Effect of Oligomer Segregation on the Aggregation State and Strength at the Polystyrene/Substrate Interface

The interfacial strength of polystyrene (PS) with and without PS oligomers in contact with a glass substrate was examined to determine the relationship between the interfacial aggregation state and adhesion. The shear bond strength and adsorbed layer thickness of neat PS exhibited a similar dependence on the thermal annealing time: they increased to constant values within almost the same time. This implies that the adhesion of the polymer is closely related to the formation of an adsorbed layer at the adhesion interface. Nevertheless, in the case of PS with a small amount of oligomer, the shear bond strength decreased, while the adsorbed layer thickness was almost the same as that of neat PS. Based on the results of interfacial analyses, we propose that the interfacial segregation of the oligomer reduced the entanglement between the interfacial free chains in the adsorbed layer and the bulk chains.

Automated summary

The study showed that the presence of oligomers in PS reduced the interfacial entanglement between free chains and bulk chains in the adsorbed layer, leading to a decrease in shear bond strength despite having a similar adsorbed layer thickness to neat PS.