Effects of Silane Chemical Structures on the Surface Properties of Silanized Cardboard: Inverse Gas Chromatography and Complementary Analysis

Abstract

In this study, silanized cardboard samples (HSi-CB, MeSi-CB, EtSi-CB, and PrSi-CB) were prepared by reacting bare cardboard with ethoxysilane/chlorosilanes bearing different substituents (H-, CH₃-, CH₃CH₂-, and CH₃CH₂CH₂-) in toluene. Characterization using FTIR spectroscopy, elemental analysis, and surface area/pore volume measurements confirmed successful silanization, with HSi-CB exhibiting the largest amount of grafted silanes and branched polymeric/oligomeric siloxane networks. However, inverse gas chromatography (IGC) revealed that MeSi-CB exhibited the highest adsorption affinity toward hydrocarbons due to its larger dispersive surface energy \(\left( {\mathop \gamma \nolimits_{{\text{S}}}^{{\text{D}}} } \right)\) , resulting from grafted methylsilane groups, reduced hydroxyl groups, and the formation of micropores and channels via siloxane condensation. In contrast, EtSi-CB and PrSi-CB displayed lower \(\mathop \gamma \nolimits_{{\text{S}}}^{{\text{D}}}\) values due to the grafting of fewer silane groups and the limited formation of branched siloxane networks. Although HSi-CB exhibited the highest amount of silanes, its \(\gamma_{{\text{s}}}^{{\text{D}}}\) values remained comparable to those of bare cardboard. These results underscore the critical role of surface dispersive components and micropore/channel formation in boosting the adsorption performance of silanized cardboard. These results also provide valuable insights for the development of more efficient adsorbents for hydrocarbon capture and separation applications.