Amphiphilic polymer model networks synthesized by different hetero-complementary coupling reactions of Tetra-PEG and Tetra-PCL stars

Amphiphilic co-networks (ACN) are synthesized by hetero-complementary reaction of hydrophilic tetra-PEG and hydrophobic tetra-PCL stars. Networks obtained via three different cross-linking reactions are compared. This concerns two oxazinone-amine reactions with different reaction rates and the carboxy-amine reaction activated by CDI. Reaction parameters such as temperature, concentration, and solvent, as well as the molar masses of the stars used, are comparable. For the ACNs, equilibrium volume swelling degrees (Qv) are determined. Information about the micro structure of the ACNs (connectivity distribution) is obtained from proton low-resolution multiple-quantum NMR investigations. Although the coupling reactions differ distinctly in terms of reaction speed and coupling mechanism, ACNs with similar properties are obtained. In multiple determinations with de- and re-swelling cycles, a reduction in the Qv values is observed, which indicates that the reaction progresses in the dried state of the samples. The connectivity distributions determined by multiple quantum NMR show for all ACNs distinct deviations from a statistical distribution. This can be seen by the fact that double and triple links are formed preferably between neighboring stars. This distinguishes ACNs from tetra-PEG networks described in the literature, for which a statistical distribution is found. The possible reason for these deviations is discussed.