Bottlebrush Elastomers: A New Platform for Freestanding Electroactuation

Vatankhah‐Varnoosfaderani, Mohammad; Daniel, William F. M.; Zhushma, Alexandr P.; Li, Qiaoxi; Morgan, Benjamin; Matyjaszewski, Krzysztof; Armstrong, Daniel P.; Spontak, Richard J.; Dobrynin, Andrey; Sheiko, Sergei S.

doi:10.1002/adma.201604209

Cited by 166 publications

(228 citation statements)

References 39 publications

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“…The differences observed between comb and bottlebrush structures were related to the Gaussian and stretched conformations of the backbone and side chains. [3,24,25,32,44] Side chains in comb polymers increase the friction of the backbone chain with neighboring molecules in the melt or solution state, which enhances the strain hardening (see below) of the polymer melt under processing conditions. The side chains of the comb topologies can easily overlap physically with each other, while densely grafted bottlebrush molecules are segregated and weakly penetrated.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 2d-f shows the advantages of using bottlebrush elastomers as solvent-free, supersoft, and superelastic materials compared with hydrogels and conventional elastomers. [24,44] One example is that a poly(dimethylsiloxane) (PDMS) bottlebrush elastomer exhibits a considerably higher fracture energy than its poly(acrylamide) (PAM) hydrogel counterpart with a similar backbone volume fraction (Figure 2d,e), even though both materials show a similar modulus. Moreover, bottlebrush elastomers exhibit substantially higher compression ratios at break, ≈10, relative to hydrogels, ≈3.…”

Section: Introductionmentioning

confidence: 99%

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Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties

2019

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combined with the grafting-to method [1,10] results in comb polystyrenes (PSs) with well-entangled monodisperse backbone and side chains; however, branch points along the backbone are randomly distributed. This random distribution of branch points has no distinct effect on the rheological properties of dense comb topologies; however, it will broaden the backbone relaxation time of loose comb topologies even though the molecular weight distribution is narrow enough. [11] A controlled branching point spacing can be achieved through the coupling of living macroanions; [12] however, this method is prone to slightly high molecular weight distribution, Ð > 1.5. Synthesis of welldefined densely grafted bottlebrushes using ROMP and grafting-through method guarantees the presence of one side chain per repeating unit on the backbone. Bottlebrushes with more than one branch per backbone repeating unit can also be synthesized using ROMP and macromonomers with more bulky groups referred as wedge polymers. [13] These bottlebrushes are similar to that of the dendronized polymer with only one layer of grafting. Loosely grafted bottlebrushes with longer distance between the branching points can be achieved using ROMP technique through copolymerization of macromonomer and a diluent molecule, e.g., racemic endo,exo-norbornenyl diesters, with different ratios. However, different reactivity of macromonomer and diluent leads to a gradient of branching point spacing along the backbone, [14] where the conformations of side chains along the backbone are affected by this gradient. [15] It should be mentioned that the bottlebrushes synthesized with ROMP technique have different repeating units in the backbone than the side chains which might cause microphase separation. However this issue could be ignorable in dense bottlebrushes where the volume fraction of backbone is less than 1 wt%. In order to avoid any microphase separation, Sheiko and co-workers [16] synthesized a series of dense combs and loose bottlebrushes homo poly(n-butyl acrylates) (PBA) with similar side chains and systematically varied grafting density through copolymerization of nonfunctional n-butyl acrylates with trimethylsilyl-protected acrylates by ATRP. However, in order to achieve high degree of polymerization (DP) of backbone (entangled system) for dense bottlebrushes, they had to use slightly different backbones, i.e., poly(n-butyl methacrylate). An organometallic coordinative insertion polymerization of α-olefins results in entangled densely grafted bottlebrushes with rod-like side chains where both backbone and side chains have alkane groups. However the dispersity index of such homopolymer bottlebrushes would Comb and bottlebrush polymers present a wide range of rheological and mechanical properties that can be controlled through their molecular characteristics, such as the backbone and side chain lengths as well as the number of branches per molecule or the grafting density. This review investigates the impact of these characteristics specifically on the zero sh...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties

2019

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“…An alternative approach to lowering the Young's modulus is the recent methodology initially introduced by Weitz et al [114,115] and then further elaborated by Sheiko et al, [116] whereby x -…”

Section: Empirical Descriptions Of Figures Of Merit For Elastomers Wimentioning

confidence: 99%

Optimization Techniques for Improving the Performance of Silicone‐Based Dielectric Elastomers

Skov

2017

Adv Eng Mater

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Dielectric elastomers are possible candidates for realizing products that are in high demand by society, such as soft robotics and prosthetics, tactile displays, and smart wearables. Diverse and advanced products based on dielectric elastomers are available; however, no elastomer has proven ideal for all types of products. Silicone elastomers, though, are the most promising type of elastomer when viewed from a reliability perspective, since in normal conditions they do not undergo any chemical degradation or mechanical ageing/relaxation. Within this review, different pathways for improving the electro-mechanical performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are investigated and discussed, with special emphasis placed on the promise each method holds. The compositing and blending of elastomers are shown to be simple, versatile methods that can solve a number of optimization issues. More complicated methods, involving chemical modification of the silicone backbone as well as controlling the network structure for improved mechanical properties, are shown to solve yet more issues. From the analysis, it is obvious that there is not a single optimization technique that will lead to the universal optimization of dielectric elastomer films, though each method may lead to elastomers with certain features, and thus certain potentials.

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“…Moreover, the degree of crosslinking affects the actuation response of PDMSbased DEAs as shown in the literature. 4,19,21 Therefore, the current condition of crosslinking should be one reason for such low actuation.…”

Section: Electromechanical Actuationmentioning

confidence: 99%

“…[18][19][20] Very recently, it is reported that silicone rubbers with a bottlebrushlike molecular architecture exhibited ultralow elastic modulus and an over 300% areal strain under an electric eld lower than 10 kV mm À1 . 21 All these ndings conrmed that decreasing the elastic modulus of elastomers to reduce the blocking force is very promising for advanced DEAs.…”

Section: Introductionmentioning

confidence: 99%

Remarkably improved electromechanical actuation of polyurethane enabled by blending with silicone rubber

et al. 2017

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Herein we report the highly improved electromechanical actuation of thermoplastic polyurethane (TPU) by blending with polydimethylsiloxane (PDMS) to construct a bicontinuous structure. TPU/PDMS blend films with various PDMS loadings were fabricated through a simple solution-assisted casting method. Infrared spectroscopy measurements confirmed that TPU and PDMS are thermodynamically incompatible with each other. For TPU 80 with 80 parts of PDMS, a bicontinuous phase structure was achieved. The TPU 80 film showed greatly decreased elastic modulus and improved elongation at break compared to pristine TPU. It also showed the highest dielectric constant among the TPU/PDMS blend films with various contents of PDMS due to strong interfacial polarization. Most importantly, the TPU 80 film exhibited a maximum areal strain of 2.3% under an electric field of 40 V mm À1 , which is about 60 times higher than that of pristine TPU. The results described in this work demonstrate that the construction of a bicontinuous interface structure at the micrometer scale is very effective to develop elastomers with superior electromechanical actuation performance.

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Bottlebrush Elastomers: A New Platform for Freestanding Electroactuation

Cited by 166 publications

References 39 publications

Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties

Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties

Optimization Techniques for Improving the Performance of Silicone‐Based Dielectric Elastomers

Remarkably improved electromechanical actuation of polyurethane enabled by blending with silicone rubber

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