ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Poly-γ-methyl-L-glutamate was obtained by the NCA method in a chloroform solution using trimethylamine as initiator. After polymerization, the solution was left alone for a long time at room temperature before spherulites formed. A film was casted very slowly from this aged solution in a desiccator at room temperature. We could then obtain spherulites in these thin films. This aging treatment was one of the main factors in making the spherulites. The morphological structure, optical properties, and the molecular orientation of the spherulites were examined by infrared spectroscopy, the x-ray method, and electron microscopy. After short aging periods (1-6 months), we could obtain positive spherulites. After much longer aging periods (6-10 months), negative spherulites were obtained. The conformation of the molecules in both spherulites was the same - the so-called α-helical conformation, but the orientation of the α-helical axis in the spherulites was just the opposite. In the positive spherulites, the helical axes oriented along the radius, but in negative spherulites, the helical axes oriented along the tangential direction. These positive and negative spherulites were constructed with microfibriles the diameters of which were about 45-67 A. The orientation of these microfibriles in the spherulites was just the same as the α-helical axes' orientation. These microfibriles oriented by side-by-side association in making the layer structure in the spherulites so that the α-helical axes were aligned parallel to these layers. Also, no evidence was observed of the presence of the so-called folding orientation of these α-helical molecules or microfibriles, as was pointed out in the case of polyethylene. From these results, we know that the crystallization habits of helical molecules, such as polypeptides, were different from those of polyethylene. The helical axes of the polypeptide molecules were not oriented perpendicular to the layer surface of the spherulites, but parallel to the layer surface. The crystallization mechanism of polypeptide was not by the so-called folding mechanism, but by the side-by-side crystallization mechanism.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1964.100020524
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