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[Display omitted] • Thermotropic phase behaviours of α -D-mannosides containing nonsymmetrical Guerbet branched chains at sub-zero temperatures. • Occurrence of rippled structures implies the competition between hydrophobic volume and headgroup surface packing. • Temperature-dependent changes in the primary relaxation time were investigated through distortion-sensitive analyses. • Shear viscosity test indicates all liquid crystal phases exhibits shear thinning behaviour. Many aspects govern the nature of the resulting phase of a self-assembly of glycolipid, including its detailed stereochemical structure, solvent type, and state condition. Glycolipid has attracted considerable attention due to its extensive lyotropic applications in surfactant industry and material science. However, its application as thermotropic liquid crystal is unknown and rarely investigated. Herein, the thermotropic properties of a series of glycolipids, namely Guerbet branched chain α -D-mannosides (C 8 to C 24 total carbons) were studied by X-ray scattering, dielectric spectroscopy, and rheology. The shortest chain α ManC 6 C 2 exhibited lamellar phase over the entire temperature range whereas both α ManC 8 C 4 and α ManC 10 C 6 only at elevated temperatures since these have larger hydrophobic volumes. Interestingly, at the room temperature, both anhydrous α ManC 8 C 4 and α ManC 10 C 6 showed formation of rippled structures. Prior to transforming into the fluid lamellar phase, these complex structures possess greater viscosity than the former. The longer chain mannosides (α ManC 12 C 8 and α ManC 14 C 10) adopted an inverse bicontinuous Ia 3 d cubic and inverse hexagonal phases, respectively. The temperature-dependent evolution of dielectric relaxation times, τ (T) of primary relaxation within the lamellar, hexagonal, and isotropic phases is explored. Distortion-sensitive tests, enabled by derivative-based analysis, evaluate the suitability of τ (T) parametrisation using the Vogel-Fulcher-Tammann (VFT) and critical-like equations. According to the dielectric and rheological analyses, as the temperature increases, both ε ‖ a n d ε ⊥ increased, while the viscosity decreased. The findings suggest that higher temperatures are accountable for higher molecular mobility and fluidisation of the phase structure. These fundamental investigations are important to the bottom-up approach development of regulated and specially designed nanoscale material (e.g., a cryoprotective agent). [ABSTRACT FROM AUTHOR]

Medium-chain-length poly-3-hydroxyalkanoates (mcl-PHAs) with varied monomeric compositions were biosynthesized by producer bacteria fed with different fatty acids as carbon source. Octanoic-, lauric-, stearic-, and oleic acids were used to produce four types of mcl-PHAs viz. PHA-OC, PHA-LA, PHA-ST, and PHA-OL, respectively. The mcl-PHAs as film-casted preparations exhibit distinct traits e.g., PHA-OC and PHA-ST films are less flexible than PHA-LA while PHA-OL is a sticky, glue-like material; PHA-ST is opaque whereas PHA-OC, PHA-LA, and PHA-OL displayed transparent layers. The observation is attributed to polymer chain packing and side chain crystallization. A structure-property investigation of these biopolymers was carried out employing different spectroscopic and microscopic analyses in addition to thermal analyses. Comparative analyses of the results were applied in the interpretation and discussion of structure-property relationship. [ABSTRACT FROM AUTHOR]

Radical copolymerization of medium-chain-length poly-3-hydroxyalkanoate (PHA) with methyl acrylate (MA) assisted by high-energy sound wave was investigated. Successful graft copolymerization of poly-3-hydroxyalkanoate –graft– poly-methyl acrylate (PHA-g-PMA) was inferred from the increase in molecular weight of initial neat PHA. The presence of PMA backbone in the graft copolymer was also authenticated by two additional proton peaks at 1.85 and 3.7 ppm. The concentration of PHA, MA and hydrogen peroxide (H2O2) showed significant effects towards the change in the graft copolymer molecular weight. The ideal amount of PHA, MA and H2O2 for graft copolymerization under ultrasonication were determined at 20 g L−1, 0.12 M and 20 μL, respectively. The copolymerizing process between PHA chains and PMA was investigated by analyzing the physicochemical properties of the produced graft copolymers. To this end, dielectric spectroscopy (DS) was used in corroboration to conventional thermal analyses, i.e., differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In addition, small-wide angle X-ray spectroscopy (SWAXS), field emission scanning electron microscopy (FESEM) and contact angle (CA) analysis were used to characterize the film morphology of the graft copolymers. From the results, it is suggested that PHA chains are subjected to pre-fragmentation prior to random grafting with PMA chains. [ABSTRACT FROM AUTHOR]