Synthesis and viscoelastic properties of acrylated hyperbranched polyamidoamine UV-curable coatings with variable microstructures

Exact probe of microstructure of hyperbranched polymers is not either experimentally or theoretically a simple task. A simple yet useful approach was performed here to evaluate structure-performance relationships in hyperbranched polyamidoamine UV-curable (HPAMAMU) coatings. A series of homologous of HPAMAMU having hexamethylenediamine as core were synthesized via a two-step method, and then acrylated with glycidyl methacrylate. Formation of functional groups was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopic analyses. To uncover structure-performance relationship, HPAMAMUs with different branching features were synthesized by reacting methyl acrylate and hexamethylenediamine monomers in the first step in 1:1, 1:2, 1:3 and 1:4 ratios. Rheological and calorimetric analyses simply provided with a deeper understanding of molecular-scale changes. Then, 7 wt.% of each hyperbranched polymer was added to a system of UV-curable epoxy methacrylate to probe the performance of the resulting coatings in terms of thermal, adhesion, physical and mechanical properties. The presence of such hyperbranched polymers decreased the glass transition temperature of HPAMAMUs, but improved adhesion and flexibility of hard and brittle epoxy acrylate coatings. Particular attention was paid to speculate change in properties in terms of structural evolutions.