Ultraviolet (UV)-Curable Amide Imide Oligomers

We have prepared two blends of ultraviolet (UV)-curable oligomers, based on a reaction of cyclic dianhydrides with (omega)-hydroxysubstituted acrylate and with isophorone diisocyanate (IPDI). Each reaction was solventless and performed in one pot at a temperature no greater than 90 °C. We used benzene-1,2,4,5-tetracarboxylic acid dianhydride (PMDA) and benzophenone-3,3ʹ,4,4ʹ-tetracarboxylic dianhydride (BTDA) as cyclic anhydrides. Dianhydrides were used in both reactions, in the same molar concentration. Oligomers based on PMDA are designated as P, whereas oligomers based on BTDA are designated as B. Caprolactone-modified acrylate Tone M100 (from Dow) was used as a hydroxyl acrylate. Infrared (IR) and nuclear magnetic resonance (1H and 13C NMR) allowed the structure of each blend of oligomers P and B to be determined. These two oligomers are poly(imide amide) end-capped by Tone M100. There is also an ester link formed between the anhydride and the alcohol (Tone M100). Oligomer B has a remarkable property: it is self-initiating, i.e., it does not require an addition of any photoinitiator to be cured by UV light. This property apparently is due to the presence of a benzophenone fragment in its structure. Moreover, B can serve as an initiator for other free-radical UV-light-induced curing of acrylated and/or methacrylated oligomers being added in a concentration of 5.0 wt % and, in some cases, as low as 1.0 wt % to a formulation. Mechanical properties of cured P and B were studied. Because of the presence of an imide fragment, both P and B demonstrate good high-temperature performance; they manifest an increase of a tensile strength at break after aging at high temperature.