Exploiting Feedstock Diversity To Tune the Chemical and Tribological Properties of Lignin-Inspired Polymer Coatings

Abstract

Biobased polymers present an immense opportunity to design and manufacture new coating materials largely as a result of their feedstock diversity and inherent functionality, yet unraveling the key structure/property relationships inherent in these environmentally friendly systems remains a considerable challenge. A major focus of this work was to develop functional group−property design rules for a representative library of lignin-inspired polymers. Of particular interest were the polymers' solubilities, surface energies, and friction coefficients because of their relevance to coatings applications. The structural diversity of our bioinspired library, consisting of various polymers generated from methacrylate-functionalized lignin pyrolysis products, arose from the differing moieties at the para and ortho positions on the polymer repeat units relative to the methacrylate backbone. Polymer compatibilities with organic solvents studied herein increased with greater aliphatic content in the para functionality and decreased with the incorporation of methoxy groups ortho to the polymer backbone. The surface energies of the films followed similar trends between the interaction parameters and the functional group. By linking solvent compatibility to surface energy, it was demonstrated that changes in polar moieties, such as aldehydes and methoxies, have greater effects on solubility, surface energy, and friction than changes in the aliphatic (dispersive) groups. Thus, the target material properties can be understood and tuned through careful consideration of the pendant group functionalities inherent in the bioinspired materials, unlocking enhanced property design for next-generation coatings.

Dual‐functional, aromatic, epoxy‐methacrylate monomers from bio‐based feedstocks and their respective epoxy‐functional thermoplastics

“…Surface energy determines the behavior of coatings on substrates and coating interactions with fluids. Comparing surface energies to poly(GMA) is useful for determining the possible applications of the homopolymerized epoxy‐methacrylates . Static contact angles for DI water and CH 2 I 2 were measured for thin films (< 50 nm) prepared by flow coating onto silicon wafers as described above .…”

“…Comparing surface energies to poly(GMA) is useful for determining the possible applications of the homopolymerized epoxy‐methacrylates . Static contact angles for DI water and CH 2 I 2 were measured for thin films (< 50 nm) prepared by flow coating onto silicon wafers as described above . The relationship between the three‐phase contact angle and interfacial interactions is given by Young's equation (eq.…”

“…Surface properties were measured for thin films (< 50 nm) prepared by flow coating onto silicon wafers (N < 100>, Wafer World, Inc.) . For each polymer (except poly(TEM) due to low yields of the dual‐functional monomer TEM and the reduced thermal stability of poly(TEM) relative to poly(GMA)), a 2 wt% solution in THF was prepared, and 50 μL of filtered (0.45 μm) solution was flow coated onto a clean (triple rinsed with toluene), ultraviolet‐ozone‐treated (Jelight, Model 342, 30 min treatment) silicon wafer at 10 mm/s with an acceleration and deceleration of 100 mm/s 2 and a gap height of 20 μm.…”

“…The film thicknesses were remeasured to quantify any changes after the washing process. Static contact angles were measured in triplicate for DI water and diiodomethane (CH 2 I 2 ) using a contact angle goniometer (Krüss Drop Shape Analyzer, DSA25S) with a sessile drop technique (2 μL drop size) . Images were analyzed using Krüss Advance software with a Young‐Laplace model for water and an ellipse‐tangent model for CH 2 I 2 , and surface energies were calculated using the two‐fluid Owens‐Wendt model …”

“…The resultant homopolymers were compared to poly(GMA) to assess the effect of molecular structure on thermal and surface properties. All polymers were characterized for their molecular weight, thermal stability, and glass transition temperature, with surface energies evaluated for thin films prepared by flow coating . These bio‐based materials exhibited substantially higher thermal stabilities and comparable surface energies relative to poly(GMA), leading to potential for use in high‐temperature applications including coatings and adhesives.…”