The poly (imide siloxane) block copolymer were synthesized at different forms with resistance to dissolve in several corrosive environments. The optimum gamma shielding of the poly (imide siloxane) block copolymer was obtained with the comparison of flexible sheet and pelletized forms to be tolerant at harsh environment. The comparison in the improvement of thermal performance was performed in two different forms of the poly (imide siloxane) block copolymer (such as the flexible sheet and the pelletized form). The shielding tolerance against gamma radiation was specified to identify their gamma shielding capacity with low-energy ( 1 MeV) gamma photons by using Cs-137 radioisotope and with high energy ( 1 MeV) gamma photons by using Co-60 radioisotope. The variations in the flexible sheet and the pelletized form were significant that the linear attenuation coefficient of flexible sheet form has presented the highest gamma shielding capacity. The flexible shield form of the poly(imide siloxane) block copolymer has exhibited optimum radiation shielding with the resistance against gamma radiation in extreme environment with high temperature and corrosive ambient.