Study on new polymer crosslinking agents and their functional hydrogels

Functional hydrogels have been used in various fields, but their development might be limited due to the finite variety of crosslinking agents, complicated functional monomer design and synthesis. To address these issues, a new series of polyamino acid-based multifunctional coupling agents, polyaspartic hydrazide-co-aspartic acid polymers (PHAs), were synthesized through a very simple ring-opening reaction in a short time. The structures of these polymers with gradient content of acylhydrazine and carboxyl groups were characterized through 1H NMR and FT-IR. The molecular weight of PHAs and the content of acylhydrazine and carboxyl groups were tested through GPC and colloidal titration method, respectively. By crosslinking between acylhydrazine groups of PHA crosslinkers and carbonyl of diacetone acrylamide (DAAM), DAPHA hydrogels with different PHA structures and contents were prepared from acrylamide (AAM), DAAM and PHA crosslinkers in a one-step reaction. Furthermore, through coordination between pendant carboxyl of PHAs and metal cations, DAPHA-Fe3+ hydrogels were prepared by soaking DAPHA hydrogels in ferric chloride solution. And the structures and mechanical properties of both DAPHA and DAPHA-Fe3+ hydrogels were investigated. Moreover, taking advantage of the complexation and dissociation of DAPHA hydrogel with Fe3+, their shape memory properties were investigated. Finally, magnetic DAPHA-Fe3O4 hydrogels were prepared through in-situ precipitation method, and their magnetism has been studied.