A copolymer composition comprises a polysiloxane block of Formula XIX or XXII, having 4 to 50 siloxane units, and a polyarylate-polycarbonate block consisting essentially of 50 to 99 mol % arylate polyester units and 1 to 50 mol % aromatic carbonate units, wherein 1 to 30 mole percent of the aromatic carbonate units are resorcinol carbonates, and 0 to 35 mol % of the aromatic carbonate units are bisphenol carbonates; wherein the sum of mole percentages of arylate polyester units, and aromatic carbonate units is 100 mol %; the polysiloxane blocks connect to an arylate ester unit, and/or an aromatic carbonate unit; the siloxane units of the polysiloxane block are present at 0.2 to 10 wt % based on weight of the copolymer composition; and a molded article of 3.2.+-.0.12 millimeters thickness and consisting of the copolymer composition has a percent transmittance greater than or equal to 70%, according to ASTM D1003-00.