Adaptable Intelligent Filters of Dual Thermo- and pH- Responsive Filter Material

Abstract

In this study, the development of novel pH-responsive and dual thermo- and pH-responsive filter materials is described. The dual-responsive system combines poly(N-isopropylacrylamide) (PNIPAM) for temperature sensitivity and poly(acrylic acid) (PAA) for pH responsiveness, which offers dynamic filtration capabilities tailored to environmental changes. PNIPAM is a thermo-responsive polymer that undergoes significant conformational changes in response to temperature variations. The present work integrates PNIPAM's temperature sensitivity with the pH-responsive properties of PAA, a versatile polymer widely recognized for its ability to change its conformation in response to pH variations. The dual materials developed here undergo conformational changes at specific temperatures and pH levels, modifying their hydrophilicity, pore size, and permeability. In particular, when exposed to higher temperatures, PNIPAM transitions from a hydrated, expanded state to a dehydrated, collapsed state, directly influencing the flow rate and selectivity of the filter medium that comprises it. On the other hand, PAA responds to pH changes by ionizing or deprotonating, causing swelling or shrinkage that alters the filtration performance of the media with embedded PAA. This dual responsiveness allows for the development of advanced filtration systems that can adapt to varying environmental conditions, optimize the capture of specific contaminants, and reduce fouling.