One of the main research goals in the Savin group is to understand and control the assembly and responsiveness of polypeptide-based block copolymers in solution. In general, the behavior of polyelectrolytes in solution is not well understood, in part due to their complexity. Synthetic polypeptides in solution can be used as a model for synthetic polyelectrolytes due to the ability to control the charge-charge interactions between ionizable units. In addition, by using polypeptides we can incorporate pH and T responsiveness into a material based in part on the secondary structure changes that occur within the peptide chain. We can also dictate the geometry of specific interactions to induce folding and assembly into responsive hydrogels, crosslinked core-shell structures and multiply-responsive or 'schizophrenic' materials. The use of polypeptides in these materials introduces an immense toolbox that allows for control over the specific structure-property relationships that govern the resultant material.

Collaborators:
Prof. Brent Sumerlin (Southern Methodist U), Profs. Charles Hoyle, Charles McCormick and Robson Storey (USM), Prof. Barney Grubbs (Stony Brook U), Prof. Jeffrey Pyun (U Arizona)

Recent Publications:
A. Smith, X. Xu, D. Savin and C. McCormick.  “Reversible Gold Locked Synthetic Vesicles Derived from Stimuli-Responsive Diblock Copolymers.” Polym. Chem. 2010. 1 (5), 628-630.

A. Smith, X. Xu, S. Kirkland-York, D. Savin, C. McCormick. "Schizophrenic” Self-Assembly of Block Copolymers Synthesized via Aqueous RAFT Polymerization: From Micelles to Vesicles."Macromolecules 2010. 43 (3), 1210.

A. Magenau, N. Martinez-Castro, D. Savin and R. Storey.  “Site Transformation of Polyisobutylene Chain Ends to RAFT Polymerization: Synthesis of Poly(isobutylene-b-N-isopropylacrylamide).” Macromolecules 2009.  42 (21), 8044.

K. Gebhardt, S. Ahn, G. Venkatachalam and D. Savin. "Temperature and pH Response of Poly(butadiene)-Poly(L-Lysine) Block Copolymer Assemblies in Aqueous Media." J. Colloid Interface Sci. 2008, 317. 70.

K. Gebhardt, S. Ahn, G. Venkatachalam and D. Savin. "Rod-Sphere Transition in Poly(butadiene)-Poly(L-Lysine) Block Copolymer Assemblies." Langmuir, 2007, 23(5), 2851.

Recent Presentations:
D. Savin.  “Responsive Micelles, Vesicles and Organogels from Polypeptide-based Block Copolymers.” ACS National Meeting, San Francisco, CA, March 2010. (Invited)

D. Savin.  “Interfacial Curvature Effects in Polypeptide-based Block Copolymer Assemblies.” ACS National Meeting, San Francisco, CA, March 2010. (Invited)

D. Savin, S. Naik, J. Ray and A. Montgomery.  “Responsive micelles, vesicles and organogels from poly(lysine)-containing block copolymers.” APS National Meeting, Portland, OR. March 2010.

J. Ray, S. Naik, D. Savin.  “Stimuli-responsive polypeptide-based triblock copolymers.” APS National Meeting, Portland, OR. March 2010. (Poster)

A. Montgomery, S. Naik, J. Ray, D. Savin. “Peptide and micelle morphologies in ionic liquid.”  APS National Meeting, Portland, OR. March 2010. (Poster)

S. Naik, J. Stempien and D. Savin. "Responsive Micelles and Organogels from Polypeptide-based Block Copolymers" ACS PMSE Division, 237th National Meeting. Salt Lake City, UT. March 2009.

Block copolymers containing based on poly(lysine) form gels in organic solvents as a result of peptide chains assembling into long fibrils.  Some of these systems form organogels with moduli as high as 350 Pa for 4 wt% solutions in THF.  We are generally interested in determining the factors that dictate property-structure relationships for these materials.  These include the role of poly(lysine) molecular weight and concentration on the mechanical properties and range of linear viscoelastic response.  In addition, we attempt to introduce specific interactions to alter the interfacial curvature to control fibril length.

