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Selective Surface Modification of Biopolymers

Selective Surface Modification of Biopolymers

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Selective Surface Modification of Biopolymers

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  1. Selective Surface Modification of Biopolymers REU Progress Presentation Presented by Alicia Certain Advisor Jeffrey Youngblood August 4, 2004

  2. Polymers vs. Biopolymers • Familiar examples: garbage bags, milk jugs, car bumpers, motor oil, carpet fibers, plumbing pipes • Biopolymers: The “green” materials • Made from renewable resources • Biodegradable • Have different properties than traditional polymers

  3. Wettability and Applications • An increase in wettability would be desirable for applications such as textiles, cleaning wipes, household fabrics • A decrease in wettability would be desired for packaging

  4. The First Biopolymer • Family of polyhydroxyalkanoates (PHAs) • Worked with poly(lactic acid) (PLA) • Trade name “Natureworks” • Produced from corn

  5. The Next Polymer • From the family of 1,3, propanediol • Specific polymer is poly(propylene-terephthalate) (PPT) • Trade name “Sorona” • Also comes from corn

  6. Modification of Biopolymers • Samples were spin coated onto glass slides • Goal was to modify the surface of the polymers in order to change wettability • Worked with three chemical modifications • APTES • Hydrolysis • Aminolysis

  7. APTES modification • 3-aminopropyltriethoxysilane • Previously used to modify PET • Increased wettability • What will it do to biopolymers?

  8. Hydrolysis • Immersion in aqueous alkaline base • Breaks up chain, adding hydroxyl group to one end, hydrogen to the other • Should increase wettability • Simplest procedure

  9. Aminolysis • Similar to hydrolysis, using an amine instead • Tried n-butylamine, which is known to increase wettability in PET – very slow! • Used n-lithiodiamine to decrease reaction times

  10. Contact Angle Analysis • Liquid drop on solid surface modifies its shape based on the interfacial tensions • Creates a material property of the system called the “contact angle”

  11. Characterization • Contact angle measurements primary characterization • Tests done through the goniometer • AFM imaging used to augment

  12. Wettability Results

  13. Untreated PLA

  14. 2 minutes

  15. 15 minutes

  16. Optimal Times

  17. Wettability Results

  18. Contact Angles 30 minutes 15 minutes 45 minutes

  19. Wettability Results

  20. Wettability Results

  21. PPT and APTES • Most successful in decreasing wettability • 6 hours led to approx. 55 degree advancing, 0 receding • 24 hours led to approx. 45 degree advancing, 0 receding • 72 hours created an increase back to approx. 60 advancing, 0 receding

  22. Flourinated APTES • 24 hour APTES reaction on PLA with concentration cut in half • Subsequent reaction with tridecaflouro-1,1,2,2-tetrahydrooctyltri-chlorosilane • APTES on PLA only increases wettability slightly, but surface is functionalized and flourination successfully decreases wettability

  23. Possible Future Directions • APTES optimization • Pinpointing a more definite optimum PLA hydrolysis time • Vapor phase reactions • Subsequent reactions on functionalized surfaces to increase hydrophobicity rather than decrease

  24. Thanks! Prof. Youngblood and Prof. Kvam John, Ben, and Phil Allen and Kendra The REU Group