Making color changing plastic

this video has been sponsored by Nord VPN you can go to Nord VPN comm / nyle read to get 77 percent off a three year plan today I'll be making a chemical called two to four die nitro benzyl pyridine or DN BP for short which exhibits something called photochromism this means that when it's exposed to light it undergoes a reversible change in color under normal conditions it's a brownish yellow but when it's exposed to UV or sunlight it turns blue then if it's left in the dark for several hours it slowly reverts back there are some photochromic compounds that are relatively fast in both directions though and they're used to make things like those glasses that darken when you go outside other compounds also transition between different colors and are used in many products like toys clothing and cosmetics I don't plan to at the moment but in the future I might try to make some of these other photochromic compounds for most of my videos I just make the chemical for fun and to explore the science but this time there was another reason the only chemical company that I can order from a sigma and they sell 50 milligrams of d + BP for a hundred and sixty three dollars which is insanely overpriced Sigma sells its precursor for way cheaper though so it made a lot more sense for me to just buy that and to make it myself I don't really have exact numbers but I think to make fifty milligrams it cost me something like 25 cents in any case my main goal for this video was to make the D and BP and then to try out a few things with it that I thought might be cool for example I wanted to try developing a photo from a negative print and making a color-changing plastic I also just wanted to mess around with it in general and to test out some of its properties now in terms of chemicals I'll be using sulfuric acid nitric acid diethyl ether sodium hydroxide and two benzyl pyridine that I got from Sigma all the other chemicals were either purchased locally or from eBay to start things off I added 12 mils of concentrated sulfuric acid and a stir bar to a small flask then I set up an ice bath and I let it cool to around 5 c2 the acid I slowly add two and a half mill of two benzyl pyridine and a faint yellow color appeared I let the stir for a few minutes and then I added 2.25 mils of concentrated nitric acid this entire addition was done carefully and dropwise over the course of about 4 minutes during this time it went through a range of colors but by the end it was pretty much colorless at this point the flask was taken out of the ice bath and the next step was to heat it so I put it into a hot water bath and I also added an air-cooled condenser to help stop the vapors from escaping I turned on the hot plate and the reaction was heated to a hundred C for about twenty minutes what was going on here was a nitration reaction where two nitro groups were being added to the two benzyl pyridine to make dn BP in a bit more detail the first step was a reaction between the sulfuric and nitric acid to make nitronium ions these were the active nitrating species and they were attacked by the two benzyl pyridine under these conditions dean BP was the major product but I'm sure that to a certain extent other nitrated forms were also made these just had to be purified out in the workup and you'll see how I did that when it was done I took away the water bath and I let it cool a bit then I poured it into about 200 grams of ice I also used this small amount of water to wash the flask and I dumped that in as well what I had here was a mixture of my product and concentrated acids and the next step was to neutralize it this was done by using a solution of sodium hydroxide that I made by mixing 20 grams in 250 mils of water when it was added it immediately reacted with the acid to form sodium sulfate sodium nitrate and water these reactions generated a lot of heat which is why it was important to include all the ice it was also important to keep it at or below room temperature and you'll see why in a minute when it was done I tested the pH and I saw that it was strongly basic which was good then on top of this I added 200 mils of diethyl ether I took out the glass rod and turned on the magnetic stirring and the mixture quickly started darkening I don't think the color change was because of the ether though and I think it was just the strong base causing some side products to polymerize it wasn't stirring as well as it should have been so I swapped out the stir bar for a much larger one it was a lot better this time and I was able to mix in all the ether what I was doing here was a solvent extraction where the desired product was getting dissolved into the ether most of the other junk like sodium sulfate sodium nitrate and other side products should stay dissolved in the water the reason why the temperature had to be low for this was because diethyl ether has a very low boiling point and it's extremely volatile I needed to let this stir for about 20 minutes and if the solution were hot all my ether would have just boiled away in any case after stirring it for 20 minutes I poured it all into a separatory funnel it very quickly separated where the upper layer was the ether and the bottom was the water just to make sure that the separation fully went to completion I let it sit here for about an hour I then drained off the bottom water layer which at this point is just waste and it contains side products and other junk as a safety note it also has a bit of ether dissolved in it so even though it's water it can still pose a fire hazard what I did to deal with this waste was I just drained it all into a beaker and then I put it at the back of my fume hood and I let it evaporate for about a week then I put