Polymers with individually adjusted optical and rheological properties are gaining more and more importance in industrial applications, like in information technology. To modify the refractive index n , an electron-rich organic dopant is added to a commercially available polymer-based resin. Changes in viscosity for applications like inkjet printing can be achieved by using a comonomer with suitable properties. Therefore, we used a commercially available epoxy acrylate based UV-curable polymer matrix to investigate the influence of ethylene glycol dimethacrylate on viscosity and phenanthrene on refractive index. Refractive index was measured at a wavelength of 589 nm and 20°C using an Abbe refractometer. As a result, the change in viscosity decreased linearly from 47 Pa·s to 4 mPa·s, which is a more suitable region for inkjet printing. However, the refractive index decreased, at the same time, from 1.548 to 1.514. On adding phenanthrene, the refractive index increased linearly from 1.548 up to 1.561. It was shown that both viscosity and refractive index can be successfully adjusted in a wide range depending on desired properties.