Facile fabrication of novel pH-sensitive poly(aspartic acid) hydrogel by crosslinking nanofibers

Stable pH-sensitive poly(aspartic acid) (PASP) hydrogel in nanofibrous structure was successfully manufactured. Firstly, polysuccinimide (PSI), the intermediate of PASP, was synthesized by thermal polymerization of aspartic acid and electrospun into nanofibrous mat. Secondly, imide rings on the main chains of PSI were partly opened to form crosslinking points by amino groups of ethylenediamine. Eventually, the residual imide rings of PSI were opened to obtain PASP hydrogel nanofibers by hydrolysis. The PASP hydrogel nanofibers exhibited significant hydrogel characteristics with fast swelling, high water absorption and pH-sensitivity. Durability test showed the morphological robustness and stability of PASP hydrogel nanofibers. The swelling ratio of pH-sensitive PASP hydrogel nanofibers ranged from 14.8   g/g to 128.1   g/g with the pH values increasing from 1.0 to 10.0.