Name: preparation of monodomain liquid crystal elastomers and liquid crystal elastomer nanocomposites
Uploaded: 2016-02-06T15:00:00
Description: Watch this Scientific Journal Video about Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites at JoVE.com

This work was supported by the National Career Foundation (CBET-1336073 to RV), the ACS Petroleum Research Fund (52345-DN17 to RV), the American Heart Association (BGIA to JGJ), the National Science Foundation (CAREER CBET-1055942 to JGJ), the National Institutes of Health/ National Heart, Lung and Blood Institute (1R21HL110330 to JGJ), Louis and Peaches Owen and Texas Children&#39;s Hospital.

1. Synthesis of Aligned Polysiloxane LCEs
<ol>
	<li>Combine 166.23 mg of reactive mesogen (4-methoxyphenyl 4-(3-butenyloxy)benzoate), 40 mg of poly(hydromethylsiloxane), and 12.8 mg of crosslinker (1,4-di(10-undecenyloxybenzene)30 with 0.6 ml of anhydrous toluene in a small vial (approximately 13 mm in diameter and 100 mm in length) charged with a stirring bar. Stir the solution at 35 &#176;C for 25 min to dissolve.</li>
	<li>In a separate vial, prepare a solution of 1 wt % dichloro(1,5-cyclooctadiene)-plati...

<ol>
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In order to produce monodomain LCEs, the LCEs need to be uniaxially loaded during crosslinking. This is challenging in practice because the LCE is loaded when it is only partially crosslinked, and therefore is not mechanically robust and can easily break or tear. The procedure described above (steps 1.1 - 1.4) can produce monodomain LCEs consistently. One critical step is the removal of the LCE from the PTFE mold for loading at the appropriate time. If the LCE is removed too quickly, it will easily break or tear. On the...

Materials that can exhibit fast, reversible, and programmable shape changes are desirable for a number of emerging applications1-9. Shape-responsive stents can assist with wound healing and treatment7. Artificial robots can aid in exploration or in carrying out tasks in environments that are harmful or unsafe for humans10. Shape-responsive elastomers are desirable for use in active cell culture, in which cells are cultured in an active environment.11-14 Other applications include packaging, sensing, and drug delivery.
Liquid crystal elastomers (LCE) are polymer networks with liquid crystal ordering15-20. LCEs are made by combining a flexible polymer network with liquid crystal molecules known as mesogens. The responsiveness of LCEs is derived from the coupling of liquid crystal order to strains in the polymeric network, and stimuli that influence the ordering of mesogens will generate network strains, and vice versa. In order to achieve large and reversible shape-changes in the absence of an external load, the mesogens must be aligned in a single direction in the LCE. A common practical challenge in working with LCEs is generating monodomain LCEs. Another challenge is generating shape changes in response to stimuli other than direct heating. This can be done through the addition of nanoparticles or dyes to LCE networks21-28.
Here, we demonstrate the preparation of monodomain LCEs and LCE nanocomposites. First, we demonstrate the preparation of monodomain LCEs using the two-step method first reported by Kupfer et al.29 This is still the most popular and well-known method for preparing monodomain LCEs, but achieving uniform alignment and consistency between samples can be challenging. We demonstrate an approach that can be easily implemented using standard lab equipment, including full details on sampling handling and preparation. Next, we show how conductive carbon black nanoparticles can be added to LCEs to produce conductive, electrically responsive LCEs. We then demonstrate the synthesis and alignment of epoxy-based LCEs. These materials exhibit exchangeable network bonds and can be aligned by heating to elevated temperatures and applying a uniform load. All LCEs are characterized through macroscopic sample imaging, X-ray diffraction measurements, and dynamic mechanical analysis. Finally, we demonstrate one potential application of LCEs as shape-responsive substrates for active cell culture.

