The critical deprotonation model

Reiser, Photoreactive Polymers The Science and Technology of Resists, p. 218, John Wiley Sons, Hohoken, NJ (1989). 

They reported that the dissolution rate is determined by the kinetics of the last step  

Furthermore, the state of critical deprotonation involves a multistage acid-base equilibrium, comprising very fast processes that are diffusion limited, even in fluid solution. The rate of phenolate formation in the penetration zone in this case is determined by the rate of supply of the reactants. Consequently, the rate of dissolution of the resin, which is dependent on the deprotonation process, is controlled by the diffusion of the developer into the polymer matrix.  

and Reiser have estimated the diffnsion coefficient of some cations from the dissolution rate and the width of the penetration zone. Using the observed dissolution rate R (200 A/s) and an estimated penetration width d of 20-100 A, the authors have estimated the diffusion coefficient of the cations in novolac resins to be on order of 

These authors have also constructed a model for the diffusion coefficient in terms of the base concentration in the penetration zone D(c) as 

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Examples of models that have been proposed in an attempt to link the above steps into a coherent mechanism include the membrane model, the secondary structure model, the critical deprotonation model, the percolation model, the critical ionization model, and the stone wall model, to mention but a few. In the following sections, we briefly review the aspects of these models. 

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