ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The principles of nuclear magnetic resonance, NMR, are briefly reviewed and the use of proton resonance for the study of segmental motion in solid high polymers is outlined. Studies of the temperature dependence of NMR spectra have shown that both completely amorphous and partially crystalline polymers exhibit NMR line narrowing processes at temperatures near the respective glass transition temperature due to increased segmental motion. The presence of small molecules, such as H2O or D2O in the polyamides, or a change of tacticity to a greater isotatic content, such as for poly(methyl methacrylate), is found to lower this line narrowing process on the temperature scale. Heating of polyethylene single crystal aggregates at temperatures somewhat below the melting point also leads to a decrease in temperature for this line narrowing process, presumeably due to the introduction of defects in the polymer crystals. In the ≤ 77°K to 200°K region numerous polymers having methyl and methyl group containing side chains are found to exhibit line width and second moment dispersions, attributed to methyl group rotation. If the methyl group is attached to a phenyl or ester side chain, methyl rotation takes place at 77° K and below.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760020115
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