Probing Structure-property Relationships of Stimuli-responsive Polymers by Multi-dimensional Mass Spectrometry

Download or read book Probing Structure-property Relationships of Stimuli-responsive Polymers by Multi-dimensional Mass Spectrometry written by Savannah R. Snyder and published by . This book was released on 2020 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following dissertation focuses on utilizing mass spectrometry (MS) and its hyphenated techniques to understand the structure-property relationships of various stimuli-responsive polymers. By exploiting these materials' reactions to an outside stimulus, parallels can be made between the information from the mass spectral analyses and the materials' physical properties. Using techniques like tandem mass spectrometry (MS/MS), liquid chromatography (LC), and ion mobility (IM), properties of these materials were correlated to their microstructures and resultant physical functionalities. Side-chain liquid crystalline (SCLC) homopolymers and copolymers are a type of stimuli-responsive macromolecule that respond to incident light. The side-chains are generally comprised of oxygen, nitrogen, phenyl rings, etc., making their resulting structures conjugated systems. These properties allow them to polarize light. They are used in various optical applications as these mesogenic (i.e., liquid crystalline) side chains give the molecules optical anisotropy. These side-chains are what control the physical properties of these polymers and when two different types of liquid crystalline side chains are polymerized, the resultant copolymer can have vastly different properties than their respective homopolymers. Additionally, the sequence of the side-chains being random, block, alternating, or tapered also affects the physical properties. The copolymers in this study were synthesized with oxiranemethanol reacted with the mesogenic side-chains (4-cyano-4'hydroxybiphenyl, 4-[4'-pentylcyclohexyl]phenol) through a four carbon linker. Using matrix-assisted laser desorption/ionization-tandem mass spectrometry (MALDI-MS/MS) via laser-induced fragmentation (LIFT) allowed for the sequences of the designed SCLC copolymers to be identified. Particulate accumulation and deposition in the in-take valve of a vehicular engine can be the cause of many engine issues, though the cause of this buildup is not well studied. Using mass spectrometry to analyze these deposits can give insight into what they are comprised of, how they were made, and potentially, how to prevent them. Oils and fuels can mix with the air in the presence of harsh engine conditions to cause such deposits, but the formulations have components in them intended to deter this unwanted product, like detergents, dispersants, viscosity modifiers, etc. Oftentimes, these additives are low molecular weight polymers that respond to an increase in temperature, or another stimulus, aiding in the engine's cleanliness and maintenance. The more polar constituents in these blends are thought to contribute to these deposits, and also makes them more amenable to mass spectral analysis. Mass spectrometry and a variety of its hyphenated techniques (ASAP-, LC-, IM-) were used to acquire insight into the composition of these unknown samples to potentially aid in their preclusion.Finally, thermoresponsive polymers (TRPs) are stimuli-responsive polymers that alter their architecture when subjected to energy in the form of heat. They are used in biological applications for drug delivery, vehicular applications in fuels, and various other temperature-sensitive practices. The ability to change conformation in response to temperature aids in the herein studied samples' biological applications by changing hydrophobicity for sensitive biotic needs. These alterations are essentially changes to the conformation of the polymer chain itself, and generally are produced from p-NIPAM-like and methacrylate-like polymers. In order to observe this change, ion mobility-mass spectrometry (IM-MS) was used in a novel analysis to detect changes in polymer architecture when stimulated by increasing collision energy (collisional heating). The energy was then correlated to the varying pendant structures of the polymers, which showed a direct structure-property relationship between energy needed for conformational change and overall hydrophilicity/bulkiness.