Co-crystallization of poly(ethylene-butene) copolymers and paraffin molecules in decane studied with small-angle neutron scattering1

PEB-n semicrystalline poly( ethylene - butene) random copolymers may become important in industrial applications because of their capability to modify the paraffin crystals and to improve the viscoelastic properties of crude oil and refined fuel. The copolymer - paraffin interaction is rather complex and is not yet understood. Therefore, these polymers may also be of much interest in basic research. Systematic small-angle neutron scattering investigations of different polymer - paraffin systems have shown that PEB-n copolymers are selective in their paraffin-modification capacity, depending on the crystalline degree which is tuned by the number 'n' of ethyl side branches/100 backbone C atoms. Two mechanisms of polymer - paraffin interaction have been identified: on the one hand, co-crystallization of the paraffin and copolymer within thin platelets occurs as a consequence of a good fit between the self-assembling properties of the investigated polymer/paraffin pairs (PEB-7.5/C-36 and PEB-11/C-24); on the other hand, primordial polymer aggregates act as a template for a subsequent paraffin crystallization when the polymer has a higher self-assembling point (PEB-7.5/C-24) than the paraffin. Both mechanisms were found for the PEB-7.5/C-30 mixture.