Polymer design for high temperature shape memory: Low crosslink density polyimides

Koerner, Hilmar; Strong, Robert J.; Smith, Matthew L.; Wang, David H.; Tan, Loon‐Seng; Lee, Kyung Min; White, Timothy J.; Vaia, Richard A.

doi:10.1016/j.polymer.2012.11.007

Cited by 93 publications

(84 citation statements)

References 73 publications

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“…are required to store elastic energy, which essentially provides the driving force for shape recovery [10]. Figure 5II) A lot of polymers, such as EVA and polyurethane (PU) [3,19,45,75,87], have a hard/soft segment structure, while some polymers and polymer hybrids/blends have an inclusion-matrix microstructure [4,7,[88][89][90][91][92][93][94][95][96]. If the hard segment or matrix is elastic within the temperature range of our interest, and the soft segment or inclusion is able to significantly alter its stiffness when being heated by means of either the glass transition or melting, we are able to realize the heating-responsive SME in these polymers.…”

Section: Figurementioning

confidence: 99%

Mechanisms of the Shape Memory Effect in Polymeric Materials

et al. 2013

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Abstract:This review paper summarizes the recent research progress in the underlying mechanisms behind the shape memory effect (SME) and some newly discovered shape memory phenomena in polymeric materials. It is revealed that most polymeric materials, if not all, intrinsically have the thermo/chemo-responsive SME. It is demonstrated that a good understanding of the fundamentals behind various types of shape memory phenomena in polymeric materials is not only useful in design/synthesis of new polymeric shape memory materials (SMMs) with tailored performance, but also helpful in optimization of the existing ones, and thus remarkably widens the application field of polymeric SMMs.

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Section: Figurementioning

confidence: 99%

Mechanisms of the Shape Memory Effect in Polymeric Materials

et al. 2013

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“…A permanent network structure, usually in the form of chemical bonds or strong physical crosslinks, is required to “remember” the original shape, which can be restored after heating through the transition. [5] Recent focus in the field has shifted towards engineering SMPs to achieve desired properties like high glass transitions[6], soft shape memory[7], triple and even multiple shape memory[8], and light induced shape memory[9, 10] among others.…”

Section: Introductionmentioning

confidence: 99%

Photo-mediated copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) “click” reactions for forming polymer networks as shape memory materials

McBride

Gong

Nair

et al. 2014

Polymer

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The formation of polymer networks polymerized with the Copper (I) – catalyzed azide – alkyne cycloaddition (CuAAC) click reaction is described along with their accompanying utilization as shape memory polymers. Due to the click nature of the reaction and the synthetic accessibility of azide and alkyne functional-monomers, the polymer architecture was readily controlled through monomer design to manipulate crosslink density, ability for further functionalization, and the glass transition temperature (55 to 120°C). Free strain recovery is used to quantify the shape memory properties of a model CuAAC network resulting in excellent shape fixity and recovery of 99%. The step growth nature of this polymerization results in homogenous network formation with narrow glass transitions ranges having half widths of the transition close to 15°C for these materials resulting in shape recovery sharpness of 3.9 %/°C in a model system comparable to similarly crosslinked chain growth polymers. Utilization of the CuAAC reaction to form shape memory materials opens a range of possibilities and behaviors that are not readily achieved in other shape memory materials such as (meth) acrylates, thiolene, thiol-Michael, and poly(caprolactone) based shape memory materials.

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“…a) Azo-F photo-isomerizes from the trans to the cis form under irradiation with visible (l > 420 nm) or UV light (l = 365 nm). [14] Thus we anticipated that the cross-linking density would have to be adjusted. c) UV/Vis absorption spectra showing that Azo-F in dichloromethane switches from the trans form to the cis form under irradiation with light.…”

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confidence: 99%

Fluorinated Azobenzenes for Shape‐Persistent Liquid Crystal Polymer Networks

et al. 2016

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Liquid crystal polymer networks respond with an anisotropic deformation to a range of external stimuli. When doped with molecular photoswitches, these materials undergo complex shape modifications under illumination. As the deformations are reversed when irradiation stops, applications where the activated shape is required to have thermal stability have been precluded. Previous attempts to incorporate molecular switches into thermally stable photoisomers were unsuccessful at photogenerating macroscopic shapes that are retained over time. Herein, we show that to preserve photoactivated molecular deformation on the macroscopic scale, it is important not only to engineer the thermal stability of the photoswitch but also to adjust the cross-linking density in the polymer network and to optimize the molecular orientations in the material. Our strategy resulted in materials containing fluorinated azobenzenes that retain their photochemical shape for more than eight days, which constitutes the first demonstration of long-lived photomechanical deformation in liquid-crystal polymer networks.

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Polymer design for high temperature shape memory: Low crosslink density polyimides

Cited by 93 publications

References 73 publications

Mechanisms of the Shape Memory Effect in Polymeric Materials

Mechanisms of the Shape Memory Effect in Polymeric Materials

Photo-mediated copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) “click” reactions for forming polymer networks as shape memory materials

Fluorinated Azobenzenes for Shape‐Persistent Liquid Crystal Polymer Networks

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