HEAs are also characterized by their configurational entropy of mixing
([DELTA][S.sub.conf]) of at least 1.5R, where R = 8.314 J x [mol.sup.-1] x [K.sup.-1] is the gas constant.
Our non-crystallizable molecular glass mixture binders have very high entropy of mixing
value, and high glass transition temperature necessary to transform those OLED materials into useful formulations.
During the process of polymerization due to the transition of monomer molecules to polymer chain, there is a sharp decrease in the combinatorial entropy of mixing
of the system.
This means the entropy of mixing
([DELTA]S= k ln[ohm]) is reduced and if the enthalpy of mixing is unfavorable, then the free energy of mixing will be insufficient and spontaneous phase separation will occur.
The second term represents the geometric entropy of mixing
, assuming the additive to behave as a hard sphere.
During thermoset crosslinking within a thermoplastic, phase separation is usually driven by the decrease in the entropy of mixing
, raising the free energy of the system.
However, the entropy of mixing
polymers [S.sup.M] does not play a smaller role (8), especially its noncombinatorial part, arising as a result of disintegration of initial structures of individual polymers and of the formation of a new structure of the blend.