Soft and responsive: rheological insights into PNIPAM based microgels and applications

In this Review, we synthesize and critically evaluate past and recent findings on the rheology of microgels based on poly(N-isopropylacrylamide) (PNIPAM), versatile soft materials with tunable properties, providing a comprehensive analysis of their flow behaviour. Differences and similarities are pointed out depending on their structure: homopolymeric, core-shell, copolymeric and interpenetrate polymer networks microgels. We discuss rotational and oscillatory shear rheology measurements and examine the influence of crosslinker density, temperature, pH, and polymer concentration. Additionally, we highlight the practical implications in the knowledge of the rheological properties for applications. Through this review, therefore, we aim to create a solid starting point for all scientists involved in this research area with a powerful source identifying current challenges and potential future research directions.