CAREER: Enabling the Design of Versatile Hybrid Materials using Polymerization-Induced Nanostructural Transitions

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Part 1: NON-TECHNICAL SUMMARYAchieving simultaneous maximization of contrasting materials properties such as toughness and modulus is a daunting challenge for single-component materials. Biology is able to diverge from the inherent limitations of single-component materials by hierarchically organizing multiple components (biopolymers and minerals) with disparate physical properties. The static structure and hierarchical order of biomaterials is only part of the story; biology and living systems create complex materials through nonequilibrium processes. The goal of the CAREER proposal is to investigate nonequilibrium chemical functionalization and self-assembly methods to create multifunctional hybrid polymeric/inorganic materials. Two polymer/nanoparticle material systems will be explored: 1) flexible and electrically conductive co-continuous networks and 2) nanostructured materials exhibiting exceptional strain-stiffening mechanical properties. Establishing and integrating nonequilibrium chemical processes into materials design will potentially lead to new materials with applications in infrastructure, transportation, health care, and information processing. The research aims of the proposal will be integrated into teaching methods by: 1) developing polymer/materials science modules and labs for professors at nondoctorate-granting institutions within Pennsylvania to augment the undergraduate curriculum and 2) creating open-access video-standard operating procedures (VSOP) for all interested researchers to learn detailed methods for polymer synthesis, sample preparation, and characterization.Part 2: TECHNICAL SUMMARYThe hybrid polymer/inorganic materials field has been working under the premise that equilibrium concepts will lead to the complex materials seen in nature, yet biology utilizes nonequilibrium processes to create biomaterials. The overarching aim of the proposal is to identify design criteria using nonequilibrium chemical functionalization and self-assembly methods to create multifunctional hybrid polymeric/inorganic materials via polymerization-induced nanostructural transitions. In this research, in-situ polymer grafting and in-situ block polymer synthetic methods from polymers attached to nanoparticle surfaces will be used to create flexible and electrically conductive co-continuous networks and nanostructured materials exhibiting strain-stiffening properties. The synthetic approach used here will facilitate complex polymer architecture formation in situ and will generate hierarchically ordered materials in which polymer and nanoparticle domains are organized from the nanometer to the micrometer scale. Characterization methods using X-ray and neutron scattering, oscillatory shear dynamic mechanical spectroscopy, and dielectric relaxation spectroscopy during polymerization will reveal the self-assembly mechanism, and lead to fundamental insight for designing hierarchically-ordered materials. Merging in-situ polymerization and structural characterization to investigate structure-property relationships will establish foundational science in nonequilibrium processing that mimics natural systems and harnesses simultaneous property combinations, which are not currently possible in hybrid polymer/inorganic materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.