Impact of molecular weight on polyelectrolyte multilayer assembly and surface properties Elizabeth G. Towle a , Ivan Ding b , Amy M. Peterson a,c,⇑ a Department of Chemical Engineering Department, Worcester Polytechnic Institute, 100 Institute Rd., Worcester, MA 01609, USA b Department of Chemical Engineering, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, USA c Department of Plastics Engineering, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, USA graphical abstract article info Article history: Received 24 June 2019 Revised 25 February 2020 Accepted 27 February 2020 Available online 28 February 2020 Keywords: Polyelectrolyte multilayer Layer-by-layer Surface roughness Surface energy abstract Polyelectrolyte multilayers (PEMs) are a versatile category of materials due to their ability to modify sur- face properties for applications ranging from protective coatings to improved cell adhesion. Polyelectrolyte choice, including its structure and molecular weight (MW), is known to greatly influence PEM assembly and surface properties. In this work, poly(acrylic acid)/poly-L-lysine PEMs using three pairs of MWs (1.8k/15–30k, 100k/120k, and 250k/275k) were studied to determine the effects of their MWs on PEM assembly, topography and surface energy. PEMs assembly was monitored in a quartz crystal microbalance with dissipation, resulting in masses of 3.90 ± 0.87 mg/cm 2 , 10.80 ± 4.189 mg/cm 2 , and 30.04 ± 13.68 mg/cm 2 for 10 bilayers of low, medium, and high MW pairs, respectively. The low MW PEM was more rigid. Low and high MW PEMs exhibited higher roughness than medium MW, caused by polyelectrolyte stripping. Surface energy remained constant with bilayer count in the low and high MW PEMs, but steadily increased in the medium MW PEM. Differences between medium MW PEMs from low and high MW systems indicate that, while PEM properties change with MW, they are not monoton- ically correlated and are instead related to changes in internal charge distributions and the resultant stripping that may occur. Ó 2020 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jcis.2020.02.114 0021-9797/Ó 2020 Elsevier Inc. All rights reserved. ⇑ Corresponding author at: Department of Plastics Engineering, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, USA. E-mail address: amy_peterson@uml.edu (A.M. Peterson). Journal of Colloid and Interface Science 570 (2020) 135–142 Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis