COMPTON-SCATTERING FROM PTFE - PROBING ELECTRON-CHARGE REDISTRIBUTIONIN POLYMER PHASE-TRANSITIONS

Compton profiles of polytetrafluoroethylene (PTFE) at room temperature and at higher temperatures up to and above the melting point are repo rted. For the first time, one has experimental evidence that thermally induced conformational excitations of the polymer chains are accompan ied by a charge transfer, related to the sigma- and pi-molecular orbit als (MO) of the C-F bond. It is argued that localization of the pi-MO related to the fluorine atom facilitates the translational movements o f the chains, while the weakening of the C-F bond and the transition f rom a crystalline to an amorphous phase are associated with delocaliza tion of sigma-MOs. [S0031-9007(98)06632-0].