the solid crust that remained into a dry waste container getting back to the preparation though the upper ether layer that was still in the separatory funnel was poured into a flask just like how the water layer contained a bit of ether my ether layer contained a bit of water I needed to get rid of it and to do this I added anhydrous magnesium sulfate magnesium sulfate form stable complexes with water so when it's added it pulls it from the ether and when it does this it tends to just clump up and sit at the bottom when there's little to no water left though it stays loose and the solution becomes cloudy when it's shaken it's usually best to add small amounts and to wait for it to pick up the water but I was a bit impatient I almost definitely added way too much which might slightly impact the yield but it's really not a big deal to separate the magnesium sulfate it's really easy and I just filtered everything through a cotton ball when everything had passed through I washed the magnesium sulfate in the flask and the bit that was in the cotton with a small amount of ether I originally planned to set up a distillation and to recover the ether but at the last minute I decided not to I instead went with the lazy method and I poured it all into a beaker then it turned on the hot plate and I set up a fan off screen to help evaporate it just as a point of safety diethyl ether is extremely flammable so this had to be done in a very well ventilated area when it got down to around 40 mils I transferred it to a smaller beaker I ended up missing the exact moment but a lot of solid quickly precipitated from the solution which was actually the dn BP I kept heating and evaporating it until it got to about 30 mils and then I put it into an ice bath to get out as much as possible then to separate it off I gravity filtered it when all the ether had passed through I watched the filter and the beaker with a small amount of ice-cold ethanol I spread out the filter on some paper towel to dry and this is what it looked like the next day the final yield was 2.05 grams and I think it cost me like $10 to make this to test it out and to see if it was actually photochromic I just had to expose it to sunlight it very quickly started to change colour and it told me that my synthesis worked what was going on here was a UV induced change in the structure of the molecule according to a paper that I found the hydrogen in red is first transferred to an oxygen in the nitro group generating the so called OAH form the nitro group then quickly flips to the other side and the hydrogen's picked up by the nitrogen generating the NH form which is blue this one's much longer lived and can last for hours because shifting the hydrogen back to the carbon isn't very favourable the reason that changes color is because the NH form has a different absorption spectrum in its initial form it mostly absorbed light around 400 nanometers which is a deep violet most of the light that it doesn't absorb is selected though and it's what we see to predict what this color should be I can just take a look at a complementary color wheel and I quickly see that its complement is yellow the NH form instead absorbs light around 600 nanometers which is a light orange and now if I take another look at the color wheel I see that the complement of this is a dark blue this reversible shift in absorption spectra as is the general mechanism behind most forms of photochromism something that I find interesting is that not all forms of Dean VP are necessarily photochromic and it can depend on what solvent to is crystallized from the rotation of the Nitro group is extremely important and some crystalline forms of Dean BP just don't really allow it to happen in my case it all worked out fine but apparently some commercial sources of it don't exhibit photochromism until there recrystallized from an appropriate solvent another thing that I find interesting is that the NH forms only long-lived when the Dean BP is a solid like it is here the basic explanation for this is that the rigid crystalline structure prevents the molecules from moving around and shifting back to their old state when it's dissolved in a small amount of acetone though the molecules are able to move around much more freely and they can quickly revert back just for fun I let all the acetone evaporate I read the sunlight and added more acetone when I did it this way I felt that not only did it look cooler but the effect was also a lot more evident what I wanted to try next was to see if I could use it to develop a photo I thought it would be cool to use the same process that I did for my cyanotype video except I'd be able to reuse this paper over and over to do this I needed to coat some paper with the dnvp and I tried several ways but pretty much all of them failed I only found one that kind of worked okay where it was first dissolved in a small amount of acetone and then slightly precipitated by adding water the struggle here though was that if too little water were used it wouldn't go on the paper very well but if too much were used the dnvp would crystallize out as solid chunks however after a couple attempts I managed to get a good mixture and I used it to coat two pieces of watercolor paper I'm each of them I applied several coats let them dry overnight and the next day I tried to develop something I converted one of my digital photos to a negative and printed it onto a transparency I then put this on top of the paper and I sandwiched it between two pieces of glass I took this all outside and the moment I exposed it to sunlight it immediately started to darken I had no idea how long I should have exposed it for so I just let it go until I thought it was done which was about four minutes