Observing a Chemical Reaction at a Buried Solid/Solid Interface in Situ

Abstract

Chemical reactions are the most important phenomena in chemistry. However, chemical reactions at buried solid/solid interfaces are very difficult to study in situ. In this research, the chemical reaction between two solid polymer materials, a nylon film and a maleic anhydride (MAH) grafted poly(ethylene-octene) (MAHgEO) sample, was directly analyzed at the buried nylon/MAHgEO interface at the molecular level in real time and in situ, using surface and interface sensitive sum-frequency generation (SFG) vibrational spectroscopy. Disappearance of nylon signals indicated a chemical reaction between amine and hydrolyzed amide groups of nylon and MAH groups on the MAHgEO at the buried interface. The appearance of SFG signals from reaction products was also observed at the buried nylon/MAHgEO interface. The mechanism of the observed interfacial reaction was further analyzed. Temperature-dependent SFG experiments were performed to measure the activation energy of the interfacial reaction, enabling a comparison with that reported for the bulk materials. The interfacial chemical reaction between nylon and MAHgEO greatly improved the adhesion of these dissimilar materials. The detailed analysis of a chemical reaction between two polymers at the polymer/polymer buried interface underscores the utility of SFG as a powerful analytical tool to build understanding of buried interfaces and to accelerate the design of interfacial structures with desired properties.

Probing Molecular Behavior of Carbonyl Groups at Buried Nylon/Polyolefin Interfaces in Situ

“… It is interesting to see that the nylon CO signal, observed previously from the nylon surface and buried nylon/EO interface, almost disappeared in the ssp spectrum and decreased tremendously in the ppp spectrum at the buried nylon/MAHgEO interface. Such different interfacial structures at the buried nylon/EO and nylon/MAHgEO interfaces can be correlated to varied adhesion strengths for these two interfaces . A peak at 1725 cm –1 was found to dominate the SFG spectrum collected from the buried nylon/MAHgEO interface.…”

“…A peak at 1725 cm –1 was found to dominate the SFG spectrum collected from the buried nylon/MAHgEO interface. This band is related to the carboxylic acid groups and imide groups in the reaction product . The current study focuses on the peak assignment of the SFG spectra collected from the nylon/polyethylene interfaces.…”

“…In this study, we expand this to investigate the molecular structure of the nylon/MAH-grafted polyethylene buried interface, focusing on the polar CO groups of MAH-grafted polyethylene at buried CaF 2 and nylon interfaces in situ. The results on the interfacial chemical reactions between nylon and MAH-grafted polyethylene probed using SFG have been summarized in a different article, which is being submitted . It is worth mentioning that in real production, the polymer pellets (nylon and MAH-grafted polyolefins) are melted, co-extruded, and blown at high temperature to make multilayer films.…”

“…The results on the interfacial chemical reactions between nylon and MAH-grafted polyethylene probed using SFG have been summarized in a different article, which is being submitted. 54 It is worth mentioning that in real production, the polymer pellets (nylon and MAH-grafted polyolefins) are melted, coextruded, and blown at high temperature to make multilayer films. Spin-coated and melted films serve as a model to study interfaces of the multilayer films, which may not totally represent the real films, but can provide a basic understanding of molecular behavior at the buried interfaces.…”

Analyses of the Adhesion Interphase of Isotactic Polypropylene Using Hot-Melt Polyolefin Adhesives

“…Recent drastic developments of the instruments for interfacial analyses and inspection have revealed not only the structure and properties of the interphase but also molecular behaviors of the polymer chains at the interphase. There are various candidates of instruments for the precise analyses of the interphase, for example, transmission electron microscope (TEM), ,− atomic force microscope (AFM), − confocal Raman scattering microspectroscope, ,,− AFM-infrared spectroscope (AFM-IR), − sum frequency generation (SFG) vibrational spectroscope, − X-ray photoelectron spectroscope (XPS), − neutron reflectometer (NR), − X-ray absorption fine structure (XAFS) measurement, , Rutherford scattering measurements, − and so on. These advanced analysis technologies provide the information at the interphase including nanostructure, molecular orientation, distribution, and chemical bond states.…”