A detailed investigation of the reactions of diaryldiazo compounds for the surface modification of several polymers has been conducted. This has revealed that the rate of reaction of diaryldiazo compounds is influenced by their substituents, that the reaction is exothermic, and that the polymer itself exerts an influence on the surface modification. The results are consistent with the formation and insertion of a carbene intermediate at the polymer surface. It was further shown that such surface modified polymers, characterized using surface sensitive techniques, display macroscopic behavior consistent with the presence of the newly introduced surface chemical functionality, characterized using a combination of surface sensitive and bulk analytical techniques. This approach is complementary to directed energy deposition approaches, offers an alternative route to functional polymers, and provide a direct link between surface chemistry and observable macroscopic properties.