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Abstract
The energies of interaction of phenol, monomethylol and dimethylol phenols, trimethylol phenol, and of three dihydroxydiphenylmethanes with the surfaces of an elementary model of the crystallite of cellulose II were obtained by molecular mechanics techniques. The results indicated that in the case of phenol-formaldehyde (PF) oligomers, methylolation at least in the monomeric phenol species does not enhance adhesion, with the exception of the case of trimethylol phenol. This appeared to be due to strong steric hindrance counteracting the normally highly attractive interaction induced in resins by methylol groups. All the phenolic oligomers, with the exception of one, were still found by computation to present strong attractive interactions to the cellulose substrate, confirming again the strong adhesion of PF resins to lignocellulosic substrates which has been found experimentally many times before. In the complex case of the separation of a homologous series of oligomers of increasing molecular mass, the good correspondence between the computed results and the experimental chromatography Rf values indicated that computationally obtained energies of adhesion are capable of modelling well experimental realities. This result is of interest because the hydroxybenzyl alcohols and dihydroxydiphenylmethanes do not belong to the same homologous series. The model, at least for these compounds, did not require additional modelling of water molecules other than introducing its dielectric constant in the electrostatic forces calculations.