Self-assembly and morphology of gel networks in l,3:2,4-bis- O-( p-methylbenzylidene)-D-sorbitol/ n-dibutylphthalate

Abstract

We investigated the self-assembling structure of the 1,3:2,4-bis- O-( p-methylbenzylidene)-D-sorbitol (PDTS)/ n-dibutylphthalate (DBP) system in the parameter space of temperature T and solute concentration Φ PDTS. Optical microscopic studies revealed that the phase diagram can be divided into four regions. In region I at high T the system is a homogeneous solution. In region II at lower T and low Φ PDTS, the system still has fluidity but has microgels having spherulitic texture of PDTS crystallites. Regions III and IV at even lower T but higher Φ PDTS are in a gel state. In region III, the PDTS forms volume-filling spherulites due to the solid–liquid phase transition of the saturated PDTS solutions. In region IV at the lowest T, both the liquid–liquid phase-separation process and the solid–liquid transition of the PDTS are involved in the self-assembling processes. In this region a bicontinuous phase-separated structure is first formed by liquid–liquid phase separation via spinodal decomposition (SD). The subsequent solid–liquid transition of the PDTS in the PDTS-rich region forms percolating crystalline fibrils rather than spherulites. The formation of the crystalline fibrils pins further growth of the bicontinuous structure via SD.