Organogels are an interesting class of soft materials where an organic fluid is immobilized by the addition of a suitable organogelator. A variety of organogelators, ranging from small molecules to polymers, have been researched and developed for novel applications ranging from drug delivery to consumer products such as deodorant and shampoo. In this study, the ability of trans-1,4-polyisoprene (TPI) to act as an organogelator is examined. TPI is the geometric isomer of cis-1,4-polyisoprene (CPI). While CPI is a viscoelastic liquid at room temperature, TPI is semi-crystalline with a melting temperature of ca. 60 °C.  TPI’s crystallinity provides high mechanical strength, cut abrasion and electrical insulation, and it is used as a processing additive, such as improving the green strength of synthetic polyisoprene. It was hypothesized that TPI would act as a good organogelator if it was able to crystallize in organic solution and form a three-dimensional percolating network. Gelation of TPI/organic solvent was tested by dissolving TPI (10 wt%) at elevated temperature and then cooling. Gelation was qualitatively confirmed by inversion, where a gelled solution did not flow over long time scales. TPI was observed to gel n-alkanes, anisole and butyl acetate. TPI failed to gel phthalates (insoluble) and aromatic solvents (soluble at RT), THF (soluble at RT) and ethyl acetate (insoluble). The gels were further characterized to determine the minimum gelation concentration, gel transition temperatures as a function of composition, and gel morphology. The gel transition temperature vs. concentration curve was consistent with the melting point depression of a solute in solution expected for gelation driven by the crystallization of TPI. Finally, efforts to dry the TPI gels to generate functional xerogels will be presented.

Investigation of trans-1,4-polyisoprene as an organogelator for organic solvents

249th National Meeting (2015)

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