Emerging Macromolecular Approaches to Pore Engineering and Interfacial Control Using Interpenetrating Polymer Networks: Recent Developments

The growth of the population and rapid industrialization have a critical impact on water quality. Pollution of water bodies by heavy metals, dyes, plastics, and pharmaceutical waste poses a significant hazard to human health and potentially leads to the release of carcinogenic, non-biodegradable toxins into the environment. The removal of pollutants in wastewater has been carried out by several methods, including filtration, adsorption, biological advanced oxidation processes, photocatalysis, electrochemical, and ion exchange. Interpenetrating polymer networks (IPNs), according to IUPAC, are materials composed of two or more polymer networks that are not covalently bonded and cannot be separated without breaking bonds. They offer capabilities beyond single-network systems, block copolymers, or polymer blends. Their dual-network design enables control over porosity, d-spacing, interfacial interactions, selectivity, and charge density, while minimizing creep and swelling. This results in membranes that maintain their structure when exposed to water and can withstand sustained high pressure over time. By carefully matching polymers based on surface energies and functionalities, IPNs create synergistic interfacial interactions (such as electrostatic forces, hydrogen bonding, π-π interactions, and van der Waals forces) that stabilize the interface, boost mechanical strength, and allow precise tuning of pore architecture for desired transport properties. These features lead to performance enhancements, including antifouling and antibacterial abilities, selective removal of heavy metals and dyes, improved desalination with a better permeability-selectivity ratio, and even microplastic removal through pore engineering and tailored interfacial chemistry. Additionally, IPNs serve as stable matrices for integrating nanofillers that do not leach out. They can be processed using scalable methods, such as phase inversion, interfacial polymerization, ultraviolet irradiation, and thermal polymerization. Overall, IPNs offer a more promising platform compared to conventional polymer systems, especially for long-term, high-capacity water treatment applications. This review paper provides insight into the latest developments of IPNs, various surface modification methods implemented to optimize their performance, and developments in pore engineering and interfacial control strategies. The review explored successful water purification, acid recovery, removal of microplastics and pathogens, heavy metal adsorption, removal of dyes and volatile organic compounds, and rare-earth metal extraction using IPN membranes, with a broader objective of sustainability.