Evaluation of new 3‐mercaptopropionate thiols for thiol‐ene photopolymerization coatings using experimental design

Abstract

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.

Efficient initiation of radical‐mediated thiol‐ene chemistry with photoactive silica particles

“…Synthesis of 3‐(trimethoxysilyl)propyl 3‐[bis(2,4,6‐trimethylbenzoyl)phosphinyl]‐2‐methyl‐propionate (TEMSI 2 ‐BAPO) was performed according to ref. . 1,3,5‐Triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TATATO) was supplied by Sigma‐Aldrich (St. Louis, United States).…”

“…Irgacure 819 (bis(2,4,6‐trimethylbenzoyl)‐phenylphosphineoxide, BAPO) was provided by BASF (Ludwigshafen, Germany). 1,6‐Hexane bis(3‐mercaptopropionate) (HD‐SH) was synthesized according to previous literature . Precipitated silica particles (PERKASIL KS 408) with a BET surface area of 180 m 2 /g and a primary particle size of 18 nm were obtained from Grace (Düren, Germany).…”

Thiol‐Ene versus Binary Thiol–Acrylate Chemistry: Material Properties and Network Characteristics of Photopolymers

“…[36,38] All other chemicals were purchased from Sigma-Aldrich (St. Louis, United States) and were used without further purification. 4,4 0 -Isopropylidenedicyclohexane bis(3-mercaptopropionate) (HPBA-SH), 1,6-hexane bis(3-mercaptopropionate) (HD-SH) and di[trimethylolpropane tri(3-mercaptopropionate)] (di-TMPMP) were synthesized according to previous literature.…”

“…[38] 11.38 g Di (trimethylolpropane), 22.29 g 3-mercaptopropionic acid, and 0.20 g p-toluene sulfonic acid were mixed in 150 mL anhydrous toluene and put into a 500 mL round-bottom three-necked flask equipped with mechanical bar, Dean-Stark apparatus, and reflux condenser. [38] 11.38 g Di (trimethylolpropane), 22.29 g 3-mercaptopropionic acid, and 0.20 g p-toluene sulfonic acid were mixed in 150 mL anhydrous toluene and put into a 500 mL round-bottom three-necked flask equipped with mechanical bar, Dean-Stark apparatus, and reflux condenser.…”

“…This trend can be explained by the combined effect of low SH-conversions and high amount of acrylate homopolymerization observed in TAIC/HPBA-SH systems, which lead to a very broad glass transition region (DT ¼ 44 C). [38] Along with the chemical structure, the functionality of the thiol plays also an important role in the thermal and mechanical performance of the corresponding thiol-ene networks. The photochemical crosslinking of TATATO with HPBA-SH yields rigid networks with a low tensile strain at break (3.5%), high Young's modulus (484.2 MPa) and high tensile strength (15.6 MPa).…”