Sustainable Sorbitol Dehydration to Isosorbide using Solid Acid Catalysts: Transition from Batch Reactor to Continuous-Flow System

A Study of Isosorbide Synthesis from Sorbitol for Material Applications Using Isosorbide Dimethacrylate for Enhancement of Bio-Based Resins

Bio-based cross-linkers can fulfill the role of enhancing additives in bio-sourced curable materials that do not compare with artificial resin precursors. Isosorbide dimethacrylate (ISDMMA) synthesized from isosorbide (ISD) can serve as a cross-linker from renewable sources. Isosorbide is a bicyclic carbon molecule produced by the reaction modification of sorbitol and the optimal conditions of this reaction were studied in this work. The reaction temperature of 130 °C and 1% w/w amount of para-toluenesulfonic acid (p-TSA) were determined as optimal and resulted in a yield of 81.9%. Isosorbide dimethacrylate was synthesized via nucleophilic substitution with methacrylic anhydride (MAA) with the conversion of 94.1% of anhydride. Formed ISD and ISDMMA were characterized via multiple verification methods (FT-IR, MS, 1H NMR, and XRD). Differential scanning calorimetry (DSC) proved the curability of ISDMMA (activation energy Ea of 146.2 kJ/mol) and the heat-resistant index of ISDMMA (Ts reaching value of 168.9) was determined using thermogravimetric analysis (TGA). Characterized ISDMMA was added to the precursor mixture containing methacrylated alkyl 3-hydroxybutyrates (methyl ester M3HBMMA and ethyl ester E3HBMMA), and the mixtures were cured via photo-initiation. The amount of ISDMMA cross-linker increased all measured parameters obtained via dynamic mechanical analysis (DMA), such as storage modulus (E') and glass transition temperature (Tg), and the calculated cross-linking densities (νe). Therefore, the enhancement influence of bio-based ISDMMA on resins from renewable sources was confirmed.

Comparison of Eco-friendly Ti-M Bimetallic Coordination Catalysts and Commercial Monometallic Sb- or Ti-Based Catalysts for the Synthesis of Poly(ethylene-co-isosorbide terephthalate)

Sustainable development greatly benefits from the effective synthesis of bio-based copolymers that are environmentally friendly. To enhance the polymerization reactivity for the production of poly(ethylene-co-isosorbide terephthalate) (PEIT), five highly active Ti-M (M = Mg, Zn, Al, Fe, and Cu) bimetallic coordination catalysts were designed. The catalytic activity of Ti-M bimetallic coordination catalysts and single Sb- or Ti-based catalysts was compared, and the effects of catalysts with a different type of coordination metal (Mg, Zn, Al, Fe, and Cu) on the thermodynamic and crystallization properties of copolyesters were explored. In polymerization, it was found that Ti-M bimetallic catalysts with 5 ppm (Ti) had higher catalytic activity than traditional antimony-based catalysts or Ti-based catalysts with 200 ppm (Sb) or 5 ppm (Ti). The Ti-Al coordination catalyst showed the best-improved reaction rate of isosorbide among the five transition metals used. Utilizing Ti-M bimetallic catalysts, a high-quality PEIT was successfully synthesized with the highest number-average molecular weight of 2.82 × 10⁴ g/mol and the narrowest molecular weight distribution index of 1.43. The glass-transition temperature of PEIT reached 88.3 °C, allowing the copolyesters to be used in applications requiring a higher T_g, like hot filling. The crystallization kinetics of copolyesters prepared by some Ti-M catalysts was faster than that of copolyesters prepared by conventional titanium catalysts.

Coordination of sorbitol to Ga(OTf)3 in the liquid phase: an experimental and theoretical study

In a solution of sorbitol (SBT) and Ga(OTf)₃ compounds, the coordination of sorbitol (SBT) to [Ga(OTf)_n]^3-n (n = 0-3) has been investigated, using both ESI-MS spectra and density functional theory (DFT) calculations at the M06/6-311++g(d,p), aug-cc-pvtz level using a polarized continuum model (PCM-SMD). In sorbitol solution, the most stable conformer of sorbitol includes three intramolecular H-bonds, i.e., O2H⋯O4, O4H⋯O6, and O5H⋯O3. Through ESI-MS spectra, in a tetrahydrofuran solution of both SBT and Ga(OTf)₃ compounds, five main species are observed, i.e., [Ga(SBT)]³⁺, [Ga(OTf)]²⁺, [Ga(SBT)₂]³⁺, [Ga(OTf)(SBT)]²⁺, and [Ga(OTf)(SBT)₂]²⁺. Through DFT calculations, in a solution of sorbitol (SBT) and Ga(OTf)₃ compounds, the Ga³⁺ cation tends to form five six-coordination complexes, i.e., [Ga(η2O,O-OTf)₃], [Ga(η3O2-O4-SBT)₂]³⁺, [(η2O,O-OTf)Ga(η4O2-O5-SBT)]²⁺, [(η1O-OTf)(η2O2,O4-SBT)Ga(η3O3-O5-SBT)]²⁺, and [(η1O-OTf)(η2O,O-OTf)Ga(η3O3-O5-SBT)]⁺, which are in good agreement with the experimental observation of the ESI-MS spectra. For both [Ga(OTf)_n]^3-n (n = 1-3) and [Ga(SBT)_m]³⁺ (m = 1, 2) complexes, the negative charge transfer from ligands to the Ga³⁺-center plays an important role in their stability, because of the strong polarization of the Ga³⁺ cation. For [Ga(OTf)_n(SBT)_m]^3-n (n = 1, 2; m = 1, 2) complexes, the negative charge transfer from ligands to the Ga³⁺-center plays an essential role in their stability, accompanied by an electrostatic interaction between the Ga³⁺-center and ligands and/or spatial inclusion of ligands toward the Ga³⁺-center.