What is happening during phaseseparation of different polymers?
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NUCLEATION & GROWTH AND SPINODAL DECOMPOSITION
Polymer blends can either form homgenous mixtures or they can undergo phase separation. The formation of a two-phase structure is usually induced by a change in temperature or molecular weight.
Whether two polymers are mutually miscible or whether a polymer is soluble in a solvent depends on the composition and the shape of the free energy curve. In general, blends are miscible if the free energy of mixing is negative, Δgmix < 0. However, this criterion alone is not sufficient to determine if a mixture is truly stable against phasing into two polymer mixtures of different composition. It only states that the mixture will not separate into two phases of pure components, like pure solvent and polymer. To better understand the phase behavior of polymer blends and solutions, we have to understand how the shape of the free energy curve of mixing effects the stability of the system. The figure below shows as an example the Gibbs free energy per unit volume of a blend of 100k/100k polystyrene (PS) and poly(cyclohexyl methacrylate) (PCHMA) as a function of composition for four different temperatures.
Polymer blends can either form homgenous mixtures or they can undergo phase separation. The formation of a two-phase structure is usually induced by a change in temperature or molecular weight.
Whether two polymers are mutually miscible or whether a polymer is soluble in a solvent depends on the composition and the shape of the free energy curve. In general, blends are miscible if the free energy of mixing is negative, Δgmix < 0. However, this criterion alone is not sufficient to determine if a mixture is truly stable against phasing into two polymer mixtures of different composition. It only states that the mixture will not separate into two phases of pure components, like pure solvent and polymer. To better understand the phase behavior of polymer blends and solutions, we have to understand how the shape of the free energy curve of mixing effects the stability of the system. The figure below shows as an example the Gibbs free energy per unit volume of a blend of 100k/100k polystyrene (PS) and poly(cyclohexyl methacrylate) (PCHMA) as a function of composition for four different temperatures.
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