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Poly-(ethylene oxide) crystalline behavior using polarized o

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katie thielmann

on 27 March 2014

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Transcript of Poly-(ethylene oxide) crystalline behavior using polarized o

Poly-(ethylene oxide) crystalline behavior using polarized optical microscopy
Tina Berthiaume, Mollie Hoffman, Katie Thielmann

Introduction
A polarized optical microscope was used to observe the crystallization of spherulite crystals in a sample of poly-(ethylene oxide) as it underwent thermal cooling. Images of the poly-(ethylene oxide) crystallization were analyzed to determine the growth rate of the crystals.

Poly-(ethylene oxide)
A synthetic polymer
Ranges in Molecular Weight
Poly-(ethylene glycol)
PEG
<1000 MW
clear
colorless
Viscous fluid
Poly-(ethylene oxide)
PEO
MW in the millions
waxy, white solids,
range of melting points depending on MW, up to the limit ca. 67°C
Figure 1: A monomer form of a Poly-(ethylene oxide)

Figure 2: Example of PEO used in Pharmaceuticals

water soluble
thermoplastic
Common Uses
binding
thickening
lubricity
water retention
film formation
Commercial Uses
pharmaceuticals
mining
paper and cleaning products
Manufacturing
extruded, injection molded, cast


PEO Uses

Olympus Optical Microscope
Eyepiece
Objective Lens
Translational Stage
Polarizer
Digital Camera
Objective Device Selection Slider
Analyzer
Power Switch
Coarse Focus Adjustment
Fine Focus Adjustment
Light Intensity Adjustment
Figure 3: A olympus polarized optical microscope

Figure 4: The effect of a polarizer on ordinary light is the elimination of all but the transmission direction of the polarizer.

Ordinary light passes by or is reflected by a polarizing optic which makes all directions of light vibrations get absorbed except for transmission direction of polarizer
polarized light:
shows nature of incoming light
shows internal characteristics of material
enhances contrast between different refractive indices in directions of material
polymers and polarized light:
amorphous regions will appear tan
crystalline regions will appear white or dark
dark regions are crystals perpendicular to polarizer light source
white/light regions are crystals parallel to polarizer light source


Polarized Light

Sample Preparation
1. Four drops of PEO-chloroform cast on a clear microscope slide
2. Solvent evaporated
3. Left thin film of semicrystalline polymer to examine under the microscope

Microscope Preparation
1. Objective lens was set to 5X
2. Light intensity in polarizer was adjusted
3. Focus was adjusted using coarse and fine focus adjustment knobs
4. Temperature limit was set to 80oC and rate to 8oC/min
5. Objective lens was changed to 10x and refocused for recrystallization part

Sample and Microscope Preparation

Results
Figure 6: Image captured of the PEO sample under a polarized optical microscope at approximately 63.07°C

Figure 5: First captured image of PEO sample under a polarized optical microscope at 44.1°C

Results

Figure 7: Image captured of the PEO sample under a polarized optical microscope at approximately 65.33°C

Figure 6: Image captured of the PEO sample under a polarized optical microscope at approximately 64.4°C

Results

Figure 9: The last image captured of the PEO sample under a polarized optical microscope at 80°C

Figure 8: Image captured of the PEO sample under a polarized optical microscope at approximately 67.07°C

Results

2:35

2:15

1:55

B

C

A

Figure 10A-10C: Images from the video of the PEO sample crystallizing under polarized light in an optical microscope

PEO Crystallization

3:30

3:15

2:55

F

E

D

Figure 10D-10F: Images from the video of the PEO sample crystallizing under polarized light in an optical microscope

PEO Crystallization

4:00

3:35

H

G

Figure 10G-10H: Image from the video of the PEO sample crystallizing under polarized light in an optical microscope

PEO Crystallization

4:00

3:35

H

G

Figure 10G-10H: Image from the video of the PEO sample crystallizing under polarized light in an optical microscope

PEO Crystallization

Results and Calculations

Calculations:
1. Length of the crystal was measured in pixels using the software ImageJ for 5 crystal formations

2. The measurements were converted using 640 pixels:1325 microns

3. To determine the average growth rate for each of the five crystals
the following equation was used:
=(change in length/change in time)

4. The average from all five of the crystal formations was calculated and converted into microns/minute.

Growth rate average= 221.99 µm/min or 222 µm/min

The amorphous and crystalline regions within the PEO polymer respond to polarized light through interference. The amorphous regions appear dark as they are optically transparent and react with destructive interference, and the crystalline regions lie along the light’s transmission axis and appear lighter in the image.
The melting temperature of PEO is in the range of 63.07°C to 67.07°C.
The growth rate of PEO spherulite in the sample observed was determined to be 222 µm/min.

Conclusions
[1] http://www.dow.com/dowwolff/en/industrial_solutions/polymers/polyethylene/ 3/25/14.

[2] Bailey, F.E.; Koleske, J.V. Poly(Ethylene Oxide), Academic Press, New York, (1976).



This experiment performed at Iowa State University in the Materials Science and Engineering department with the polarized optical microscope under the guidance of Dr. De León.

References and Acknowledgments
Full transcript