PHASE-TRANSITIONS OF POLY(OCTYL ISOCYANATE) - SIMULATION OF THE EPR-SPECTRA OF A DRY SPIN-LABELED POLYMER

The basic ideas of a novel way to simulate electron paramagnetic reson ance (e.p.r.) spectra of spin-labelled polymers are described. The sim ulation method has been applied in the analysis of the e.p.r. spectra of dry spin-labelled poly(octyl isocyanate) (POIC). POIC is a semiflex ible, helical polymer capable of forming a thermotropic Liquid crystal line phase. The spectra of a fractionated POIC sample have been analys ed in order to find out how the mobility and flexibility of the chain change with increasing temperature, when the polymer turns from the se micrystalline into the liquid crystalline state. The results imply tha t the sample contains both helical and random chain sequences through the whole temperature range studied. However, the proportion of the he lical sequences is dependent on temperature. (C) 1998 Elsevier Science Ltd. All rights reserved.