Effects of Hydrophobe Addition Strategy and Seed Composition on Surfactant-Free Nanogel Formation for PFAS-Free Aqueous Coatings

PFAS-based food-packaging coatings are being phased out worldwide, requiring polymer particles that are aqueous-processable yet hydrophobic after drying. A hydrophobe-containing nanogel was designed by introducing IBOA and 2-OA into a crosslinked DMAAm/DEAEMA/TEGDMA seed via two-stage surfactant-free emulsion polymerization, to examine how the monomer-addition procedure and seed composition govern particle-size distribution and colloidal stability. From one seed batch, batch addition and starved feeding were compared by DLS, zeta-potential, and Turbiscan analyses. The seed particles showed pH-dependent zeta potentials and dispersion-medium-dependent apparent sizes, suggesting coupled swelling and ionization. Batch addition produced smaller apparent sizes and narrower distributions, whereas starved feeding gave larger sizes, broad aggregate-associated distributions, and a faster rise in the Turbiscan Stability Index, indicating that the local monomer-concentration history affects the final particle population. The roles of TEGDMA and IBOA were examined with composition-controlled seeds. Removing IBOA shifted the products from the several-hundred-nanometer regime to tens of nanometers, whereas moderate IBOA loadings preserved the larger particle population. This suggests IBOA is critical for growth of hydrophobe-rich nanogel particles but may also promote aggregation when unevenly incorporated. These results show that nanogel formation and colloidal stability are jointly governed by the monomer-addition procedure and the hydrophobe-crosslinker balance, whose reproducible control is a prerequisite for PFAS-free aqueous coatings. (Acknowledgement: This work was supported by the MOTIE (RS-2024-00430401, RS-2025-11162970) and undertaken at KNU, supported by the Regional Innovation System & Education (RISE) program through the Daegu RISE Center, funded by the Ministry of Education (MOE) and the Daegu Metropolitan City, Republic of Korea (2025-RISE-03-001).)