Chemically Cross-Linked Polycyclooctene:  Synthesis, Characterization, and Shape Memory Behavior

Liu, Changdeng; Chun, Seung B.; Mather, Patrick T.; Zheng, Liping; Haley, E; Coughlin, E. Bryan

doi:10.1021/ma021141j

Cited by 262 publications

(211 citation statements)

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“…[26][27][28] It is important to note that actuation phenomena in LCEs are governed mainly by: (i) their isotropization/anisotropization capabilities, which in turn dictate the conditions for actuation to occur and to what extent, and (ii) the transition temperatures, which trigger the mechanical transitions of the resulting actuators. It is the combination of these two effects that dictates the overall performances of the system.…”

Section: Figurementioning

confidence: 99%

Tailored Phase Transitions via Mixed-Mesogen Liquid Crystalline Polymers with Silicon-Based Spacers

2005

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Control over thermotropic phase behavior in low-Tg main-chain liquid crystalline polymers (LCPs) is desired for a variety of applications, including soft actuation when cross-linked. Here, we describe the synthesis of new silicon-based main-chain LCPs, including homopolymers, blends, and copolymers, with tunable clearing temperatures as governed by their chemical composition. Two mesogenic groups, namely, 1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone (M 1) and 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)-benzoyl]hydroquinone (M2), were polymerized with various silicon-based flexible spacers, specifically, 1,4-bis(dimethylsilyl)benzene (S1), 1,1,3,3,5,5-hexamethyltrisiloxane (S2), and hydride-terminated poly-(dimethylsiloxane) (DP ) 8) (S3) spacers, following routine hydrosilation reaction techniques. These mesogens and flexible spacers were chosen so that both copolymerization and blending of homopolymers would allow for potential tailoring of phase behavior. Indeed, despite their similar chemical structure, the clearing transition temperatures of M 1 and M2 differ dramatically (∆TNI ) 140°C), while the siliconbased spacers offer accessibility to a large range of molecular flexibility. High-molecular-weight LCPs were successfully prepared using Pt-catalyzed addition polymerization. Interestingly, the polymers exhibited wide liquid crystalline windows with relatively high degree of order (smectic phases) except for the S 1-based blends, which, in addition to a smectic phase, also displayed a narrow nematic phase. As expected, a drastic decrease of the glass transition temperature arose on polymerizing with longer, more flexible spacers, from about 56 to -17°C. Finally, in comparing the two approaches to phase behavior tailoring, namely, blending vs copolymerization, the former led to apparently immiscible systems with constant isotropization temperatures, while the latter yielded homogeneous, single-phased materials with tunable isotropization temperatures dictated by the M 1/M2 ratio of the copolymers. IntroductionGlassy side-chain liquid crystalline polymers (SCLCPs) have been widely studied in the past 1 as a materials approach that uniquely combines the mechanical and thermal properties of polymers with the optical properties of small-molecule liquid crystals, with numerous possible applications. 2 It is over the past two decades that researchers have focused more on crosslinked SC-LCPs because of the interesting thermomechanical properties they exhibit as liquid crystalline elastomers (LCEs). 3 Indeed, side-chain nematic LCEs have been shown to display spontaneously large strainreversible actuation and soft elasticity when exposed to specific stimuli. 4,5 Here, a thermally stimulated actuation behavior, shrinking on heating through a clearing transition and expanding on cooling through the same, has been explained by a coupling between liquid crystalline order and rubber elasticity resulting from the underlying cross-linked structure. 6 Yet higher actuator performance has been anticipated 7 and recently ...

