The acid-functional polymer of claim 19 whereinR1 is aliphatic or cycloaliphatic hydrocarbon containing one or more oxygen, nitrogen, or sulfur moieties; R2 is hydrogen, C1-20 alkyl, C1-20 haloalkyl, C1-20 alkenyl or phenyl; X is S, O, or NH; and n is an integer from 1 to 10. 21.