Synthesis of Highly Ordered Amphiphilic Polymer Conetwork Hydrogels via the Topologically Precise Interconnection of Two Highly Incompatible Polymers.

Here, hydrophobic polyisobutylene and hydrophilic poly-(ethylene glycol), both of reasonably high molar masses, have been end-linked, yielding amphiphilic polymer conetwork (APCN) hydrogels that can self-organize in water into well-ordered lamellar structures. The cross-linking of hydrophobic and hydrophilic polymer segments produces networks that typically exhibit sphere-like nanodomains in water and in the bulk, but the orderly interconnection of relatively large and highly incompatible polymers leads to hydrogels that internally assemble into lamellae. This unprecedented result may be attributed to the weak force-field established by the presence of a minimal concentration of homogeneously distributed cross-links in the case of the present system, which must be contrasted to a higher concentration of randomly placed cross-linking points, which destroy long-range ordering in conventional APCN hydrogels. Significantly, the presently developed APCN hydrogels maintain good tensile mechanical properties, with their strain-at-break reaching a value of 800%. This study puts forward the design concepts for attaining highly ordered hydrogels, which would confer upon them better transport and mechanical properties and broaden their utility in biomedical and energy applications.