Housing tubes from the XXXX Chaetopterus sp.: biomaterials with exceptionally broad thermomechanical properties.

@entity3884 @entity15188 @entity12638 @entity2144 @entity5274
The housing tube material of the @entity15188 Chaetopterus sp. exhibits thermal stability up to 250  C, similar to other biological materials such as mulberry @entity12638 cocoons. Interestingly, however, dynamic mechanical thermal analysis conducted in both air and water elucidated the lack of a glass transition in the organic tube wall material. In fact, the viscoelastic properties of the anhydrous and undried tube were remarkably stable (i.e. constant and reversible) between -75  C and 200  C in air, and 5  C and 75  C in water, respectively. Moreover, it was found that hydration and associated-water plasticization were key to the rubber-like flexible properties of the tube; dehydration transformed the material behaviour to glass-like. The tube is made of bionanocomposite fibrils in highly oriented arrangement, which we argue favours the biomaterial to be highly crystalline or cross-linked, with extensive @entity3884 and/or covalent bonds. Mechanical property characterization in the longitudinal and transverse directions ascertained that the tubes were not quasi-isotropic structures. In general, the higher stiffness and strength in the transverse direction implied that there were more nanofibrils orientated at    45   and    65   than at 0   to the @entity5274 . The order of the mechanical properties of the soft-tough tubes was similar to @entity2144 and even some viscid silks. The complex structure-property relations observed indicated that the worm has evolved to produce a tubular housing structure which can (i) function stably over a broad range of temperatures, (ii) endure mechanical stresses from specific planes/axes, and (iii) facilitate rapid growth or repair.
