polymer synthesis report

Polymer synthesis.

Final report.

Submitted to:

The faculty of the school of chemistry

Shawnee Mission Northwest High School.

By:

Charles McAnany

May 2, 2007

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Abstract:

Polymers are a very important aspect of our life; they provide easy materials to work with

that are resistant to many forms of attack. All plastics are polymers, as are most fabrics.

An understanding of polymer chemistry will allow a person to contribute to this

enormous field by designing polymers that have desirable properties.

Polymers are chains of molecules made of similar repeating subunits called monomers.

Monomers are molecules of low molecular weight that have reactive or excitable ends

that will form bonds with other monomers. It is the monomer that ultimately determines

the properties of a polymer; even a slight variation in the properties of a monomer can

greatly affect the properties of its polymer.

Of particular interest, both commercially and biologically, is condensation

polymerization. Condensation polymerization is the name given to reactions that form

polymers by “dehydrating” the monomers. Condensation polymerization is responsible

for all biological polymers, and requires far less exotic conditions than other types of

polymerization reactions, such as addition reactions.

This research was conducted to better understand the relation of the size of the monomer

to the properties of the polymer in polyamids, which are better known by the trade name,

nylon. Nylons are named for the length of the carbon chains that make them up.

Nine different nylons were synthesized: nylon 6-6, nylon 6-8, nylon 6-10, nylon 8-6,

nylon 8-8, nylon 8-10, nylon 10-6, nylon 10-8, and nylon 10-10.

The properties of these polymers were studied, and measurements were taken for density

and tensile strength of the polymers.

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The results showed that, overall, the smaller carbon chains yield stronger polymers, and

that large diamines (one of the monomers) are not effective.

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Introduction:Polymerization is the process of reacting small molecules called monomers in such a way that they form chains, called polymers. Polymers are very useful materials. Depending on the structure of the monomer units, the length of the polymer chains, and other factors such as branching of the chains, the properties of the polymer can vary from a brittle plastic that melts in hot water, like wax, or a rubbery, malleable material that will not melt at all. The range of properties makes polymers suitable for numerous common applications. They are often formed into filaments, as their chain-like structure gives them great structural integrity, and, hence, tensile strength. Certain polymers, notably aramids, are strong enough to stop a bullet. Kevlar, for example, is a woven aramid.

Polymerization reactions are usually lumped into two categories, free radical polymerization and condensation polymerization. Free radical polymerization occurs when double bonds in a monomer break, leaving an electron that will form a covalent bond with an adjacent monomer unit. An example of free radical polymerization is the polymerization of polytetrafluoroethylene, better known as Teflon. The monomer in this reaction is tetrafluoroethylene, F2C=CF2. During the polymerization reaction, the double bond in the molecule breaks, leaving electrons on both ends. The molecule at this stage is drawn as:.F2C-CF2

., where the dots on the end represent free electrons. If the radical comes into contact with another tetrafluoroethylene monomer, the loose electrons will excite it, and its double bond will break, yielding two radicals. The electrons on the ends of these radicals merge to form a single bond, yielding, .F2C-CF2-F2C-CF2

.. The ends of the molecules are still radicals, so the reaction can continue.

In order for a condensation reaction to occur, the reagents must exhibit acidic or basic properties. An example of condensation polymerization is the formation of nylon 6-10. In this reaction, there are two monomers, 1,6-diaminohexane and sebacic acid. Their structural formulae are, accordingly, H2N(CH2)6NH2 and HOOC(CH2)8COOH. A hydroxyl group from the acid and a hydrogen from the amine join together and form water, leaving what are effectively radicals of the monomers. The CO and NH join together to form an amid bond, COHN, and the two monomers are joined as H2N(CH2)6NHOC(CH2)8COOH. The reaction can continue at the ends of the molecule. In the research done here, the sebacic acid has been replaced with sebacoyl chloride, which has ClOC as its functional group instead of HOOC. This substitution encourages the reaction, and allows it to proceed under normal conditions. Usually, when using the HOOC functional group, the reagents are heated to over 100o so that the water produced boils off and the Le Chatelier principle drives the reaction to the right, to produce more water.