when I went back inside and took a look at it though it was severely overexposed so I did it again using my other paper but this time I only developed it for 40 seconds the image from this run was a lot better but it was honestly still pretty bad I think the biggest issue was just applying the Dean BP to the paper and if I found out a better method I can improve the quality a lot if any of you happen to have any ideas on how I could do this I'd love to hear about it in the comments Wendy and BP's left in the dark for several hours it slowly converts back to its yellow form using the thermal energy that's present at room temperature if it's heated though this conversion happens way faster to demonstrate this I used one of my papers from before which had already faded quite a bit I wanted it all to be in the blue form though so I just let it sit in sunlight for about a minute I then blasted it with my heat gun and almost like magic the color started disappearing it only took me about 30 seconds to completely erase everything [Music] I tried exposing it to sunlight again but it seemed like it was dead after five minutes there was very little change and I figured that I just heated it up too much and destroyed the dnvp there were still a few spots that managed to survive though so I blasted them with more heat just for fun I decided to shoot some water and acetone onto it and I honestly expected nothing to happen to my surprise though the water apparently fixed the dnvp somehow and allowed it to become blue again the acetone on the other hand didn't seem to do anything I'm not exactly sure why this happened but I think the heat put it into a non photochromic conformation and the water somehow put it back into the other form I didn't explicitly try it but I feel like it could be an interesting way to write a secret message I could make ink with the dnvp write a letter develop it and then erase it using heat to see what I wrote it would have to first be treated with water dried and then exposed to sunlight the last thing that I wanted to do was to see if I could make some color-changing plastic I could have used a lot of different resins but I happen to have some epoxy from another project I was working on so I just decided to use that a small amount of the Dean BP was added to a mortar and then I poured in Part A of the epoxy the Dean BP was able to dissolve into it and I mixed it around as thoroughly as I could after a couple minutes I poured it into a plastic cup and added the other part of the epoxy this caused a slight color change to occur which normally doesn't happen the addition of the Dean BP definitely caused it but I don't really know why in any case I mix this as thoroughly as I could poured it into another cup and then stirred it for another couple minutes I then added all of it to a teddy bear mold that I got from Amazon what was weird though was that as it cured it slowly changed colors I'm not sure why but for some reason in this epoxy the DM BP seems to be more stable in its blue form I thought that maybe it would eventually change back but it never did the next day I tried D molding it but it was honestly kind of a pain I eventually got it out though and in my opinion the bear turned out pretty well at first I thought it was just locked in the blue form and that it was no longer photochromic however I figured it wouldn't hurt to just put it in sunlight and to see what happened to my surprise it was actually still photochromic but instead it was backwards this time most of the sunlight was also coming from the left side so the color change wasn't even through the bear I thought this was kind of cool though so when it got to about the midpoint I took it out of the light I honestly would have really liked if it stayed like this but because it's photochromic it eventually goes back I found the process to be extremely slow though and over a day later it still hadn't completely reverted another thing to mention is that most epoxies don't do well in sunlight and it slowly dis colors I just used it because it was something I had on hand but if I were to do it again I'd probably use a different polymer anyway I made a couple other bears and I did some more runs just to check a couple things for this one I just wanted to confirm that it was possible to change the entire color of the bear if it just sat there long enough and not surprisingly it was it just took about twice as long as the other time this last run had a much lower concentration of Dien BP and it changed much quicker it was also colorless instead of being yellow I then left them for a couple more days just to see how long they take to turn back the only one that really reverted was the one that was left in the sunlight for the least amount of time the first one that I did appears to still be slowly changing but I'm not sure if it'll ever fully go back the one that I turned completely orange and let's sit in the sunlight for the longest amount of time seemed to be stuck that way maybe it will eventually change though and if it does I'll be sure to update you guys anyway I think that's about it for now feel free to share your theories about what you saw here and other things you'd like me to try also I've decided to give away three of these bears that I made along with a beaker mug to three lucky winners I'll ship it anywhere in the world 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Channel: NileRed

Views: 1,254,488

Rating: 4.9516358 out of 5

Keywords: nile, red, science, chemistry, photo, photochromism, organic, dnbp, color, change, sunlight, uv, vpn, net neutrality, online privacy, vpn for android, vpn for travel, nilered

Id: YfjoU1_9GQ8

Length: 19min 42sec (1182 seconds)

Published: Thu Jun 28 2018