Synthesis and characterization of poly(aspartic acid) composite hydrogels with inorganic MCM-41 cross-linker

Abstract

A novel KPAsp/MCM-41 composite hydrogel was synthesised in an aqueous system from poly(aspartic acid) grafted with γ-aminpropyltriethoxysilane (KH550) (KPAsp) and the mesoporous molecular sieve MCM-41 (mobile composition of matters); here, inorganic MCM-41 particles were utilised as a direct cross-linker. The effects of different amount, average particle size of MCM-41, various salt solutions on the composite hydrogel swelling ratio were investigated. The composition and structure of the KPAsp/MCM-41 composite hydrogels were determined by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results indicated that MCM-41 addition could improve the physicochemical properties of the synthesised composites. At the amount of 10 wt% of MCM-41 (particle size, 462 nm) the swelling ratios of composite hydrogels prepared in distilled water and physiological saline reached 284 and 87 g/g (enhanced by 1.56- and 1.35-fold, respectively, compared with hydrogels without MCM-41). In chloride salt solution of 0.9 wt% concentration, the water absorbency of the hydrogels was increased in the following order Na+ > Ca2+ > Fe3+. The recorded FTIR spectra showed that MCM-41 nanoparticles are effectively introduced into the KPAsp network structure and form KPAsp/MCM-41 composite hydrogels. SEM images confirmed that introduction of MCM-41 inorganic particles into the organic network structure can optimise the pore morphology of the composite hydrogels. Thermogravimetric analysis showed that the thermal stability of the KPAsp/MCM-41 composite hydrogels significantly improves at 27 °C, which is an indication of successful introduction of MCM-41 into the hydrogels.