Structurally-defined semi-interpenetrating amphiphilic polymer networks with tunable and predictable mechanical response

The synthesis of structurally-defined semi-interpenetrating amphiphilic networks is realized by employing an easy and versatile synthetic concept based on the encapsulation of well-defined hydrophobic linear polymer chains within a structurally-defined 1,2-bis-(2-iodoethoxy) ethane (BIEE)-crosslinked hydrophilic polymer network. Both, the hydrophobic (poly(n-butyl methacrylate)) and hydrophilic poly(2-(dimethylamino) ethyl methacrylate) linear chain precursors to the networks have been synthesized by Reversible Addition Fragmentation chain Transfer (RAFT) polymerization. A series of BIEE-crosslinked amphiphilic semi-IPN networks was prepared by retaining the network hydrophilic content and varying only the hydrophobic content from 0-50% wt. The mechanical properties of the resulting networks containing different loadings of the encapsulated hydrophobic linear chains were tested under compressive loading conditions in their aqueous swollen state. A nonlinear hyperelastic constitutive equation was used to predict the elastic response of all network structures demonstrating that for low poly(n-BuMA) loading (i.e. up to 10% wt), no change in the materials' mechanical response is observed whereas for greater loading percentages (i.e., 35% and 50%) the networks become stiffer. The present work creates new prospects in the development of amphiphilic semi-IPN polymer networks with controllable compositional and structural characteristics and predictable mechanical behaviour realized via mathematical modeling.