Self-assembled liquid-crystalline gels designed from the bottom up

Kempe, Michael; Scruggs, Neal R.; Verduzco, Rafael; Lal, Jyotsana; Kornfield, Julia A.

doi:10.1038/nmat1074

Cited by 78 publications

(102 citation statements)

References 32 publications

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“…In general, a gel is considered as a semi-rigid network in which a liquid is held. [26] However, the gel-like state induced because of ultralarge GO sheets prepared in our study exhibits fundamental characteristics that ordinary gels do not have. These characteristics include exceptional uniformity of the network structure (large domain LC), and the anisotropy arising from having LC in the network, which are the common features of liquid crystalline gel structures (solvent content > 99%).…”

Section: Birefringence Rheological Behavior and Spinnability Of Go Dmentioning

confidence: 60%

“…These characteristics include exceptional uniformity of the network structure (large domain LC), and the anisotropy arising from having LC in the network, which are the common features of liquid crystalline gel structures (solvent content > 99%). [15,26] These unique features enable our as-prepared dispersions to be aligned by shear, as demonstrated by rheological studies, and ensure the preservation of the order even at low concentrations as they form a gel-like LC fiber as a result of wet-spinning.…”

Section: Birefringence Rheological Behavior and Spinnability Of Go Dmentioning

confidence: 90%

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Scalable One‐Step Wet‐Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Jalili

Aboutalebi

Esrafilzadeh

et al. 2013

Adv Funct Materials

379

426

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. (2013). Scalable one-step wet-spinning of graphene fibers and yarns from liquid crystalline dispersions of graphene oxide: towards multifunctional textiles. Advanced Functional Materials, 23 (43), 5345-5354.Scalable one-step wet-spinning of graphene fibers and yarns from liquid crystalline dispersions of graphene oxide: towards multifunctional textiles AbstractKey points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet-spinning to produce long lengths of micrometer-dimensional fibers and yarns are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO "inks" in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non-solvent precipitation, dispersion destabilization, ionic cross-linking, and polyelectrolyte complexation. One-step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post-treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials. New insights are provided into the processing of liquid crystalline graphene oxide (GO) dispersion (containing large GO sheets) demonstrating a facile and scalable production of GO and reduced GO fibers and yarns with exciting properties such as high thermal conductivity. These results provide a universal platform for the development of solution-based processing methods, properties, and applications of liquid crystalline GO-based architectures. AbstractIn the present work, we address key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet-spinning to produce long lengths of micron dimensional fibers and yarns. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity and spinnability is proposed leading to the understanding of 2 lyotropic LC behavior and fiber spinnability. The knowledge gained from our straightforward formulation of LC GO "inks" in a range of processable concentrations enabled us to spin continuous conducting, strong and robust fibres at concentrations as low as 0.075 wt. % eliminating the need for relatively concentrated spinning dope dispersions. This concentration is the lowest ever rep...

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Section: Birefringence Rheological Behavior and Spinnability Of Go Dmentioning

confidence: 60%

Section: Birefringence Rheological Behavior and Spinnability Of Go Dmentioning

confidence: 90%

Scalable One‐Step Wet‐Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Jalili

Aboutalebi

Esrafilzadeh

et al. 2013

Adv Funct Materials

379

426

View full text Add to dashboard Cite

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“…More recently, self-assembly of block copolymers has been used as an approach to create model liquid crystal networks [10 -12]. We have utilized self-assembly of a triblock copolymer that has a narrow molar mass distribution and a very long midblock to produce well-defined nematic gels [10,11]. This gel facilitates comparison to present theories which assume the material is lightly cross-linked and single phase.…”

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confidence: 99%

Buckling Instability in Liquid Crystalline Physical Gels

et al. 2006

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In a nematic gel we observe a low-energy buckling deformation arising from soft and semisoft elastic modes. We prepare the self-assembled gel by dissolving a coil -side-group liquid-crystalline polymercoil copolymer in a nematic liquid crystal. The gel has long network strands and a precisely tailored structure, making it ideal for studying nematic rubber elasticity. Under polarized optical microscopy we observe a striped texture that forms when gels uniformly aligned at 35 C are cooled to room temperature. We model the instability using the molecular theory of nematic rubber elasticity, and the theory correctly captures the change in pitch length with sample thickness and polymer concentration. This buckling instability is a clear example of a low-energy deformation that arises in materials where polymer network strains are coupled to the director orientation. DOI: 10.1103/PhysRevLett.96.147802 PACS numbers: 61.30.ÿv, 61.41.+e, 82.70.Gg Liquid-crystalline elastomers and gels combine the orientational order of liquid crystals and the translational order of a polymer network. The coupling of these two effects in liquid-crystalline elastomers and gels gives rise to unique phenomena such as soft elasticity in which certain director rotations and network strains cost no free energy in the ideal case. Soft elastic modes are predicted and well understood theoretically by a molecular theory of nematic rubber elasticity [1][2][3]. However, a significant limitation in testing existing theories is the difficulty in preparing well-characterized networks. Many approaches have been undertaken to prepare liquid crystal elastomers, including free-radical polymerization of bulk liquid crystal acrylates and diacrylates [4], free-radical polymerization of diacrylates in the presence of liquid crystals [5,6], and side-coupling reactions with poly(methylsiloxane) [7]. Unfortunately, these approaches result in nematic elastomers and gels with heterogeneities in the polymer network and, in the case of many gels, phase separation of the polymer network from the liquid crystal host [8,9]. More recently, self-assembly of block copolymers has been used as an approach to create model liquid crystal networks [10 -12]. We have utilized self-assembly of a triblock copolymer that has a narrow molar mass distribution and a very long midblock to produce well-defined nematic gels [10,11]. This gel facilitates comparison to present theories which assume the material is lightly cross-linked and single phase.In this Letter, we present a study of the effects of nematic rubber elasticity in thin layers of uniformly aligned gels contained between rigid parallel plates. Using polarized optical microscopy, we observe a banded texture that arises in response to small temperature changes. We propose that this texture represents a buckling deformation made possible by the presence of soft and semisoft elastic modes. We formulate a description based on the molecular theory of nematic elastomers that incorporates soft and semisoft elasticity as well as l...

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“…Mesogens with acrylate or methacrylate moieties, which are readily polymerised, may be varied to adapt the material properties. ABA triblock copolymers allow the construction of alternative structures, such as dilute gels [54]. Options for components and synthetic routes are discussed by Ohm [51], and other useful reviews may be found in Jiang et al [55], Chambers et al [56], and White et al [37].…”

Section: Skeletal Muscle-active Contractionmentioning

confidence: 99%

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

2016

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Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materials-skeletal muscle, tendons and plant tissues-and compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.

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Self-assembled liquid-crystalline gels designed from the bottom up

Cited by 78 publications

References 32 publications

Scalable One‐Step Wet‐Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Scalable One‐Step Wet‐Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Buckling Instability in Liquid Crystalline Physical Gels

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

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