Crystalline-amorphous features fibril

An important feature of cellulose is its crystalline structure [180], which shows highly ordered crystalline domains interspersed by amorphous regions [177]. The high-crystallinity of cellulose fibrils renders the internal surface of the biopolymer inaccessible to hydrolyzing enzymes, as well as water. 

The following types of relaxation can be identified (i) Relaxations in the amorphous phase, e.g. the glass transition, (ii) Relaxations within the crystalline phase. These could be movements of defects (such as dislocations) or cooperative movement of chains, (iii) Relaxations which occur in both the crystalline and the amorphous phases. Small differences in the relaxation process may be found depending on which phase is involved, (iv) Relaxations involving large-scale features of the crystalline morphology. Relaxations of this type might involve shear deformations between lamellae or fibrils. 

The main characteristic feature of highly oriented semicrystalline homopolymers is the existence of a regular sequence of crystalline and amorphous layers placed normally to the orientation axis and giving rise to the long spacing in SAXS. They are linked by a large number of tie molecules. Another peculiarity of oriented polymers is the existence of microfibrils aligned parallel to the orientation axis, as concluded mainly from microscopic observations. Farther, it is known that the amorphous phase is situated mainly inside the fibrils between the crystalline lamellae (intrafibrillar amorphous phase) y whereas a relatively small amount exists between the fibrils interfibrillar amorphous phase). The latter equals 10-15% for poly (ethylene terephthalate) [9] and PBT [10]. 

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