An X-ray Diffraction Study of γ-Irradiated Siloxane Block Copolymers

Abstract

It was found that 20 : 5 and 40 : 10 siloxane block copolymers of the general formula { (CH3)2SiO}m {[C6H5SiO1.5]a [C6H5SiO · (OH)]1 − a}n are structurally different: the 20 : 5 siloxane block copolymers consisted of 8–10 pairs of blocks, whereas the 40 : 10 siloxane block copolymers consisted of 1–2 pairs of blocks. The diffraction patterns of the initial 20 : 5 siloxane block copolymers were characterized by two reflections with 2θ maximums at 7.7° and 12.2°, whereas the diffraction patterns of the initial 40 : 10 siloxane block copolymers were characterized by a reflection with a 2θ maximum of ∼8.3°. After irradiation to a dose higher than the dose of gelation (∼100 kGy), two reflections with maximums at ∼7.6° and 12.5° appeared in the diffraction pattern of 40 : 10 siloxane block copolymers. This suggests a structural rearrangement and offers possibilities for the radiation crosslinking and regulation of the supramolecular structure of block copolymers.