Fibrillar crystals of isotactic polystyrene. I. Morphological aspects
作者:
A.G. Wikjord,
R.St. John Manley,
期刊:
Journal of Macromolecular Science, Part B
(Taylor Available online 1970)
卷期:
Volume 4,
issue 2
页码: 397-412
ISSN:0022-2348
年代: 1970
DOI:10.1080/00222347008212510
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Fibrillar crystals have been prepared by the crystallization of isotactic polystyrene from stirred solutions in 1,3,5-trimethylben-zene and cyclohexanol. Similar microfibrils have been prepared in the nascent state by the polymerization of styrene in 1,3,5-trimethyl-benzene with a heterogeneous Ziegler-Natta catalyst. The microfibrils varied in width between 140 and 250 Å and were characterized by periodic lamellar overgrowths which were believed to give rise to a discrete X-ray reflection having a d-spacing of 90 A. Thermal analysis suggested that high growth temperatures favored greater crystal perfection. During crystallization from stirred cyclohexanol solutions, a fractionation of high molecular weight chains occurred which was more efficient at higher crystallization temperatures. In comparison to crystallizations under quiescent conditions, a marked facility of the crystallization process was observed in the formation of stirrer-crystallized and Ziegler-Natta polystyrene. The ease of crystallization of the shear-regenerated and nascent microfibrils has been related to a reduction in the free energy of nucleation. Mechanisms have been proposed to account for a favored nucleation process.
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