Interfacial rheology for probing the in-situ chemical reaction at interfaces of molten polymer systems

Abstract

The design of new functional materials from immiscible polymers or multi-layered structures using reactive compatibilisation is an efficient approach that has been extensively employed in a wide range of applications. The adhesion/interfacial properties in these multiphase polymeric systems depend on the extent of reaction occurring at the interface. However, probing in-situ interfacial reactions in the molten state has proved challenging. In this study, interfacial shear rheology is used for the first time to directly probe the reaction at the interface between maleic anhydride-grafted polyethylene (PEgMA) and aminopropyl-terminated polydimethylsiloxane (PDMS-(PropNH2)2) used as model reactive polymer systems. Then the reaction at the interface was investigated using interfacial shear rheology based on a newly homemade, lightweight biconical setup. Thereafter, the time evolution of the interfacial tension with the progress of interfacial reaction was assessed using the pendant drop method. First, the extent of reaction was checked using differential scanning calorimetry (DSC) and dynamic rheology coupled with fast-scan FTIR spectroscopy. It has been demonstrated that the molecular weight of the aminated PDMS and the temperature of the medium markedly affect the rate of melt reaction at the interface and related interfacial rheological properties. Interestingly, the ability to assess the reactions at the interface in PEgMA/PDMS-(PropNH2)2 systems, even with low concentrations of reactive functionalities, demonstrates that interfacial rheology is a suitable, sensitive probe that could be applied to other reactive polymer systems, allowing better control of the resulting physical properties.