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

Crystallization Studies of PE-PEG Graft Copolymers P. R. Mark, G. Hovey, and N. S. Murthy Physics Department, University of Vermont K. Breitenkamp, M. Kade and T. Emrick Department of Polymer Science and Engineering, University of Massachusetts, Amherst

Polymers in Agriculture 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

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

The full line is initial heat. This is followed by cooling shown in dotted lines. The last reheated scan is shown in dashed line T m vs. Grafted PEG Length 25 repeats50 repeats 100 repeats

/n Tm Nearly quantitative agreement between T m for grafted PEG domains upon initial heating with PEG homopolymers T m 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 Dependence of T m on PEG chain-length

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 -1 and 1.5 nm -1 indicate the various orders of the 15 nm lamellar spacing in PEG domain

Ambient X-ray Diffraction Scans x10^ Intensity (Counts) #1 = 25 repeats #2 = 50 repeats #3 = 100 repeats 2  (Degrees) PEO PE PEO PEG

x10^  (Degrees) Intensity (Counts) 25°C 80°C 135°C 40°C 25°C (a) Variable Temperature X-ray Diffraction Scans: 50 Repeats of PEG * Domain sizes are retained upon heating and cooling

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

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

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

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

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

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

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

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

Block Copolymer Characterization MeO-PEO macroinitiator from Aldrich As MW increases, systematic decrease in V e Block copolymer pdi ~ 1.1 PEO 114 -PLA 70 PEO 114 -PLA 29 PEO 114 -PLA 209 TGA shows nearly quantitative agreement between theoretical and observed weight fractions

Dynamic Light Scattering The scattered intensity at time (t) is correlated with the scattered intensity at time (t + τ). * Plot of  vs. q 2 is linear with slope D m Concentration ~ 0.01 % (w/w)

Micelle Formation Systematic decrease in aggregate size with increasing hydrophilic fraction f PEO

Block Copolymer Adsorption 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

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

Adlayer Thickness vs w PEO PEO 114 -PCL 22 w PEO = 0.65 * * *

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 NSF EPS