Abstract
Amylose–glycerol films prepared by casting from solution were hydrated
to different water contents. Wide-angle X-ray diffraction analysis
suggested that the films were partially crystalline and contained the B
polymorph. At a given hydration level, the presence of glycerol did not
affect the extent of crystallinity or polymorphism of amylose. Proton
NMR relaxometry was used to study the effects of water and glycerol on
the molecular mobility of amylose. Spin–spin and spin-lattice relaxation
parameters suggested a step change in the mobility of amylose when
sufficient plasticiser, water and glycerol, was added to decrease the
glass transition temperature (Tg) such that it became equal to or smaller than the observation temperature (T), i.e. (T−Tg)≥0.
The mobility of amylose probed through the properties of the rapidly
decaying component of the spin–spin relaxation varied with temperature
in an identical fashion for films in the glassy state regardless of
their composition. In the rubbery state, the mobility of amylose
increased with increasing glycerol and water contents, i.e. with
increasing (T−Tg). The mobility of amylose
in the glassy state was best assessed through the spin-lattice
relaxation times which suggested that at a given (T−Tg),
the addition of glycerol leads to a decreased mobility probably through
its well documented antiplasticising role. The findings were discussed
in relation to documented changes in important physical properties of
amylose films such as elongation and gas permeability.
Original language | English |
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Pages (from-to) | 147-155 |
Journal | Carbohydrate Polymers |
Volume | 56 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2004 |
MoE publication type | A1 Journal article-refereed |
Keywords
- Amylose
- Molecular mobility
- NMR relaxation
- Glass transition