Probing the Nanostructure and Reactivity of Epoxy-Amine Interphases.

Understanding and controlling the structure of interphase regions in epoxy resins have been a long-standing goal in high-performance composite and coating development, since these are widely considered to be weak points in the microstructure of these materials, determining key properties such as fracture strength and barrier performance. These buried nanoscale regions are, however, inaccessible to conventional analytical techniques, and little is understood about their underlying formation mechanism. Here, we combine molecular dynamics (MD) simulation with nanoscale infrared chemical mapping to develop new understanding of the interphase using model epoxy-amine binders composed of diglycidyl ether of bisphenol A (DGEBA) cross-linked using -xylylenediamine (MXDA).

Molecular origins of Epoxy-Amine/Iron oxide interphase formation.

Hypothesis: Interphase properties in composites, adhesives and protective coatings can be predicted on the basis of interfacial interactions between polymeric precursor molecules and the inorganic surface during network formation. The strength of molecular interactions is expected to determine local segmental mobility (polymer glass transition temperature, Tg) and cure degree.

Experiments: Conventional analysis techniques and atomic force microscopy coupled with infrared (AFM-IR) are applied to nanocomposite specimens to precisely characterise the epoxy-amine/iron oxide interphase, whilst molecular dynamics simulations are applied to identify the molecular interactions underpinning its formation.

Reflectance in AFM-IR: Implications for Interpretation and Remote Analysis of the Buried Interface.

AFM-IR combines the chemical sensitivity of infrared spectroscopy with the lateral resolution of scanning probe microscopy, allowing nanoscale chemical analysis of almost any organic material under ambient conditions. As a result, this versatile technique is rapidly gaining popularity among materials scientists. Here, we report a previously overlooked source of data and artifacts in AFM-IR analysis; reflection from the buried interface.

Origin of micro-scale heterogeneity in polymerisation of photo-activated resin composites.

Photo-activated resin composites are widely used in industry and medicine. Despite extensive chemical characterisation, the micro-scale pattern of resin matrix reactive group conversion between filler particles is not fully understood. Using an advanced synchrotron-based wide-field IR imaging system and state-of-the-art Mie scattering corrections, we observe how the presence of monodispersed silica filler particles in a methacrylate based resin reduces local conversion and chemical bond strain in the polymer phase.

The Unexpected Role of Carbonate Impurities in Polyphosphate Corrosion Inhibition.

Polyphosphate corrosion inhibitors are increasingly marketed as chromate replacements for coil coated steel. The mechanisms underpinning corrosion prevention by these species is, however, not fully understood; corrosion inhibition is ordinarily assessed using electrochemical techniques, followed by ex-situ surface analysis. As a result, the formation of a clear film over cathodic sites is known to contribute to corrosion prevention, but little is known about its formation.

Investigating the Photocatalytic Degradation of Oil Paint using ATR-IR and AFM-IR.

As linseed oil has a longstanding and continuing history of use as a binder in artistic paints, developing an understanding of its degradation mechanism is critical to conservation efforts. At present, little can be done to detect the early stages of oil paint deterioration due to the complex chemical composition of degrading paints. In this work, we use advanced infrared analysis techniques to investigate the UV-induced deterioration of model linseed oil paints in detail.

Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR.

The first direct observation of a chemically heterogeneous nanostructure within an epoxy resin is reported. Epoxy resins comprise the matrix component of many high performance composites, coatings and adhesives, yet the molecular network structure that underpins the performance of these industrially essential materials is not well understood. Internal nodular morphologies have repeatedly been reported for epoxy resins analyzed using SEM or AFM, yet the origin of these features remains a contentious subject, and epoxies are still commonly assumed to be chemically homogeneous.