IR-visible sum-frequency generation (SFG) spectroscopy has been used to study structure and melting transition temperatures of alkyl side chain acrylate comb polymers at air and solid interfaces. At the air interface, the SFG spectra show methyl bands and two transitions are observed: The first, near the bulk melting temperature, Tm, and the second 10-20oC higher than Tm. The shorter the alkyl side chain, the larger the difference between the two transition temperatures. In contrast, methylene bands are observed at sapphire interface with a single transition near Tm (C-18).