Grafting acid effect, mechanisms

Further work (10) with acid effects in the radiolysis of binary mixtures such as benzene-methanol and pyridine-methanol indicates that the acid phenomenon is more complicated than the simple H atom model originally developed ( ). These more recent experiments (10) show that whilst increased hydrogen atom yields in the presence of acid enhance the overall grafting yield, other mechanisms also contribute to this acid effect. Thus the acid stability of intermediate radicals (I-III) and also analogous species involving the trunk polymer are important. With radicals (I-III), at low styrene concentrations in methanol, these intermediates (MR-) will predominantly react with other available... 

Mechanism of Acid Effect in Radiation Grafting. In earlier studies (13,14,15,21) on the mechanism of the acid effect on radiation grafting of styrene (MH) in dioxan or methanol (SH) to cellulose(Cell-OH)the sequence of events depicted in Equations (1) - (9) was proposed to explain the phenomenon. Thus, cellulose can undergo bond... 

Mechanism of Acid Effect in Cellulose UV Comonomer Grafting Procedure. In the earlier work (7) involving the UV grafting of monomers to cellulose, it was shown that radical sites, where copolymerization can occur, are formed in cellulose either by the direct action of UV on... 

More recent detailed work indicates that the acid enhancement in grafting is more complicated than previously considered. Chappas and Silverman have confirmed the presence of the acid effect and have suggested that hydrogen atoms need not be the only explanation although they proposed no alternative mechanism. 

This viscosity increase would then lead to an enhanced Trommsdorff peak as observed in the presence of acid. In reverse, the acid effect in grafting may well be used to substantiate the proposed viscosity explanation for the mechanism of the Trommsdorff effect in general polymerization reactions. 

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