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This paper proposes a simple method for estimating organogel formation, andhighlights the important role played by solvent viscosity （η） and molecular size （V） ininfluencing the gel properties and the aggregate structures of methyl4,6-O-（p-chlorobenzylidene）-α-D-glucopyranoside （MPBG, a novel gelator） indifferent solvents. Furthermore, a novel form-stable composite phase change material（PCM2） was prepared by incorporating MPBG,1,3:2,4-di-（3,4-dimethyl） benzylidenesorbitol （DMDBS, a gelator） and expanded graphite （EG） into glyceryl tristearate （GT）matrix, and its thermal and structural characteristics were analyzed by DSC, TG-DTA,FT-IR, SEM, TEM and XRD. The form-stability mechanism of PCM2was alsorevealed.The research of gelation tests shows that Teas plot derived from solubilityparameters can be used to estimate the behaviour of a known gelator in untestedsolvents. The method has successfully been tested on the eight gelators reported inliteratures and the untested solvents in the gelation test of MPBG. The research ofsolvent role reveals that the aggregate morphologies of MPBG and the main factorsdetermining the gel properties are obviously different in the monohydric alcohols andthe aromatic hydrocarbons. According to SEM images and X-ray diffraction patterns,in monohydric alcohols with high viscosity value, the self-assembly of MPBG is adiffusion-limited aggregation process resulting from solvent viscosity. Furthermore, itis found that solvent viscosity, compared with the secondary role of polar solubilityparameter （δa）, plays a key role in determining the morphologies of aggregates, thesol-gel phase-transition temperature (Tgel) and the gelation number(Ngel). In contrast,for the aromatic hydrocarbon gels, solvent molecular size is very important indetermining Tgeland Ngelalthough δais the key factor.In PCM2, GT （86.6wt％） is used as the phase change material for thermalenergy storage, and EG （4.6wt%） acted as the thermal conductivity filler. In order toprevent the leakage of GT, gelators （MPBG and DMDBS）, as the supporting material,were added in the composite. The DSC results show that PCM2solidifies at46℃with a latent heat of69J/g and melts at49℃with a latent heat of97J/g when themass percentage of GT in the composite is86.6％. The TG-DTA and FT-IR resultssuggest that PCM2, in operating temperature range, exhibits good thermal stability and chemical compatibility（between the components of the composite）. According toSEM/TEM images and FT-IR spectroscopies, The MPBG and DMDBS molecules, inPCM2, self-assemble into nanofibers that form three-dimensional （3D） networksembedding EG with a3D lamellar network structure. By capillary and surface tensionforces, GT is retained in the pores of the3D networks, so leakage of the melted GTfrom PCM2is prevented. X-ray diffraction patterns and FT-IR data reveal thatadditives （MPBG, DMDBS and EG）in PCM2do not affect the crystal structure ofglyceryl tristearate, and the3D networks of gelators and EG confine the molecule heatmovement of GT in PCM2, which leads to the decrease in the latent heat of theform-stable composite phase change material.
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