The goal of the project is to analyze the effects of changing the length of the monomers in polyamids. Nine polymers were synthesized, nylon 6-6, nylon 6-8, nylon 6-10, nylon 8-6, nylon 8-8, nylon 8-10, nylon 10-6, nylon 10-8, and nylon 10-10. The polymers were examined and tested for tensile strength and density. Unfortunately, some of the polymers, notably the 10-n polyamids, were uncooperative, and no data could be taken.

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Method:The official procedure follows:Materials:Hexane.Water.Adipoyl chloride.Suberoyl chloride.Sebacoyl chloride.1,6, hexanediamine.1,8 octanediamine1,10 decanediamine

Equipment:Beaker, 50 ml. (4)Buchner funnel.Filter paper to fit funnel. (20 sheets)Side-arm flask.Stopper for side arm flask.Glass stirring rod. (2)Vacuum tubing.Petri dishes. (5)Stir plate, bars.Graduated cylinder. (3)Volumetric flask, 25 ml or 50 ml. Wash bottle.Vials for storage of the polymers synthesized.Labels.

Safety considerations:Acyl chlorides fume HCl, so only use them under a fume hood.Always safely dispose of unused solutions.Wear gloves and safety glasses.

Procedure:1. Obtain all materials and equipment. 2. Create the solutions of the amines.3. Hexanediamine: 3.26 ml molten hexanediamine and water to 50 ml, or 1.63 ml

molten hexanediamine and water to 25 ml.4. Octanediamine: 3.61 g and water to 50 ml or 1.80 g and water to 25 ml.5. Decanediamine: 4.31 g and water to 50 ml or 2.15 g and water to 25 ml.6. Label them. 7. Create the solutions of the acyl chlorides. 8. Note: the finished solutions are all 50 or 25 ml. Add the hexane until the solution

reaches the desired volume. 9. Sebacoyl chloride: 5.33 ml chloride and hexane to 50 ml or 2.66 ml chloride and

hexane to 25 ml.

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10. Adipoyl chloride: 3.63 ml chloride and hexane to 50 ml, or 1.81 ml and hexane to 25 ml.

11. Suberoyl chloride: 4.50 ml chloride to 50 ml hexane, or 2.25 ml to 25 ml hexane. 12. Label these solutions. 13. Synthesize the nylons by pouring the amine solution in a beaker and then slowly

adding the acyl chloride. 14. If the solution produces a strand of nylon, remove it with a stirring rod. 15. If the solution fails to produce a strand, mix it with a stirring rod and wait for a

polymer to form as a precipitate. 16. Note the style and rate of polymerization. 17. After the solution has stopped producing nylon, scrape the nylon off the rod or pour

the beaker containing the nylon into the Buchner funnel.18. Activate the aspirator, and wait until the nylon is not sopping wet. Now, squirt the

nylon with a wash bottle. This will remove the aqueous components of the solution. (Unreacted diamine, HCl, etc.)

19. After several rounds of squirting, turn off the aspirator and dump the filtered solution into an appropriate waste container. Save the polymer that was filtered in a weigh dish.

20. Add a small amount of water to the side-arm flask, enough to fill it up ¼ of the way. 21. Place the filtered nylon in the flask, and stopper it. 22. Activate the aspirator and allow the hexane in the nylon to boil off. This will also

help loosen up the nylon threads.23. Pour everything in the flask into another beaker, and re-attach the Buchner funnel. 24. Filter the boiled nylon and wait until it’s dry. 25. Dispose of all garbage and place the nylon in a vial and label it. 26. Repeat this process with the other acyl chlorides and amines and make sure that

everything is labeled. 27. After the polymers have been synthesized, place the vials in a dark, damp place.

Analysis procedure:Purpose: to begin accumulating data on the properties of the different nylons.Materials: nylons synthesized above.

Equipment:Beakers, 50 ml.Fume hood.Labels.Scale. (to .001g)Tensile testing apparatusAccurate graduated cylinders.Tweezers.Tongs.Calipers.Nice microscope.Slides, coverslips.Digital camera

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Safety: wear gloves and goggles.

Procedure:

Weight of the monomers:These data should be found on the side of the reagent bottles. Record them.