<table border="0" cellpadding="0" cellspacing="0" width="859">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:379px;">4-methoxyphenyl 4-(3-butenyloxy)benzoate</td>
			<td style="width:167px;">TCI America</td>
			<td style="width:145px;">M2106</td>
			<td style="width:168px;">Reactive mesogen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">poly(methylhydrosiloxane)</td>
			<td style="width:167px;">Gelest</td>
			<td style="width:145px;">HMS-993</td>
			<td>Reactive polysiloxane</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1,4-di(10-undecenyloxybenzene)</td>
			<td style="width:167px;">N/A</td>
			<td style="width:145px;">N/A</td>
			<td>see: Ali, S. A., Al-Muallem, H. A., Rahman, S. U. &#38; Saeed, M. T. Bis-isoxazolidines: A new class of corrosion inhibitors of mild steel in acidic media. Corrosion Science 50 (11), 3070&#8211;3077, doi:10.1016/j.corsci.2008.08.011 (2008)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">(dichloro(1,5-cyclooctadiene)-platinum(II)&#160;</td>
			<td style="width:167px;">Sigma Aldrich</td>
			<td style="width:145px;">244937</td>
			<td>Pt catalyst</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">PTFE mold</td>
			<td style="width:167px;">N/A</td>
			<td>N/A</td>
			<td>fabricated at Rice machine shop</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">carbon black nanoparticles</td>
			<td style="width:167px;">Cabot</td>
			<td>VULCAN&#174;&#160;XC72R</td>
			<td>used in the synthesis of LCE nanocomposites</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">polystyrene</td>
			<td style="width:167px;">Sigma Aldrich</td>
			<td>331651</td>
			<td>linear polystyrene&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">4,4&#39;-diglycidyloxybiphenyl</td>
			<td style="width:167px;">N/A</td>
			<td style="width:145px;">N/A</td>
			<td>see:&#160; Giamberjni, M., Amendola, E. &#38; Carfagna, C. Liquid Crystalline Epoxy Thermosets. Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 266 (1), 9&#8211;22, doi:10.1080/10587259508033628 (1995).</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">sebacic acid</td>
			<td style="width:167px;">Sigma Aldrich</td>
			<td style="width:145px;">283258</td>
			<td>C8 linking group for epoxy-LCE synthesis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">hexadecanedioic acid</td>
			<td style="width:167px;">Sigma Aldrich</td>
			<td style="width:145px;">177504</td>
			<td>C16 linking group for epoxy-LCE synthesis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">carboxydecyl-terminated polydimethylsiloxane</td>
			<td style="width:167px;">Gelest</td>
			<td style="width:145px;">DMS-B12</td>
			<td>Siloxane linking group for epoxy-LCE synthesis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">1,5,7-triazabicyclo[4.4.0] dec-5-ene</td>
			<td style="width:167px;">Sigma Aldrich</td>
			<td style="width:145px;">345571</td>
			<td>catalyst for reversible LCEs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:379px;">carbon rods</td>
			<td style="width:167px;">Ladd Research&#160;</td>
			<td style="width:145px;">30250</td>
			<td>used in cell culture experiments</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:379px;">medical grade silicone adhesive</td>
			<td style="width:167px;">Silbione</td>
			<td style="width:145px;">MED ADH 4100 RTV</td>
			<td>used to adhere carbon rods to vessel</td>
		</tr>
	</tbody>
</table>

preparation of monodomain liquid crystal elastomers and liquid crystal elastomer nanocomposites

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs &#8212; polysiloxane-based and epoxy-based &#8212; are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 &#176;C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

Monodomain LCEs are shape-responsive due to coupling of network conformation with liquid crystal ordering. Heating LCEs results in a decrease in the liquid crystal order parameter, producing a contraction of the polymeric network along the primary alignment direction. This is easily visualized by placing an LCE on a hotplate, as shown in Figure 1A and 1B. In heating up from RT, the LCE contracts along the length of the sample, and above the isotropic tran...

Watch this Scientific Journal Video about Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites at JoVE.com

Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites

We demonstrate the preparation of siloxane-based and epoxy-based liquid crystal elastomers (LCEs) and LCE nanocomposites. The LCEs are characterized with respect to reversible strain, liquid crystal ordering, and stiffness. As a potential application, we demonstrate their use as shape-responsive substrates in a custom device for active cell culture.

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and ...

Research

JoVE Journal

Bioengineering

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

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