Photopolymerization kinetics of difunctional thiols with alkenes were studied. Two of the thiols, trans‐1,4‐bis(mercaptomethyl)cyclohexane (CHDMT) and 1,4‐bis(mercaptomethyl)benzene (BDMT) were synthesized. The CHDMT was synthesized via a two step process using potassium thioacetate and hydrochloric acid as reagents. The BDMT was synthesized by a one step process using 1,4‐benzenedimethanebromine with thiourea and potassium hydroxide as reagents. Three types of alkenes (divinyl ether, diallyl ether, and dimethacrylate) were reacted with CHDMT, BDMT or 1,8‐octanedithiol (ODT). The photopolymerization was investigated with and without a photoinitiator. The kinetics of the thiol‐ene photopolymerization was investigated by time‐resolved infrared spectroscopy. It was proposed that the steric hindrance of the cyclohexane (CHDMT) resulted in a lower rate of photopolymerization compared to BDMT and ODT. The vinyl ether (alkene) exhibited the highest activity compared to allyl ether and acrylate which was attributed to a high electron density of the alkene. Incorporation of photoinitiator increased the reaction rate and final conversion of the system, particularly in the ODT system.

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Three new reactive diluents were prepared from tung oil using a Diels‐Alder reaction. The dienophiles were methacryloxypropyl trimethoxysilane (MAS), 2,2,2‐trifluoroethyl methacrylate (TFM) and triallyl ether acrylate (TAEA). The chemical structures were evaluated using 1H NMR, 13C NMR, FT‐IR, GPC and MALDI‐TOF‐MS. Spectra evidence (NMR, MS) indicated that a six‐member ring were formed in all three reactions indicating a Diels‐Alder adduct. The reactive diluents were formulated with a soya‐based alkyd to evaluate viscosity reduction and drying time. The viscosity of alkyd was reduced up to 70% using the reactive diluents. The drying time for the autoxidative reactive diluents with alkyds were 1.8‐1‐7 times faster than alkyd alone. magnified image

Three 3-mercaptopropionate thiols, 1,6-Hexane bis(3-mercaptopropionate) (HD-SH), trans-1,4-Cyclohexanedimethyl bis(3-mercaptopropionate) (CHDM-SH), and 4,4 0 -Isopropylidenedicyclohexane bis(3-mercaptopropionate) (HBPA-SH) were formulated with 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO) and photoinitiator. The formulations were photopolymerized via thiol-ene photopolymerization. A ternary experimental design was employed to elucidate the influence the three thiols on the thermomechanical and coatings properties of thiol-ene photopolymerizable materials. Tensile strength, tensile modulus, elongation-to-break, glass transition temperature (T g ), and crosslink density (XLD) were investigated. Coating properties including pencil hardness, pull-off adhesion, MEK double rubs, and gloss were also investigated. Relative reaction conversion was determined by photo differential scanning calorimeter (PDSC). Thiol-ene photopolymerizable materials containing HBPA-SH resulted in improving tensile strength, tensile modulus, T g , and pencil hardness but lowering of crosslink density and relative conversion. This was attributed to steric and rigidity of the double cycloaliphatic structure. The inclusion of CHDM-SH into the systems resulted in the synergistic effect on elongation-to-break and pull-off adhesion. The HD-SH generally resulted in a diminution of thermomechanical and coating properties, but improved the crosslink density.