Tailoring the Mechanics of Freestanding Multilayers

Fery, Andreas; Tsukruk, Vladimir V.

doi:10.1002/9783527646746.ch16

Cited by 3 publications

(3 citation statements)

References 106 publications

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“…The Young’s modulus of the dry hydrogel films was found to be homogeneous over the analyzed areas (Figure a,d) and was similar for both (40-PMAA) 40 and (280-PMAA) 40 hydrogels with elasticity values of 2.0 ± 0.2 and 2.0 ± 0.1 GPa, respectively (Table ). These results are consistent with earlier findings for polyelectrolyte multilayer films in the dry state, where Young’s modulus was typically measured within a range of a few gigapascals depending on preparation technique and film composition. , The Young’s modulus of both (PMAA) 40 dry hydrogel films found in this work agrees with the elasticity modulus of 1.9 GPa reported for (PMAA) 60 dry hydrogel films in an earlier study …”

Section: Resultssupporting

confidence: 93%

“…These results are consistent with earlier findings for polyelectrolyte multilayer films in the dry state, where Young's modulus was typically measured within a range of a few gigapascals depending on preparation technique and film composition. 78,81 The Young's modulus of both (PMAA) 40 dry hydrogel films found in this work agrees with the elasticity modulus of 1.9 GPa reported for (PMAA) 60 dry hydrogel films in an earlier study. 78 Upon hydration, (40-PMAA) 40 and (280-PMAA) 40 hydrogels exhibited a several-order-of-magnitude homogeneous decrease in the elastic modulus over 1 μm 2 analyzed surface areas (Figure 5b,c,e,f).…”

Section: ■ Results and Discussionsupporting

confidence: 90%

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Controlling Mechanical Properties of Poly(methacrylic acid) Multilayer Hydrogels via Hydrogel Internal Architecture

Dolmat,

Kozlovskaya,

Ankner

et al. 2023

Macromolecules

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Hydrogel materials are crucial in many applications due to their versatility and ability to mimic biological tissues. While manipulating bulk hydrogel cross-link density, polymer content, chemical composition, and microporosity has been a main approach to controlling hydrogel rigidity, altering the internal organization of hydrogel materials through chain intermixing and stratification can bring finer control over hydrogel properties, including mechanical responses. We report on altering the mechanical properties of ultrathin poly(methacrylic acid) (PMAA) multilayer hydrogels by controlling the internal organization of the PMAA network. PMAA multilayer hydrogels were synthesized by cross-linking PMAA layers in poly(N-vinylpyrrolidone) (PVPON)/PMAA hydrogen-bonded multilayer templates prepared by dipped or spin-assisted (SA) layerby-layer assembly using sacrificial PVPON interlayers with molecular weights of 40,000 or 280,000 g mol −1 . The effect of PVPON molecular weight on PMAA hydrogel stratification and network swelling and hydration was assessed by in situ spectroscopic ellipsometry and neutron reflectometry (NR). In a new NR modeling of polymer intermixing, we have inferred nanoscopic structure and water distribution within the ultrathin-layered films from measured continuum neutron scattering length density (SLD) and related those to the mechanical properties of the hydrogel films. We have found that hydrogel swelling, the number of water molecules associated with the swollen hydrogel, and water density within the SA PMAA hydrogels can be controlled by choosing low-or high-M w PVPON. While cross-link densities determined by ATR-FTIR were similar, greater swelling and hydration at pH > 5 were observed for SA PMAA hydrogels synthesized using higher-M w PVPON. The enhanced swelling of these SA hydrogels resulted in softening with a lower Young's modulus at pH > 5 as measured by colloidal probe atomic force microscopy (AFM). The effect of PMAA layer intermixing on hydrogel mechanical properties was also compared for dipped and SA (PMAA) multilayer hydrogels of similar thickness and cross-linking degree. Despite similar values of gigapascal-range Young's modulus for dry PMAA multilayer hydrogel films, an almost twice greater softening of the SA (PMAA) hydrogel compared to that prepared by dipping was observed, with Young's modulus values decreasing to tens of megapascals in solution at pH > 5. Our study demonstrates that, unlike simply changing bulk hydrogel cross-link density, programming polymer network architecture via controlling the nanostructured organization of SA PMAA hydrogels enables selective modulation of the cross-link density within hydrogel strata. Control of polymer chain intermixing through hydrogel stratification offers a framework for synthesizing materials with finely tuned hydrogel internal structures, enabling precise control of such physical properties as the internal architecture, hydrogel swelling, surface morphology, and mechanical response, which are critical for the application of th...

