Abstract
Stackable gels comprised of layers of dissimilar polymers were synthesized by combining conventional free radical polymerization (FRP) and atom transfer radical polymerization (ATRP) using two approaches: (i) polymerization of a pre-gel solution containing a monomer and cross-linker introduced on top of a previously prepared gel, and (ii) simultaneous polymerization of two immiscible pre-gel solutions remaining in contact. All permutations of FRP and ATRP yielded single-piece, connected, amphiphilic gels regardless of the order of polymerization. Furthermore, multi-layer ATRP gels combining different polymers were synthesized with the FRP layer as a gluing agent. A 10-layer amphiphilic stackable gel combining n-butyl methacrylate (BMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA), and a 10-layer stackable gel combining BMA, DMAEMA and di(ethylene glycol) methyl ether methacrylate (PEO2MA) were synthesized. This patching method, combining conventional FRP gels with ATRP ones, offers an efficient path to the formation of complex stackable gel architectures.
Highlights
Polymer gels constitute an important class of soft materials due to their wide range of chemical and mechanical properties
The stackable gels were successfully synthesized by combining atom transfer radical polymerization (ATRP) and free radical polymerization (FRP) layers
To overcome overcome this this limitation, limitation, an an FRP layer was used as a two layers prepared in amphiphilic, multi-layer gels were efficiently connected independent of theFRP
Summary
Polymer gels constitute an important class of soft materials due to their wide range of chemical and mechanical properties. Acylhydrazone dynamic bonds formed by condensation of the aldehyde and acylhydrazine groups between the macroscopic gels acted as ‘gluing’ agents This method allowed for reversible connections and relatively short reaction times, but it was applicable to a limited selection of monomers. One of the limitations of using consecutive ATRP polymerizations in the preparation of multilayered gels, revealed in our past studies, was the poor connectivity between the two layers if the polymerization was carried out in immiscible solvents [33] This limitation was not encountered when using the same solvent, dimethylformamide (DMF), for the two pre-gel solutions. Layers prepared by the variant of ATRP with low ppm Cu catalyst, known as ICAR (initiators for continuous activator regeneration) ATRP were successfully glued together using interlayers prepared by FRP [34,35] This combination of FRP and ATRP polymerization techniques offers an efficient strategy for the direct synthesis of flexible, multi-functional, and multi-layer materials
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