A composition comprising: a cross linked polysiloxane/polyimide block copolymer having a siloxane content of 10 to 45 weight percent, based on the total weight of the block copolymer, wherein the cross linked polysiloxane/polyimide block copolymer has a heat distortion temperature measured at 0.44 megaPascals that is at least 5 degrees Celsius greater than the heat distortion temperature of the polysiloxane/polyimide block copolymer prior to cross linking, wherein the cross linked polysiloxane/polyimide block copolymer has an E' modulus measured at 30 degrees Celsius that is greater than or equal to 115% of the E' modulus measured at 30 degrees Celsius of the polysiloxane/polyimide prior to cross linking, wherein the polysiloxane/polyimide block copolymer comprises a non-siloxane polyimide block comprising repeating units of Formula wherein a is more than 1, U is a tetravalent linker comprising a monocyclic group having 5 to 50 carbon atoms, a polycyclic group having 6 to 50 carbon atoms, an alkyl group having 1 to 30 carbon atoms or a combination thereof, and R 10 comprises an aromatic hydrocarbon having 6 to 20 carbon atoms, alkylene groups having 2 to 20 carbons, cycloalkylene groups having 3 to 20 carbon atoms or divalent moieties of Formula (VIII) wherein Q is a divalent group comprising -O-, -S-, -C -, -SO 2 -, -SO-, - C 2 H 2y - and y is an integer from 1 to 20, and an extended siloxane block comprising repeating units of Formula wherein R 1-6 are independently at each occurrence selected from the group consisting of monocyclic groups having 5 to 45 carbon atoms, polycyclic groups having 10 to 45 carbon atoms, alkyl groups having 1 to 30 carbon atoms and alkenyl groups having 2 to 30 carbon atoms, V is a tetravalent linker selected from the group consisting of monocyclic groups having 5 to 50 carbon atoms, polycyclic groups having 6 to 50 carbon atoms, alkyl groups having 1 to 30 carbon atoms, alkenyl groups having 2 to 30 carbon atoms and combinations comprising at least one of the foregoing linkers, g equals 1 to 30, and d is greater than or equal to 1, wherein E' modulus is determined according to ASTM D4065-01. a cross linked polysiloxane/polyimide block copolymer having a siloxane content of 10 to 45 weight percent, based on the total weight of the block copolymer, wherein the cross linked polysiloxane/polyimide block copolymer has a heat distortion temperature measured at 0.44 megaPascals that is at least 5 degrees Celsius greater than the heat distortion temperature of the polysiloxane/polyimide block copolymer prior to cross linking, wherein the cross linked polysiloxane/polyimide block copolymer has an E' modulus measured at 30 degrees Celsius that is greater than or equal to 115% of the E' modulus measured at 30 degrees Celsius of the polysiloxane/polyimide prior to cross linking, wherein the polysiloxane/polyimide block copolymer comprises a non-siloxane polyimide block comprising repeating units of Formula wherein a is more than 1, U is a tetravalent linker comprising a monocyclic group having 5 to 50 carbon atoms, a polycyclic group having 6 to 50 carbon atoms, an alkyl group having 1 to 30 carbon atoms or a combination thereof, and R 10 comprises an aromatic hydrocarbon having 6 to 20 carbon atoms, alkylene groups having 2 to 20 carbons, cycloalkylene groups having 3 to 20 carbon atoms or divalent moieties of Formula (VIII) wherein Q is a divalent group comprising -O-, -S-, -C -, -SO 2 -, -SO-, - C 2 H 2y - and y is an integer from 1 to 20, and an extended siloxane block comprising repeating units of Formula wherein R 1-6 are independently at each occurrence selected from the group consisting of monocyclic groups having 5 to 45 carbon atoms, polycyclic groups having 10 to 45 carbon atoms, alkyl groups having 1 to 30 carbon atoms and alkenyl groups having 2 to 30 carbon atoms, V is a tetravalent linker selected from the group consisting of monocyclic groups having 5 to 50 carbon atoms, polycyclic groups having 6 to 50 carbon atoms, alkyl groups having 1 to 30 carbon atoms, alkenyl groups having 2 to 30 carbon atoms and combinations comprising at least one of the foregoing linkers, g equals 1 to 30, and d is greater than or equal to 1, wherein E' modulus is determined according to ASTM D4065-01. wherein R 1-6 are independently at each occurrence selected from the group consisting of monocyclic groups having 5 to 45 carbon atoms, polycyclic groups having 10 to 45 carbon atoms, alkyl groups having 1 to 30 carbon atoms and alkenyl groups having 2 to 30 carbon atoms, V is a tetravalent linker selected from the group consisting of monocyclic groups having 5 to 50 carbon atoms, polycyclic groups having 6 to 50 carbon atoms, alkyl groups having 1 to 30 carbon atoms, alkenyl groups having 2 to 30 carbon atoms and combinations comprising at least one of the foregoing linkers, g equals 1 to 30, and d is greater than or equal to 1, wherein E' modulus is determined according to ASTM D4065-01.