Amphiphilic resin-linear organosiloxane block copolymers

1. A resin-linear organosiloxane block copolymer comprising:

i) a linear block of repeating units having the formula B-[AB] n

wherein:

B is a diorganopolysiloxane having an average of from 10 to 400 disiloxy units of the formula [R 1 2 SiO 2/2 ]

A is a divalent organic group comprising at least one polyether group, and

n is ≧1

ii) a resinous block of repeating units of the formula [R 2 SiO 3/2 ] arranged in non-linear blocks having a molecular weight of at least 500 g/mol,

wherein

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

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

each linear block is linked to at least one non-linear block by a divalent C 2 to C 12 hydrocarbylene group, and

the organosiloxane block copolymer has a molecular weight of at least 20,000 g/mole.

2. The resin-linear organosiloxane of claim 1 , wherein the linear block has the formula

—R 1 2 SiO(R 1 2 SiO) x SiR 1 2 [[R 5 (C m H 2m O) y R 5 ][R 1 2 SiO(R 1 2 SiO) x ]R 1 2 Si] n —

wherein x is ≧0, m is from 2 to 4 inclusive, y is ≧3, n is ≧1,

R 1 is independently a monovalent hydrocarbon group containing 1 to 30 carbons, and

R 5 is a divalent hydrocarbon containing 2 to 30 carbons.

3. The resin-linear organosiloxane of claim 2 , wherein R 1 is methyl, R 5 is ethylene, propylene, or isobutylene, and m is 2.

4. The resin-linear organosiloxane of claim 2 , wherein R 2 is phenyl.

5. A solid composition comprising the resin linear organosiloxane of claim 1 .

6. The solid composition of claim 5 , wherein the solid composition has a storage modulus (G′) at 25° C. of at least 1 KPa.

7. The solid composition of claim 6 having a water vapor permeation rate of at least 30 g/m 2 ·day.

8. The solid composition of claim 5 , which is curable.

9. The cured product of the composition of claim 5 .

10. A process for preparing a resin linear organosiloxane block copolymer comprising:

I) reacting:

a) a linear organosiloxane of the formula:

R 3 R 1 2 SiO(R 1 2 SiO) x SiR 1 2 [[R 5 (C m H 2m O) y R 5 ][R 1 2 SiO(R 1 2 SiO) x ]R 1 2 Si] n —R 3

Wherein x is ≧0, m is from 2 to 4 inclusive, y is ≧3, n is ≧1,

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

R 5 is a divalent hydrocarbon containing 2 to 30 carbons,

R 3 is independently H or R 4 ,

wherein R 4 is a C 2 to C 12 hydrocarbyl having at least one aliphatic unsaturated bond;

b) an organosiloxane resin having the average formula;

[R 2 2 R 3 SiO 1/2 ] a [R 2 R 3 SiO 2/2 ] b [R 3 SiO 3/2 ] c [R 2 SiO 3/2 ] d [SiO 4/2 ] e

where the subscripts a, b, c, d, and e represent the mole fraction of each siloxy unit present in the organosiloxane resin and range as follows: a may vary from 0 to 0.7,

b may vary from 0 to 0.3,

c may vary from 0 to 0.8,

d may vary from 0 to 0.9,

e may vary from 0 to 0.7,

with the provisos that a+b+c≧0, c+d+e≧0.6, and a+b+c+d+e≈1,

with the proviso at least one R 3 substituent is H on either of the linear organosiloxane or organosiloxane resin, and one R 3 substituent is R 4 on the other organosiloxane, and

c) a hydrosilylation catalyst;

to form a resin-linear organosiloxane block copolymer;

wherein the amounts of a) and b) used in step I are selected to provide the resin-linear organosiloxane block copolymer with 10 to 90 mol % of disiloxy units [R 1 2 SiO 2/2 ] and 10 to 70 mol % of [R 2 SiO 3/2 ] or [SiO 4/2 ] siloxy units, and

at least 95 weight percent of the linear organosiloxane added in step I is incorporated into the resin-linear organosiloxane block copolymer.

11. The process of claim 10 , further comprising a solvent.

12. The process of claim 10 further comprising:

II) reacting the resin-linear organosiloxane block copolymer from step I) to crosslink the [R 2 SiO 3/2 ] and/or [SiO 4/2 ] siloxy units of the resin-linear organosiloxane block copolymer sufficiently to increase the average molecular weight (M W ) of the resin-linear organosiloxane block copolymer by at least 50%.

13. The process of claim 10 , wherein R 1 is methyl, R 5 is ethylene, propylene, or isobutylene, and m is 2.

14. The process of claim 10 wherein R 2 is phenyl.