NSF Center for Molecularly Optimized Networks

Project: Research project

Project Details


The work performed at Northwestern in the Kalow lab will include the synthesis and characterization of polymers and networks related to Thrusts 1 and 2 of the MONET proposal, and collection and analysis of literature data for GIGA related to Thrust 3. Specifically, one postdoc (Dr. Bassil El-Zaatari, 6 months) will perform nonlinear rheology on vitrimers with varying exchange kinetics. One graduate student (Alexis Martell, 12 months) will synthesize vitrimers with different polymer backbones and exchangeable cross-links to establish the effect of structure and exchange mechanism on mechanical properties and topological defects. One graduate student (TBN, 12 months) will synthesize and characterize networks with photoresponsive cross-links for patterned materials and triplet-triplet annihilation upconversion, and will synthesize and characterize covalent adaptable networks containing strands with low-force transitions developed by other MONET collaborators. The structures of these polymers and their constituent monomers will be characterized at Northwestern, including NMR, SEC, IR, MALDI, TGA, and DSC. Bulk characterization such as rheology will also be performed at Northwestern. All 3 researchers will contribute to literature searching, data extraction and analysis, and database entry for GIGA.

The work performed at Northwestern in the Olvera de la Cruz lab will include the application of all-atom simulations and development of coarse-grained models for calculating the responses of the synthesized materials to external fields. Charge groups will be used to design hydrogels that respond to mechanical deformations as well to electric fields. Specifically, one researcher (postdoc) will design amphiphilic polymers with charge groups and hydrophobic groups capable of assembling into gels. The goal is to produce assemblies that respond to external fields in a prescribed manner; that is, the assemblies should change into new morphologies with specified properties upon applying external fields. Different polymer backbones and non-covalent cross-links will be investigated to seek sufficiently robust yet deformable crosslinkers, for instance, by adding opposite charges to the polymers as well as hydrophobic groups. One graduate student (75%) will calculate the interactions between all chemical groups of interest by all-atom simulations, and then develop coarse-grained potentials to be used in continuum models. Specifically, all-atom explicit solvent simulations will be employed for quantifying the non-covalent interactions within the assemblies, which will be associated with the deformation of the hydrogens against external fields. The configurations and non-covalent energies obtained from all-atom simulations serve as reference for parameterizing the coarse-grained potentials. A series of coarse-grained simulations will be performed in which the parameters are optimized by iterative Boltzmann and relative entropy algorithms. The accuracy of the coarse-grained potentials is measured by the difference between the pair correlation function of the degrees of freedom, or their relative entropy, between the all-atom and coarse-grained representations. These developments will be used to determine macroscopic properties of the synthesized materials
Effective start/end date9/1/218/31/26


  • Duke University (333-2766//2116298)
  • National Science Foundation (333-2766//2116298)


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