Density of the polymer:Firstly, make sure the polymer sample you’re using has been very thoroughly washed and boiled. Allow the polymer sample to dry overnight.Compress it into a convenient geometric shape.Measure, using calipers, the dimensions of the polymer. Be sure to record the units, some calipers measure in inches.Calculate the volume of the polymer sample. Measure the mass of the polymer using the scale.

Microscopic analysis: Firstly, create a slide of the polymer using water as the fixative. (Adhesives may interfere with the results.) The sample used should be a piece of the strand cut from the middle. Place the sample in a microscope and adjust the focus. Now put a camera on the eyepiece, and make sure that you can see the sample in the viewfinder. Take the picture, silly. Now take a picture of the name of the polymer, for example, a label on a bottle. Record the shape of the edges, the end of the strand, appearance of crystals, irregularities, and general shape of the polymer.

Rate of polymerization: This is a simple measurement taken during the synthesis. If the polymer takes a while to form, make a note of this.

Shape of polymer: Immediately after the polymer is synthesized, observe the shape of the polymer. After washing and handling the polymer may become distorted, so this is the only time it can be done. Record the shape.

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Tensile strength:If possible, send the polymers, clearly labeled, to a laboratory capable of analyzing the tensile strength. If no lab exists, use the following apparatus to test the tensile strength.

Set up the experiment as in the diagram, with the strand dangling from the spring. Simply wrap the strand around the end of the spring, and it should stick there. Measure the length of the spring using the meter stick, record it. Slowly and carefully wrap the other end of the strand, (the one that’s dangling) around your finger, do not pinch it. Gently pull down on the strand and keep your eye on the length of the spring. Keep a mental count of the spring’s length, as it will return to its initial length when the strand snaps. When the strand snaps, record the final length of the spring, and use the equation:

Where K is the spring constant, which should be previously determined, H(f) is the final length of the spring, and H(o) is the initial length of the spring.When choosing a spring, try to keep the spring constant low. 10-20N/M is ideal. Malleability: This is a very qualitative test, simply attempt to squish the polymer. Record any observations.

Bar clamp

Spring.

Strand.

Meter stick

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Opacity: Look at the polymer. If you can see through it, record this. If not, record that.

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Results:

Data for nylon 6-6:Weight of acyl chloride 183.03Weight of amine 116.2(density test) mass of blob .022Volume of blobDensity of blob .359 g/cm3

Notes from microscopic analysis. (Attach picture to back of report with a label.)The nylon formed a sheet, which was pulled out as a pleated strand.. Shown are the entire strand and a piece of the pulled sheet that was cut from the strand.

Rate of polymerization InstantaneousShape of polymer Strand, thick.Force required to break strand .054 NMalleability Silky, bends easily.Opacity Rather opaque.


Notes from microscopic analysis. (Attach picture to back of report with a label.)The polymer formed more strands, unlike the 6-6, which formed sheets. The strands bent at points, and not in a continuous arc.

Rate of polymerization InstantaneousShape of polymer StrandForce required to break strand .071 NMalleability Less malleable than 6-6, still very

malleable.Opacity Translucent.Data for nylon 6-10:

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Weight of acyl chloride 239.14Weight of amine 116.2(density test) mass of blob .203Volume of blobDensity of blob .396 g/cm3

Notes from microscopic analysis. (Attach picture to back of report with a label.)

The strand was notably thinner, and did not fray like the 6-8. It also bent more smoothly, and was covered with very small bubbles. Rate of polymerization Instantaneous.Shape of polymer StrandForce required to break strand .054 NMalleability Between 6-6 and 6-8.Opacity Clear when thin.

Data for nylon 8-6:Weight of acyl chloride 183.03Weight of amine 144.26(density test) mass of blobVolume of blobDensity of blobNotes from microscopic analysis. (Attach picture to back of report with a label.)The polymer stuck to the weighing dish, and was unrecoverable. No microscopic analysis was possible.

Rate of polymerization Fast.Shape of polymer Sheet, not strand. Force required to break strand No strand.Malleability Same as 6-8.Opacity Opaque.

