NMR studies of molecular mobility in uniaxially stretched oriented polymers

摘要: The effect of elasticlike uniaxial tension on molecular mobility in polymers have been studied over a wide temperature range using the broad-line NMR technique. studies were carried out oriented semicrystalline samples nylon 6, poly(ethylene terephthlate), polypropylene, polyethylene, polyoxymethylene, poly(vinyl alcohol), and polytetrafluorethylene. Above low-temperature transition spectra are reversibly transformed under tension. Increases second moments attributed to weaker motion stressed polymers. only exception is which reverse, i.e., enhancement mobility, can be observed certain range. In stretched above glass narrow component decreases, thus indicating inhibition micro-Brownian motion, phenomenon we call “mechanical vitrification.” Such mechanical vitrification proved result from reduction number possible tie-chain conformations non-crystalline regions not closer packing chains. discussing results use experimental data gauche isomers (on average, one link trans state causes at least five methylene groups main chain become immobile). used for more accurate definition mechanisms different temperatures. A method evaluation energy intermolecular interactions hinder small-scale low suggested.