Provided herein are compounds of the formula: wherein m is an integer greater than or equal to 1; n is an integer greater than or equal to 0; Z is selected from NR5, S, and O; Z′ is, independently for each occurrence, selected from NR5, S, and O; R1 is, independently for each occurrence, is an optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; R2 is selected from hydrogen and optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; R5 is, independently for each occurrence, selected from hydrogen and optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; and R3 and R4, independently for each occurrence, are selected from optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched. Also provided are compositions containing the compounds and methods of making both the compounds and compositions thereof.