An official website of the United States government
Polymer infiltrated nanoporous gold is prepared by infiltrating polymer melts into a bicontinuous, nanoporous gold (NPG) scaffold. Polystyrene (PS) films with molecular weights (Mw) from 424 to 1133 kDa are infiltrated into a NPG scaffold (∼120 nm), with a pore radius (Rp) and pore volume fraction of 37.5 nm and 50%, respectively. The confinement ratios (Γ=RgRp) range from 0.47 to 0.77, suggesting that the polymers inside the pores are moderately confined. The time for PS to achieve 80% infiltration (τ80%) is determined using in situ spectroscopic ellipsometry at 150 °C. The kinetics of infiltration scales weaker with Mw, τ80%∝Mw1.30±0.20, than expected from bulk viscosity Mw3.4. Furthermore, the effective viscosity of the PS melt inside NPG, inferred from the Lucas–Washburn model, is reduced by more than one order of magnitude compared to the bulk. Molecular dynamics simulation results are in good agreement with experiments predicting scaling as Mw1.4. The reduced dependence of Mw and the enhanced kinetics of infiltration are attributed to a reduction in chain entanglement density during infiltration and a reduction in polymer–wall friction with increasing polymer molecular weight. Compared to the traditional approach involving adding discrete particles into the polymer matrix, these studies show that nanocomposites with higher loading can be readily prepared, and that kinetics of infiltration are faster due to polymer confinement inside pores. These films have potential as actuators when filled with stimuli-responsive polymers as well as polymer electrolyte and fuel cell membranes.
more »
« less
This content will become publicly available on December 18, 2025
POLYMER INFILTRATED NANOPOROUS GOLD: KINETICS AND OPTICAL PROPERTIES OF NOVEL POLYMER NANOCOMPOSITES
One of the biggest challenges in the field of polymer nanocomposites (PNCs) is to disperse high nanofiller loadings into the polymeric matrix. The high loading and uniform dispersion are limited by the unfavored polymer/nanofiller thermodynamics and the tendency for nanofiller to aggregate. In this thesis, these are circumvented by using nanoporous gold (NPG) as a scaffold for polymers to fill. The ultra-high loading (>50 vol%) is achieved by infiltrating polymer melts into NPG to produce a polymer infiltrated nanoporous gold (PING) composite. This novel composite provides promises for the next generation advanced materials for coating, optical sensors, actuators, and batteries. This thesis contributes to the better understanding of polymer kinetics under moderate confinement by varying the interfacial energy between polymer and pore wall and investigating the temperature dependence of infiltration. Confinement enhances polymer kinetics while decreasing the infiltration time dependence on Mw due to the combined effect of loss in entanglement and adsorbed chain fraction. When polymer and the wall interfacial energy is stronger, a physiosorbed layer forms, resulting in slower kinetics compared to that for weaker interfacial energy. The temperature dependence of the polymer kinetics inside NPG follows the bulk WLF behavior at lower confinement degrees, while the kinetics deviate from the bulk WLF at higher confinement levels due to the decrease in thermal expansion coefficient. Those fundamental studies on polymer kinetics enable the optimization of preparing PING composites for the use of industrial scale applications and encourage additional studies such as ion conductivities of PING. The optical properties study established UV-Vis spectroscopy as a new approach to track polymer kinetics while simultaneously broadening the potential PING applications to optically responsive membranes. This thesis presents a pathway of fabricating PING composite while kinetics studies as well as the optical study enable scientists to better understand polymers behavior under confinement and advance the toolbox for creating interconnected polymer/filler systems at high filler concentrations.
