Synthesis of novel acryloyloxyalkyl and methacryloyloxyalkyl 6,8-dithiooctanoates and evaluation of their bonding performances to precious metals and alloys

This study investigated the bonding effectiveness of novel acryloyloxyalkyl and methacryloyloxyalkyl 6,8-dithiooctanoates (dithiooctanoate monomers) to precious metals and alloys. Eight kinds of dithiooctanoate monomers were synthesized in 16.09–39.34% yields. They were characterized and confirmed as new compounds using 1H- and 13C-NMR spectroscopy and mass spectral analysis. Eight experimental primers each containing 5.0 wt% of a novel dithiooctanoate monomer in acetone were prepared. After primer treatment and 2,000 thermal cycles, tensile bond strengths of MMA-PMMA/TBBO resin to seven metal adherends were measured. Results were as follows: 17.2–29.3 MPa (Au), 41.9–49.6 MPa (Ag), 36.8–47.6 MPa (Pt), 36.7–47.5 MPa (Pd), 34.0–48.9 MPa (Au alloy), 24.3–49.6 MPa (Ag alloy), 35.0–48.8 MPa (Au-Ag-Pd alloy). 10-Methacryloyloxydecyl 6,8-dithiooctanoate exhibited the highest mean bond strength to gold (29.3 MPa) and 12-methacryloyloxydodecyl 6,8-dithiooctanoate to Au alloy (48.9 MPa). Therefore, it was found that the novel dithiooctanoate monomers synthesized in this study exhibited excellent bonding to precious metals and alloys.