Eur. Phys. J. E 8, 289-297 (2002)
DOI: 10.1140/epje/i2002-10015-3
Branched crystal morphology of linear polyethylene crystallized in a two-dimensional diffusion-controlled growth field
F. Zhang, J. Liu, H. Huang, B. Du and T. HeState Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun, Jilin, 130022, PRC tbhe@ns.ciac.jl.cn
(Received 15 March 2002 and Received in final form 29 April 2002)
Abstract
The branched crystal morphology of linear polyethylene formed at various
temperatures from thin films has been studied by atomic-force microscopy
(AFM), transmission electron microscopy (TEM), electron diffraction (ED)
pattern and polymer decoration technique. Two types of branched patterns,
i.e. dendrite and seaweed patterns, have been visualized. The fractal
dimension
of both dendrite and some of seaweed patterns was
obtained by using the box-counting method, although most of the seaweed patterns
are compact. Selected-area ED patterns indicate that the fold stems tilt
about 34.5
around the
b-axis and polymer decoration patterns show that
the chain folding direction and regularity in two (200) regions are quite
different from each other. Because of chain tilting, branched crystals show
three striking features: 1) the lamella-like branches show two (200)
regions with different thickness; 2) the crystals usually bend towards
the thin region; 3) the thick region grows faster by developing branches,
thus branches usually occur outside the thick region. The
branched patterns show a characteristic width
w, which gives a linear
relationship with the crystallization temperature on a semilogarithmic plot.
61.41.+e - Polymers, elastomers, and plastics.
68.55.-a - Thin film structure and morphology.
81.10.Aj - Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002
