Swelling Behavior and Nanomechanical Properties of (Peptide-Modified) Poly(2-hydroxyethyl methacrylate) and Poly(poly(ethylene glycol) methacrylate) Brushes

Abstract

Poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(poly(ethylene glycol) methacrylate) (PPEGMA) brushes represent a class of thin, surface-tethered polymer films that have been extensively used e.g. to generate non-biofouling surfaces or as model systems to study fundamental biointerfacial questions related to cell− surface interactions. As the properties of PHEMA and PPEGMA brushes depend on the hydration and swelling of these thin films, it is important to understand the influence of basic structural parameters such as the composition of the polymer brush, the film thickness, or grafting density on these phenomena. This article reports results of a series of experiments that were performed to investigate the swelling behavior and mechanical properties of a diverse library of PHEMA and PPEGMA brushes covering a range of film thicknesses and grafting densities. The swelling ratios of the PHEMA and PPEGMA brushes were determined by ellipsometry and neutron reflectivity experiments and ranged from ∼1.5 to ∼5.0. Decreasing the grafting density and decreasing the film thickness generally results in an increase in the swelling ratio. Modification of the PHEMA and PPEGMA brushes with the cell adhesive RGD peptide ligand was found to result in a decrease in the swelling ratio. The neutron reflectivity experiments further revealed that solvated PHEMA and PPEGMA brushes are best described by a two-layer model, consisting of a polymer-rich layer close to the substrate and a second layer that is swollen to a much higher degree at the brush−water interface.

Shape Shifting of Cup Shaped Particles on Growing poly (2‐hydroxy ethyl methacrylate) Brushes by “Grafting From” Approach and Dissipative Particle Dynamics Simulation

“…Swollen brush is typically observed when polymer chains are grown by ‘grafting from’ technique from soft surface and immersed in good solvent (water) in which the end grafted polymer brushes adapt a stretched configuration to avoid interaction between neighboring chains, which is distinctly different from a spin coated surface layer . The swelling ratio found in this study is comparable to the literature reported values for flat silicon dioxide surface modified with dense Poly(HEMA) brushes (grafting density or immobilized initiator concentration∼75%) . However, the concentration of ATRP initiator (BEMA fragment in the copolymer) used in this study was only ∼ 2.5%.…”

Assessment of persistent antimicrobial and anti-biofilm activity of p-HEMA hydrogel loaded with rifampicin and cefixime

“…Moreover, because RIF is zwitterionic, it would act as anion at pH 9 leading to higher ionization and subsequent enhancement in water uptake. The observed elevation in EWC% at pH 9 in all tested films is due to the ionization of the hydroxyl group in p-HEMA that leads to enhance water uptake and entrapment 49 , 50 . The protonation of the primary alcohol groups in p-HEMA would result in ionic repulsion leading to expansion and increasing the probabilities of interaction with water.…”

Angle-Dependent Atomic Force Microscopy Single-Chain Pulling of Adsorbed Macromolecules from Planar Surfaces Unveils the Signature of an Adsorption–Desorption Transition

“…The PHEMA chains swell in aqueous solution with a hydration layer formed via hydrogen bonding with water molecules. 34 The strong increasing trend observed for PHEMA adhesion can be explained by hydrophobic interactions and a high van der Waals attractive interaction between the hydrophobic backbone of the polymer and the substrate. An adsorption energy per monomer ranging from 3.7 to 6.7 kT is observed, where kT refers to the thermal energy (see Table 1 ).…”