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Combinatorial Chemistry. High-Throughput Methods for Developing New Materials. Group Members: Christopher Gold, Melissa Lackey, Chih-Fang Liu, Ryan Wu Advisors: Dr. Earl Ryba, Kevin Gallagher - PPG Industries. Project Statement.

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Combinatorial chemistry

Combinatorial Chemistry

High-Throughput Methods for Developing New Materials

Group Members: Christopher Gold, Melissa Lackey, Chih-Fang Liu, Ryan Wu

Advisors: Dr. Earl Ryba, Kevin Gallagher - PPG Industries


Project statement
Project Statement

  • Develop a high-throughput process that employs the principles of combinatorial chemistry to dramatically reduce the time and labor required to evaluate the durability of new resins and coatings, specifically abrasion resistant clear coatings on a polycarbonate substrate.


Goals
Goals

  • Research combinatorial chemistry and high-throughput methods to present a means of drastically increasing productivity and efficiency


Goals1
Goals

  • Research combinatorial chemistry and high-throughput methods to present a means of drastically increasing productivity and efficiency

  • Reduce cost and increase profit through miniaturization of sample size and increased coating discovery rate


Combinatorial chemistry1
Combinatorial Chemistry

  • Miniaturization and automation yield high-throughput experimentation

  • Decreased sample size

  • Processes almost completely automated


Combinatorial chemistry2
Combinatorial Chemistry

  • Miniaturization and automation yield high-throughput experimentation

  • Decreased sample size

  • Processes almost completely automated

  • Quantitative analysis of data

  • All steps linked to central database

    • Self-updating processes

  • Easy to use

  • Reliable and versatile


Automation of production and testing
Automation of Production and Testing

  • Faster formulation of wide array of coatings

  • Fast, accurate, and quantitative testing


Automation of production and testing1
Automation of Production and Testing

  • Faster formulation of wide array of coatings

  • Fast, accurate, and quantitative testing

  • Immediate data feedback to central database

  • Enables coatings to be produced and tested at rates > 100x conventional methods


The combinatorial factory
The Combinatorial Factory

  • Formulation of coatings

  • Creation of coating arrays

  • Preliminary screening

    • Optical, abrasion, and adhesion testing

  • Secondary screening

    • Weathering

    • Integrity evaluation

  • Larger scale testing to meet industry specifications


Schematic of the combinatorial factory
Schematic of The Combinatorial Factory

Capable of screening 100 to 200 coatings per day



Formulation and creation of arrays1
Formulation and Creation of Arrays

  • Easily accomplished with robot mixing technology

  • Quickly create arrays with formulations of varying composition and thickness

    • Rates of > 1 array/2 hours

  • Coating and curing accomplished at rates > 1 array/hour


The array
The Array

  • Polycarbonate base film, 0.5-mm thick

  • 6x8 array of coatings

    • each sample is 2-5-μm thick and 10-mm in diameter

  • Flexible silicon rubber template to create wells


Spin casting

Positive aspects

Coating can be leveled after array creation

Allows for very diverse library of coatings to be produced on substrate

Spin Casting


Spin casting1

Positive aspects

Coating can be leveled after array creation

Allows for very diverse library of coatings to be produced on substrate

Problems arise after array creation

Meniscus

Differential evaporation

Coffee ring effect

Spin Casting



Leveling and curing the array
Leveling and Curing the Array

  • Coatings leveled via horizontal centrifuge at 2000-3000 rpms

  • Curing can take place separately by UV, thermal, as necessary


Problems during leveling
Problems during leveling

  • Problems arise due to meniscus and air flow in centrifuge


Problems during leveling1
Problems during leveling

  • Problems arise due to meniscus and air flow in centrifuge

    • At 2000 rpms, air speeds reach up to 60 mph

    • Heavy air flow causes differential evaporation and coffee ring effect



The effect of covered wells
The Effect of Covered Wells

  • Cover well with permeable layer

    • Solvent can still evaporate

    • Air flow from above no longer affects samples


Conquering differential evaporation
Conquering Differential Evaporation

  • Hole in center of permeable layer allows solvent in center to evaporate at rate equal to that at well edges

  • Consistent evaporation eliminates liquid flow to well walls



High throughput screening

High-Throughput Screening

Primary

Secondary


Multilevel performance screening
Multilevel Performance Screening

  • 1st stage screening

    • Test optical clarity, abrasion resistance, and adhesion

    • Eliminates ~ 90% of samples

  • 2nd stage screening

    • Test weatherability, integrity, gloss, and surface smoothness

  • Rapidly identify coating samples with desired properties

    • Candidates for scale up

    • Test according to the customer’s specifications


Multilevel performance screening1
Multilevel Performance Screening

  • 1st stage

    • 100-200 samples per day

  • 2nd stage

    • ~10% of the samples

  • Rapidly identified materials

  • Candidates for scale up



High throughput screening1

High-Throughput Screening

Primary: Optical Clarity


Optical clarity
Optical Clarity

  • Crucial property – clear coating on polycarbonate, needs to be able to replace glass

