Poly(N-isopropylacrylamide)-interpenetrated chitosan coils working as nanoreactors for controlled silver nanoparticle growth

A new precursor (Ag+/CS/PNIPA) arranged as a nanogel (nanoreactor) is obtained from the aqueous mixture of Ag+, chitosan (CS) and poly(N-isopropylacrylamide) (PNIPA). A model synthetic system based on the thermally induced aqueous silver ions-CS reaction to form silver nanoparticles (AgNP) is used as a starting point to assess the PNIPA role as a thermo-sensitive additive of synthesis in a low content for the production of size-controlled AgNP. As expected, the PNIPA phase transition produced by the temperature increase leads to chitosan nanogel contraction, lowering the diffusion of ionic species. PNIPA behaves as a successful additive between 5.6 and 10.5 wt% of content blended with chitosan, noticeably improving AgNP nucleation during thermal treatment at 90 degrees C. Higher PNIPA contents are less effective in achieving size control and broader size distributions are generated. The PNIPA effect on the nanoreactor structure is characterized by rheology, modelled and analyzed against the AgNP morphology obtained.

Automated summary

A new nanogel (nanoreactor) is obtained by adding PNIPA to the Ag+/CS reaction system, which is used to produce size-controlled silver nanoparticles (AgNP). The thermo-sensitive nature of PNIPA improves the nucleation of AgNP. However, higher content of PNIPA reduces the effectiveness of size control and leads to broader size distributions.