Observations of Self Assembled Bolaform Amphiphiles on Cellulose

1. Observations of Self Assembled Bolaform Amphiphiles on Cellulose Sunkyu Park 1, Joseph J. Bozell 1, Josef Oberwinkler 2 June 14, 2007 1 Forest Products Center, University of Tennessee 2 Salzburg University of Applied Sciences, Salzburg, Austria

2. 2 Presentation Contents

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4. 4 Bolaform Amphiphiles 4. Bolaform amphiphiles are a general term for molecules consisting of two hydrophilic headgroups on both ends linked by a long hydrophobic chain. 4. Bolaform amphiphiles are a general term for molecules consisting of two hydrophilic headgroups on both ends linked by a long hydrophobic chain.

5. 5 Bolaforms as Self Assembling Systems 5. These molecules have recently received a great attention due to the ability to form self-assembled structures, which can be used in template synthesis, drug delivery, and functional materials. Self assembly scheme has been proposed by Shimizu a few years ago. Bolaform molecules could be associated together by non-covalent bonds such as H-bond, hydrophobic interactions, and Van der Waals forces to make a sheet, ribbon, or tube structure.5. These molecules have recently received a great attention due to the ability to form self-assembled structures, which can be used in template synthesis, drug delivery, and functional materials. Self assembly scheme has been proposed by Shimizu a few years ago. Bolaform molecules could be associated together by non-covalent bonds such as H-bond, hydrophobic interactions, and Van der Waals forces to make a sheet, ribbon, or tube structure.

6. 6 Ferrier Bolaform Synthesis 6. Recently we, actually Joe Bozell, were able to synthesize bolaform amphiphiles in the lab. The approach for synthesis uses a well known, characteristic reaction of glycals, called the Ferrier reaction. I am not going into the detail of the steps. What I would like to point out is that the final product is potentially from biomass carbohydrates, which could be one stream of biorefinery.6. Recently we, actually Joe Bozell, were able to synthesize bolaform amphiphiles in the lab. The approach for synthesis uses a well known, characteristic reaction of glycals, called the Ferrier reaction. I am not going into the detail of the steps. What I would like to point out is that the final product is potentially from biomass carbohydrates, which could be one stream of biorefinery.

7. 7 Other Types of Bolaform Amphiphiles 7. This slide shows the summary of transformations. We were able to synthesize different structures of bolaform amphiphiles, e.g. different hydrophobic chain length. I would like to emphasize that the bolaforms have double bonds at the both ends, which increase the reactivity with other molecules.7. This slide shows the summary of transformations. We were able to synthesize different structures of bolaform amphiphiles, e.g. different hydrophobic chain length. I would like to emphasize that the bolaforms have double bonds at the both ends, which increase the reactivity with other molecules.

8. 8 Materials Used in this Study 8. The molecule here is the bolaform amphiphiles that we have used in this study. This has C12 backbone and symmetric structure. As we are in cellulose and forest society, we have started to look at how the bolaforms interact with cellulose. 8. The molecule here is the bolaform amphiphiles that we have used in this study. This has C12 backbone and symmetric structure. As we are in cellulose and forest society, we have started to look at how the bolaforms interact with cellulose.

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10. 10 Materials Cellulose: Microcrystalline cellulose (Avicel) Pretreatments MeOH exchange �3 DMAc exchange �3 Solvent 8% LiCl in DMAc (N,N-dimethylacetamide) Solution Cellulose + Bolaforms + LiCl/DMAc Methods A drop on glass-slide Drying Polarized optical microscope Materials and Methods 10. Microcrystalline cellulose is used as a starting material. To produce dissolved cellulose, cellulose powders were activated by the swelling in water followed by the solvent exchange of MeOH and DMAc. 8% LiCl in DMAc was prepared and used as a solvent system for cellulose. Once cellulose is dissolved in solvent, experiments were easy and simple. A small drop of solution was placed on a microscope slide and this drop is allowed to slowly evaporate in an atmospheric condition. Polarized optical microscope was used to study bolaform crystallization.10. Microcrystalline cellulose is used as a starting material. To produce dissolved cellulose, cellulose powders were activated by the swelling in water followed by the solvent exchange of MeOH and DMAc. 8% LiCl in DMAc was prepared and used as a solvent system for cellulose. Once cellulose is dissolved in solvent, experiments were easy and simple. A small drop of solution was placed on a microscope slide and this drop is allowed to slowly evaporate in an atmospheric condition. Polarized optical microscope was used to study bolaform crystallization.

