Betaines are materials with both a positively charged functional group and a negatively charged functional group linked by an alkyl chain spacer. This combination of functional groups causes betaines to strongly attract water, which makes them useful for water retention. Betaines prevent cell dehydration in organisms and also play roles in some reactions. Commercially, betaines are used in DNA amplification and chemical synthesis. Betaine groups can be included in polymer brushes, which are polymers that are tethered to a surface. The resulting polymer brushes are attractive for use in lubrication and anti-fouling applications because the hydrated betaine groups prevent adhesion of other materials. However, the hydration states of polymer brushes are still poorly understood.