Synthesis of well-defined cross-linkable zwitterionic macromolecular building blocks for hydrogels

Abstract

A modular synthesis platform for cross-linkable polyzwitterions has been achieved. Therefore, atom transfer radical polymerization (ATRP) was used to establish polymers, mainly based on dimethylaminoethyl methacrylate (DMAEMA), with defined molecular weights and low polydispersity index. 2-Hydroxyethyl methacrylate (HEMA) was introduced via copolymerization with DMAEMA without changing the ATRP reaction conditions. Dimethylaminoethyl groups in PDMAEMA were either partially or completely sulfobetainized with 1,3-propane sultone, resulting in materials with different fraction of poly(sulfobetain methacrylate) (PSBMA), with only small deviation compared to target values set by stoichiometry of reactants. Further modification of PSBMA-co-PDMAEMA with 3-bromopropylamine led to PSBMA-co-PAPDMAEMA, a primary amine containing polyzwitterion, while reaction with allyliodide led to PSBMA-co-PADMAEMA, an allyl containing polyzwitterion. Rheological measurements were used to prove the ability to cross-link the building blocks with commercially available cross-linkers containing epoxy or thiol groups. Gelation temperatures for the different coupling mechanisms (amine-epoxy, hydroxyl-epoxy, ene-thiol) were in the range of 40 °C to 50 °C. This proof-of-feasibility is the basis for further development of tailored and stable hydrogels, for instance as antifouling coatings.