Topological Mechanism of Nucleation of Cyclic Polyethylene(Knots and soft-matter physics: Topology of polymers and related topics in physics, mathematics and biology)

Abstract

In order to clarify the effects of entanglement species on nucleation of polymers, we studied the nucleation rate I of cyclic and linear polyethylenes (C-PE and L-PE) from the melt as a function of degree of supercooling ΔT by means of polarizing optical microscope. We prepared several C-PEs with different weight average molecular weights M_w=4600-114800. I of all the sample were obeyed the equation, I=I_0exp(-C/ΔT^2). I_0s of C-PE with M_w=114800 and L-PE with M_w=35400 were almost the same. This indicates that C-PE is easier to nucleate than L-PE due to lack of knot entanglements. On the other hand, Cs for C-PE significantly increased with increasing M_w. This tendency is quite different with L-PE previously reported. The increase of C indicates that folding regularity of end surface of nucleus increases. Since topological constraint of C-PE arose from the lack of chain ends is relatively decreased with increasing M_w, it was implied that the nucleation behavior of C-PE approaches that of L-PE.