a hydrocarbon radical (C4H9)
"The chemist explained that adding butyl groups to the polymer chain would significantly increase its flexibility and resistance to cold temperatures."
Any of four isomeric univalent hydrocarbon radicals, C₄H₉, formally derived from butane by the loss of a hydrogen atom.
"The chemist explained that the polymer's stability was due to the presence of bulky butyl groups attached along the main chain."