Curable compositions of resin-linear organosiloxane block copolymers

1. A curable solid film composition comprising:

i) an organosiloxane block copolymer comprising:

40 to 90 mole percent disiloxy units of the formula [R 1 2 SiO 2/2 ],

10 to 60 mole percent trisiloxy units of the formula [R 2 SiO 3/2 ],

0.5 to 35 mole percent silanol groups [≡SiOH ];

wherein:

R 1 is independently a C 1 to C 30 hydrocarbyl,

R 2 is independently a C 1 to C 20 hydrocarbyl;

wherein:

the disiloxy units [R 1 2 SiO 2/2 ] are arranged in linear blocks having an average of from 10 to 400 disiloxy units [R 1 2 SiO 2/2 ] per linear block,

the trisiloxy units [R 2 SiO 3/2 ] are arranged in non-linear blocks having a molecular weight of at least 500 g/mole, and about 30% to about 80% of the non-linear blocks are crosslinked with each other, each linear block is linked to at least one non-linear block, and the non-linear blocks are predominately aggregated together in nano-domains; and

the organosiloxane block copolymer has a weight average molecular weight (M W ) of at least 20,000 g/mole; and

ii) a base selected from the group consisting of:

1,8 -Diazabicyclo [5.4.0 ]undec-7 -ene(DBU),

1,5,7 -Triazabicyclo [4.4.0 ]dec-5 -ene(TBD),

1,4 -Diazabicyclo [2.2.2 ]octane(DABCO),

1,1,3,3 -Tetramethylguanidine(TMG),

1,5 -Diazabicyclo [4.3.0 ]-5 -nonene(DBN),

7 -Methyl-1,5,7 -triazabicyclo[4.4.0 ]dec-5 -ene(MTBD) and combinations thereof;

wherein the curable solid film composition has an optical transmittance of at least 95 %.

2. The curable composition of claim 1 , wherein the base is 1,8 -Diazabicyclo [5.4.0 ]undec-7 -ene.

3. The curable composition of claim 1 , wherein R 2 is phenyl.

4. The curable composition of claim 1 , wherein R 1 is methyl or phenyl.

5. The curable composition of claim 1 , wherein the disiloxy units have the formula [(CH 3 )(C 6 H 5 )SiO 2/2 ].

6. The curable composition of claim 1 , wherein the disiloxy units have the formula [(CH 3 ) 2 SiO 2/2 ].

7. The curable composition of claim 1 , wherein the superbase is a silanol condensation enhancing agent.

8. The cured product of the curable solid film composition of claim 1 .

9. The solid film composition of claim 1 , wherein the composition has a storage modulus (G′) at 120° C. ranging from 10 Pa to 1,000,000 Pa and a loss modulus (G″) at 120° C. ranging from 10 Pa to 1,000,000 Pa.

10. The solid film composition of claim 1 , wherein the film has a viscosity of at least 1700 Pa·s at 120° C.

11. The solid film composition of claim 1 , wherein the film has a tensile strength of at least 1.0 MPa.