Linear and hyperbranched reactive polymers containing diacetylene units with controllable refractive indices

A series of linear and hyperbranched poly(ether imides) containing diacetylene moieties are synthesized. Control of refractive index of the polymers can be achieved by varying the ratio imide/ether content. For the linear polymers the in-plane refractive index (nm) at 1550nm can be tuned between 1.5454 and 1.6313 by changing the ratio of two monomers. The maximum value is reached at 100 mol% of the imide monomer. The arm value can also be controlled between 1.5329 and 1.6283 by varying the monomer ratio. Decrease of birefringence was obtained by increasing the ether monomer content, from 1.25x10-2 to 3x10-3. The refractive indices of the hyperbranched polymers vary from 1.5646 to 1.6263 for nm and from 1.5584 to 1.6277 for nm. The chain branching causes a significant reduction of the birefringence to as low as 2x104 for polyTPPE and 6.2x10-3 for the hyperbranched poly(ether imides). UV curing of the thin polymeric films produces small changes in both nm and aim, lowering their value with an average of 5.5x10-3. Thermal curing produces coloration of the films, with an increase in refractive indices, both nm and arm