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Section: Figurementioning

confidence: 99%

Tailored Phase Transitions via Mixed-Mesogen Liquid Crystalline Polymers with Silicon-Based Spacers

2005

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“…A poly(cyclooctene) (PCO) SMP was synthesized following a literature procedure (Liu et al, 2002): (i) PCO was dissolved in tetrahydrofuran (THF) to form PCO solution at 80 °C.…”

Section: Materials Preparationsmentioning

confidence: 99%

“…Many experimental studies have been carried out to characterize the macro-and microscopic material properties of SMPs and to investigate one-way shape memory in SMPs. Various SMPs have been studied, including epoxy resin (Chen et al, 2014;Song et al, 2011), polyurethanes (Hong et al, 2007;Tobushi et al, 1996;Wang et al, 2010), polyimide (Xiao et al, 2015), commercially available SMPs (Richard and Lisa Mauck, 2008), and poly(cyclooctene) (PCO) (Liu et al, 2002). Two-way shape memory, i.e., reversible deformation behavior in response to an on-off stimulus, has also been demonstrated using one-way SMPs and bias loads (Chung et al, 2007;Hong et al, 2010;Pandini et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional constitutive model for shape memory polymers using multiplicative decomposition of the deformation gradient and shape memory strains

Park

Harrison

Zhang

et al. 2016

Mechanics of Materials

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“…From a mechanical point of view, PCO behaves like an elastomer, and its application is often limited by the low melting temperature. To extend the application range above its melting temperature PCO can be crosslinked [40]. For example, the chemical crosslinking with dicumylperoxide (DCP) allows to improve the dimensional stability of the material at elevated temperatures and to enhance its mechanical properties [41,42].…”

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Phase changing nanocomposites for low temperature thermal energy storage and release

Dorigato¹,

Canclini²,

Unterberger³

et al. 2017

Express Polym. Lett.

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It is well known that through thermal energy storage (TES) systems it is possible to store (release) thermal energy by heating (cooling) a medium in order to utilize the stored energy when required. Possible applications involve power generation systems [1][2][3][4] and building constructions [5], where about one half of the energy demand is in the form of thermal energy, and the requirement may markedly vary in time [6][7][8]. TES technology have been also investigated in the textiles industry for the production of 'smart' fabrics able to maintain the right temperature of the body [9][10][11][12][13][14]. Other applications could be represented by the food storage [15,16] and the development of innovative solar plants [17][18][19]. Latent heat TES systems has recently attracted the attention of researchers, because these systems are characterized by a high energy storage density at constant temperature corresponding to the transition temperature of the phase change material (PCM) [18,20]. Generally speaking, a solid/liquid or a solid/solid phase transition could occur, and depending on their chemical nature these materials can be classified as organic, inorganic or eutectic. Organic PCM have several advantages [21,22] Abstract. The aim of this paper is to develop new elastomeric phase change materials (PCM) for the thermal energy storage/release below room temperature. In particular, poly(cyclooctene) (PCO)/paraffin blends filled with various concentrations of carbon nanotubes (CNTs), were prepared by a melt compounding process. The microstructural, thermo-mechanical and electrical properties of the resulting materials were investigated. The microstructure of these materials was characterized by the presence of paraffin domains inside the PCO, and CNTs were located only inside the paraffin domains in forms of aggregated clusters. DSC tests evidenced the existence of two distinct crystallization peaks at -10 and at 6°C, respectively associated to the paraffin and the PCO phases, indicating that both the polymeric constituents are thermally active below room temperature. Moreover, CNT addition did not substantially alter the melting/crystallization properties of the material. Noticeable improvements of the mechanical properties and of the electrical conductivity with respect to the neat PCO/paraffin blend could be obtained upon CNT addition, and also thermal conductivity/diffusivity values were considerably enhanced above the percolation threshold. Finite element modeling demonstrated the efficacy of the prepared nanocomposites for applications in the thermal range from -30 to 6°C.

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Chemically Cross-Linked Polycyclooctene: Synthesis, Characterization, and Shape Memory Behavior

Cited by 262 publications

References 12 publications

Tailored Phase Transitions via Mixed-Mesogen Liquid Crystalline Polymers with Silicon-Based Spacers

Tailored Phase Transitions via Mixed-Mesogen Liquid Crystalline Polymers with Silicon-Based Spacers

Three-dimensional constitutive model for shape memory polymers using multiplicative decomposition of the deformation gradient and shape memory strains

Phase changing nanocomposites for low temperature thermal energy storage and release

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