Swelling during dissolution

Surface erodible matrix systems. The first system is a solid matrix that does not disintegrate nor swell during dissolution but dissolves from the surface that is exposed to a dissolution medium. In this case, the drug is released from the eroding surface, and the dissolution profile simply... 

The resist has a high sensitivity and high resolution capability. The suitable photo absorption, excellent dissolution kinetics and no swelling during development contribute to such superior characteristics of this resist. 

Nonerodible systems. In the second matrix system, the matrix does not change during dissolution (insoluble, no disintegration, and no swelling). Polymers that are hydrophobic or cross-linked polymers often are used for the matrix. The drug solid is dissolved inside the matrix and is released by diffusing out of the matrix. Both dissolution and diffusion contribute to the release profile of this type of matrix systems. The mathematical expression for this system can be derived from the following equation ... 

The amplitude of the oscillations in reflected light intensity appears to remain constant as the blends dissolve. This would indicate that the undissolved portion of the film is not undergoing swelling or extraction to any noticeable extent. The second feature, observable especially in the high molecular weight PMMA blend, is an increased offset between the maximum amplitude during dissolution and the reflection from the bare wafer after dissolution is complete (Figure 6). 

Chemical, mechanical, and thermal stability. Resistance to both microbial degradation and swelling or dissolution in the reaction medium. High permeability to reactant and product species (and to the enzyme during the immobilization process) (pore diameters in the 10-50 nm range and porosities of 50% or better). 

Unlike classic solvent-developed negative resists such as cychzed rubber/ bisazide resist, which swell during development, the positive DNQ/novolac resists do not appreciably swell during their development in aqueous alkaline solutions. It should be emphasized that the dissolution of novolac is not exactly the same as that of the usual case II mass transfer kinetics in that it is not physical relaxation of the polymer molecules that is rate controlling. In case II dissolution, the rate-determining events occur at the polymer-gel interface. ... 

A very important property of novolak is that the resolution of photoresists based on this resin is not limited by swelling during development in aqueous base. Recently, it was argued that some swelling, at least superficial, may occur This enables penetration of ions into the layer which can explain the observation that the rate of dissolution decreases, when the cation of the aqueous base developer increases in size. 

J. Voelkel, Salt effect during the swelling and dissolution of poly(vinyl alcohol). Influence on the nature of ions, Pol J Chem, 55 445-455,1981. 

Light scattering experiments should be performed in dilute solution. Since the size of the clusters may increase during dissolution due to swelling, it is not evident that the radius measured can be compared with expression (20). The same difficulty is encountered in intrinsic viscosity measurements. 

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