Non-bonding orbital interaction

On the other hand, the rapid and extensive association facilitated by protonation of kraft lignin phenoxide moieties as the pH of the aqueous solution is lowered, or when they are present in non-aqueous solvents, is presumably mediated by hydrogen bonding and/or dipolar interactions, with non-bonded orbital interactions remaining the primary intermolecular forces. It has been shown that the absolute molecular weights of associated kraft lignin complexes encountered in /V,/V-dimethylformamide (DMF) could exceed values 1000 times larger than those observed in aqueous alkaline solutions. ... 

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