The mechanisms which have been suggested to explain the deformation of crystalline polymers are reviewed. Emphasis has been placed upon the type of information that can be gained from experimental observations and on the extent to which those observations are consistent with suggested deformation mechanisms and current ideas on polymer structure and morphology.

Deformation mechanisms in crystalline polymers

Enzymatic degradation behavior of porous silk fibroin sheets.

A survey of recent high-resolution solid-state 13C NMR studies is given to illustrate how and to what extent 13C chemical shifts of a variety of molecular systems are displaced upon conformational changes. Examples are taken from studies of alkanes, polysaccharides, polypeptides, and naturally occurring and synthetic ionophores, in which more than single conformations are available owing to either crystalline polymorphs or a variety of metal-ligand interactions. The magnitude of the conformation-dependent 13C chemical shifts are in many instances as large as 8 ppm and are well related to a set of torsion angles of nearby single bonds. The application of this concept to conformational characterization is also discussed.

Conformation‐dependent 13C chemical shifts: A new means of conformational characterization as obtained by high‐resolution solid‐state 13C NMR

Recent research on the yield behaviour of polymers is reviewed. Particular attention is given to the importance of the hydrostatic component of stress, the viscoelastic nature of the yield process, and the behaviour of oriented polymers.

Review: The yield behaviour of polymers

The chemical structure and the crystalline structures of Bombyx mori silk fibroin

In the preceding paper the results of electron microscopic examination on the precipitates Fcp and Fcplx are reported. The former was obtained from the aqueous solution of silk fibroin (bombyx mori) hydrolyzed by chymotrypsin, the later being obtained when the former was dissolved in cupri-ethylenediamine and dialyzed. Fcp and Fcplx showed the structures of beta-fibroin and alpha-fibroin, respectively.To examin further the structure of alpha-fibroin, the sedimented mat of Fcp 1x was prepared and submited to the X-ray diffraction measurements.A clear fiber diagram was not obtained from X-ray diffraction pattern of a Fcp 1x mat, but were led to assign the following rectangular unit cell to the alpha-fibroin: a=4.59 A (direction of hydrogen bonding), b=7.20 A, c=9.08 A (fiber axis), This unit cell includes one polypeptide chain and the polypeptide molecule may take a helical conformation of four-fold, where the residue translation should be 2.27 A.X-ray diffraction photographs of the mat of Fcp 1x and thin film adilute (0.1%) solution of regenerated silk fibroin shows long periods beginning with a spacing of 48.2 A as well as the ordinaly periods. At the present moment no definite relationship between the two kinds of the period is found. One plausible explanation would be that the log periods are caused by the globular structure formed by folded molecules.Infrared absoption spectra indicates the existence of beta-structure for the Fcp. In Fcp 1x, no sign of the presence of alpha-helix is detected, but the feature of the spectra is close to that of the random coil structure.

THE STRUCTURE OF SILK FIBROIN-α

When well oriented and crystallized high density polyethylene film was redrawn, slip deformation and twin deformation, the mode of which depends upon the redrawing angle to the original drawn structure, could be observed. When the redrawing angle is very small, single slips, the direction of which is [001] to the original drawn structure, and homogeneous deformation bands attached to them are usually observed. The [001] directions of slipped and unslipped regions are slightly at an angle to each other. As the redrawing angle approaches a right angle, kink bands can be observed. From these results we may conclude that the structure of this drawn polyethylene film is very similar to that of a single crystal or metal.

Slip deformation in drawn polyethylene films

Band structure in the hydroxypropylcellulose (HPC) specimen shear-deformed at liquid crystalline state has been examined by the X-ray diffraction, small angle light scattering and microscopic observation. There appeared the periodic band structure perpendicular to the direction of shear, when axially oriented liquid crystalline specimens were relaxed freely for several tens second. Band width, crystalline orientation in the band and light scattering from these band structures were investigated for thin-film from 50% HPC liquid crystalline solution.Hv scattering exhibited two-point patterns extending at right angle to bands, and the maximum of scattering intensity was observed from which the period of band was estimated. The obtained value, 3μm was twice of band width. Crystallographic C-axis, chain direction, in band were inclined about 40 degrees to the direction of shear and the direction of inclination changed alternately from band to band.

https://www.jstage.jst.go.jp/article/fiber1944/38/9/38_9_T375/_pdf

Band structure in shear-deformed hydroxypropylcellulose liquid crystalline solution

When aqueous solution of silk fibroin are acted on by chymotrypsin, a precipitate (Fcp) is formed. Its molecular weight is estimated at about 3, 000 by means of the titration of terminal amino acids. From the result of paperchromatography, it is ascertained that the Fcp is composed of the four amino acid residues of glycine, alanine, serine and tyrosine.When the Fcp is dissolved in cupri-ethylenediamine and dialyzed, a white precipitate (Fcp 1×) of about 80 weight percent of the original Fcp is obtained again.The X-ray powder diffraction patterns of the Fcp show that its structure is highly crystalline and resembles closely to the β-structure of fibroin proposed by ‘Shimizu’. The electron micrograph of the Fcp shows that small rod-shaped particles aggregate ramdomly. The X-ray diffraction patterns of the Fcp 1× resemble in α-structure of fibroin proposed by ‘Shimizu’ and show higher crystallinity than the Fcp. The electron micrograph of the Fcp 1× shows the spherulitic aggregates formed by the fibrillar single crystal.From the reciprocal lattice patterns on xy-plane estimated from the selected area diffraction patterns, it may be expected that α-structure of fibroin is orthorhombic and has the dimensions, 7.20A, 4.49A and C-axis (chain axis) perpendicular to xy-plane. Selected area micrograph shows that the planes correspond to plane distance 7.20A and 4.49A are oriented parallel to and perpendicular to the fibrillar axis respectively.

On the structure of silk fibroin under the enzymic hydrolysis

Electron microscopic observations of the deformation in compression of biaxially oriented nylon 6.10

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