Polymer Mixing... Updated!
Why a new mixing method and recipe?
- It's the best of course! We wouldn't put it on the website unless it was.
- * Allows for greater Flexibility and Reliability:
- • We are using several different types of polymer in the lab. Different polymer characteristics are desirable for specific applications.
- • By creating a consistent mixing and labeling system we are better able to keep track of what we currently use, what has worked, and how to recreate it!
- • In previous years we have had trouble recreating the same polymer characteristics. With this method, we know why each polymer is different, we know exactly what went into it, and we know exactly how to recreate it.
-       (Useful since we need to replace each old polymer every few weeks due to oxidation, solvent loss, particle formation, etc.)
- • We can use this method to systematically find out the best combination of thickness, index, and non-linearity to get low-loss modulating devices.
- * Benefits of using Dioxane:
- Easily wets- Dioxane wets the surface better than cyclohexanone
- Hosts DR1 well- PMMA acts as a host and dioxane easily dissolves and retains DR1. Allows for higher concentrations of DR1
- Uniform surface- reduces chunks of materials and 'holes'
- Double spin capabilities- surface tension and adhesion promotes thicker films
- * What characteristics create the best devices?
- Of course that depends on what kind of device you are making.
- Slab Coupling Fibers - Currently being developed using a thicker blend of polymer with a high DR1 concentration.
- Electric Field Detectors
- Traditional method: Loss typically comes from the transition regions where the modes are easily coupled into the high index polymer. Thin polymer (with high DR1) or thicker polymer (with low DR1) will
- Rib Waveguide technique:
- 1. Choose your Ingredients (Solvent, Polymer Host, Chromophore)
- a) Solvents: See table below & heed warnings! Current best results come with Dioxane.
-       * If using Dioxane do not put contaminated waste (used vials, pipettes, towels) in the trash. Place in a sealed waste bag.
- b) Polymer Host: PMMA or APC. We typically use PMMA because it has a lower index of refraction (n=~1.5) vs. APC (n=~1.6)
- c) Chormophore: Only one choice... Red Disperse 1 (95%). Unless you're able to find a cheap material with a higher r33...
- 2. Go to polymer_calc.phtml to create recipe.
- a) Link to Polymer Recipe Calculations
- b) The small glass vials hold ~10mL of polymer comfortably.
-       The small portions forces you to replace the polymer after a certain time...
-       * (necessary every ~2 weeks because of oxidation, solvent loss, particle formation, etc.)
- c) The lower % of thickness = thinner polymer. Higher % =thicker polymer. Typical values are around 7-9%.
-       * (Max = ~18% : polymer becomes un-mixable)
- d) A higher concentration % of DR1 makes the index increase. Typical values are around 7% to 20%.
- 3. Measure your polymer - by weight - into a small glass vial.
- a) Prepare and clean a new vial (Use a nitrogen gun to clean with air).
- a) Measure weight of glass vial.
- b) Calculate the total expected weight of vial and polymer
- c) Add polymer to vial until expected weight is reached
- 4. Measure solvent - by volume
- * Do this step in the fume hood. Put down a layer of paper towels to absorb any spills.
- a) Use the 10mL graduated cylinder to measure out the desired solvent volume.
- b) Use a plastic pipette to move solvent from the solvent bottle to the graduated cylinder.
- c) Replace the parafilm covering on the solvent bottle. -Parafilm stretches-
- c) Use a pipette to insert solvent from the graduated cylinder into the glass vial (with the PMMA).
- d) Insert a magnetic stirring rod (or 2 if they are small) before sealing the vial with parafilm.
- 5. Mix solvent and polymer on stirring hot plate
- a) Place vial in a larger glass beaker to hold it steady
- b) Set temperature dial to 60C. (60C is approximately the Black line on the dial)
- c) Turn on stirring dial. The "Slow" setting usually works fine.
-       * If set too high the stirring will raise the level of the polymer in the vial.
- d) Continue to let stir until no particles are visible. (a few hours)
- 6. Measure DR1 - by weight
- a) Measure the weight of the plastic cup.
- b) Calculate the total weight of desired DR1 + the weight of the cup.
- c) Deposit DR1 into cup until desired weight is reached.
-       * I add a little bit more to make up for some that is lost while transferring to vial
- d) Place DR1 in the vial with the PMMA/solvent mixture.
-       * Do this in the fume hood. Can be very messy.
- e) Replace parafilm seal on the vial.
- 7. Mix on stirring hotplate
- a) Again turn temperature Dial to 60C.
- b) Set spinning dial.
- c) Allow to mix until DR1 particles are dissolved.
-       * some particles may stick to the sides of the vial. Swish the solvent onto the sides a little to try to loosen and dissolve those particles.
- 8. Filter Polymer into new vial
-       * Do this step in the fume hood with a layer of paper towels. Makes cleaning easier.
- a) Prepare and clean a new vial. (Use nitrogen gun to clean with air)
- b) Open a 5cc syringe, remove the "plunger" part. Attach a .2um filter on the end. Set on top of the open new vial.
- c) Use a pipette to deposit the polymer from the old vial into the 5cc syringe.
- d) Let polymer drip through the filter, or use the plunger to help it along. Continue until all polymer is filtered.
- e) Seal filtered polymer with parafilm.
- f) If using dioxane: place used syringe, filter, pipettes, and vial in the waste bag.
-       * DO NOT deposit in the trash, remember dioxane is dangerous and we want to reduce exposure to it.
-         When waste bag is full or vials need to be thrown away call Chem Management: 2-6156
- 9. Label and Store
- a) Create label from a small square of towel.
- b) Use tape to attach to the lid of the vial.
- c) Record what recipe you used and the date it was filtered.
- d) Store in the cubby with other vials.
-       * if needed, use larger jars to hold small vials so they don't tip over.
Table of Solvent Characteristics and Warnings:
||Density (g/cm3) @ 20 C
||Viscosity @ Temp(c)
||Refractive index at 589 nm
||1.26 @ 20 C
||Used Currently. Provides very uniform polymer films. About the same volatility as Chloro/MEK, but dissolves PMMA/DR1 better.
||Extremely toxic. Will form explosive peroxides when exposed to O2 and sunlight. Cover vials with Parafilm after each use. Causes cancer in animals. Toxic to liver and kidneys. Easily absorbed through skin, causing poisoning without any warning signs. Only work with small amounts <10mL.
||112.56 / 72.11
|1.107 / .805
|? / .423 @ 15 C
||1.524 / 1.397
||To mix use 3:1 ratio of Chlorobenzene to MEK. Used back in the day (Ben Ipson) does not hold DR1 very well (falls out over time)
||Irritant. Do not inhale. Not very toxic - May cause nerve damage
||2.543 @ 15 C
||Used for "thick" polymer. Does not wet well when spun thin - leaves large bubbles and sometimes particles in the film. Filter periodically.
||Not very toxic. Irritant. Easily absorbed through skin. Will eat through most plastics
||May be used with APC. Does not dissolve DR1 very well. Evaporates VERY quickly and leaves chunks.
||Highly toxic. Minimize Exposure- Carcinogen
Old Mixing Page Below
Link to Old Polymer mixing page