstructure of Poly (Vinyl Alcohol)... 

---