This procedure describes the preparation of spin-cast side chain LCE developed in Heino Finkelmann's lab. The total preparation for the material is approximately 48 hours. The image to the right shows an LCE film at the end of the spin casting process.

Chemical CAS #
mesogen
crosslinker  
platinum catalyst (COD)
methyl-hydrosiloxane
Toluene [65-45-3]
De-ionized H2O  

  • balance
  • weighing boat | paper
  • glass vial | plastic > 5mL
  • glass | plastic transfer pipette
  • Teflon film (~20um thick)
  • spin casting head
  • heated centrifuge | spinning apparatus
  • dry-ice | liquid nitrogen
  • Tefzel tape (DuPont)
  • 15 cm plastic | wood | metal rod for hanging LCE
  • drying oven
  • addition funnel
  • glass dish
  • aluminum foil | parafilm
  • Luer tip filter 0.2 um
  
  1. After everything is dissolved, add the platinum catalyst using a pipettor or Hamilton syringe, gently swirl for a few seconds. Highslide JS

    Addition of catalyst solution using through a plastic pipette tip

  2. Prepare all needed tools/materials for preparation of the spin casting head
  3. Collect the solution in a syringe (disposable is fine). Place a 0.2 um syringe tip filter on the syringe and transfer the mixture to the spin casting apparatus. Highslide JS

    loading the reaction solution into spin casting head through a syringe tip filter

  4. Tightly seal the spin casting head so that no liquid may escape.
  5. Centrifuge apparatus @ 60 to 65oC, for sixty to seventy minutes.
  6. 6. After the spinning is complete, cool the centrifuge using liquid nitrogen or dry ice. Please note that you are cooling the elastomers film inside the spin casting head to slightly below room temperature, so while the spin casting head may be very cold, it is the temperature of the LCE film that is of concern. If the LCE is much above room temperature, the toluene may evaporate from the film too quickly, effecting LC alignment. If the LCE is ice cold, it can be more difficult to work with during the handing process
  7. Open the spin casting head, the LCE film should now be formed. Highslide JS

    LCE film in the spin casting head

    If the material is still a liquid inside the spin casting head, add a few uL of catalyst solution, and spin for an additional 30 to 40 minutes. Highslide JS

    Unreacted solution that failed to form an LCE film

  8. Remove the elastomer strip from the spin casting apparatus using tweezers, grasping the Teflon support film behind the LCE film. The LCE will stay on the Teflon support film if you handle it gently. Lay on LCE| Teflon support film on a large piece of Teflon film, LCE side up. Secure both ends of the LCE | Teflon film with tape. The LCE is now swollen with toluene and is isotropic. Highslide JS

    Unreacted solution that failed to form an LCE film

  9. During the spin casting process, formation of chemical crosslinks is initiated, but not completed. At this stage, the LCE is a swollen polymer network that is partially crosslinked. After the LCE film is removed from the spin casting head, it is hung and weights are attached, uni-axially stretching the LC-polymer network while the final crosslinks are formed, establishing an aligned network.
  10. You now have approximately 20 to 25 minutes to hang the LCE film. First cut the LCE into 2 or 3 pieces of equal length. As the toluene evaporates, stress builds inside the LCE, and it will twist and curl on the Teflon support film, and may crack. Sectioning the film helps to relieve this stress.
  11. Attach a small piece of Tefzel tape, approximately 1cm x 1cm, to the center of a metal thin metal, wood, or rod, diameter ~ 4mm. Carefully attach the tape to one end of the LCE film, and gently pull up the LCE from the support film. Highslide JS

    Image of Tefzel tape on wood stick, pulling up LCE from the support film

    (see image gallery for more images)
  12. Place the rod in a support so the LCE may hang freely. It will also stretch as weights are added to the systems, so be sure to leave room below the LCE to allow for an increase in length. Ideally, the distance between the bottom of the LCE and the bench surface should be at least 3X the length of the LCE film. Place a large piece of Teflon film underneath the area where the LCE are hung in case the films fall. Hang all pieces of LCE before proceeding to the next step. Highslide JS

    Image of Tefzel tape on wood stick, pulling up LCE from the support film

  13. After all LCE strips are hung, the need to be watched as may fall off from the tape. In the initial 30 minutes after the LCE are hung, as the toluene evaporates, the LCE tends to lift from the tape, and may fall.
  14. If it appears the LCE is about to fall, lift the LCE by its support rod and gently lay the LCE film on the large Teflon sheet below the LCE. Place a new piece of tape on the rod, and re-hang the LCE. In most instances, the LCE will only need to be re-hung one time.