Radiation curable siloxane compositions and methods for their preparation and use

A method for making a transparent cured film, wherein the method comprises;

• 1) preparing a composition by a method comprising mixing starting materials comprising (A) (B), (C), (D) and (E), where
• starting material (A) is an ethylenically unsaturated polydiorganosiloxane comprising unit formula (A1):
• (R43SiO1/2)a(R42R5SiO1/2)b(R42SiO2/2)c(R4R5SiO2/2)d, where
• each R4 is an independently selected monovalent hydrocarbyl group free of aliphatic unsaturation;
• each R5 is an ethylenically unsaturated monovalent hydrocarbyl group of 2 to 12 carbon atoms;
• subscripts a, b, c, and d, each represent an average number of siloxane units per molecule and have values such that
• 0≤a≤2,
• 0≤b≤2,
• (a+b)=2,
• c≥0,
• d≥0,
• 10≤(c+d)≥1,000, and
• (b+d)≥2;
• starting material (B) is a radical curable siloxane-urethane/urea copolymer comprising formula (B1):
• where
• each R2 is an independently selected ethylenically unsaturated monovalent hydrocarbyl group;
• each R6 is independently selected from H or R2,
• each X is independently selected from O or NH,
• each D1 is a divalent hydrocarbyl group or an oxyhydrocarbyl group,
• each R1 an independently selected monovalent hydrocarbyl group that is free of aliphatic unsaturation, and
• subscript n≥0, and
• starting material (C) is a reactive diluent distinct from starting materials (A) and (B), and starting material (C) comprises, per molecule, at least one radical curable group selected from the group consisting of vinyl, vinyl ether, acrylate, and methacrylate;
• and starting material (C) has a solubility parameter δ≤19 (MPa)1/2 when estimated by method of Fedors,
• starting material (D) is a crosslinker, and
• starting material (B) is a photoinitiator,
• 2) forming the composition into a liquid film, and
• 3) exposing the liquid film to UV radiation, thereby forming the transparent cured film.