11. 11 Cellulose Film in Absence of Bolaforms

12. 12 Bolaform Crystallization in Absence of Cellulose 11. First we tried without cellulose in solution. In the absence of cellulose, self assembly of the bolaforms led to isolated plate- and needle-like structures as shown in figures.11. First we tried without cellulose in solution. In the absence of cellulose, self assembly of the bolaforms led to isolated plate- and needle-like structures as shown in figures.

13. 13 Bolaform Crystallization in Presence of Cellulose 12. Now� we dissolved cellulose with bolaforms in the same solvent and place a drop on glass slide. Then, we found a much higher level of organization! In the left, we see the transition from the edge of a film, leading to a greater proportion of small crystals, and then moving into the bulk of the drop, where a greater proportion of organized structures are observed. 12. Now� we dissolved cellulose with bolaforms in the same solvent and place a drop on glass slide. Then, we found a much higher level of organization! In the left, we see the transition from the edge of a film, leading to a greater proportion of small crystals, and then moving into the bulk of the drop, where a greater proportion of organized structures are observed.

14. 14 13. This self assembly process is captured with time. Gel-like film was formed first and then, bolaform molecules creates a higher order structure on cellulose surface. Finding this beautiful structure was exiting, but soon after that, we ended up with two questions. First, is this tree structure really bolaform? Second, why this unique structure was found in the presence of cellulose? To answer the first one, we performed FT-IR experiments.13. This self assembly process is captured with time. Gel-like film was formed first and then, bolaform molecules creates a higher order structure on cellulose surface. Finding this beautiful structure was exiting, but soon after that, we ended up with two questions. First, is this tree structure really bolaform? Second, why this unique structure was found in the presence of cellulose? To answer the first one, we performed FT-IR experiments.

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16. 16 FT-IR Imaging Characterization (1)

17. 17 FT-IR Imaging Characterization (2)

18. 18 14. The first image was taken from FT-IR imaging system showing self assembly on cellulose film. Red box zone was scanned and FTIR image map is shown on right side. After that, a regression model was built to predict bolaform concentration using various ratios of cellulose and bolaforms. Then whole spectra were converted to bolaform concentration image. Multivariate analysis was used during this step. Based on this result, higher concentration of bolaform matches the visual image of film, indicating that tree-structure is truely bolaforms.14. The first image was taken from FT-IR imaging system showing self assembly on cellulose film. Red box zone was scanned and FTIR image map is shown on right side. After that, a regression model was built to predict bolaform concentration using various ratios of cellulose and bolaforms. Then whole spectra were converted to bolaform concentration image. Multivariate analysis was used during this step. Based on this result, higher concentration of bolaform matches the visual image of film, indicating that tree-structure is truely bolaforms.

19. 19 MeOH Washing MeOH washing All bolaform crystals were immediately dissolved in MeOH 15. To check the effect of different template, glucose was used instead of cellulose. However, glucose was not able to form a film, so no highly ordered crystallization was found. Interesting observation is MeOH washing. When a drop of MeOH is placed on top of bolaform crystals, all crystals were immediately disappeared. 15. To check the effect of different template, glucose was used instead of cellulose. However, glucose was not able to form a film, so no highly ordered crystallization was found. Interesting observation is MeOH washing. When a drop of MeOH is placed on top of bolaform crystals, all crystals were immediately disappeared.

20. 20 Cellulose Film in Absence of Bolaforms 11. First we tried without cellulose in solution. In the absence of cellulose, self assembly of the bolaforms led to isolated plate- and needle-like structures as shown in figures.11. First we tried without cellulose in solution. In the absence of cellulose, self assembly of the bolaforms led to isolated plate- and needle-like structures as shown in figures.

