Study of gradient copolymers auto-association in supercritical CO2 thanks to synchrotron and in-house small-angle X-rays scattering measurements

•In-house SAXS measurements are possible thanks to specific HP cell and 17 keV X-rays.•Copolymers with relevance in the field of metal recycling have been studied.•CO2-phobic part of the copolymer tends to favour nano-object aggregation.

Specific comblike gradient copolymers made of metal-complexing CO2-phobic units and fluorinated CO2-philic units were designed to study their auto-association when solubilised in supercritical CO2 (scCO2). This paper shows that in-house SAXS measurements on scCO2 systems are now possible thanks to both high-energy X-rays and specific high-pressure cell designed with beryllium windows. The copolymer system poly(1,1,2,2-tetrahydroperfluorodecylacrylate-co-4-(diphenylphosphino)styrene), poly(FDA-co-DPPS) was compared to homopolymer poly(FDA)-SH and more classical molecule, C8F17C2H4-SH (RfSH). The results show that the presence of the CO2-phobic part of the copolymer does not necessarily tend to favour auto-association due to the comblike gradient design. However, this CO2-phobicity favours inter-object correlation leading to aggregation.

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