more »
« less
- Award ID(s):
- 2407300
- PAR ID:
- 10598432
- Publisher / Repository:
- Scholarly Commons
- Date Published:
- Subject(s) / Keyword(s):
- Nanocomposites infiltration kinetics
- Format(s):
- Medium: X
- Institution:
- University of Pennsylvania
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Polymer infiltration is studied in a bicontinuous, nanoporous gold (NPG) scaffold. For poly(2-vinylpyridine) (P2VP) with molecular weights (M_w) from 51k to 940k Da, infiltration is investigated in a NPG with fixed pore radius (R_p= 34 nm) under moderate confinement (Γ = R_g/R_p ) 0.18 to 0.78. The time for 80% infiltration (τ_(80%)) scales as M_w^1.43, similar to PS, but weaker than bulk behavior. Infiltration of P2VP is slower than PS due to stronger P2VP-wall interactions resulting in a physisorbed P2VP layer. This interpretation is supported by the similar scaling of τ_(80%) for P2VP and PS, as well as Molecular Dynamics (MD) simulations. Simulations show that infiltration time scales as M_w^1.43and that infiltration slows as the polymer-wall attraction increases. As M_w increases, the effective viscosity transitions from greater than to less than the bulk viscosity due to pore narrowing and a reduction entanglement density. These studies provide new insight for polymer behavior under confinement and a new route for preparing nanocomposites at high filler loadings.more » « less
-
Incorporation of nanoparticles into polymer blend films can lead to a synergistic combination of properties and functionalities. Adding a large concentration of nanoparticles into a polymer blend matrix via conventional melting or solution blending techniques, however, is challenging due to the tendency of particles to aggregate. Herein, we report a straightforward approach to generate polymer blend/nanoparticle ternary composite films with extremely high loadings of nanoparticles based on monomer-driven infiltration of polymer and photopolymerization. The fabrication process consists of three steps: (1) preparing a bilayer with a nanoparticle (NP) layer atop a polymer layer, (2) annealing of the bilayer with a vapour mixture of a monomer and a photoinitiator, which undergoes capillary condensation and imparts mobility to the polymer layer and (3) exposing this film to UV light to induce photopolymerization of the monomer. The monomer used in this process is chemically different from the repeat unit of the polymer in the bilayer and is a good solvent for the polymer. The second step leads to the infiltration of the plasticized polymer, and the third step results in a blend of two polymers in the interstices of the nanoparticle layer. By varying the thickness ratio of the polymer and nanoparticle layers in the initial bilayers and changing the UV exposure duration, the volume fraction of the two polymers in the composite films can be adjusted. This versatile approach enables the design and engineering of a new class of nanocomposite films that contain a nanoscale-blend of two polymers in the interstices of a nanoparticle film, which could have combinations of unique mechanical and transport properties desirable for advanced applications such as membrane separations, conductive composite films and solar cells. Moreover, these polymer blend-filled nanoparticle films could serve as model systems to study the effect of confinement on the miscibility and morphology of polymer blends.more » « less
-
We explore the effect of confinement and polymer–nanoparticle interactions on the viscosity of unentangled polymers undergoing capillary rise infiltration (CaRI) in dense packings of nanoparticles. In CaRI, a polymer is thermally induced to wick into the dense packings of nanoparticles, leading to the formation of polymer-infiltrated nanoparticle films, a new class of thin film nanocomposites with extremely high concentrations of nanoparticles. To understand the effect of this extreme nanoconfinement, as well as polymer–nanoparticle interactions on the polymer viscosity in CaRI films, we use two polymers that are known to have very different interactions with SiO 2 nanoparticles. Using in situ spectroscopic ellipsometry, we monitor the polymer infiltration process, from which we infer the polymer viscosity based on the Lucas–Washburn model. Our results suggest that physical confinement increases the viscosity by approximately two orders of magnitude. Furthermore, confinement also increases the glass transition temperature of both polymers. Thus, under extreme nanoconfinement, the physical confinement has a more significant impact than the polymer–nanoparticle interactions on the viscosity of unentangled polymers, measured through infiltration dynamics, as well as the glass transition temperature. These findings will provide fundamental frameworks for designing processes to enable the fabrication of CaRI nanocomposite films with a wide range of nanoparticles and polymers.more » « less
-
Abstract Both experimental results and theoretical models suggest the decisive role of the filler–matrix interfaces on the dielectric, piezoelectric, pyroelectric, and electrocaloric properties of ferroelectric polymer nanocomposites. However, there remains a lack of direct structural evidence to support the so‐called interfacial effect in dielectric nanocomposites. Here, a chemical mapping of the interfacial coupling between the nanofiller and the polymer matrix in ferroelectric polymer nanocomposites by combining atomic force microscopy–infrared spectroscopy (AFM–IR) with first‐principles calculations and phase‐field simulations is provided. The addition of ceramic fillers into a ferroelectric polymer leads to augmentation of the local conformational disorder in the vicinity of the interface, resulting in the local stabilization of the all‐transconformation (i.e., the polar β phase). The formation of highly polar and inhomogeneous interfacial regions, which is further enhanced with a decrease of the filler size, has been identified experimentally and verified by phase‐field simulations and density functional theory (DFT) calculations. This work offers unprecedented structural insights into the configurational disorder‐induced interfacial effect and will enable rational design and molecular engineering of the filler–matrix interfaces of electroactive polymer nanocomposites to boost their collective properties.more » « less
