Surfactant

1. A surfactant of formula (I):

A-(L 1 ) a -(CH 2 ) b -(L 2 ) c -X  (I)

wherein

A is a perfluoropolyether, wherein said perfluoropolyether comprises a repeat unit of the formula -[CF(CF 3 )CF 2 O] m —, wherein m is an integer from 10 to 100;

L 1 is CONR′, wherein R′ is selected from H and C 1-6 alkyl;

a is 0 or 1;

b is 0 or an integer between 1 and 10;

L 2 is a linking group;

c is 0 or 1; and

X is selected from:

(a) any one of

wherein R 3 is selected from C 1-6 alkyl, and (CH 2 ) d O(CH 2 CH 2 O) e R x , wherein R x is H or C 1-6 alkyl, d is a positive integer from 2 to 6, and e is 0 or a positive integer from 1 to 100; R 4 is selected from C 1-6 alkyl; and W − is a counter ion; (b)-any one of

wherein R 1 and R 2 are independently selected from C 1-6 alky; R 4 is selected from C 1-6 alkyl; Z is —(CH 2 ) r O(CH 2 CH 2 O) g (CH 2 ) s —Y-(L 2 ) c -(CH 2 ) b -(L 1 ) a -A, wherein r is a positive integer from 2 to 6, g is 0 or a positive integer, s is 0 or a positive integer from 2 to 6, Y is

wherein R 1 and R 2 are independently selected from H and C 1-6 alkyl; R 4 is selected from C 1-6 alkyl; and W − is a counter ion.

2. A surfactant as claimed in claim 1 , wherein m is an integer from 10 to 25.

3. A surfactant as claimed in claim 1 , wherein a is 0.

4. A surfactant as claimed in claim 1 , wherein a is 1 and L 1 is CONH or CONCH 3 .

5. A surfactant as claimed in claim 1 , wherein b is an integer from 1 to 10.

6. A surfactant as claimed in claim 1 , wherein c is 0.

7. A surfactant as claimed claim 1 , wherein said surfactant is selected from:

wherein

m is an integer from 10 to 100

e is 0 or a positive integer from 1 to 100; and

g is 0 or a positive integer from 1-100.

8. A method for making the surfactant of formula (I) of claim 1 ,

the method comprising:

reacting a compound of formula (a):

A-(L 1 ) a -(CH 2 ) b -(L 2 ) c -X′  (a)

wherein

A, L 1 , a, L 2 , and c are as defined with respect to formula (I);

b is 0 or an integer between 1 and 6; and

X′ is selected from:

wherein

R 4 is as defined with respect to formula (I);

with R 3 -W, wherein

R 3 is as defined with respect to formula (I); and

W is a leaving group.

9. A composition comprising the surfactant of formula (I) as claimed in claim 1 , wherein said composition further comprises a multicharged compound or polymer, and wherein said multicharged compound or polymer is oppositely charged to said surfactant.

10. The composition as claimed in claim 9 , wherein the composition is an emulsion comprising a discontinuous aqueous phase and a continuous oil phase.

11. A method of preparing an emulsion as claimed in claim 10 comprising:

(i) providing an aqueous phase;

(ii) providing an oil phase; and

(iii) mixing said aqueous phase, said oil phase and the surfactant of formula (I)

wherein said mixing is by a flow focus junction, a T-junction or step emulsification nozzles of a microfluidic device.

12. A method comprising performing one or more chemical and/or biological reactions, and/or biological processes in the discontinuous aqueous phase of an emulsion as claimed in claim 10 .

13. A method for sorting, coalescing, introducing a fluid into, or splitting droplets in a microfluidic device or extracting a molecule from a fluid, the method comprising any one of methods (A) to (F), wherein sorting method (A) comprises:

(i) providing a stream of aqueous droplets in an emulsion as claimed in claim 10 in a channel of the microfluidic device;

(ii) illuminating the stream from a first direction;

(iii) detecting light from analytes within the droplets in a second direction; and

(iv) sorting the droplets into one of a plurality of differentiated streams in response to the detected light or a measurable signal;

wherein coalescing method (B) comprises:

(i) providing at least two aqueous droplets in an emulsion as claimed in claim 10 in a channel of the microfluidic device; and

(ii) forcing said aqueous droplets to contact, thereby causing coalescence of the at least two aqueous droplets into a single droplet;

wherein method of introducing a fluid (C) comprises:

(i) providing an aqueous droplet in an emulsion as claimed in claim 10 in a channel of the microfluidic device; and

(ii) contacting the aqueous droplet with a stream of fluid, thereby introducing said fluid into the aqueous droplet;

wherein splitting method (D) comprises:

(i) providing a microfluidic device comprising a microfluidic junction, said microfluidic junction comprising a first microfluidic channel, a second microfluidic channel and a third microfluidic channel;

(ii) providing an aqueous droplet in an emulsion as claimed in claim 10 in said first microfluidic channel; and

(iii) passing the aqueous droplet through the microfluidic junction, thereby splitting said aqueous droplet into at least a first daughter droplet and a second daughter droplet, the first daughter droplet in the second microfluidic channel and the second daughter droplet in the third microfluidic channel;

wherein sorting method (E) comprises:

(i) providing a microfluidic device comprising a microfluidic junction, said microfluidic junction comprising a first microfluidic channel, a second microfluidic channel and a third microfluidic channel;

(ii) providing an aqueous droplet in an emulsion as claimed in claim 10 in said first microfluidic channel;

(iii) passing the aqueous droplet through the microfluidic junction, thereby splitting said aqueous droplet into at least a first daughter droplet and a second daughter droplet, the first daughter droplet in the second microfluidic channel and the second daughter droplet in the third microfluidic channel;

(iv) detecting said first daughter droplet by mass spectroscopy; and

(v) sorting said second daughter droplets into one of a plurality of differentiated streams responsive to the mass spectroscopy

wherein extracting method (F) comprises:

(i) dissolving a surfactant of formula (I):

A-(L 1 ) a -(CH 2 ) b -(L 2 ) c -X  (I)

wherein

A is a perfluoropolyether, wherein said perfluoropolyether comprises a repeat unit of the formula —[CF(CF 3 )CF 2 O] m —, wherein m is an integer from 10 to 100;

L 1 is CONR′, wherein R′ is selected from H and C 1-6 alkyl;

a is 0 or 1;

b is 0 or an integer between 1 and 10;

L 2 is a linking group;

c is 0 or 1; and

X is selected from:

a) any one of

wherein R 3 is selected from C 1-6 alkyl, and (CH 2 ) d O(CH 2 CH 2 O) e R x , wherein R x is H or C 1-6 alkyl, d is a positive integer from 2 to 6, and e is 0 or a positive integer from 1 to 100; R 4 is selected from C 1-6 alkyl; and W − is a counter ion;

(b) any one of

wherein R 1 and R 2 are independently selected from C 1-6 alky; R 4 is selected from C 1-6 alkyl; Z is —(CH 2 ) r O(CH 2 CH 2 O) g (CH 2 ) s —Y-(L 2 ) c -(CH 2 ) b -(L 1 ) a -A, wherein r is a positive integer from 2 to 6, g is 0 or a positive integer, s is 0 or a positive integer from 2 to 6, Y is

wherein R 1 and R 2 are independently selected from H and C 1-6 alkyl; R 4 is selected from C 1-6 alkyl; and W − is a counter ion, in carbon dioxide to form a carbon dioxide/surfactant mixture; and

(ii) adding a fluid comprising the molecule to the carbon dioxide/surfactant mixture, thereby extracting the molecule from the fluid into the carbon dioxide.