Data for nylon 8-8:

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Weight of acyl chloride 211.09Weight of amine 144.26(density test) mass of blob .08Volume of blobDensity of blob .327 g/cm3

Notes from microscopic analysis. (Attach picture to back of report with a label.)This sample had no interesting characteristics microscopically.

Rate of polymerization FastShape of polymer StrandForce required to break strand .0599 NMalleability Breaks then bends. Opacity Very opaque.


Notes from microscopic analysis. (Attach picture to back of report with a label.)Like the 8-8, the 8-10 had no interesting characteristics.

Rate of polymerization Fast.Shape of polymer Strand. Force required to break strand .0599 NMalleability Fragile, breaks, then bends. Opacity Extremely opaque.

Data for nylon 10-6:

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Weight of acyl chloride 183.03Weight of amine 172.32(density test) mass of blobVolume of blobDensity of blobNotes from microscopic analysis. (Attach picture to back of report with a label.)

This polymer produced very little product, and virtually none of it was in the form of a strand. Interestingly, the tiny strand that was produced (in the picture) was very malleable. It was also very opaque.

Rate of polymerization Slow, does not go very far. Shape of polymer Dust, occasional strand. Force required to break strand 0 NMalleability Like 6-6.Opacity No light transmission.

Data for nylon 10-8:Weight of acyl chloride 211.09Weight of amine 172.32(density test) mass of blobVolume of blobDensity of blobNotes from microscopic analysis. (Attach picture to back of report with a label.)

The polymer formed as a dust, although there was a significant amount produced. Pictured here is a very small piece of the polymer that formed as a sheet. Additionally, black specks were found in the polymer, their

origin is unknown. Rate of polymerization Faster than 10-6.Shape of polymer Dust.Force required to break strandMalleabilityOpacity No transmission, retsin.Data for nylon 10-10:Weight of acyl chloride 239.14

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Weight of amine 172.32(density test) mass of blob .07Volume of blobDensity of blob .328 g/cm3

Notes from microscopic analysis. (Attach picture to back of report with a label.)The polymer formed a slab, which was too opaque for a proper microscopic analysis.

Rate of polymerization Slower than 6 and 8-n faster than other 10-ns.

Shape of polymer Sheet, breaks when attempt is made for strand.

Force required to break strand 0 NMalleability Shatters when touched.Opacity Opaque.

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Analysis:

This graph clearly shows the relation of polymer weight to tensile strength. As the monomers that made up the polymers got heavier, the polymers got weaker. Most likely, the heavier monomers are too large to be held together by a single covalent bond, and therefore tend to fall apart.

Tensile strengthy = -0.0005x + 0.2241

0

0.02

0.04

0.06

0.08

0.1

0 100 200 300 400 500

Polymer weight

Tensile strength

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While the small coefficient of correlation would appear to invalidate the initial predictions, upon analysis, it makes sense that the density of the polymers would remain constant. Take, for example, the densities of the following molecules. (Ignore the density of the substance, the molecular formula is of interest here.)

Dodecane. HexaneWhile these molecules have different sizes and masses, their “structural” density

is identical. That is, their densities are (12 carbons)/(12 bonds long) and (6 carbons)/(6 bonds long). If this idea is extrapolated to very long molecules, such as polymers, the trend would continue.

Supposing this is a polymer, the density is still (n carbons)/(n bonds long). Theoretically, the smaller monomers would yield heavier polymers, because the NHOC bond would be heavier than CH2CH2. In all likelihood, the differences in density were due to experimental error. A method to compress the polymer into a solid block should be explored for future research.

Densityy = 0.0003x + 0.2434

0

0.1

0.2

0.3

0.4

0.5

0 100 200 300 400 500

Polymer weight

Density

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Please note, when reading this graph, the higher fragility values represent brittle polymers. These data agree with those collected during the tensile testing, although there are more data points. The data are entirely qualitative, although a qualitative test was not necessary, as the main goal of this research was to determine patterns, not exact values.

When plotted by amine weight, the fragilities show the same patterns.