21. 21 Cellulose Film in Presence of Bolaforms

22. 22 Cellulose as a Template for Assembly 16. The question is that why we observe a much higher order of structure in the presence of cellulose. The use of cellulose for patterning has been reported by Kondo�s group a few years ago. They have examined the use of patterned cellulose, called nematic ordered cellulose, as a template for laying down of bacterial cellulose. In their work, they find that the NOC serves as a pattern for the microbes to follow. Along with Kondo�s finding, our hypothesis at this moment is that self assembled bolaform crystals can follow the cellulose surface structure like a molecular track. These are quite recent results, so I don�t want to move too far into speculation. However, we now hope to understand what is going on at the molecular level between the bolaforms and cellulose. If we understand the mechanism, we might be able to design and control the structure with cellulose. 16. The question is that why we observe a much higher order of structure in the presence of cellulose. The use of cellulose for patterning has been reported by Kondo�s group a few years ago. They have examined the use of patterned cellulose, called nematic ordered cellulose, as a template for laying down of bacterial cellulose. In their work, they find that the NOC serves as a pattern for the microbes to follow. Along with Kondo�s finding, our hypothesis at this moment is that self assembled bolaform crystals can follow the cellulose surface structure like a molecular track. These are quite recent results, so I don�t want to move too far into speculation. However, we now hope to understand what is going on at the molecular level between the bolaforms and cellulose. If we understand the mechanism, we might be able to design and control the structure with cellulose.

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24. 24 Control of Bolaform Crystallization 11. First we tried without cellulose in solution. In the absence of cellulose, self assembly of the bolaforms led to isolated plate- and needle-like structures as shown in figures.11. First we tried without cellulose in solution. In the absence of cellulose, self assembly of the bolaforms led to isolated plate- and needle-like structures as shown in figures.

25. 25 MeOH Washing 15. To check the effect of different template, glucose was used instead of cellulose. However, glucose was not able to form a film, so no highly ordered crystallization was found. Interesting observation is MeOH washing. When a drop of MeOH is placed on top of bolaform crystals, all crystals were immediately disappeared. 15. To check the effect of different template, glucose was used instead of cellulose. However, glucose was not able to form a film, so no highly ordered crystallization was found. Interesting observation is MeOH washing. When a drop of MeOH is placed on top of bolaform crystals, all crystals were immediately disappeared.

26. 26 Bolaform Re-crystallization 15. To check the effect of different template, glucose was used instead of cellulose. However, glucose was not able to form a film, so no highly ordered crystallization was found. Interesting observation is MeOH washing. When a drop of MeOH is placed on top of bolaform crystals, all crystals were immediately disappeared. 15. To check the effect of different template, glucose was used instead of cellulose. However, glucose was not able to form a film, so no highly ordered crystallization was found. Interesting observation is MeOH washing. When a drop of MeOH is placed on top of bolaform crystals, all crystals were immediately disappeared.

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28. 28 Materials Cellulose: Microcrystalline cellulose (Avicel) Pretreatments MeOH exchange �3 DMAc exchange �3 Solvent 8% LiCl in DMAc (N,N-dimethylacetamide) Solution Cellulose + Bolaforms + LiCl/DMAc Methods Slow casting in Petri-dish Washing with H2O Drying at 60�C (restrained drying) AFM, SEM, NMR, Sorption test Materials and Methods 18. The same materials were used and then the solutions were poured and slowly cast in Petri-dishes. After washing the films in H2O, films were dried at 60C.18. The same materials were used and then the solutions were poured and slowly cast in Petri-dishes. After washing the films in H2O, films were dried at 60C.

29. 29 Cellulose-bolaform Film Preparation (1) 19. It is noted that bolaforms can be precipitated at high concentration. This picture shows the precipitation of bolaforms at 20%. It was found that the critical concentration was just above 5%, so it is considered that homogeneous films can be made, when the bolaforms were added between 0 to 5% in films.19. It is noted that bolaforms can be precipitated at high concentration. This picture shows the precipitation of bolaforms at 20%. It was found that the critical concentration was just above 5%, so it is considered that homogeneous films can be made, when the bolaforms were added between 0 to 5% in films.

