Chemical Science International Journal

Aims: The study aims to synthesise a novel thiourethane-group oligomeric modifier (TGF-8) from thiourea, glycerol and formaldehyde using locally available raw materials, and to determine its molecular structure, molecular mass and thermal behaviour, thereby establishing the scientific basis for its subsequent use as an adhesion- and hydrophobicity-enhancing modifier for sodium liquid-glass adhesives.

Study Design: A two-stage laboratory synthesis (formation of an intermediate dithiourethane, followed by its alkaline polycondensation with formaldehyde), purification by selective liquid–liquid extraction, and structural characterisation by cryoscopic molecular-mass determination, infrared (IR) spectroscopy, gas chromatography–mass spectrometry (GC–MS), and simultaneous differential thermal–thermogravimetric analysis (DTA/TGA). For comparison, an ethylene-glycol-based analogue (TEF-7) was synthesised under identical conditions.

Place and Duration of Study: Department of Chemical Technology, Bukhara State Technical University, Republic of Uzbekistan; the synthesis and the spectroscopic and thermal-analytical work were carried out over the period 2024–2026.

Methodology: Thiourea and glycerol were reacted in a 2:1 molar ratio at 100–110 °C, with ammonia evolution monitored, to give an intermediate dithiourethane. This intermediate was then polycondensed with formalin in an alkaline medium (NaOH) at 120–140 °C to form the target oligomer; the optimal temperature range was established from a series of trials at 110, 120 and 140 °C, with the reaction monitored through the relative viscosity of the reaction mass. The product was separated from unreacted thiourea, formaldehyde and low-molecular-weight fractions by exploiting its selective solubility in dimethyl sulfoxide (DMSO). Molecular mass was determined cryoscopically (GOST 20287-2023 / ISO 3016:2019, triplicate measurements); molecular structure was probed by IR spectroscopy (Shimadzu IRAffinity-1S, 4000–400 cm⁻¹) and GC–MS, while thermal behaviour was examined by DTA/TGA on a LINSEIS synchronous thermal analyser fitted with a K-type thermocouple. The isolated (purified) product yield was not gravimetrically quantified in the present preliminary study and is reported as a target for the companion and follow-up work.

Results: The optimal synthesis temperature was found to be 120–140 °C; below this range methylolation and polycondensation remained incomplete, while above it uncontrolled branching and reduced product solubility were observed. The average molecular mass of the bulk TGF-8 oligomer, determined cryoscopically (colligative, ensemble-averaged measurement), was 2880–3110 g mol⁻¹. IR spectra confirmed hydroxyl (3301.68 and 3184.12 cm⁻¹), amine (1607.11 cm⁻¹), thiourethane [N–C(=S)–O, 1519.66 cm⁻¹] and thiocarbonyl (C=S, 1263.04 cm⁻¹) bands, while the absence of a carbonyl (C=O) absorption is consistent with a thiourethane — rather than urethane — linkage. GC–MS, which is only applicable to volatile, low-molecular-weight species, showed a dominant ion at m/z = 254; this value is far below the cryoscopic average and is interpreted as arising from a low-molecular-weight monomeric/precursor-related species (or an injection-port thermal-decomposition product) rather than from the intact bulk oligomer, and should not be read as the molecular mass of TGF-8 itself. Simultaneous DTA/TGA showed that TGF-8 was thermally stable up to ≈613 °C, above which an exothermic pyrolytic decomposition occurred, the overall mass loss reaching 37.5%; the glycerol-based TGF-8 exhibited a smaller mass loss and higher thermal stability than the ethylene-glycol-based TEF-7 (mass loss 40.5%, decomposition onset ≈556 °C), a difference attributable to the additional hydroxyl group of glycerol.

Conclusion: A new thiourethane-group oligomeric modifier (TGF-8) was successfully synthesised from inexpensive, locally available raw materials and consistently characterised by complementary spectroscopic and thermal methods; full structural elucidation (e.g., by NMR and X-ray diffraction) was not undertaken and remains a target for future work. The oligomer's confirmed thiourethane functionality, cryoscopically determined bulk molecular mass and thermal stability up to industrially relevant temperatures establish it as a promising modifier for silicate-based (liquid-glass) adhesive systems, whose adhesion- and hydrophobicity-enhancing performance is examined in a companion study.