Surface coatings

A substrate having a coating thereon, said coating being deposited by pulsed plasma deposition and being derived from a compound of formula (I)

• where R1, R2 and R3 are independently selected from hydrogen, alkyl, haloalkyl or aryl optionally substituted by halo, provided that at least one of R1, R2 and R3 is hydrogen, and
• R4 is a group X—R5, where R5 is an alkyl or haloalkyl group, and X is:
• a bond;
• or
• a group of formula —C(O)O(CH2)nY— where n is an integer of from 1 to 10 and Y is a bond or a sulphonamide group;
• or
• a group —(O)pR6(O)q(CH2)t— where R6 is aryl optionally substituted by halo, p is 0 or 1, q is 0 or 1 and t is 0 or an integer of from 1 to 10, provided that where q is 1, t is other than 0, the compound of formula (I) having been treated such that the double bond reacts to form the coating but otherwise, the structure of the monomer is substantially retained,
• and wherein the coating is such that were it present on a planar glass surface, it would have a surface energy of 5-6 mNm−1.

A method of coating a surface with a polymer layer, which method comprises exposing said surface to a pulsed plasma comprising a compound of formula (I)

• R1R2C═CR3R4 (I)
• where R1, R2 and R3 are independently selected from hydrogen, alkyl, haloalkyl or aryl optionally substituted by halo, provided that at least one of R1, R2 and R3 is hydrogen, and R4 is a group X—R5, where R5 is a perhaloalkyl group having from 6 to 20 carbon atoms and X is:
• a bond;
• or a group of formula —C—(O)O(CH2)nY— where n is an integer of from 1 to 10 and Y is a bond or a sulphonamide group;
• or
• a group —(O)pR6(O)q(CH2)t— where R6 is aryl optionally substituted by halo, p is 0 or 1, q is 0 or 1 and t is 0 or an integer of from 1 to 10, provided that where q is 1, t is other than 0;
• wherein a glow discharge is ignited by applying a high frequency voltage and wherein pulses are applied in a sequence which yields an average power density equivalent to less than 50 W in a volume of 470 cm3 so as to form an oil and water repellent coating on said surface.