30. 30 Cellulose-bolaform Film Preparation (2) 20. Bolaform-incorporated cellulose films were found smooth and transparent.20. Bolaform-incorporated cellulose films were found smooth and transparent.

31. 31 FT-IR: Multivariate Analysis

32. 32 Film Surface: (1) AFM Images 21. Upon close examination of the surface of films by AFM, we get suggestions of the higher level of organization in the presence of bolaform. The AFM on the left are scans of cellulose film without bolaform. When bolaform is added 5%, it looks to have some stratification, running in a pattern from top L to bottom R with a lower roughness value.21. Upon close examination of the surface of films by AFM, we get suggestions of the higher level of organization in the presence of bolaform. The AFM on the left are scans of cellulose film without bolaform. When bolaform is added 5%, it looks to have some stratification, running in a pattern from top L to bottom R with a lower roughness value.

33. 33 Film Surface: (2) SEM Images 22. A similar increase in smoothness was observed in the SEM as if bolaform might be filling in some of the irregular surface. 22. A similar increase in smoothness was observed in the SEM as if bolaform might be filling in some of the irregular surface.

34. 34 Wide Angle X-ray Diffraction

35. 35 Diffraction Patterns for Powders/ Films

36. 36 1D Integrated WAXD Profiles

37. 37 Structural Information for Cellulose Films Crystallinity index, CI Crystal size, L

38. 38 Structural Information: Crystallinity, Crystal Size Crystallinity � a little or no increase Crystal size � same Orientation � Increase! R2 and F show that curve fitting was very good ? Cellulose chains are oriented, but stretching up to 30% is not enough to change crystal structure in cellulose filmsCrystallinity � a little or no increase Crystal size � same Orientation � Increase! R2 and F show that curve fitting was very good ? Cellulose chains are oriented, but stretching up to 30% is not enough to change crystal structure in cellulose films

39. 39 Low Resolution NMR Experimental Parameters CPMG procedures tau 0.05 ms 256 echoes 750 scans 5 second recycle delay 23. Relaxation time of water in films was measured using low resolution NMR. The idea of this experiment is that the film has bound water, which is associated with hydroxyl groups in either cellulose or bolaforms. The mobility of bound water is characterized as a relaxation time. Higher relaxation time indicates that the water molecules have higher mobility in films. 23. Relaxation time of water in films was measured using low resolution NMR. The idea of this experiment is that the film has bound water, which is associated with hydroxyl groups in either cellulose or bolaforms. The mobility of bound water is characterized as a relaxation time. Higher relaxation time indicates that the water molecules have higher mobility in films.

40. 40 NMR Relaxation Time 24. Based on the results here, bolaform-incorporated cellulose films have higher relaxation time than cellulose films. This might be attributed that bolaform molecules disrupt the interaction between cellulose hydrophilic sites and water molecules, resulting that water molecules bind less tightly in bolaform-incorporated cellulose films. 24. Based on the results here, bolaform-incorporated cellulose films have higher relaxation time than cellulose films. This might be attributed that bolaform molecules disrupt the interaction between cellulose hydrophilic sites and water molecules, resulting that water molecules bind less tightly in bolaform-incorporated cellulose films.

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42. 42 Summary Bolaform amphiphiles were successfully synthesized and the interactions with cellulose were studies. Highly-ordered self assembly of bolaform amphiphiles were observed on cellulose template, while individual self-assembled structures were found in the absence of cellulose. Bolaform-incorporated cellulose film showed higher relaxation time, which might be attributed to the interaction between cellulose hydroxyl groups and bolaform molecules. 28. Summary28. Summary

43. 43 Thomas Elder USDA-Forest Service Southern Research Station Pineville, LA Nicole Labb� Forest Products Center The University of Tennessee John R. Dunlap Program in Microscopy The University of Tennessee