Study of the pre-melting behavior of polyethylene using Raman spectroscopy combined with two-dimensional (2D) correlation spectroscopy

The thermal behavior of polyethylene (PE) below its melting temperature (T-m) in relation to the density variation was studied by Raman spectroscopy combined with two-dimensional (2D) correlation analysis. The Raman spectra of homo and 1-octene copolymerized PEs were collected by varying the sample temperature from 30 to 100 degrees C, where pre-melting would occur. The spectral variation upon temperature perturbation was dependent on the density. For a deeper understanding of the thermal behaviors, 2D hetero correlation analysis was performed for the temperature-dependent Raman spectra of homo and 1-octene copolymerized PEs. The hetero-sample correlation analysis revealed that even below T-m, co-monomer side chains excluded from the crystalline lattice of the PE underwent partial fusion, indicating that such a conformational defect was closely related to the pre-melting of PE. (C) 2011 Published by Elsevier B.V.This research was supported by Basic Science Research Program through the National Research Foundation (NRF) funded by Ministry of Education. Science and Technology (No. 2009-0075648)