Amphiphilic polymer conetworks with ideal and non-ideal swelling behavior demonstrated by small angle X-ray scattering

Abstract

Amphiphilic polymer conetworks (APCNs) combine two incompatible properties within one material by featuring two interconnected independently swelling nanophases. To simultaneously address both properties, the APCNs need to be swellable in orthogonal solvents without changing their nanostructure. This has not been demonstrated yet. Two novel APCN families applying the macromeric cross-linker approach have been synthesized by cross-linking the hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) or poly(N,N-dimethylacrylamide) (PDMA), respectively, with the hydrophobic poly(2-(1-ethylpentyl)-2-oxazoline) (PEPOx). For the first time, the APCN PHEA-l-PEPOx could be proven to swell in two orthogonal solvents, water and n-heptane, retaining its nanostructure in a broad range of compositions by using small-angle X-ray scattering (SAXS). PDMA-l-PEPOx seems to show a similar behavior according to swelling experiments, but SAXS revealed that particularly the PDMA phase reversibly changes its nanostructure upon swelling. Thus, the structural integrity of APCNs upon swelling depends on the topology as well as the chemical nature of the polymer phases. Altogether, SAXS experiments are required and well suited to judge changes in nanostructure upon swelling of APCNs.