Fragilityy = 0.0386x - 10.277

012345678

0 100 200 300 400 500

Polymer weight

Fragility (arbitrary

units)

Fragility

y = 0.0594x - 5.1241

012345678

0 50 100 150 200 250

Amine weight

Fragility by amine

weight

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When plotted by amine weight, the tensile strength showed a nearly linear correlation. This is an exciting fact, as is means that the experiments yielded fairly accurate data.

The density graphed by amine weight showed the correlation that was predicted in the analysis of the density by polymer weight, namely that there is no correlation.

Tensile strength by amine weighty = -0.001x + 0.1834

-0.02

0

0.02

0.04

0.06

0.08

0.1

0 50 100 150 200 250

Amine weight

Tensile strength

Densityy = -3E-05x + 0.3621

0

0.1

0.2

0.3

0.4

0.5

0 50 100 150 200 250

Amine weight

Density

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Conclusion:The results indicate that polymers of higher molecular weight are less suitable for

most applications. They are generally more fragile than the short-chain polymers, and the very high chain-length polymers refused to form strands. From a purely practical standpoint, the monomers of higher molecular weight were very expensive, and it is likely that in the rare occasion where these properties would be desirable, a more inexpensive polymer would be used.

The polymers of high weight also were reluctant to polymerize, even when the carboxylic acids were replaced with acyl chlorides. It is possible that these monomers would not polymerize at all if the acyl chloride were not present. Unfortunately, the polymerizations involving carboxylic acids often take place under exotic reaction conditions that cannot be easily duplicated in a research situation. Another possibility is that the 1,10 diaminodecane was not soluble enough in water to form an acceptable polymer, and therefore the reaction was the problem.

The most useful polymer synthesized was the nylon 6-6. It polymerized readily, and was extremely strong. Additionally, it was made with adipoyl chloride, which is less expensive than other acyl chlorides. Should this research continue, it would be advisable to attempt to synthesize nylon 6-6 using bulk polymerization methods, or a carboxylic acid in place of an acyl chloride. Several problems were encountered during the research, perhaps the most notable was that the 1,10 diaminodecane was not soluble in cold water. The other diamine solutions were made as .25 M solutions, but the diaminodecane was not soluble enough. The solution that was used was to mix the diaminodecane with water in a flask, and then to place the flask in a hot water bath. The diaminodecane was soluble at elevated temperatures, and after all the diaminodecane had dissolved, the flask was allowed to cool. After the diaminodecane had precipitated, it was assumed that the solution would be saturated with the monomer. Using a hot solution was not an option, as the acyl chloride was dissolved in hexane which might have boiled and ignited. The unknown concentration of the solution may have influenced the results.

Initially, the testing that was planned included a melting point test. However, the ovens available did not melt the polymers, and so the test was abandoned. Should an oven capable of melting the polymers be found, this test is strongly encouraged, as it does not depend on the conditions of the polymerization.

Another set of data that were abandoned were the enthalpies of the reactions. This turned out to be impossible to measure, as the heat was not evenly distributed, and the product was removed from the reaction vessel. If bulk polymerization had been attempted, determining the enthalpy of the reaction would have been feasible.

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Future studies:While the results from this research have yielded various insights into polymer

chemistry, there are many exciting discoveries that can still be made.Some of the polymers synthesized did not form strands, which certainly would

have affected properties such as tensile strength. A more reliable route of polymerization, such as bulk polymerization, may yield more similar reactions, which would allow higher certainty in the data. Additionally, bulk polymerization would allow measurements of enthalpy, which might allow insight into the mechanics of the reaction.

A method of compressing the polymers synthesized would be very useful. Most of the commercially available polymers are drastically altered from their initial state, either by compression or heating. Nylons are thermoset polymers, so melting them to form them would be impractical. Most likely, high pressure would force the strands to form a brick, which would allow more accurate testing.

In terms of the monomers, increasing the molecular weight would likely have a limited benefit. Experimentation with smaller monomers may yield polymers which are much stronger, and easier to manufacture. Additionally, adding unusual functional groups may create useful polymers.

An aspect of research which was not pursued was synthesizing aramids. Aramids are condensation polymers that involve benzene rings. In addition to having a very different shape, benzene rings can have more than two functional groups, as in 1,3,5 triaminobenzene. Such highly branched polymers may have very interesting properties.

polymer synthesis report

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