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A series of polyester prepolymers was synthesized from itaconic acid, phthalic anhydride, propane-1,2-diol and diethylene glycol by condensation polymerization. The use of itaconic acid as a source of unsaturation (instead of more common maleic anhydride giving fumarate moieties) enabled to replace styrene reactive diluent by methyl methacrylate. Room temperature curing of a model polyester resin was initiated by butanone peroxide in combination with several cobalt-, iron- and vanadium-based accelerators. Measurements of gelation time and exothermic behavior in thermally isolated installation revealed very promising catalytic properties for oxidovanadium(IV) dibutylphosphate. In follow-up tests, mechanical properties of the model unsaturated polyester resin were tuned by variation in propane-1,2-diol/diethylene glycol ratio and composition of acrylate/methacrylate reactive diluent. Mixtures of methyl methacrylate with secondary crosslinking agents (e.g., ethylene dimethacrylate, triethyleneglycol dimethacrylate and trimethylolpropane triacrylate) enabled to improve ultimate tensile strength, Young's modulus, tensile toughness and impact toughness. Reported experimental data indicate that the described styrene- and cobalt-free system is very promising for reduction in health and ecological issues of currently used unsaturated polyester resins curable at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: The sol–gel polymerization and resulting structures of organic-inorganic systems based on hybrid methacrylate oligomers have been studied using SEC, DSC, and SAXS. The block and random oligomers with narrow polydipersity were prepared by group transfer polymerization. All the oligomers contain 3-(trimethoxysilyl)propyl methacrylates in the chain and form silsesquioxane (SSQO) clusters by hydrolytic polycondensation, serving as cross-linking domains of the organic-inorganic network. The water miscibility and gelation of synthesized oligomers were evaluated. The systems studied can be divided into two groups—gelling and non-gelling oligomers as a result of the competition between cyclization and intermolecular reaction. The extent of cyclization and intermolecular polycondensation depends on the oligomer structure, i.e. position and number of the functional trimethoxysilyl-monomer units, and on molecular weight of the oligomeric chains. Due to the incompatibility of the SSQO framework and organic chains, microphase separation and structure ordering occur during polymerization. [Copyright &y& Elsevier]