Microstructure and morphology of self-assembling multiblock poly(ethylene-1-butene)-n copolymers in solution studied by wide-Q small-angle neutron scattering and microscopy

Abstract

Multiblock ethylene-1-butene copolymers (PEB-n) with graded ethylene content (where n is the number of ethyl branches per 100 backbone carbons) represent efficient cold filter plugging point (CFPP) depressants for crude oils and middle distillates. The aggregation behavior and the interaction with wax molecules of a tetrablock PEB-2.6/PEB-6.0/PEB-10.9/ PEB-13.2 and triblock PEB-6.5/PEB-8.9/PEB-10.1 copolymers in decane solutions were investigated over a wide temperature range by combining different small-angle neutron scattering techniques and optical microscopy. The experimental results revealed in the decrease of temperature formation and evolution of multisized structural levels showing a hierarchical organization on the length scale from 1 nm up to 10 μm. One-dimensional polymer aggregates arising as initial structures associate and branch that lead to the occurrence of complex macroaggregates with diffusive interfaces and sizes of several microns. The one-dimensional copolymer structure shows longitudinal density modulation and micellar-like substructures in neat polymer solutions. When wax is added, this structure becomes more homogeneous in decrease of temperature as a consequence of the cocrystallization of wax and copolymer. The wax crystallization in board-like objects of much smaller size than required by the CFPP criterion of oil and refinery industry (filter mesh size of 45 μm) is templated and controlled by the assembling features of the crystalline-amorphous PEB-n multiblock copolymers.