Photomechanical Response of Glassy Azobenzene Polyimide Networks

Wang, David H.; Lee, Kyung Min; Yu, Zhenning; Koerner, Hilmar; Vaia, Richard A.; White, Timothy J.; Tan, Loon‐Seng

doi:10.1021/ma200427q

Cited by 123 publications

(140 citation statements)

References 46 publications

(54 reference statements)

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“…Fig. 3 illustrates the response of a film composed of an azobenzene-functionalized polyimide similar to those characterized in references (20,21) displaced into a bistable arch with α ∼ 130. The sample is illuminated from the bottom with 445-nm irradiation at an intensity of 18 mW/cm 2 and a diameter (d) of 5 mm, the center of which was aligned to the midpoint of the arch.…”

Section: Resultsmentioning

confidence: 83%

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Shankar

Smith

Tondiglia

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Photomechanical effects in polymeric materials and composites transduce light into mechanical work. The ability to control the intensity, polarization, placement, and duration of light irradiation is a distinctive and potentially useful tool to tailor the location, magnitude, and directionality of photogenerated mechanical work. Unfortunately, the work generated from photoresponsive materials is often slow and yields very small power densities, which diminish their potential use in applications. Here, we investigate photoinitiated snap-through in bistable arches formed from samples composed of azobenzene-functionalized polymers (both amorphous polyimides and liquid crystal polymer networks) and report ordersof-magnitude enhancement in actuation rates (approaching 10 2 mm/ s) and powers (as much as 1 kW/m 3 ). The contactless, ultra-fast actuation is observed at irradiation intensities <<100 mW/cm 2 . Due to the bistability and symmetry of the snap-through, reversible and bidirectional actuation is demonstrated. A model is developed to elucidate the underlying mechanics of the snap-through, specifically focusing on isolating the role of sample geometry, mechanical properties of the materials, and photomechanical strain. Using light to trigger contactless, ultrafast actuation in an otherwise passive structure is a potentially versatile tool to use in mechanical design at the micro-, meso-, and millimeter scales as actuators, as well as switches that can be triggered from large standoff distances, impulse generators for microvehicles, microfluidic valves and mixers in laboratory-on-chip devices, and adaptive optical elements.photochemistry | elastic instability T ransduction of light into work in photoresponsive polymeric materials does not require contact and can be remotely triggered potentially over long distances. The ease with which light can be manipulated spatio-temporally in intensity, phase, and polarization further distinguish this novel input stimulus in mechanically active systems. Prior demonstrations of photomechanical effects in polymeric materials have used both photothermal (1) and photochemical (2-4) mechanisms. Photochemical routes, in nearly all cases using the photoisomerization of azobenzene, are particularly interesting because they offer broader opportunities for modulating photomechanical responses with irradiation wavelength and polarization.The basis of light-to-work transduction (actuation) in azobenzenefunctionalized polymeric materials is the rate and efficiency of the isomerization/reorientation of the embedded azobenzene chromophores. The extent of azobenzene isomerization (efficiency) is considerably lessened by embedding this photochromic moiety in a polymeric material-evident in the work of Morawetz, which contrasts the kinetics and photostationary state concentration of azobenzene photoisomerization in dilute solution, plasticized, and bulk forms (5). Photoisomerization in polymeric materials becomes less efficient and slower with increase in storage modulus (6). Accordingly, pho...

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Section: Resultsmentioning

confidence: 83%

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Shankar

Smith

Tondiglia

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…54 Therefore, a quantum correction function must be used, in order to approximate better the exact I(ω) as Q QC (ω, T)I cl . Among the several available models, 55 the so-called "harmonic" approximation is used here (16) In brief, the vibrational spectra were calculated as (17) UV-visible spectra were derived by averaging QM calculations performed over different sets of snapshots, purposely extracted from the trajectory as indicated in the following.…”

Section: Trajectory Analysismentioning

confidence: 99%

“…In order to allow a direct comparison with experiments, the IR absorption spectrum was calculated for the isolated and the grafted dye, by using the quantum corrected Fourier transform of the electric dipole ACF, according to Equation (17). The Fourier Transform IR spectra reported in Ref.…”

Section: Dynamic Propertiesmentioning

confidence: 99%

“…However, the synthetic route required in this case is very elaborate and should be specifically defined for each polymer and dye. 12,16,17 The structures of the resulting assemblies can be inferred from spectroscopic or kinetic measurements (distance dependencies of energy transfer, electron-transfer quenching, etc.) 18,19 Among many different kinds of "smart" polymers, functionalized polyolefins have attracted a lot of attention, and their synthesis and application have been recently reviewed.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Structural, dynamic and photophysical properties of a fluorescent dye incorporated in an amorphous hydrophobic polymer bundle

Mitri

Prampolini

Monti

et al. 2014

Phys. Chem. Chem. Phys.

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The properties of a low molecular weight organic dye, namely 4-naphtoyloxy-1-methoxy-2,2,6,6-tetramethylpiperidine, covalently bound to an apolar polyolefin are investigated by means of a multi-level approach, combining classical molecular dynamics simulations, based on an purposely parameterized force fields, and quantum mechanical calculations, based on density functional theory (DFT) and its time-dependent extension (TD-DFT). The structure and dynamics of the dye in its embedding medium is analyzed and discussed in the light of the entangling effect of the surrounding polymer, also by comparing it to the results obtained for a different environment, i.e. toluene solution. The influence on photophysical properties of long lived cages, found in the polymeric embedding is eventually investigated in terms of slow and fast dye's internal dynamics, by comparing computed IR and UV spectra with their experimental counterparts.

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“…Azobenzene liquid crystal polymer networks of a variety of domain structures and orientations were prepared as specified in previous reports (monodomain [10,14], polydomain [8,9], twisted nematic [24], polyimide [32]). In general, a mixture composed of 20 wt% 4-4'-bis[6-(acryoloxy)hexyloxy]-azobenzene (2azo, BEAM Engineering for Advanced Measurements) was mixed with RM257 (Merck) (chemical structures shown in Figure 1).…”

Section: Methodsmentioning

confidence: 99%

Photomechanical Response of Composite Structures Built from Azobenzene Liquid Crystal Polymer Networks

Lee

White

2011

Polymers

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Abstract:Optically directed shape adaptive responses have been sought after for many decades in photoresponsive polymeric materials. A number of recent examinations have elucidated elucidated the unique opportunities of photomechanical responses realized in azobenzene-functionalized liquid crystalline polymer networks (both elastomers and glasses). This work summarizes and contrasts the photomechanical response of glassy polydomain, monodomain, and twisted nematic azo-LCN materials to blue-green irradiation. Building from this summary, the combinatorial photomechanical response observed upon irradiation of composite cantilevers is examined. Large scale shape adaptations are realized, with novel responses that may be of potential use in future employment of these materials in actuation.

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Photomechanical Response of Glassy Azobenzene Polyimide Networks

Cited by 123 publications

References 46 publications

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Contactless, photoinitiated snap-through in azobenzene-functionalized polymers

Structural, dynamic and photophysical properties of a fluorescent dye incorporated in an amorphous hydrophobic polymer bundle

Photomechanical Response of Composite Structures Built from Azobenzene Liquid Crystal Polymer Networks

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