Collaborators:
Profs. Robert Lochhead and Kenneth Mauritz (USM)

Recent Publication:
S. Naik and D. Savin. “Poly(Z-Lysine)-based Organogels: Effect of Interfacial Frustration on Gel Strength.”Macromolecules, 2009, 42 (18), 7114–7121.

Recent Presentations:
D. Savin.  “Responsive Micelles, Vesicles and Organogels from Polypeptide-based Block Copolymers.” ACS National Meeting, San Francisco, CA, March 2010. (Invited)

D. Savin.  “Interfacial Curvature Effects in Polypeptide-based Block Copolymer Assemblies.” ACS National Meeting, San Francisco, CA, March 2010. (Invited)

S. Naik, J. Stempien and D. Savin. "Responsive Micelles and Organogels from Polypeptide-based Block Copolymers" ACS PMSE Division, 237th National Meeting. Salt Lake City, UT. March 2009.

S. Naik and D. Savin. "Poly(Lysine(Z))-based Block Copolymer Organogels" APS National meeting. Pittsburgh, PA. March 2009.

D. Savin, D. Bercovici, S. Naik. "Organogels from Polypeptide-based Block Copolymers" APS National Meeting. New Orleans, LA. March 2008.

The objective of this activity is to study the dispersion of polymer-modified silica nanoparticles in cured vinyl ester and epoxy composites. This dispersion is highly dependent on the polymer/matrix interactions, and the physical properties (i.e.: fracture toughness) of the composites will be improved with homogeneous dispersion of nanoparticle filler.  We focus on polystyrene-functionalized and poly(ethylene oxide)-functionalized silica nanoparticles for potential applications as self-healing composites or as antifouling coatings.

The USM SPHPM was recently awarded an NSF REU Site for Sustainable Aerospace and Marine Polymer Composites (2010-2013 Savin, PI)!

Collaborators:
Prof. Phil Costanzo (Cal Poly SLO), Profs. Joe Griffitt and Sarah Morgan (USM), Profs. Frederic Sansoz, Dryver Huston, Yves Dubief (U Vermont

Recent Presentation:
D. Savin, A. Richardson, O. McNair, G. Strange, P. Costanzo. “Nanoparticle Dispersion and Energy Damping in Polymer Composites.”  ACS National Meeting, Boston, MA, August 2010. (Invited)

G. Strange, A. Richardson, D. Savin, P. Costanzo. "Controlling nanoparticle dispersion via Diels-Alder chemistry" ACS National Meeting, San Francisco, CA, March 2010. (Poster)

A. Richardson, G. Strange, P. Costanzo, D. Savin. “Enhancement of nanoparticle dispersion in crosslinked network composites through surface modification.”  APS National Meeting, Portland, OR. March 2010.

O. McNair, A. Senyurt, H. Wei, T. Gould, S. Piland, C. Hoyle, D. Savin. Thiol-Ene/Methacrylate Systems for Mechanical Damping.” APS National Meeting, Portland, OR. March 2010. (Poster)

C. Comer, O. McNair, C. Hoyle, D. Savin.  “Kinetics and physical properties of photolatent base catalyzed thiol-epoxy resins.” APS National Meeting, Portland, OR. March 2010. (Poster)

D. Savin, A. Richardson, O. McNair, G. Strange, P. Costanzo. “Improved Nanoparticle Dispersion in Epoxy Composites”  ACS POLY: Composite Matrix Science Workshop, New Orleans, LA, February 2010.

