n-Paraffin solid solutions: Modification of phase separation with carbon number

Small-angle neutron scattering is used to monitor microphase formation in the solid state in equimolar binary hydrocarbon systems CnH2n+2:CmD2m+2, for selected n = 20-34 and m = 36. Microphase formation is maximum for n = 28 and negligible for n = 20, 32 and 34. n = 30 is found to be intermediate,These observations are explicable in terms of increasing molar volume differences between the two components forming the mixture. As the chain length difference increases, the formation of a lamellar microphase occurs in preference to a continuous solid solution until this is itself overtaken by two-phase separation.