Various solubility parameters are used to determine miscibility of drug in polymer in solid dispersion. How can we conclude miscibility by using solubility parameter?
I think that your question can be answered by the english science dictionary:
Miscibility Relating to two or more substances, such as water and alcohol, that can be mixed together or can dissolve into one another in any proportion without separating.
Solubility
1. the ability of a substance to dissolve; the quality of being soluble
2. a measure of this ability for a particular substance in a particular solvent, equal to the quantity of substance dissolving in a fixed quantity of solvent to form a saturated solution under specified temperature and pressure. It is expressed in grams per cubic decametre, grams per hundred grams of solvent, moles per mole, etc
Thus it seems that the only difference is the fact that two miscible substances are substance completely soluble one in each other.
Thank you Sir.Two miscible polymers can not completely soluble in each other at a molecular level.
I suppose you should read this paper to fully understand the meaning of miscible polymers, blends and composites (you can find it here in researchgate)
Pure Appl. Chem., Vol. 76, No. 11, pp. 1985–2007, 2004.
Any good book on polymers or polymer blends and solution can provide the relevent basic information.
The Hildebrand solubility parameter (δ) provides a numerical estimate of the degree of interaction between materials, and can be a good indication of solubility. The Hildebrand solubility parameter is the square root of the cohesive energy density,The cohesive energy density is the amount of energy needed to completely remove unit volume of molecules from their neighbours to infinite separation. For a material to dissolve, these same interactions need to be overcome as the molecules are separated from each other and surrounded by the solvent. It can be developed for polymers.
In addition to the above great comments, you should consider that the solubility parameter approach cannot predict miscibility in the systems that exhibit LCST behaviour. In fact, Flory–Huggins interaction approach fails to predict LCST behaviour as it can only predict positive values for the interaction parameter. For most, small molecules/polymer systems (such as polymer/solvent) this approach should work fine but if you have specific interactions between the components, then the solubility parameter approach cannot be used.
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