| Abstract
| - Poly(ethylene oxide) (PEO) is a key material in solid polymer electrolytes, biomaterials, drugdelivery devices, and sensors. Through the use of hydrogen bonds, layer-by-layer (LBL) assemblies allowfor the incorporation of PEO in a controllable tunable thin film, but little is known about the bulk propertiesof LBL thin films because they are often tightly bound to the substrate of assembly. The constructiontechnique 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 interdigitatedlayers of PEO and poly(acrylic acid) (PAA). Here, we introduce a new method of LBL film isolation usinglow-energy surfaces that facilitate the removal of substantial mass and area of the film, allowing, for thefirst 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 functionof assembly pH via differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Theresulting trends give clues as to how the morphology and composition of a hydrogen-bonded compositefilm evolve as a function of pH. We also demonstrate that LBL films of PEO and PAA behave as flexibleelastomeric 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-statepolymer electrolytes.
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