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

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

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

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

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

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

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

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

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

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”

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

Wettability Results

Untreated PLA

2 minutes

15 minutes

Optimal Times

Wettability Results

Contact Angles 15 minutes 30 minutes 45 minutes

Wettability Results

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

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

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

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