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Section: Resultssupporting

confidence: 93%

Section: ■ Results and Discussionsupporting

confidence: 90%

Controlling Mechanical Properties of Poly(methacrylic acid) Multilayer Hydrogels via Hydrogel Internal Architecture

Dolmat,

Kozlovskaya,

Ankner

et al. 2023

Macromolecules

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“…Stimuli-responsive polymeric structures have attracted much attention in recent years due to their diverse range of potential applications . There are many different categories of responsive polymeric structures, such as brushes, thin films, micro- and nanogels, micelles, , hybrid particles, , nanotubes, microcapsules, biomaterial sheets, and thin shells for cells. , Among these different materials, responsive microcapsules have their unique and superior properties, such as easy fabrication, high stability, high loading capacity, and controlled release of cargo molecules. , During the past decade, layer-by-layer (LbL) assembly has emerged to be an important tool to fabricate microcapsules because of its many advantages, such as high versatility, uniformity, broad choice of materials, and facile incorporation of multiple functionalities. − …”

Section: Introductionmentioning

confidence: 99%

Multiresponsive Microcapsules Based on Multilayer Assembly of Star Polyelectrolytes

Ledin

Plamper

et al. 2014

Macromolecules

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Star polyelectrolytes (poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA)) with dual (temperature and pH) responsive properties were utilized to fabricate multiresponsive microcapsules via layer-by-layer (LbL) assembly. The LbL microcapsules are very robust and uniform, with higher stability and different internal structure compared with conventional microcapsules based on linear polyelectrolytes. Ionic strength in the polyelectrolyte solution during the microcapsule assembly process has a significant influence on the thickness and permeability of microcapsules. With increasing pH, the permeability of microcapsules decreases, and the transition from “open” to “closed” state for target molecules can be achieved within a narrow pH range (from pH 7 to 8). On the other hand, the overall size and permeability of the microcapsules decrease with increasing temperature (with a shrinkage of 54% in diameter at 60 °C compared with room temperature), thus allowing to reversibly load and unload the microcapsules with high efficiency. The organization and interaction of star polyelectrolytes within confined multilayer structure are the main driving forces for the responsiveness to external stimuli. The multiresponsive LbL microcapsules represent a novel category of smart microstructures as compared to traditional LbL microcapsules with “one-dimensional” response to a single stimulus, and they also have the potential to mimic the complex responsive microstructures found in nature and find applications in drug delivery, smart coatings, microreactors, and biosensors.

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Robust Microcapsules with Controlled Permeability from Silk Fibroin Reinforced with Graphene Oxide

Combs

Calabrese

et al. 2014

Small

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Robust and stable microcapsules are assembled from poly-amino acid-modified silk fibroin reinforced with graphene oxide flakes using layer-by-layer (LbL) assembly, based on biocompatible natural protein and carbon nanosheets. The composite microcapsules are extremely stable in acidic (pH 2.0) and basic (pH 11.5) conditions, accompanied with pH-triggered permeability, which facilitates the controllable encapsulation and release of macromolecules. Furthermore, the graphene oxide incorporated into ultrathin LbL shells induces greatly reinforced mechanical properties, with an elastic modulus which is two orders of magnitude higher than the typical values of original silk LbL shells and shows a significant, three-fold reduction in pore size. Such strong nanocomposite microcapsules can provide solid protection of encapsulated cargo under harsh conditions, indicating a promising candidate with controllable loading/unloading for drug delivery, reinforcement, and bioengineering applications.

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Tailoring the Mechanics of Freestanding Multilayers

Cited by 3 publications

References 106 publications

Controlling Mechanical Properties of Poly(methacrylic acid) Multilayer Hydrogels via Hydrogel Internal Architecture

Controlling Mechanical Properties of Poly(methacrylic acid) Multilayer Hydrogels via Hydrogel Internal Architecture

Multiresponsive Microcapsules Based on Multilayer Assembly of Star Polyelectrolytes

Robust Microcapsules with Controlled Permeability from Silk Fibroin Reinforced with Graphene Oxide

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