Nanoprotective Layer-by-Layer Coatings with Epoxy Components for Enhancing Abrasion Resistance: Toward Robust Multimaterial Nanoscale Films

Abstract

Layer-by-Layer (LbL) assembled films offer many interesting applications (e.g., in the field of nanoplasmonics), but are often mechanically feeble. The preparation of nanoprotective films of an oligomeric novolac epoxy resin with poly(ethyleneimine) using covalent LbL-assembly is described. The film growth is linear, and the thickness increment per layer pair is easily controlled by varying the polymer concentration and/or the adsorption times. The abrasion resistance of such cross-linked films was tested using a conventional rubbing machine and found to be greatly enhanced in comparison to that of classic LbL-films that are mostly assembled through electrostatic interactions. These robust LbL-films are then used to mechanically protect LbL-films that would completely be removed by a few rubbing cycles in the absence of a protective coating. A 45 nm thick LbL-film composed of gold nanoparticles and poly(allylamine hydrochloride) was chosen as an especially weak example for a functional multilayer system. The critical thickness for the protective LbL-coatings on top of the weak multilayer was determined to be about 6 layer pairs corresponding to about only 10 nm. At this thickness, the whole film withstands at least 25 abrasion cycles with a reduction of the total thickness of only about 2%.

Epoxy‐based multilayers for flame resistant flexible polyurethane foam (FPUF)

“…A homogenous and exponential growth of multilayers having architecture PEI(CNER/NH 2 ‐MMT/PEI) n was optimized by depositing the films as a function of concentration and dipping time on quartz slides and silicon wafers. The absorbance was measured at λ max of 202 and 230 nm corresponding to the aromatic and cresol group of epoxy novolac, respectively . Uniform increase in absorbance was obtained with the increase in dipping time as shown in Figure (a,b).…”

“…Table presents the cone calorimetric data and Figure (a,b) depicts the HRR curves and residues left after the test (Figure S1; Supporting Information). When uncoated FPUF was exposed to heat flux, it showed a significant reduction in volume with the release of volatile gases which propagate the fire . This rapid burning results in melting of sample yielding low viscosity liquid with the HRR value reaches 885 kW/m 2 and TTI of 11 s (Figure ).…”

Nanoindentation of Functionally Graded Polymer Nanocomposites: Assessment of the Strengthening Parameters through Experiments and Modeling

“…However, these works lack systematic studies of the effect of the gradient morphology on the obtained properties, when it was made clear that the properties directly reflect the concentration gradients of the constitutive elements (Nardi et al, 2014a). The attractiveness of such materials derives from their intrinsic ability to combine different and apparently incompatible features in a single body, making them appealing candidates for applications, such as coatings for either oxidation (Smeacetto et al, 2002), corrosion (Alegría-Ortega et al, 2012), or abrasion protection (Qureshi et al, 2013). Although a general increment of the mechanical properties (e.g., hardness) is desirable for many applications, a more precise design of the gradient morphology could lead to materials that perform better under loading conditions encountered during their operational life.…”

Stress reduction mechanisms during photopolymerization of functionally graded polymer nanocomposite coatings

“…On the contrary, less attention has been paid to functionally graded polymer-based materials [8], even though they could find applications in many technologies currently using thin layers of dissimilar materials in order to achieve functional requirements [9]. The most important areas include electronic packaging [10] as well as coatings for either oxidation [11], corrosion [12] or abrasion protection [13]. Indeed, in all the above-mentioned applications the dissimilar nature of the constituents poses issues in terms of the mechanical integrity and reliability of the whole structure.…”