A compound of the following formula (A1) or (A2): R 1 -(PE 1 -Y) n -PE 2 -X-(SiR a k R b l R c m ) α (A1) (R c m R b l R a k Si) α -X-(PE 1 -Y) n -PE 2 -X-(SiR a k R b l R c m ) α (A2) wherein: R 1 is OH or C 1-20 -alkoxy; PE 1 each independently is a group -(C a H 2 a O) b -, wherein: a is, independently in each -C a H 2 a O- unit, an integer of 1-6; in formula (A1) or (A2) a = 4 in at least one unit; and a unit -(C 4 H 8 O)- is -((CH 2 ) 4 O)-; b each independently is an integer of 1-200; PE 2 is a single bond or -(C a H 2a O) b - as defined above; Y is a -CONH-R 5 -NHCOO-, wherein R 5 is -(CH 2 ) x' -, wherein x' is an integer of 1-6, x and y are each independently an integer of 0-6, z is an integer of 0-10, and z' is an integer of 0-4; n is an integer of 1-50; X each independently is a single bond or a 2-10 valent organic group; and further, at each occurrence and each independently R a is -Z-SiR 71 p R 72 q R 73 r , wherein Z each independently at each occurrence is O or a divalent organic group; R 71 each independently is R a' having the same definition as R a ; R 72 each independently is OH, -OR, -OCOR, -O-N=C(R) 2 , -N(R) 2 , -NHR or halogen, wherein R is optionally substituted C 1-4 -alkyl; R 73 each independently is H or C 1-20 -alkyl; p is an integer of 0-3; q is an integer of 0-3; r is an integer of 0-3; in R a the number of Si atoms which are straightly linked via the Z group is ≤ 5; and in one R a the sum of ( p + q + r ) = 3; R b is OH, -OR, -OCOR, -O-N=C(R) 2 , -N(R) 2 , -NHR or halogen, wherein R is optionally substituted C 1-4 -alkyl; R c is H or C 1-20 -alkyl; k is an integer of 0-3; l is an integer of 0-3; m is an integer of 0-3; and in a unit -SiR a k R b l R c m the sum of ( k + l + m ) = 3; α is each independently an integer of 1-9; and at least one R 72 or R b is present in the formula. R 1 is OH or C 1-20 -alkoxy; PE 1 each independently is a group -(C a H 2 a O) b -, wherein: a is, independently in each -C a H 2 a O- unit, an integer of 1-6; in formula (A1) or (A2) a = 4 in at least one unit; and a unit -(C 4 H 8 O)- is -((CH 2 ) 4 O)-; b each independently is an integer of 1-200; a is, independently in each -C a H 2 a O- unit, an integer of 1-6; in formula (A1) or (A2) a = 4 in at least one unit; and a unit -(C 4 H 8 O)- is -((CH 2 ) 4 O)-; b each independently is an integer of 1-200; PE 2 is a single bond or -(C a H 2a O) b - as defined above; Y is a -CONH-R 5 -NHCOO-, wherein R 5 is -(CH 2 ) x' -, n is an integer of 1-50; X each independently is a single bond or a 2-10 valent organic group; R a is -Z-SiR 71 p R 72 q R 73 r , wherein Z each independently at each occurrence is O or a divalent organic group; R 71 each independently is R a' having the same definition as R a ; R 72 each independently is OH, -OR, -OCOR, -O-N=C(R) 2 , -N(R) 2 , -NHR or halogen, wherein R is optionally substituted C 1-4 -alkyl; R 73 each independently is H or C 1-20 -alkyl; p is an integer of 0-3; q is an integer of 0-3; r is an integer of 0-3; in R a the number of Si atoms which are straightly linked via the Z group is ≤ 5; and in one R a the sum of ( p + q + r ) = 3; Z each independently at each occurrence is O or a divalent organic group; R 71 each independently is R a' having the same definition as R a ; R 72 each independently is OH, -OR, -OCOR, -O-N=C(R) 2 , -N(R) 2 , -NHR or halogen, wherein R is optionally substituted C 1-4 -alkyl; R 73 each independently is H or C 1-20 -alkyl; p is an integer of 0-3; q is an integer of 0-3; r is an integer of 0-3; in R a the number of Si atoms which are straightly linked via the Z group is ≤ 5; and in one R a the sum of ( p + q + r ) = 3; R b is OH, -OR, -OCOR, -O-N=C(R) 2 , -N(R) 2 , -NHR or halogen, wherein R is optionally substituted C 1-4 -alkyl; R c is H or C 1-20 -alkyl; k is an integer of 0-3; l is an integer of 0-3; m is an integer of 0-3; and <EOS>