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a non-aromatic ring with the carbon atoms to which they are attached. In this event, Re 4 , Res and the carbon atoms to which they are attached together represent a trivalent organic group of3 to 12 carbon atoms in total. Re $^{6 }$is a single bond or a C$_{1 }$-C$_{4 }$ alkylene. 

[0208] Re $^{7 }$is each independently a single bond, ---0-, or -CRe$^{1}$Re 1 -. Re 8 is a straight or branched C$_{1}$-C$_{4 }$ alkylene group, or may bond with Re $^{2 }$within a common unit to form a C$_{3}$ -C$_{6 }$ non-aromatic ring with the carbon atom to which they are attached. 

[0209] Re $^{9 }$is methylene, 1,2-ethylene, 1,3-propylene or 1,4-butylene. Re 10 is a C$_{3}$ -C$_{6 }$ linear perfluoroalkyl group, typically 3H-perfluoropropyl, 4H-perfluorobutyl, 5H-per› fluoropentyl or 6H-perfluorohexyl. 

[0210] U is each independently ----C(=0)---0-, ---0-, or -C(=0)-Re $^{11}$-C(=0)-0- wherein Rell is a straight, branched or cyclic C$_{1 }$-C$_{10 }$ alkylene group. The subscripts are in the range: 0s(a’-l)sl, 0s(a’-2)sl, 0s(a’-3) sl, 0sb’sl, 0sc’sl, and 0s(a’-l)+(a’-2)+(a’-3)+b’+c’sl. 

[0211] Examples of these recurring units are shown below, but not limited thereto. Herein Re 1 is as defined above. 

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[0212] The polymeric surfactant has a Mw of preferably 1,000 to 50,000, more preferably 2,000 to 20,000 as mea› sured by GPC versus polystyrene standards. A surfactant with a Mw within the range may be effective for surface modification and cause no development defects. 

