A copolymer preparable by copolymerization of monomer components comprising: a) polydimethylsiloxane mono(meth)acrylate having a molecular weight of from 300 to 10000 grams/mole; b) optionally C3-C10 carboxylic acid-functional mono(meth)acrylate or a salt thereof; c) at least one C5-C16 hydroxyalkyl mono(meth)acrylate; and d) at least one of: i) C10-C30 linear alkyl mono(meth)acrylate optionally having one or two carbon atoms replaced by O or S; or ii) at least one (meth)acrylate represented by the formula wherein: R1 is H or a C1-C4 alkyl group; n is an integer from 0 to 18, inclusive; each X is O, S, C2-C6 oxyalkylenoxy, C2-C6 thioalkylenethio, or a covalent bond; and R2 is independently a C5-C50 hydrocarbyl group. The copolymer is useful as a water- and oil-repellent treatment on a substrate. Certain monomers corresponding to component ii) are also disclosed.