Structural, optical and biointerface properties of two semi-alicyclic polyimide precursors have been investigated. The refractive index values are around 1.6, reflecting the impact of the polymer chain polarizability. The presence of the ethylene groups in the diamine residues leads to a higher transmittance of appreciatively 80 %. Optical energies describing absorption limits were determined using the approach of Tauc for amorphous materials, reflecting similar shape of the absorption edges with amorphous materials. The polymer with ethylene groups in the diamine moieties has an optical band-gap of 3.09 eV, indicating a lower probability of optical absorption transitions and thus a good transparency. Biointerface properties, namely the interactions occurring at polymer-blood interface, have been evaluated from the balance between the forces of adhesion and cohesion, before and after plasma treatment. Plasma active species enhance polymer surface polarity over 50 % so that the interfacial blood/sample tension is low enough to indicate a good hemocompatibility.