Nanoparticles, microgels and bulk hydrogels with very high mechanical strength starting from micelles

We report a novel method to prepare nanoparticles, microgels and bulk hydrogels starting from micelles formed by molecules of a nonionic surfactant, alkylphenol polyoxyethylene (10) ether (OP-10). The micelles can be stabilized under gamma-ray irradiation to form nanoparticles which have a similar size to that of the micelles. Microgels and bulk hydrogels can easily be obtained by controlling the reaction conditions of the grafting of a hydrophilic monomer acrylic acid (AA) onto the radiation-peroxidized micelles. The bulk hydrogels initiated and crosslinked by peroxidized micelles (pMIC hydrogels) are highly transparent, and they have very high compressive strengths, several to several tens of MPa at a strain of 0.95. The synthesis conditions such as irradiation time, OP-10 concentration and monomer concentration are optimized by measuring the compressive strengths and elastic moduli of the obtained gels. The as-prepared and swollen hydrogel samples seldom break during the compression tests even at a strain of 0.98. The hydrogels have excellent shape recoverability, they can restore their initial shapes immediately after the release of the load. The gels have an interesting oriented microstructure. By investigating the morphologies of the samples reacted for different times with SEM, the link between the polymerization process and the gel morphology has been established.