When present together in a molecule, the interplay between methyl and ethyl groups can lead to interesting effectsmethyl ethyl. For example, in the synthesis of polymers, the arrangement and ratio of these groups can dictate the material's strength, flexibility, and durability. A well-known case is the difference between polypropylene and polyethylene. The former contains pendant methyl groups along its backbone, which prevent the polymer chains from packing closely together, resulting in a more flexible yet less crystalline material.