STUDY OF MICROPHASE SEPARATION IN SOLID, BINARY ALKANE MIXTURES BY SMALL-ANGLE NEUTRON AND X-RAY-SCATTERING

A combination of small angle neutron (SANS) and small angle X-ray scat tering (SAXS) is used to study phase separation following crystallizat ion in 1:1 mixtures of n-C30H62/n-C36D74 quenched from the melt to roo m temperature. The SAXS data show that the quenched mixture is a solid solution with a well-defined lamellar structure which is established on a time scale of minutes after quenching from the melt. On this init ial time scale the SANS data indicate that the deuterated and protonat ed chains remain essentially randomly mixed. At longer times the scatt ering curves from both techniques show features consistent with phase separation in the form of nonrandom stacking of lamellae that are alte rnately enriched in one of the components. The possible effect on the neutron scattering of lateral intralamellar phase separation appears t o be overwhelmed by this interlamellar phase separated structure.