Elastomeric Flexible Free-Standing Hydrogen-Bonded Nanoscale Assemblies

Abstract

Poly(ethylene oxide) (PEO) is a key material in solid polymer electrolytes, biomaterials, drug delivery devices, and sensors. Through the use of hydrogen bonds, layer-by-layer (LBL) assemblies allow for the incorporation of PEO in a controllable tunable thin film, but little is known about the bulk properties of LBL thin films because they are often tightly bound to the substrate of assembly. The construction technique involves alternately exposing a substrate to a hydrogen-bond-donating polymer (poly(acrylic acid)) and a hydrogen-bond-accepting polymer (PEO) in solution, producing mechanically stable interdigitated layers of PEO and poly(acrylic acid) (PAA). Here, we introduce a new method of LBL film isolation using low-energy surfaces that facilitate the removal of substantial mass and area of the film, allowing, for the first time, the thermal and mechanical characterization that was previously difficult or impossible to perform. To further understand the morphology of the nanoscale blend, the glass transition is measured as a function of assembly pH via differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The resulting trends give clues as to how the morphology and composition of a hydrogen-bonded composite film evolve as a function of pH. We also demonstrate that LBL films of PEO and PAA behave as flexible elastomeric blends at ambient conditions and allow for nanoscale control of thickness and film composition. Furthermore, we show that the crystallization of PEO is fully suppressed in these composite assemblies, a fact that proves advantageous for applications such as ultrathin hydrogels, membranes, and solid-state polymer electrolytes.

Depth-profiling X-ray photoelectron spectroscopy (XPS) analysis of interlayer diffusion in polyelectrolyte multilayers

“…Therefore, in the absence of a blocking layer, chitosan interlayer diffusion was stopped by drying for analysis but continued after exposure to PBS solutions. Because hydrogenbonded PEMs require a minute or two to dissolve (56), this brief time allows for further chitosan diffusion, rendering the film insoluble in PBS.…”

Designing a Multicellular Organotypic 3D Liver Model with a Detachable, Nanoscale Polymeric Space of Disse

“…The successful detachment of the PEM was facilitated by substrate hydrophobicity. 27,28 The ease of detachment of PEMs was tested as a function of the number of BLs, PE concentration, and deposition time. To FIG.…”

Polyelectrolyte Multilayers in Tissue Engineering

“…27 The PEM must provide a mechanical support for LSEC culture, a physical barrier between hepatocytes and LSECs, but most importantly allow diffusion of signaling molecules to facilitate cell-cell communication and phenotypic maintenance of both cell types. Recent efforts to create free standing PEMs comprised of synthetic and biologically derived PEs 18,140,141 exhibit tremendous potential to be utilized as scaffolds in tissue engineering. An application with much potential in biological therapeutic applications is the coating of individual cells with biocompatible PEMs.…”