Novel citric-acid-based polyamides were synthesized by polycondensation reactions using tributyl citrate (TBC) and ethylene diamine (EDA), producing hyperbranched poly(ethylene citramide)s with NH2 termini, which were functionalized with isopropyl, n-butyl, and cyclohexyl groups via the urea group. Characterization was carried out by H-1 and C-13 nuclear magnetic resonance (NMR) spectroscopic techniques. Molecular weights in this polymer family varied from 3000 to 10 000 Da. The activity of this polymer family as gas hydrate kinetic inhibitors (KHIs) was evaluated for the first time. Constant cooling (1 degrees C/h) experiments were carried out in high-pressure steel rocking cells using a synthetic natural gas that preferentially forms structure II gas hydrates. The best KHI performance was given by poly(ethylene citramide) CONHCyHe with pendant N-cyclohexyl groups (M-n = 5.65 X 10(3), and M-w = 1.14 X 10(4)). A structure-activity relationship (SAR) analysis of the KHI test results supports the hypothesis that increasing the size of the lipophilic groups increases the KHI performance as long as water solubility is maintained through hydrogen bonding via the amide and/or urea functional groups.