Evaluation of infrared spectroscopic techniques to determine the Drago constants of a cycloaliphatic epoxy

摘要

The task of understanding adhesion is not complete without considering acid-base interactions.Such site-specific interactions play a major role in promoting adhesion.However,these interactions are often difficult to characterize or quantify.In this work,a cycloaliphatic epoxy resin is studied by Fourier Transform Infrared(FT-IR)spectroscopy to identify and quantify possible molecular interactions.As controls,simple molecules such as acetone and ethyl acetate were also studied.Moreover,interactions of molecules with structural similarities to the epoxy resin were studied to provide additional insight.Two infrared spectroscopic techniques,carbonyl peak shifts and hydroxyl peak shifts,were employed to quantify the acid-base interactions of these organic molecules.The Drago constants from carbonyl peak shifts were determined from predicted heats of complexation and also directly from hydroxyl peak shifts.The constants obtained for the control molecules were compared with published data.The Drago constants of the control molecules determined by hydroxyl peak shifts agreed well with literature values,in contrast,to those derived from the carbonyl peak shifts.This lack of correlation may be attributed to the influence of solvent effects and concentration dependence on carbonyl shifts.Using the hydroxyl peak shift approach,the Drago constants for the cycloaliphatic epoxy group of cycloaliphatic epoxy resin were found to be E_B=2.69(kJ/mol)~(1/2)and C_B=4.04(kJ/mol)~(1/2)and E_B=3.45(kJ/mol)~(1/2)and C_B=2.11(kJ/mol)~(1/2)for the ester group of the epoxy resin.The average Drago constants for the resin were found to be E_B=3.28+-0.14(kJ/mol)1/2 and C_B=2.00+-0.09(kJ/mol)~(1/2).