  • First screening of samples – immediately eliminate some

  • Corresponds to the absence of light scattering

  • Later screenings optimized for up to 30% haze


High throughput optical clarity
High-Throughput Optical Clarity

  • Fiber optic probe – measures intensity of 360o back-scattered light


High throughput optical clarity1
High-Throughput Optical Clarity

  • Maximum intensity = optical clarity

  • Lower intensity  higher optical clarity

  • Relate percent haze to scattered light:

    • S2 = SK/(1 + 100/H)

      • S2 = scattered light

      • S = transmitted light + scattered light

      • K = constant, relates methods

      • H = percent haze


High throughput optical clarity2
High-Throughput Optical Clarity

  • Valid method? Yes!

Correlation shown between scattered light intensity from the high-throughput method to percentage of haze of reference materials.


High throughput screening2

High-Throughput Screening

Primary: Abrasion Resistance


Abrasion resistance
Abrasion Resistance

  • Basic factor in durability

  • Caused by mechanical actions, such as rubbing, scraping, or erosion from wind and water

  • Related to other physical characteristics

    • Hardness

    • Cohesive and tensile strength

    • Elasticity

    • Toughness


High throughput abrasion test
High-Throughput Abrasion Test

  • Samples:

    • 10 mm diameter

    • 2-5 μm thick

    • 8x6 arrays of 48 coatings on polycarbonate substrate

  • Abrasion methods;

    • Air blast test

    • Oscillating sand test


High throughput abrasion test1
High-Throughput Abrasion Test

  • Air Blast Abrasive Test:

    • 50 μm Al2O3 particles

    • Constant pressure and flow rate

    • Nozzle with 1 mm diameter opening

    • Sheet advanced automatically, 15 cm/min

    • Change distance of nozzle to coating from 2.5 to 10 cm, 1.25 cm increments


High throughput abrasion test2
High-Throughput Abrasion Test

  • Oscillating Sand Test

    • 1,000 ml sand on array in container

    • Oscillate container for set amount of time

    • Vary level of abrasion by changing time: 10 min, 20 min, 30 min


High throughput abrasion test3
High-Throughput Abrasion Test

  • Sample analysis: spectroscopic measurements of scattered light.

  • Less scattered light = better abrasion resistance.


High throughput abrasion test4
High-Throughput Abrasion Test

  • Spectroscopic system:

    • White light source

    • Monochromator

      • Selection of illumination wavelength

      • Light focused into fiber-optic probe


High throughput abrasion test5
High-Throughput Abrasion Test

  • Spectroscopic system:

    • White light source

    • Monochromator

      • Selection of illumination wavelength

      • Light focused into fiber-optic probe

    • Portable spectrometer

      • 600-grooves/mm grating blazed at 400 nm

      • Spectral range: 250-800 nm

      • Linear CCD-array detector


High throughput abrasion test6
High-Throughput Abrasion Test

  • Excitation wavelength set at 500 nm (0 order of monochromator)

  • Setup optimized for samples with up to 30% haze

    • Probe angle – highest change in detector response over range of measured haze

    • Distance from probe to coating – ideal spot size ~4-6 mm

    • Spectral acquisition conditions


High throughput abrasion test7
High-Throughput Abrasion Test

  • Minimal contributions from light directly reflected back from coating into probe

  • Just collect diffusively reflected portion of radiation interacting with coating surface


High throughput abrasion test8
High-Throughput Abrasion Test

  • Valid method? Yes!

Correlation shown between the high-throughput method and the Taber abrasion method for abrasion resistance determination.


Data acquisition programs
Data Acquisition Programs

  • Programs constructed using LabView

    • National Instruments

  • Kaleidagraph

    • Synergy Software

  • Programs constructed using MatLab

    • The Mathworks Inc.


High throughput screening3

High-Throughput Screening

Primary: Adhesion


Adhesion
Adhesion

  • Occurs when interfacial and intermolecular forces hold two surfaces together


Adhesion1
Adhesion

  • Occurs when interfacial and intermolecular forces hold two surfaces together

  • Measuring: corresponds to the forces or work required to terminate the adhering system


Adhesion2
Adhesion

  • Occurs when interfacial and intermolecular forces hold two surfaces together

  • Measuring: corresponds to the forces or work required to terminate the adhering system

  • Quantified through a micro scratch test using a blade-like indenter


Adhesion evaluation
Adhesion Evaluation

  • Indenter positioned with a selected angle of attack between the front side and the coating surface

Blade-like micro scratch indenter with a sharp angle between edge RE and the front side, and rounded angle γ with radius R1.


