This deposition contains the data and analysis (Jupyter notebooks) detailed in “From Hofmeister to hydrotrope: Effect of anion hydrocarbon chain length on a polymer brush”. All Jupyter notebooks have also been converted into PDF files for ease of viewing. All data and code (notebooks) required to reproduce the analysis can be found within the “supporting_data_analysis.zip” archive. This archive contains four sub-directories: Computional_data Optimised geometry files (.xyz) for all short chain fatty acid (SCFA) anion-solvent and anion-NIPAM fragment structures. Summary of analysed data (“SAPT_computational_data.xlsx”) describing the different interaction energies between a SCFA anion-NIPAM fragment and anion-solvent: electrostatic, exchange, induction, dispersion and total interaction energy contributions. Ellipsometry Data directory containing all raw ellipsometry data. “refellips_Dry.ipynb” and “refellips_Spectroscopic_SL.ipynb” notebooks to reproduce the analysis of a dry (solid-air) and hydrated (solid-liquid) polymer brush, respectively. A spatial map of the polymer brush used for spectroscopic ellipsometry data analysis: “PNIPAM_brush_spatial_map.png”. “Ellipsometry_sigmoid_fitting.ipynb” notebook and “Water_data.csv” file for the demonstration of the extraction of a thermotransition temperature from an ellipsometry dataset. Relevant plotting tools can be found in the refellips repo. Neutron_reflectometry Data directory containing all relevant reduced reflectivity profiles from the Platypus reflectometry at ANSTO. “refnx_dry.ipynb”, “refnx_D2O.ipynb” and “refnx_SCFA_electrolytes.ipynb notebooks required to reproduce the analysis pertaining to a dry, polymer brush and a brush exposed to pure D2O and various SCFA electrolytes, respectively. Additional code required to model the hydrated polymer brush and various plotting tools can be in the refnxtoolbox repo. QCMD_data Data directory containing all processed QCM-D data (.csv)