wherein: each R1 is H, C1???C4 hydrocarbyl, C1???C4 alkoxyalkyl, or hydroxyalkyl; and R2 is a C5???C31 hydrocarbyl moiety; and each Z is a polyhydroxyhydrocarbyl moiety having a linear hydrocarbyl chain with at least 3 hydroxyls directly connected to the chain, or an ethoxylated derivative thereof; and each R??? is H or a cyclic mono- or poly-saccharide, or alkoxylated derivative thereof; and