The different faces of poly(ethylene glycol)

The first sign that PEO is “unusual” can be sensed from it’s unexpected water solubility or “hydrophilicity.” Thus, poly(butylene oxide), –[CH2–CH2–CH2–O–]n–, having one more methylene (CH2) group, is hydrophobic and insoluble in water, as might be expected. But so is poly(methylene oxide), –[CH2–O–]n–, which has one less methylene group.