Synthesis of cocyclic(arylene disulfide) oligomers and their adhesion properties as heating-melt adhesive

Several series of homo- and cocyclic(arylene disulfide) oligomers were synthesized by the catalytic oxidation of arylenedithiols with oxygen in the presence of a copper-amine catalyst. These cyclic(arylene disulfide) oligomers can readily undergo free radical ring-opening polymerization at elevated temperatures in the melt. The cocyclic oligomers had much lower melt flowing temperatures than those of the homocyclic oligomers, which made it possible for the former to undergo ring-opening polymerization at relatively lower temperatures. The composition of the synthesized cyclic oligomers and their ring-opening polymerization were analyzed by proton NMR and gel permeation chromatography (GPC) analyses, respectively. The bonding strength of the cocyclic(arylene disulfide) as a heating-melt adhesive was determined using an Instron tester at a cross-head speed of 5 mm/min. The experimental results showed that the ring-opening polymerization of cocyclic(arylene disulfide) oligomers took place at a temperature as low as 150°C within a short time of 5 min. The ring-opening reaction temperature of the cocyclics was 50°C lower than that of the corresponding homocyclics. The shear-strength for the aluminum substrate prepared at 150°C utilizing the cocyclics was around 5.0 MPa. The cyclic(arylene disulfide) oligomers could be used potentially as high-temperature heating-melt adhesives, coatings, and sealants, as well as matrices for high-performance composites and nanocomposites.