In papermaking, retention aids help incorporate fines and fillers into paper. One example is PEO + cofactor. Without a knowledge of the basic mechanism, costly trial-and-error runs have to be performed. Molecular Mechanics (MM) and PM3 Semi-empirical calculations are used to study flocculation of cellulose fibre fines. The interactions between non-ionic PEO, with two model cofactors, corilagin and TGG, showed that the DLMO covers the complexes.
DG, DS and DH show no PEO/cofactor complexes. The PM3 results show that the main mechanism of complexation is not hydrogen bonding in water. The flocculation of MCC with PEO and with various cofactors were studied using Photometric Dispersion Analysis (PDA). PEO-corilagin interactions were studied by Isothermal Titration Calorimetry (ITC), liquid state proton Nuclear Magnetic Resonance (1H NMR) and carbon 13C NMR. The ITC and NMR results agree with calculations: PEO/corilagin complexes do not form at room temperature. PEO and corilagin only associate in the presence of salt, confirmed by NMR. Cofactors can cluster PEO (clustering cofactors) and some do not (non-clustering cofactors).