Dimensionless plot analysis: A new way to analyze functionalized microgels

A novel dimensionless plot strategy is developed in which multiple, independently measured macroscopic variables characterizing the same microgel phase transition are reduced onto a zero-to-one scale and simultaneously plotted. This strategy allows for direct comparisons to be made between changes in these variables over the phase transition, generating graphical "fingerprints" characteristic of specific radial and chain functional group distributions. This method is applied to study the swollen state properties of pH-induced phase transitions in five poly(N-isopropylacrylamide)-based microgels with significantly different but well-understood COOH functional group distributions. Radial functional group distributions identified based on this method match the distributions observed via electron microscopy, while the impact of functional group clustering on the ionization-driven swelling response can be directly identified. Change ratio plots in which the percentage changes of two different variables are plotted as mutual functions are also applied to generate semi-quantitative diagnostic parameters for probing radial functional group distributions and gaining insights into the mechanisms of gel phase transitions.