Polyelectrolyte multilayers (PEMs), thin polymer films assembled from polyelectrolytes, are most commonly used as a coating to modify the surface properties of a bulk material, making the optimization of surface properties critical. In this study, the influence of polyelectrolyte molecular weight was examined, as well as the assembly pattern that each molecular weight produces. PEMs were created with poly(acrylic acid) (PAA) and poly-l-lysine (PLL) at low, medium, and high molecular weight to determine the effects of molecular weight on the surface properties of PEMs, specifically surface free energy (SFE) and roughness. Molecular weight has a significant impact on the assembly pattern and therefore the surface properties. Low MW PAA and PLL were found to form less massive PEMs composed primarily of PLL, while high MW PEMs had high mass and more PAA than PLL. Medium MW PEMs had the most linear assembly pattern and were the most balanced between polyelectrolytes. Medium MW PEMs were the smoothest, and had the lowest SFE, while low MW PEMs were the roughest and had the highest SFE. However, high MW PEMs were also quite rough while having a low SFE similar to that of the medium MW PEMs. While further research will be needed to understand how prevalent this specific pattern is with other polyelectrolyte combinations, these results demonstrate the tunability of surface properties including SFE and roughness with molecular weight.

Influence of molecular weight on assembly and surface properties of polyelectrolyte multilayers

256th National Meeting (2018)

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