The history of polyethylene glycols (PEGs) began in 1859 when Laurenco heated ethylene glycol and 1,2-dibromoethane and isolated oligo(ethylene glycol)s by fractional distillation.1 PEGs are synthetic, uncharged, nonbranched, hydrophilic polymers made by joining units of ethylene glycol by an ether linkage. PEGs thus have the formula of H(OCH2CH2)nOH, where n denotes the number of individual ethylene oxide units. Molecular weights vary by time of the polymerization process. When the process is stopped, the result is a relatively narrow range of ethylene oxide units, and the molecular weight given for a particular PEG is a weighted average of the individual PEG molecules.