[[Polymer Solutions]] #### Mixing: Polymers are large and have intermolecular interactions - not [[Ideal solutions]] - Entropy of mixing: $ΔS_m = -R(n_1 lnΦ_1 + n_2 lnΦ_2)$ Φ = volume fraction Intermolecular Interactions: - Solvent-Solvent (1-1), Polymer segment - Polymer segment (2-2) - Solvent- Polymer segment (1-2) Mixing breaks (1-1) and (2-2) interactions to form (1-2) - $Δg_12 = g_12 -1⁄2(g_11 + g_22)$ per (1-2) pair Flory parameter: $X = \frac{(z-2)Δg_12}{kT}$ z = # of cells surrounding each position $ΔG_m = RT(n_1 lnΦ_1 + n_2 lnΦ_2 + n_1 Φ_2 X)$ Accounts for **polymer-solvent interactions** Doesn’t account for: **volume changes** during mixing, more than 1 lattice type, **dilute** polymer solutions with large areas of pure solvent Thermodynamics of mixing: ΔG = H - TΔS - If interactions between solvent and polymer are formed, H = - (exothermic) - If solvent must organize around polymer, ΔS = - and solubility decreases at high T