Adhesion evaluation1
Adhesion Evaluation

  • Indenter positioned with a selected angle of attack between the front side and the coating surface

  • Drawn across surface with constant or progressively increasing load

Blade-like micro scratch indenter with a sharp angle between edge RE and the front side, and rounded angle γ with radius R1.


Adhesion evaluation2
Adhesion Evaluation

  • Simultaneous measurements of indenter-surface interactions taken to detect the critical load

    • Mechanical

    • Acoustical

    • Electrical

Blade-like micro scratch indenter in the direction of arrow A in previous figure, with the front attack angle, α, and the back attack angle, β. Arrow B shows the direction of movement.


Adhesion evaluation3
Adhesion Evaluation

  • Simultaneous measurements of indenter-surface interactions taken to detect the critical load

    • Mechanical

    • Acoustical

    • Electrical

  • Characterize scratch and adhesion resistance

Blade-like micro scratch indenter in the direction of arrow A in previous figure, with the front attack angle, α, and the back attack angle, β. Arrow B shows the direction of movement.


Adhesion evaluation4
Adhesion Evaluation

  • Tungsten-carbide indenter

    • Hard

    • Conductive (measure electric contact resistance)

  • No problems with stress in substrate


Adhesion evaluation5
Adhesion Evaluation

  • Tungsten-carbide indenter

    • Hard

    • Conductive (measure electric contact resistance)

  • No problems with stress in substrate

  • Works for clear, non clear, plastic, and metal substrates

  • Works for multi-layer coating systems


High throughput screening4

High-Throughput Screening

Secondary: Weathering


Weathering
Weathering

  • Similar to current method used by PPG

    Key Components:

    • Weatherometer

    • Automated measurement system


Weathering1
Weathering

  • Sample: 8x6 arrays

  • Weathering test

    •Weatherometer equipped with Xenon Lamp with inner and outer filters


Weathering2
Weathering

  • Sample: 8x6 arrays

  • Weathering test

    •Weatherometer equipped with Xenon Lamp with inner and outer filters

    • Weather cycle consists of:

    • 160 min of light (air temp. 45oC, black panel temp. 70oC, 50% relative humidity)

    • 5 min dark and 15 min of dark and water spray (air temp. 20oC, 100% relative humidity)


Weathering3
Weathering

  • Weatherometer: accelerates process to approximately 8-fold over that in Miami, FL.


Weathering4
Weathering

  • Weatherometer: accelerates process to approximately 8-fold over that in Miami, FL.

  • Samples must be subjected to at least 2000 kJ/m2 at 340 nm of UV exposure in the weatherometer for sufficient weathering


Weathering5
Weathering

  • Weatherometer: accelerates process to approximately 8-fold over that in Miami, FL.

  • Samples must be subjected to at least 2000 kJ/m2 at 340 nm of UV exposure in the weatherometer for sufficient weathering

  • Automated measurement system – generates quantitative data to database.


High throughput screening5

High-Throughput Screening

Secondary: Integrity


Integrity evaluation
Integrity Evaluation

  • Yellowness index (YI) measurements

    • Deuterium-halogen light source, transmission probe, and portable spectrometer

    • Measured over spectral range from 250-800 nm

    • Calculates YI value from absorbance values in 400-500 nm range


Integrity evaluation1
Integrity Evaluation

  • Yellowness index (YI) measurements

    • Deuterium-halogen light source, transmission probe, and portable spectrometer

    • Measured over spectral range from 250-800 nm

    • Calculates YI value from absorbance values in 400-500 nm range

  • Higher absorbance values  higher yellowness index values


Integrity evaluation2
Integrity Evaluation

  • Integrity Measurements

    • Halogen 60-W lamp uniformly illuminates the array

    • CCD detector collects images of individual coatings for evaluation

    • LABView used for image analysis

Spectroscopic system used for YI and integrity evaluation


Integrity evaluation3
Integrity Evaluation

  • Images of modes of degredation

    • A) Good condition

    • B) Crack formation

    • C) Void formation

    • D) Delamination

    • after 1738 kJ/m2 exposure


High throughput screening6

High-Throughput Screening

Secondary: Gloss, Surface Smoothness


Gloss
Gloss

  • Gloss: specular, or mirror-like, reflection of white light from a surface

  • White light source is filtered  spectrum similar to the response of the human eye

  • Hand-held gloss meters are used with flat and curved surfaces for determining the surface finish of polymer products and painted surfaces for quality control purposes


Gloss1
Gloss

  • Gloss meters provide quantitative data on the uniformity and quality of surface treatments

  • Are relatively insensitive to vibrations.


