A light guide has a transmission of greater than 90 percent, a refractive index greater than 1.4, and less than 10 haze percent. The light guide also includes an organosiloxane block copolymer having a weight average molecular weight of at least 20,000 g/mole. The organosiloxane block copolymer includes 40 to 90 mole percent disiloxy units of the formula [R12SiO2/2] arranged in linear blocks each having an average of from 10 to 400 disiloxy units [R12SiO2/2] per linear block, 10 to 60 mole percent trisiloxy units of the formula [R2SiO3/2] arranged in non-linear blocks each having a weight average molecular weight of at least 500 g/mol, and 0.5 to 25 mole percent silanol groups [≡SiOH]. R1 is independently a C1 to C30 hydrocarbyl and R2 is independently a C1 to C20 hydrocarbyl. Moreover, at least 30% of the non-linear blocks are crosslinked with another non-linear block and aggregated in nano-domains.