Structure–Property Relationships of Water‐Free Photocurable Composites Reinforced With Unmodified Starch in an Ionic–Hydrogen‐Bonded Reactive Medium

Abstract

This study investigates a water‐free photocurable composite system based on an ionic methacrylic acid (MAA)–triethanolamine (TEOA) reactive medium that includes starch as a bio‐based filler. Without pretreating the starch, the system incorporated starch as a physically dispersed filler with limited interfacial bonding in an ionic–hydrogen‐bonded reactive medium via an in situ system. Density, phase separation, mechanical properties, thermal stability, viscoelastic behavior, and morphology were evaluated in relation to starch loading and coupling agents. The findings show that starch improves hardness and density, with tensile strength reaching up to 3.2 MPa. However, it also leads to phase separation, which limits the overall performance of the composite structures. A heterogeneous network structure with broad relaxation behavior is suggested by DMA results, while gel fraction results indicate a high degree of crosslinking. This study suggests how dispersion and network homogeneity influence overall material performance.