Fundamental Studies of Dissolution Inhibitors in Poly(norbornene-alt-maleic anhydride) Based Resins

Using terpolymers of Poly(norbornene-alt-maleic ahydride-co-acrylic acid) (P(NB/MA/AA)) the dissolution inhibition mechanism for two types of common additives t-butylcarboxylate (e.g., t-butyl cholate) dissolution inhibitors (DI) and onium salt photoacid generators (PAGs) were examined. For simple cholate ester derivatives increasing interactions with maleic anhydride repeating units paralleled the dissolution inhibition (t-butyllithocholate > t-butyldeoxycholate > t-butylcholate). For a wider range of cholate derivatives, increasing hydrophobicity and ability of these DIs to interact with the terpolymer matrix as measured by easier cloud point formation in water/acetone mixtures is a good predictor of increased dissolution inhibition. Increases in dissolution promotion appeared to track with the number of carboxylic acid moieties and the hydrophobicity of carboxylic acids moieties released upon acidolytic cleavage of cholate esters. Finally, for onium salt PAGs, increasing the size of fluorinated anions decreased dissolution inhibition. This may be because these anions offer more steric hindrance which disfavors interactions with the terpolymer matrix.