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The impact of polymerization protocol on phase structure and properties of entirely lipid-derived thermoplastic poly(ester urethane)s (TPEU)s was investigated. The TPEUs were synthesized from 1,7-heptamethylene diisocyanate, polyester diols and 1,9-nonanediol (ND) as chain extender. A two-stage polymerization method was used to prepare two TPEUs; one in which ND was added in the first stage of polymerization as part of the prepolymer and another in the second stage after the prepolymer was formed. Two very different morphologies exhibiting different degrees of phase separation were obtained, driven by the sequence of addition of the chain extender. The incorporation of the chain extender in the prepolymer resulted in a TPEU with a narrow hard segment distribution, enhanced urethane-urethane hydrogen bonding and higher molecular weight. The hydrogen bond density, degree of crystallinity, glass transition temperature and mechanical properties of the TPEUs were directly related to the degree of phase separation and hence polymerization protocol.

Vegetable oils (VOs) are one of the most promising renewable sources of phase change materials (PCMs). Although several studies have been published, there are no comprehensive reviews of VO-based PCMs or the structure-property relationships governing their thermal behavior. This critical review systematically organizes the published literature on VO-based PCMs focusing on the role that structural elements play in the establishment of thermal properties relevant to thermal energy storage (TES). Thermal properties such as thermal stability, phase change temperature, enthalpy, entropy and thermal conductivity are the functional parameters examined within the context of structure. The empirical correlations between structure and thermal functionality of PCMs are assembled in predictive relationships, drawing a unified picture of the rules that govern their phase behavior. Relationships such as the effect of fatty chain length, number and types of functional groups, symmetry, and isomerism on the molecule's thermal properties were explored. Phase change temperatures and enthalpies of linear saturated PCMs with monofunctional group follow exponential rise to maximum functions while the entropy increases linearly with increasing carbon chain length. The ranges for phase change temperature, enthalpy, entropy, thermal stability, and thermal conductivity for all the VO-based PCMs in this work were −100–300 °C, 90–270 J/g, 100–500 J/mol/K, 95–350 °C and 0.1–0.4 W/mK respectively. The gathered knowledge is critically discussed to provide directions for future PCM research and development.

The molecular dynamics involved in the emergence of solidity in glass-forming organic esters are poorly understood. Some branched esters are examples of organic materials that do not crystallize under typical thermal protocols but form glasses at low temperatures. The present work investigates the solid-to-liquid phase transition of three fatty branched esters, which are synthetic mimics of compounds found in jojoba oil (so-called jojoba-like esters or JLEs), using low-field 1H NMR and differential scanning calorimetry (DSC). Spin–lattice and spin–spin relaxation times (T1and T2, respectively) measured from the solid-arrested state to the fluid state provided information about the dynamics and structures of the JLEs below and above the glass transition temperature (Tg). The T1and T2state diagrams indicated that the transition involves an intermediary viscoelastic state similar to that observed in polymers. 1H NMR detected the transition because the backbone is “arrested” at the viscoelastic–fluid transition. Tgmeasured by DSC recorded the “arrest” of the molecules when the branches enter the glassy state deep in the viscoelastic state matching the lowest temperature singularity in the T1and T2state diagrams. The rotational correlation time determined using the Bloembergen–Purcell–Pound (BPP) theory indicated an Arrhenius function for T> Tgwith an activation energy of 26.1 kJ·mol–1similar to those of other organic glass formers. The minimum of the coupling constant × T1(KT1) technique and simultaneous solution of the BPP expressions showed that the distance between neighboring protons remains constant in the glassy state (rg= 2.09 Å) and increases almost linearly in the viscoelastic and fluid states.

Thermal, flow, and oxidative stability behavior of oleyl oleate monoesters derivatized with sulfur-containing functional groups (sulfide and sulfonyl) suggests that these compounds may be suitable candidates as sustainable alternative base oils to replace mineral oils in lubricant formulations. A robust thiol-ene addition and oxidation synthesis route was utilized to prepare the materials in high yields and high purity with no byproducts. Changes in the functional properties of oleyl oleate are attributable to the enhanced intermolecular forces and irregular conformations introduced by the bulky polar sulfur-containing groups, which introduce steric hindrances and alter phase behavior. The derivatization of oleyl oleate with sulfide and sulfonyl pendant groups resulted in a lower enthalpy of crystallization (10 kJ/mol compared to 76 kJ/mol for oleyl oleate) and an increased viscosity from 16.3 mPa·s to as high as 175.5 mPa·s at 40 °C. The sulfonyl pendant groups imparted higher viscosity to oleyl oleate due to sulfonyl–sulfonyl interactions. The presence of sulfonyl and sulfide pendant groups increased oleyl oleate oxidation onset (Tonox) by 47 and 149 °C, respectively. The sulfide pendant groups converted hydroperoxides as they are formed into non-radical derivatives and thus delayed oxidation. Overall, the sulfide- and sulfonyl-branched oleyl oleate monoesters of this work presented useful thermal transition and viscosity profiles which are competitive with those of mineral oils, making them suitable alternatives for use in lubricant formulations.

•Diamides were prepared and characterized for use as phase change materials (PCM).•The competion between the dispersion forces, hydrogen bonding, and entropic effects drive the diamide's performance.•A unique role of the diamine chain length in adjusting hydrogen bonding strength was revealed.•The almost double thermal conductivity of diamides compared to paraffin correlated to hydrogen bonding.•The amides expand the range of PCM suitable for medium temperature energy storage.