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Keywords:

  • hydrogels;
  • radical polymerization;
  • self-organization;
  • stimuli-sensitive polymers;
  • thermoresponsibility

Abstract

Summary: The N-isopropylacrylamide (NIPAM) and N,N′-dimethyl-(methacryloyloxyethyl) ammonium propane sulfonate (DMAPS) copolymer networks having monomer units with an opposite thermoassembling ability are synthesized and analyzed. The network composition is of crucial importance for their degree of swelling (Q) and Q-Temperature (T) dependences. After the Q normalization these dependences outline two classes of networks which hydrogels expel or imbibe water with T. The boundary network (with 0.39 mole fraction of DMAPS monomer units) defines a critical T (Tcr) at which Q is the same as that at the initial T (To), but with a structure organization, different than that at To. The hydrogels thermoreversibility at the stepped T change, and the salt effect on the Q-T dependences are demonstrated also.