The compounds disclosed herein ( e.g. , compounds having a structure according to Formula (I/ (II)/ (III)/ (IV), and (V)) are polymers wherein an organic polymeric segment ( e.g ., a polyethylene glycol (PEG) group) comprises covalent attachments to two or more lipid substructures, and each lipid substructure independently comprises a hydrophobic moiety and a hydrophilic moiety. The compounds provided herein can be useful for delivery and expression of mRNA and encoded protein, e.g ., as a component of liposomal delivery vehicle, and accordingly can be useful for treating various diseases, disorders and conditions, such as those associated with deficiency of one or more proteins.