Determination of Thermodynamic Properties of OLED Compounds

Determination of Thermodynamic Properties of

Organic CompoundsTeam Serval: Logan Williamson, Owen Perlowski, Kristen Webster, Nick

KasperCHE 255: Chemical Engineering Processes

December 13th, 2016

Background: Molecular Glasses

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Startup founded in 2013

Non-crystallizable semiconductors

OLED longevity

www.molecularglasses.com

www.geeky-gadgets.com

Current method:

Guess and Check = Time and Money

Problem

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New Materi

al

Guess ideal temp zones

to purify product

Train sublimation

under vacuum

Successful Separation?

(HPLC)No Yes

GoalsMeasure heat of vaporization

Run experiments under reduced pressure/temperature

Required accuracy: ballpark

Stay within budget/time constraints

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Our Approach: Model Compounds

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Naphthalene Anthracene

Molecular Weight: 128.17 g/molMelting Point: 80°CBoiling Point: 218°C

Molecular Weight: 178.2 g/molMelting Point: 218°CBoiling Point: 342°C

Our Approach: ExperimentsThermogravimetric

Analysis

- Mass loss vs. temperature/time

- Clausius-Clapeyron equation

- No need to approach degradation temperature

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Differential Scanning Calorimetry

- Differential heat flow vs. temperature

- Lower pressure by sealing pans under vacuum

Pressure reduction method unsuccessful

Successful and promising for application

Thermogravimetric Analysis (TGA): What is it?

http://www.tainstruments.com/tga-5500/ https://www.researchgate.net/figure/263958136_fig2_Figure-2-Schematic-of-the-TGA

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TGA: Theory

8Source: Price, Duncan M. "Vapor Pressure Determination by Thermogravimetry."Thermochimica Acta 367-368 (2001): 253-62.

TGA: Experimental Outline

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Determine Calibration Constant (k)

Using k, Calculate Vapor Pressures of Model Compounds

Use Vapor Pressures to Calculate Heat of Vaporization of Model Compounds

Compare Calculated Values to Literature Values

Use Method to Calculate Vapor Pressures and Heat of Vaporization of Compound with No Literature Data

TGA: Output Example - Naphthalene

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TGA: Determining k for Each Compound

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Anthracene

k = 887,652

Naphthalene

k = 1,503,009

TGA: Calculating Vapor Pressure Using Optimized k

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Using Least-Squares Regression:

Naphthalene

Temp ( )℃ Lit. p (Pa)Avg.

Calculated p(Pa)

Percent Error

80 1000 828 17.2

93 1811 1672 7.7

98 2357 2036 13.6

103 2833 2418 14.7

115 4752 3754 21.0

Anthracene

Temp ( )℃ Lit. p (Pa)Avg.

Calculated p(Pa)

Percent Error

227 7000 7898 12.8

237 9000 10,227 13.6

247 12000 12,051 0.4

257 16000 13,330 16.7

Optimal k = 1,183,875Average % Error: 13%

TGA: Calculating Heats of Vaporization of Model Compounds

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Calculated ΔHVap 49.3 kJ/mol

Literature ΔHVap 56.1 kJ/mol

Percent Error 12.1


Literature ΔHVap 59.2 kJ/mol

Percent Error 30.1

TGA: Heat of Vaporization is Independent of k

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Naphthalene

kOpt = 1,183,875ΔHVap = 49.3 kJ/mol

k = 1ΔHVap = 49.3 kJ/mol

TGA: Calculating Heat of Vaporization of Unknown Compound

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Tri-p-tolylamine (TTA)

Temp ( )℃ Avg. Calculated p (Pa)

250 2692

280 5157


Molecular Weight: 287.4 g/mol

Using kOpt = 1,183,875

TGA: Summary

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● Good for determining how long it will take to vaporize any compound at a given temperature. This could help Molecular Glasses save time during their purification of materials. TGA is versatile and can reach temperatures > 1000 .℃

● Vapor pressures can be estimated within ~20% error. One possible way to reduce the error is to test more than 2 model compounds when regressing for the calibration constant. Also test wider range of temperatures.

● Heats of Vaporization can be estimated using calculated vapor pressures. Furthermore, these heats are independent of the calibration constant and can therefore be calculated strictly from a TGA test and the Clausius-Clapeyron equation.

Vacuum Bagging System Concept

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Vacuum Bagging System Build

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Changes from Initial BuildSealed areas that could

have allowed air leakage with gorilla glue

Added cardboard blast shield

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Changes from Initial Build

Changed pressure gauge after valve to a liquid filled gauge to increase readability

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Vacuum Bagging Procedure1. Cut bagging film into 3”x 8” sheets.