A. Richardson, G. Strange, P. Costanzo and D. Savin. "Effect of Polymer Tethering on Dispersions of Silica Nanoparticles in Crosslinked Epoxy Composites." ACS PMSE Division, 238th National Meeting. Washington, DC. August 2009. (Poster)

(1) Block copolymers in ion transport:

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Collaborators: Profs. Kenneth Mauritz, Derek Patton and Robson Storey (USM)

(2) Functional materials from biomass

The goal of this project is to study polymers made from biomass. First, we are interested in utilizing the degradability of hydrophobic poly(lactide) (PLA) to develop a formulation to coat hydrophobic biopesticides (entomopathogenic fungal spores) for use in a water spray delivery system. In the end, these materials will lead to greater efficiency of the pesticides and ultimately a reduction in pesticide use.delivery applications. In particular, we attempt to use PLA-based amphiphilic block copolymers as compatibilizers for the hydrophobic biopesticides. Initial experiments have focused on the adsorption behavior of such materials onto colloidal PS. Second, we attempt to use PLA derived from the fermentation of whey protein for weed mulch films. Research from this project was cited by Rep. Welch (D-VT) in a speech to Congress.

Collaborator: Prof. Mingro Guo (UVM)

Recent Publication:
K. Murphy, J. Eisenhauer and D. Savin. "Synthesis, Self-Assembly and Adsorption of PEO-PLA Block Copolymers onto Colloidal Polystyrene." J. Polym. Sci. Part B: Polym. Phys., 2008, 46 (3), 244.

Recent Presentations:
J. Eisenhauer, K. Murphy, Y. Gao, M. Guo and D. Savin. "Synthesis, self-assembly and adsorption of biomass-derived block copolymers." ACS NERM, July 2008.

Y. Gao, J. Mendes, F. Zhao, A. Richardson, D. Savin, M. Guo. "Poly(lactic acid) Production from Whey Permeate." ADSA Annual Meeting, San Antonio, TX, July 2007.

(1) Liquid crystalline behavior in polypeptide-based block copolymers

Polypeptide-based rod-coil block copolymers are lyotropic liquid crystals. In the first exploratory project, we are interested in studying the phase behavior of rod-coil block copolymers in the ‘weak segregation’ limit. We use a poly(proline) type II helix motif where the peptide chain has tethered grafts that are thermodynamically compatible with the coil block. Such materials have potential utility as medical stents and as self-healing plastics. The liquid crystalline assembly will lead to improved optical and physical properties, and the thermodynamic compatibility between blocks will facilitate processing. In a related project, we attempt to assemble multi-compartment liquid crystalline materials. Within the liquid crystal grains, we incorporate phase separated microdomains that orient normal to the grain direction.

Collaborators: Prof. Thomas Epps III (U Delaware), Prof. Randy Headrick (U Vermont)

Recent Presentation:
A. Richardson, D. Savin. "Self-Assembly of Polypeptide-based Rod-Coil Block Copolymers." ACS POLY Division, 234th National Meeting. Boston, MA. August 2007. [Invited]

(2) Polypeptide-Based Block Copolymer Micelles for Remediation

Use of histidine residues in polypeptide-based micelles introduces heavy-metal binding sites into the corona chains of the micelles. Using solid phase peptide synthesis, we can control the specific distribution and orientation of histidine units along the chain.

Collaborator: Prof. Martin Case (U Vermont)

Recent Presentation:
A. Richardson, J. Wright, S. Banerjee, M. Case, D. Savin. "Transition Metal Binding in Designed Peptide Block Copolymer Micelles." ACS PMSE Division, 234th National Meeting. Boston, MA. August 2007.

(3) Block copolymer vesicles as biomimetic membranes

Naturally occurring transmembrane proteins can be incorporated into block copolymer vesicles with local deformation of the polymer membrane near the site of the protein inclusion. Our initial target is to understand the behavior of the epidermal growth factor receptor (EGFR) protein. The EGFR contains a single transmembrane segment, is overexpressed in a number of different cancer cells, and is thus thought to promote angiogenesis in tumors. It functions via dimerization within the membrane upon activation. Our central hypothesis is that the physics that governs this dimerization process is related to the physics that governs the lateral diffusion of a block copolymer along the interface of a lamellar phase-separated system. The ability to design biomimetic membranes with other proteins such as ion channels will have numerous applications in sensing and transmembrane transport applications.