Effects of Composition and Matrix Polarity on Network Development in Organogels of Poly(ethylene glycol) and Dibenzylidene Sorbitol

Abstract

Dibenzylidene sorbitol (DBS) is a low-molecular-weight organic molecule that can gel a variety of organic solvents and polymers by self-organizing into a three-dimensional nanofibrillar network through hydrogen-bonding and phenyl interactions. In this work, we investigate the composition dependence of such “organogels” prepared with poly(ethylene glycol) (PEG) and two PEG derivatives differing in methoxy end- group substitution, which serves to reduce matrix polarity. Transmission electron microscopy reveals that individual DBS nanofibrils measure from about 10 to 70 nm in diameter, with a primary nanofibrillar diameter of about 10 nm. Dynamic rheological measurements indicate that the rate by which the elastic modulus increases during gelation, the temperatures corresponding to gel formation and dissolution, and the magnitude of the elastic modulus are all sensitive to the DBS mass concentration (φ) and the matrix polarity. Hydroxy-end-capped PEG/DBS systems gel more slowly, but dissolve faster, than their methoxy-end-capped analogues at constant φ. The elastic modulus, however, is less dependent on matrix polarity and scales as φ 1.8 over the range of φ examined in PEG/DBS organogels. Time−temperature superposition analysis provides direct evidence for the activation energy of network evolution increasing linearly with (i) decreasing φ at constant matrix polarity and (ii) increasing matrix polarity at constant φ.

Directed Crystallisation of Poly(ε‐caprolactone) using a Low‐Molar‐Mass Self‐Assembled Template

“…We have anticipated that the behaviour of the DBS is strongly dependent on the polarity of the solvent and this is indeed the case. Wilder et al [22] have shown that even changing the end groups of the polymer solvent (polyethylene glycol) can affect both the kinetics of gel formation and the dissolution temperature by up to 10 8C. Nogales et al reported that the shear-induced anisotropy in DBS/poly(propylene) was only possible during shear flow at temperatures less than 180 8C.…”

1,3:2,4-Dibenzylidene-d-sorbitol (DBS) and its derivatives – efficient, versatile and industrially-relevant low-molecular-weight gelators with over 100 years of history and a bright future

“…63 It has been reported that using PEG derivatives with a pendant methoxy group at one end tends to enhance the speed of gelation. For example, the nanofibrils of PEG-DBS gel systems were 10-70 nm in diameter with a primary nanofibrillar diameter of 10 nm; identical to those of gels of DBS in low-molar-mass organic solvents.…”

Improved photostability of Vitamin A palmitate originating from self-assembled supramolecular gels

“…The solvent composition greatly affects the formation and property of the gels [22,23]. Two kinds of solvent systems for the MDBS gels were investigated in this work.…”