2. Place connector base and DSC pan with sample and lid on top on top of one sheet.

3. Apply sealant tape around edges.

4. Place second sheet on top of the first and press down on tape to seal.

5. Connect connector to pump system and turn on pump.

6. Close valve 2 and allow pressure to build up within vessel.

7. Close valve 1 and open valve 2 to remove air from bag.

8. Clamp lid onto pan using press.

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Bag Construction

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http://youtube.com/v/IPsH_b9IoaY

DSC

24www.pcbshop.prg

DSC Procedure was split into three different sections, for the three different pans we used:

1. Non-Hermetically Sealed Pans

2. Hermetically Sealed Pans under vacuum

3. Hermetically Sealed pans not under vacuum (1 atm)

The following slides will provide a simple guide to each type of pan procedure

DSC - Procedure

(Non-Hermetic Pans Supplied by Mark Juba, Hermetically Sealed Pans provided by Anthamatten Lab)

1. Place desired sample in pan. Weigh pan before and after.

a. If Hermetically sealed, use TA clamp to seal shut

2. Determine procedure in DSC program

a. Determine max temp/temp increase.

3. Input reference pan, along with pan with sample

4. Run sample25

DSC: ResultsResults for the DSC were in this form:

This graph shows us the Heat Flow (W/g) vs. Temperature (C) .

As we know, the DSC records required heat for phase change. This is expressed as a peak on this graph.

By using manual integration present in the DSC analysis software, we are able to find the precise amount of heat required for this specific instance of phase change. These values were compared to literature for accuracy and error percentages were analyzed calculated.

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Calc H Fusion (kJ/mol)

Calc H Vap(kJ/mol)

Calc H Sub(kJ/mol)

24.966 47.241 72.206

%Error 16.222 20.201 26.244

Calc H Fusion(kJ/mol)

Calc H Vap(kJ/mol)

Calc H Sub(kJ/mol)

27.549 45.797 73.347

%Error 7.551 22.639 25.079

Anthracene Hermetic 1atm Trials

Anthracene Literature BP: 342CAnthracene Literature MP: 218C

MP & BP Found at:O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 111 27

Mass = 17.3mg

Mass = 9mg


Calc H Vap(kJ/mol)

Calc H Sub(kJ/mol)

27.549 46.778 74.327

%Error 7.551 20.983 24.078


Calc H Vap(kJ/mol)

Calc H Sub(kJ/mol)

25.251 47.793 73.044

%Error 15.265 19.268 25.389

Anthracene Hermetic Vacuum Trials


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Mass = 14.8mg

Mass = 7.2mg

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First Trial Noise Peak


Calc H Vap(kJ/mol)

Calc H Sub(kJ/mol)

- - 98.188

%Error - - 0.294

Mass(mg) Calc H Fusion(kJ/mol)

Calc H Vap(kJ/mol)

Calc H Sub(kJ/mol)

25.7 - - 93.537

%Error - - 4.456

Anthracene Non-Hermetic Trials


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Mass = 13.4mg

Mass = 25.7mg

Pan Pressurization

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DSC: SummarySaw no improvement with using vacuum bagging system to reduce pressure

inside the pan.

Increase in boiling point for sealed pans may tell us there is a small amount of pressure buildup in our pans, which is counterproductive.

We observed literature consistency with non-hermetically sealed pans, although it appears impossible to determine only heat of vaporization or only heat of fusion for these trials.

No difference when using different mass amounts. Data is consistent regardless of mass.

Observed relatively accurate heats for our compounds. This could be incredibly useful for molecular glasses to estimate properties of compounds

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ConclusionOur goal was to determine the heat of vaporization of solid compounds under

reduced pressure for application to OLED materials

2 methods:

Differential scanning calorimetry (DSC) w/ vacuum sealing

Thermogravimetric analysis (TGA)

TGA and non-hermetically sealed DSC gave results most consistent with the literature

No improvement with using vacuum bagging system to reduce pressure inside the pan due to a buildup of internal pressure in the pans

Final Recommendation: TGA

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Acknowledgments

We would like to thank everyone in the chemical engineering department for allowing us this opportunity with a special thanks to Professor Kelley, Mark Juba, Dave Weiss, Larry

Kuntz, Professor Tenhaeff, Cindy Fitzgerald, Rachel Monfredo, our TA Robbie Harding, and Dawei Chen from the

Anthamatten Lab.

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QUESTIONS?

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Additional TGA Analysis

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Error Analysis: Hypothesis: Noise in the data increases as the temperature increases.


Temperature [ ]℃dm

/dt [

g/m

in]

Temperature [ ]℃

dm/d

t [g/

min

]

ReferencesMelting Point and Boiling Point of Anthracene:O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 111

Heat of Fusion & Vaporization, Anthracene:Rojas, Aarón; Orozco, Eulogio, Measurement of the enthalpies of vaporization and sublimation of solids aromatic hydrocarbons by differential scanning calorimetry, Thermochimica Acta, 2003, 405, 1, 93-107

Heat of Sublimation, Anthracene:Oja, Vahur; Chen, Xu; Hajaligol, Mohammad R.; Chan, W. Geoffrey, Sublimation Thermodynamic Parameters for Cholesterol, Ergosterol, β-Sitosterol, and Stigmasterol, J. Chem. Eng. Data, 2009, 54, 3, 730-734.

Thermogravimetric Methodology:Price, Duncan M. "Vapor Pressure Determination by Thermogravimetry."Thermochimica Acta 367-368 (2001): 253-62.

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Determination of Thermodynamic Properties of OLED Compounds

Engineering

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