Elastomeric composites with tether-containing, conducting polymers for nanoscale diffusion control
Inventors
Martin, Brett D. • Moore, Martin H. • Ratna, Banahalli R. • Justin, Gusphyl • Naciri, Jawad
Assignees
Publication Number
US-8931114-B2
Publication Date
2015-01-13
Expiration Date
2029-09-22
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Abstract
A redox-active conductive polymer includes a charged tether. An interpenetrating network including such a conducting polymer can be switched between two states of diffusivity (porosity) by application of a voltage. Such a material can be useful in breathable protective clothing, controlled release, intelligent sensing/filtration, novel separation processes, nanomanufacturing, and other areas.
Core Innovation
The invention provides an interpenetrating polymer network (IPN) material comprising a conducting polymer with a charged tether that can be reversibly switched between two states of diffusivity (porosity) by application of a voltage. The conducting polymer, particularly tether-containing polythiophenes, can be switched between an open (oxidized) state permitting high ion diffusivity and breathability, and a closed (reduced) state restricting ion diffusivity and passage of small molecules such as chemical warfare agent simulants. This reversible switching is actuated by low voltage application (approximately ±1 volt) and can be cycled multiple times without degradation. The charged tether facilitates an intramolecular ion-pairing mechanism that controls pathways for diffusion at the nanoscale.
The problem addressed is the need for selective control of nanoscale diffusion, especially for applications such as breathable protective clothing that balance comfort and protection. Prior art protective equipment either is breathable but insufficiently protective or protective but cumbersome and non-breathable, requiring donning only upon threat which creates exposure risks. The invention solves this by enabling a single material that can be worn comfortably in an open state and rapidly switched to a protective impermeable state upon detection or presence of harmful agents, thus combining breathability with protective capability.
The disclosed material is an interpenetrating polymer network comprising the conducting polymer with a charged tether, a crosslinker to enhance mechanical strength, a support matrix such as polyurethane or nylon for breathability and toughness, milled conducting carbon fibers to improve electronic conductivity, and a room-temperature ionic liquid (RTIL) to provide a solid electrolyte effect enabling switching in a dry state without liquid electrolyte. The IPN shows a nanoscale gating effect where the charged tethers act as nanogates that are open in the oxidized state and closed in the reduced state, controlling molecular diffusion and ion transport.
Claims Coverage
The patent includes several independent claims related to materials comprising interpenetrating polymer networks and a method for modulating diffusivity, each featuring inventive structural and functional components.
Material comprising interpenetrating polymer network with a charged tether conducting polymer
A material that includes an interpenetrating polymer network (IPN) comprising a conducting polymer having the formula where X is a sulfonate salt, phosphonate salt, carboxylate salt, cyclic moiety with negatively-charged nitrogen, or boronate salt, and n is an integer from 2 to 10. This material can switch between an open state and a closed state upon receiving a voltage.
Material with a support matrix and room temperature ionic liquid
An IPN material including the above conducting polymer along with a support matrix (such as polyurethane, nylon, wool, polyester, cotton, or combinations thereof) and a room temperature ionic liquid to enable dry-state switching and maintain mechanical integrity.
Method of modulating diffusivity by redox switching
A method of modulating the diffusivity of a material comprising reducing the material to decrease diffusivity and oxidizing the material to increase diffusivity, wherein the reducing and oxidizing steps are preferably accomplished by application of an electric voltage, and the material includes the conducting polymer with a charged tether as described.
The independent claims cover materials comprising interpenetrating polymer networks having conducting polymers with charged tethers, optional support matrices and ionic liquids enabling dry switching, and methods of modulating diffusivity via reversible redox switching driven by applied voltages. These claims establish the inventive use of tether-containing conducting polymers in IPNs for voltage-controlled nanoscale diffusion control.
Stated Advantages
The described material allows reversible, voltage-actuated switching between states of high and low diffusivity at the nanoscale, enabling precise control of molecular transport.
The IPN demonstrates high breathability in the open state, with water vapor transport rates comparable to expanded Teflon, while significantly reducing permeation of harmful agents in the closed state.
The material can operate in a dry state without liquid electrolyte due to the incorporation of room-temperature ionic liquids, making it suitable for practical wearable applications.
Low voltage (approximately ±1 volt) actuation minimizes power requirements and facilitates integration into protective clothing systems.
The presence of charged tethers facilitates effective and reversible switching, providing a mechanism for nanoscale gating not achievable in similar materials lacking such tethers.
Documented Applications
Breathable protective clothing that can be switched between comfortable permeable and impermeable protective states.
Controlled release systems where diffusion rates can be modulated on command.
Intelligent sensing and filtration materials with voltage-controlled permeability.
Novel separation processes utilizing nanoscale gating of molecular transport.
Nanomanufacturing applications requiring precise control over diffusion and porosity at the nanoscale.
Chemical protective equipment (CPE) for protection against chemical, biological, radiological, and nuclear threats including airborne chemical warfare agents.
Filters for gases and liquids incorporating the switchable interpenetrating polymer network material.
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