Soft materials are matters that can easily deform from their original shapes and structures under thermal or mechanical stresses, and they range across various groups of materials including liquids, foams, gels, colloids, polymers, and biological substances. Although soft materials already have numerous applications with each of their unique characteristics, integrating materials to achieve complementary functionalities is still a growing need for designing advanced applications of complex requirements. This dissertation explores a unique approach of utilizing intermolecular interactions to accomplish not only the multifunctionality from combined materials but also their tailored properties designed for specific tasks. In this work, multifunctional soft materials are explored in two particular directions, ionic liquids (ILs)-based mixtures and interpenetrating polymer network (IPN).

First, ILs-based mixtures were studied to develop liquid electrolytes for molecular electronic transducers (MET) in planetary exploration. For space missions, it is challenging to operate any liquid electrolytes in an extremely low-temperature environment. By tuning intermolecular interactions, the results demonstrated a facile method that has successfully overcome the thermal and transport barriers of ILs-based mixtures at extremely low temperatures. Incorporation of both aqueous and organic solvents in ILs-based electrolyte systems with varying types of intermolecular interactions are investigated, respectively, to yield optimized material properties supporting not only MET sensors but also other electrochemical devices with iodide/triiodide redox couple targeting low temperatures.

Second, an environmentally responsive hydrogel was synthesized via interpenetrating two crosslinked polymer networks. The intermolecular interactions facilitated by such an IPN structure enables not only an upper critical solution temperature (UCST) transition but also a mechanical enhancement of the hydrogel. The incorporation of functional units validates a positive swelling response to visible light and also further improves the mechanical properties. This studied IPN system can serve as a promising route in developing “smart” hydrogels utilizing visible light as a simple, inexpensive, and remotely controllable stimulus.

Over two directions across from ILs to polymeric networks, this work demonstrates an effective strategy of utilizing intermolecular interactions to not only develop multifunctional soft materials for advanced applications but also discover new properties beyond their original boundaries.

This thesis investigates an interpenetrating network of polyacrylamide and poly acrylic acid for use in a dynamic tactile display, which presents traditionally two-dimensional electronic screens as three-dimensional topographical models that can be experienced through touch. This kind of display would allow for greater access to traditionally visual information for the visually impaired. This hydrogel demonstrates Upper Critical Solution Temperature (UCST) near room temperature which facilitates a swelling transition, characterized by a sharp increase in swelling as this temperature is surpassed. Through the utilization of light responsive additives, light can trigger this shift, as the additives harness visible light, convert it into heat to raise the gel’s temperature, and increase the volume of the gel. Light-responsive additives explored include chlorophyllin, gold nanoparticles, and carbon black. Each of these additives required unique synthesis planning and strategies in order to optimize the performance of the gels. Synthesized gels were characterized using thermal swelling tests, light response tests and compression tests to determine the material strength. The best performing additive was chlorophyllin and allowed for a 20.8%±4.5% percent weight increase upon exposure to light for 10 minutes. In addition to investigating light-responsive additives, modifications were pursued to alter the overall UCST behavior, such as the addition of sodium chloride. By adding sodium chloride into the hydrogel, the gel was found to have a wider transition. Overall, light-responsive behavior was developed, and further work can be done in improving the response time and degree of swelling in order to make this material more viable for use in a dynamic tactile display.

The purpose of this project is to investigate the swelling ratio exhibited due to photothermal effects of double network polyacrylamide poly(acrylic acid) hydrogels synthesized with carbon black as a light-sensitive chromophore. Optimal carbon black dispersion was achieved in solutions through sonication, using V9A32 carbon black, where dynamic light scattering recorded particle diameters in the range of 195.0-375.8 nanometers for water/carbon black mixtures, 242.4-262.6 nanometers for monomer/carbon black mixtures without initiator, and 1109.3-1783.9 nanometers for monomer/carbon black mixtures including initiator. The double network polyacrylamide poly(acrylic acid) hydrogels with carbon black yielded weight increases of 0.126% and 6.043%, respectively, after 2 minutes and 10 minutes of being exposed to a light stimulus; compared to previous work which showed a double network polyacrylamide poly(acrylic acid) hydrogel with chlorophyllin yielded weight increases of 18.3% and 20.8%, respectively, after 2 minutes and 10 minutes of being exposed to a light stimulus, the carbon black resulted in a less robust response. Future work for application of the light-responsive hydrogels includes the development of a screen covering that will be made of the hydrogels. This covering is intended for use on LED screen displays, where a light change will result in a protrusion from the screen. The purpose behind this application is that technology users who are visually impaired can still determine what their LED device is trying to communicate with them.