Journal ArticleDOI
Polymer decoration: The orientation of polymer folds as revealed by the crystallization of polymer vapors
TLDR
In this paper, a new technique of decorating the fold surface of polymer crystals is described, similar in methodology to gold decoration, but makes use of vapors of crystallizable polymers, principally polyethylene, as decorating material.Abstract:
A new technique of decoration of the fold surface of polymer crystals is described. It is similar in methodology to gold decoration, but makes use of vapors of crystallizable polymers, principally polyethylene, as decorating material. Upon condensation and crystallization, the highly anisometric decorating molecules become oriented parallel to the fold direction. They build up small crystalline lamellae which, seen edge-on, appear as elongated rods and can be easily observed by conventional transmission electron microscopy. This decoration technique reveals the sectorization of polymer single crystals grown from solution. It can be used to determine the local fold orientation (with a resolution of ca. 10 nm) of polymers crystallized under a wide range of conditions, including crystallization from the bulk. The technique reveals that under all crystallization conditions so far investigated the outermost part of the polymer fold surface is relatively ordered, and the folds and/or loops are, as a rule, oriented nearly parallel to the macroscopic growth front.read more
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Journal ArticleDOI
Polymorphism in isotactic polypropylene
TL;DR: In this article, the authors summarize the studies devoted to the elucidation of the different crystal structures and crystal morphologies and the different conditions favouring one or the other of the polymorphs of isotactic polypropylene.
Journal ArticleDOI
Epitaxial crystallization of polymers on organic and polymeric substrates
J. C. Wittmann,Bernard Lotz +1 more
TL;DR: In this paper, the authors propose an epitaxie polymere-polymere-substrat organique (polymer-polymer) for the preparation of polyethylene substrats.
Journal ArticleDOI
A critical assessment of unbalanced surface stresses as the mechanical origin of twisting and scrolling of polymer crystals
Bernard Lotz,Stephen Z. D. Cheng +1 more
TL;DR: In this paper, the authors reviewed evidence that has accumulated in favor of lamellar twist induced by surface stresses that result from differential congestion of fold surfaces, as suggested initially (in 1984) and advocated for many years by Keith and Padden.
Journal ArticleDOI
The role of metastability in polymer phase transitions
TL;DR: A review of the role of metastability in phase and phase transition behaviors can be found in this paper, where the authors describe the general principles of metastable in polymer phases and phase transitions and provide illustrations from current experimental works.
Journal ArticleDOI
Banding in Polyethylene and Other Spherulites
H. D. Keith,F. J. Padden +1 more
TL;DR: In this paper, the authors analyzed the factors leading to twisting crystallographic orientation in banded polymer spherulites, both from the standpoint of qualitative morphology and of more quantitative measurement and calculation.
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