Rapid viscoelastic switching of an ambient temperature range photo-responsive azobenzene side chain liquid crystal polymer

Petr, Michael; Helgeson, Matthew E.; Soulages, Johannes; McKinley, Gareth H.; Hammond, Paula T.

doi:10.1016/j.polymer.2013.03.040

Cited by 22 publications

(22 citation statements)

References 19 publications

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“…Previously, Petr et al observed a decrease in modulus as the cis state disrupted liquid crystalline order in a polymeric network. 25, 26 In addition, several studies have observed gel-sol transitions upon the disruption of hydrogen bonds between neighboring azobenzene units in supramolecular systems. 27, 28 Although the hydrogen bond structure in this system is still under investigation, the planar trans conformation may better be able to stabilize hydrogen bonds between the peptide crosslinkers, thereby rigidifying the substrate.…”

Section: Resultsmentioning

confidence: 99%

Photoresponsive Elastic Properties of Azobenzene-Containing Poly(ethylene-glycol)-Based Hydrogels

et al. 2015

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The elastic modulus of the extracellular matrix is a dynamic property that changes during various biological processes, such as disease progression or wound healing. Most cell culture platforms, however, have traditionally exhibited static properties, making it necessary to replate cells to study the effects of different elastic moduli on cell phenotype. Recently, much progress has been made in the development of substrates with mechanisms for either increasing or decreasing stiffness in situ, but there are fewer examples of substrates that can both stiffen and soften, which may be important for simulating the effects of repeated ECM injury and resolution. In the work presented here, poly(ethylene glycol)-based hydrogels reversibly stiffen and soften with multiple light stimuli via photoisomerization of an azobenzene-containing crosslinker. Upon irradiation with cytocompatible doses of 365 nm light (10 mW/cm2, 5 min), isomerization to the azobenzene cis configuration leads to a softening of the hydrogel up to 100-200 Pa (shear storage modulus, G’). This change in gel properties is maintained over a timescale of several hours due to the long half-life of the cis isomer. The initial modulus of the gel can be recovered upon irradiation with similar doses of visible light. With applications in mechanobiology in mind, cytocompatibility with a mechanoresponsive primary cell type is demonstrated. Porcine aortic valvular interstitial cells were encapsulated in the developed hydrogels and shown to exhibit high levels of survival, as well as a spread morphology. The developed hydrogels enable a route to the noninvasive control of substrate modulus independent of changes in the chemical composition or network connectivity, allowing for investigations of the effect of dynamic matrix stiffness on adhered cell behavior.

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Section: Resultsmentioning

confidence: 99%

Photoresponsive Elastic Properties of Azobenzene-Containing Poly(ethylene-glycol)-Based Hydrogels

et al. 2015

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“…It is obvious that the pH value plays the key role in the rheology of concentrated SPB dispersion . Further understanding of pH effect on SPB interactions can be derived from SAXS measurements (Fig.…”

Section: Resultsmentioning

confidence: 99%

Interactions among spherical poly(acrylic acid) brushes: Observation by rheology and small angle X-ray scattering

Chu

Han

et al. 2015

J. Polym. Sci. Part B: Polym. Phys.

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Interactions among annealed spherical polyelectrolyte brushes (SPB) in concentrated aqueous dispersion under the effect of concentration, pH, and salt concentration are investigated by means of rheology, and small angle X-ray scattering (SAXS). SPB consist of a solid polystyrene (PS) core and linear poly(acrylic acid) (PAA) chains densely grafted onto the core by one end. Rheological investigation demonstrates that the viscosity, the storage modulus G 0 and the loss modulus G 00 of SPB dispersion increase significantly upon increasing the SPB concentration and pH value which reflects the enhanced interactions among SPB. At high pH, a further increase in pH from 8 to 13 has almost no impact on the rheological properties and SAXS curves, while a "Uniform Shell Model" can fit the SAXS data very well probably due to the uniform filling of polyelectrolyte chains among SPB. When increasing the salt concentration from 10 25 to 10 23 M, the so-called "polyelectrolyte peak" appears at middle to high q range in SAXS curves which means the overlapped polyelectrolyte chains are associated under the bridging effect of counterions, which disappears at higher salt concentration due to the screening effect of further added salts.

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“…nonlinear phononics, ionic Raman) [5][6][7][15][16][17][18][19], and that other signals (pressure, temperature) can control c s and phonon dispersion (often by phase transitions) [12][13][14][20][21][22][23][24][25][26][27][28][29]. So far as we are aware, the only research that came close to the problem of optical control were [30][31][32]. [30] showed that the vibrational properties of a material can be optically switched in photo-responsive liquid crystal polymers.…”

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confidence: 99%

“…So far as we are aware, the only research that came close to the problem of optical control were [30][31][32]. [30] showed that the vibrational properties of a material can be optically switched in photo-responsive liquid crystal polymers. But the optical excitation was intense enough for complete switching, so their focus was rather on the thermal and strain (rather than the optical) tuning of this switching.…”

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confidence: 99%

“…Similar approaches for experimentally realizing these devices could be achieved by superlattices of photo-sensitive materials (e.g. photo-isomers [30], ionic Raman active materials [31], photo-elastic glasses like chalcogenides [32]) separated by inactive layers or by embedding these photo-sensitive materials (particularly photo-isomers, which are generally small organic molecules) within an inactive matrix (the scenario illustrated in Fig. 1).…”

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Sound and noisy light: Optical control of phonons in photoswitchable structures

Sklan

Grossman

2015

Phys. Rev. B

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Rapid viscoelastic switching of an ambient temperature range photo-responsive azobenzene side chain liquid crystal polymer

Cited by 22 publications

References 19 publications

Photoresponsive Elastic Properties of Azobenzene-Containing Poly(ethylene-glycol)-Based Hydrogels

Photoresponsive Elastic Properties of Azobenzene-Containing Poly(ethylene-glycol)-Based Hydrogels

Interactions among spherical poly(acrylic acid) brushes: Observation by rheology and small angle X-ray scattering

Sound and noisy light: Optical control of phonons in photoswitchable structures

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