Temperature-resolved derivative FTIR

The fine-structure of the 720/730 cm^-1 doublet of FTIR spectra has been evaluated by derivative spectroscopy as function of temperature on low-density poly(ethylene-co-1-octene). The pseudo-hexagonal mesophase in polyethylene, obtained at atmospheric pressure, is a non-equilibrium phase which develops preferred in presence of short-chain branches. An increasing concentration of short-chain branches slows down the ethylene-sequence selection process which is required for the formation of largely branch/defect-free orthorhombic crystals. Non-isothermal melt-crystallization at sufficiently high rate of temperature-change favors the development of metastable mesomorphic domains which likely form by entrapment of branches. It is proven that the mesophase transforms to the orthorhombic structure exclusively via the liquid phase. This revised version was published online in July 2006 with corrections to the Cover Date.