Optical characterization of urethane/urea elastomers undoped and doped with magnetic nanoparticles subjected to a uniaxial strain

We report on the optical characterization of urethane/urea elastomers (PU/PBDO), based on polypropylene oxide and polybutadiene diol, pure and doped with ferrofluid. The ratios in wt % of PU and PBDO investigated are 40/60, 50/50, 60/40, and 80/20. The incorporation of nanoparticles in the elastomeric matrices strongly depends upon the ratio of PU/PBDO, which corresponds to different degrees of cross linking. The nanoparticles were also found to act as impurities in the elastomeric matrix by reducing the initial induced anisotropy promoted by film casting and preparation. Optical experiments show that the strain-induced optical birefringence is linear with the stress in both pure and doped elastomers.