Surface smoothness
Surface Smoothness

  • Surface topography contributes mechanical adhesion

  • Statistical parameters are obtained from the surface profiles


Surface smoothness1
Surface Smoothness

  • Surface topography contributes mechanical adhesion

  • Statistical parameters are obtained from the surface profiles

  • Most common parameters used:

    • Ra = average roughness deviation

    • Rq= root mean square roughness deviation

    • (equations 1 and 2)

Eqn 1:

Eqn 2:


Surface smoothness2
Surface Smoothness

  • Non-contact (or optical) profilometers (laser triangulation systems and optical interferometers) measure 3-D surface topography and roughness.

  • Surface reflectivity measured with a reflectometer.

  • Beam of light (either filtered white light as used for gloss meters or laser) projected onto the target surface at a specific angle

  • Amount of light reflected at the same angle is measured.


Surface smoothness3
Surface Smoothness

  • Surface roughness causes incident light to be scattered at angles other than that of specular reflection  scatter increases with roughness.

Schematic of surface reflectivity measurement.


Other considerations

Other Considerations

Laser Induced Decohesion Spectroscopy (LIDS) & Multi-Lens Combinatorial Adhesion Test (MCAT)


Laser induced decohesion spectroscopy lids
Laser Induced Decohesion Spectroscopy (LIDS)

  • Possible method of adhesion evaluation

  • Photothermal ablation is directed onto the sample

  • Produces an internal pressure between the clear coating and a non-clear coating or substrate


Combinatorial chemistry
LIDS

  • Possible method of adhesion evaluation

  • Photothermal ablation is directed onto the sample

  • Produces an internal pressure between the clear coating and a non-clear coating or substrate

  • Internal pressure creates a blister at the transparent/nontransparent interface

  • The blister's internal pressure depends on the laser pulse energy


Combinatorial chemistry
LIDS

  • Blister expands radially into unablated regions, causing sample to fail at a critical pressure

  • Measure of curvature, radius, and thickness of the blister  determine the critical pressure

  • Critical internal pressure used to quantify adhesion strength


Multi lens combinatorial adhesion test mcat
Multi-Lens Combinatorial Adhesion Test (MCAT)

  • Developed to measure adhesion across a library in a high throughput fashion

  • Utilizes an array of microlenses to conduct adhesion measurements across a sample


Combinatorial chemistry
MCAT

  • The contact area between the array and the substrate is visualized with a Leica DM IRE2 inverted microscope and measured with Image Pro software

  • Labview software is used to record the actuator position and load data during an experiment


Combinatorial chemistry
MCAT

  • Multi-lens arrays may be fabricated to contain anywhere from 100 up to 1000 or even 8100 individual lenses over an area of 1 cm2


Draw backs for mcat
Draw backs for MCAT

  • The volume of data collected during each evaluation of a new sample library



High throughput process
High-Throughput Process

  • Application: Robot technology and spin casting to create 6x8 arrays of coating samples

  • Spectroscopic determination of optical clarity and abrasion resistance

  • Microscratch test with blade-like indenter for adhesion quantification


High throughput process1
High-Throughput Process

  • Weathering in xenon arc weatherometer

  • Spectroscopic determination of yellowness index and coating integrity


High throughput process2
High-Throughput Process

  • Weathering in xenon arc weatherometer

  • Spectroscopic determination of yellowness index and coating integrity

  • Quantification of gloss and surface smoothness

  • Self-updating computer database


Advantages of combi chem and high throughput methods
Advantages of Combi Chem and High-Throughput Methods

  • Automated, reliable processes

  • Quantitative analysis

  • Comprehensive database


Advantages of combi chem and high throughput methods1
Advantages of Combi Chem and High-Throughput Methods

  • Automated, reliable processes

  • Quantitative analysis

  • Comprehensive database

  • Test more samples in shorter period of time

  • Minimize cost per sample

  • Better coatings, faster!


Ge s results
GE’s results

  • Combinatorial factory capable of preparing and evaluating ~100-200 coatings/day (2-4 arrays).

  • Productivity improvement of at least 10x!

  • Measurement throughput improvement of at least 20x!

  • (same number of chemists!)


Combinatorial chemistry

Thank you!

Questions or comments?