Crystallization and Adsorption Behavior in Bio Derived Polymers

1. Crystallization and Adsorption Behavior in Bio Derived Polymers D. Savin, S. Murthy, University of Vermont NEGCC – University of Maine 31 May 2006

2. Crystallization Studies of PE-PEG Graft Copolymers P. R. Mark, G. Hovey, and N. S. MurthyPhysics Department, University of VermontK. Breitenkamp, M. Kade and T. EmrickDepartment of Polymer Science and Engineering,University of Massachusetts, Amherst

3. Water management Retention and release of water Delivery of nutrients and pesticides Targeted delivery to prevent runoff Soil management Prevent soil erosion Green platform for plant growth Polymer capsule for germination, growth or maturity Polymers in Agriculture

4. To transform commodity conventional polymers in to green polymers by making them aqueous processible while maintaining the properties inherent in the backbone (PE or PET) Grafting PEG provides a means by which these polymers could have aqueous processibility To study the crystallization behavior in these unique copolymers as a way to control the strength and processbility Motivation

5. Tm vs. Grafted PEG Length 25 repeats 50 repeats 100 repeats The full line is initial heat . This is followed by cooling shown in dotted lines. The last reheated scan is shown in dashed line

6. Dependence of Tm on PEG chain-length 80 60 40 Tm 20 0 -20 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 1/n Nearly quantitative agreement between Tm for grafted PEG domains upon initial heating with PEG homopolymers Tm is the melting point and 1/n along is the reciprocal of the chain-length. Data compiled from the information sheet from Dow Inc. for Carbowax

7. Small-angle X-ray Scans of Homo- and Co-polymers * Blue – PEG homopolymer * PEG repeats = 25, 50 and 100 for red, orange and green respectively * The arrows between Q = 0.25 nm-1and 1.5 nm -1 indicate the various orders of the 15 nm lamellar spacing in PEG domain

8. PEO PEO PE PE 70 60 #1 = 25 repeats 50 40 Intensity (Counts) #2 = 50 repeats 30 #3 = 100 repeats 20 10 PEG x10^3 12 16 20 24 28 2(Degrees) Ambient X-ray Diffraction Scans

9. Variable Temperature X-ray Diffraction Scans: 50 Repeats of PEG (a) 20.0 25°C 15.0 80°C Intensity (Counts) 135°C 10.0 40°C 5.0 25°C x10^3 12 16 20 24 28 2(Degrees) * Domain sizes are retained upon heating and cooling

10. Changes in the cell-dimensions (a- and b- axes) of the PE domains Dark circles – heating, Light circles - cooling

11. Effect of hydration (a) (b) (a) 25 repeats of PEG (b) 50 repeats of PEG. * The data show that PEG domains dissolve in water * The process is reversible

12. PE and PEG chains crystallize into separate domains, especially when PEG chains are long (~ 50 repeat units), and behave like homopolymers PEG domains can be dissolved in water without significantly affecting the mechanical properties of the graft copolymer films. Conclusions Acknowledgment: We thank Dylan Butler (Physics) who assisted in some of the data collection and analysis, and Herman Minor (Honeywell) for the DSC data. This work was supported by an EPA grant to NEGCC

13. Adsorption of PLA and PCL-Based Block Copolymers K. Murphy, J. Mendes, D. SavinDepartment of Chemistry, University of Vermont

14. Goal: Delivery of Biopesticides Entomopathogenic fungi: • Used against bugs • Safe for humans and the environment • Leave no toxic residues • Typically 3-10 mm • Extremely hydrophobic

15. Water spray application: conventional (mm) vs. Ultra-low spray (10s of mm) drop size Delivery to leaf (hydrophobic) vs. soil Use amphiphilic compatibilizer Solution: PEO-PLA and PEO-PCL block copolymers Constraints for Delivery

16. Uses of PEO-PLA and PEO-PCL • PLA/PCL ‘stick’ to fungal spores • PEO provides water solubility • Block copolymers form micelles in solution • PLA from BIOMASS source • Biodegradable coating – Since PLA and PCL have different degradation rates, release rate can be controlled by varying relative amounts of block copolymers in formulation • Will ultimately result in a reduction • in the amount of pesticide used

17. Synthesis of Copolymers Procedure from Ahmed, F., Discher, D. J. Controlled Release. 96(1), 2004, 37-53

18. Block Copolymer Characterization PEO114-PLA209 PEO114-PLA70 PEO114-PLA29 • MeO-PEO macroinitiator • from Aldrich • As MW increases, • systematic decrease in Ve • Block copolymer pdi ~ 1.1 TGA shows nearly quantitative agreement between theoretical and observed weight fractions

19. Dynamic Light Scattering The scattered intensity at time (t) is correlated with the scattered intensity at time (t + τ). * Plot of G vs. q2 is linear with slope Dm Concentration ~ 0.01 % (w/w)

20. Micelle Formation fPEO Systematic decrease in aggregate size with increasing hydrophilic fraction

21. Since fungal spores are so large, DLS is ill-suited for their characterization PS colloids as a model hydrophobic interface Adsorption is a 2-step process: Micelle adsorption Restructuring Block Copolymer Adsorption

22. Colloid Characterization scale = 100 nm scale = 100 nm scale = 200 nm * Colloidal PS from Bangs Laboratories

23. Adlayer Thickness vs wPEO PEO114-PCL22 wPEO = 0.65 * * *

24. Conclusions * PEO-PLA and PEO-PCL block copolymers self-assemble into micelles with a radius that increases with polymer MW * The adlayer thickness was determined for the adsorption of block copolymer micelles onto model hydrophobic surfaces * For larger colloids, the adlayer thickness increases with increasing fraction of the hydrophilic block as expected * Smaller colloids may become encapsulated into micelles * The adlayer thickness appears to be stable over time Funding: EPA X-83239001 NSF EPS-0236976