This thesis begins with the introduction of solvents and their classification. The two solvent system studied here are switchable polarity solvents (SPS). A switchable polarity solvent is a liquid where its polarity can change between two forms by a trigger. These two solvent systems have several similar characteristics. First, they both require CO2 as the switching agent, which can be switched back by its removal with heat or N2. The first project is the continuation of previous work with using an amidine and alcohol mixtures as a switchable polarity solvent. The second project was the development of a new switchable polarity solvent that is based on the reaction of a secondary amine with CO2. Both solvent systems are fully characterized by many analytical techniques and examples of applications in chemical reaction and separation are outlined. The final project involves using these solvent systems, among others, in the separation of soybean oil. The aim was to use SPS technology to extract soybean oil from the bean flakes, and then separate the oil from the extracting solvent. / Thesis (Master, Chemistry) -- Queen's University, 2008-02-07 15:21:31.499

Soil remediation requires technologies to restore contaminated soil to a state that is environmentally acceptable. In most cases, while the soil can be remediated the contaminant itself cannot be reclaimed. Soil washing involves cleaning contaminated soil with a wash solution, generally an aqueous solution of a surfactant. It was proposed that using switchable surfactants for washing oil-contaminated soil will not only help remove the oil from soil, but also aid in the recovery of the oil contaminant from the wash mixture. Six surfactants were evaluated for their ability to wash Ottawa Sand artificially contaminated with North Sea crude oil. A water wash solution was used as a control. Two commercial surfactants, sodium dodecyl sulfate (SDS) and Triton X-100, and four switchable surfactants, N'-octyl-N,N-dimethylamidine (C8), sodium octyl 4-hydroxy-3-nitrobenzoate (SAS1), sodium 4-(octyoxy) benzoate (SAS2) and sodium laurate (SAS3) were studied. The surfactants were assessed based on their ability to remove oil from the sand and their ability to separate the crude oil from the wash mixture after CO2 treatment. Oil removal from sand was determined by gravimetric analysis. Oil content in the wash mixture was determined using Solid Phase Extraction and gravimetric analysis. It was determined that switchable surfactants are able to remove North Sea crude oil from sand as well or better than the commercial surfactants and have the added feature of oil separation and recovery from the wash mixture after CO2 treatment. / Thesis (Master, Chemistry) -- Queen's University, 2011-02-16 17:10:16.997

Amidine-based switchable surfactants can be used as stabilizers during emulsion polymerization and the resulting latexes can then be destabilized by the removal of CO2. High Tg polymers have been successfully redispersed, as shown by recovery of primary particle size (measured by light scattering methods), but an input of energy was required. Sonication was the first method used, but lower-energy methods such as rotor-stators and a blender have also been successful in redispersing aggregated latexes. Colloidal stability was found to be reversible for at least three aggregation/redispersion cycles, and redispersibility was retained after the removal of water and addition of fresh water. Stimuli-responsive polymer colloids with reversible colloidal stability may have many uses. The shipping of latexes, for example, would be easier and less energy intensive if the latex particles could be aggregated and the bulk of the water removed. The latexes would then have to be redispersed prior to use. Switchable surfactants have also been used for the semi-continuous copolymerization of butyl acrylate and methyl methacrylate to form a high solids content (42 wt%), low-Tg latex. The latex can be destabilized with air and heat but cannot undergo redispersion because the low Tg polymer particles fuse upon aggregation. The copolymer, when dried at room temperature, formed a continuous film. Latexes with high solids content and low Tg’s are representative of latex paint formulations. Because the switchable surfactants have been shown to be successful in preparing these latexes, it is possible that they may be useful in the latex paint industry, for example as fast setting paints. / Thesis (Master, Chemistry) -- Queen's University, 2011-09-26 13:18:33.905

Stimuli-responsive polymers have attracted great attention due to their unique responses in physicochemical properties to changes in external environment and stimuli variations (e.g. pH, thermo, light, electric and magnetic field, etc.). Introduction of gas triggers has greatly expanded the family of stimuli-responsive polymers since the first work on a CO2-switchable polymer was reported in 2006. Although significant progresses have been achieved over the past decade, studies on gas-switchable polymers are still at an early stage, with many challenges in both fundamental and application areas remaining to be tackled. This thesis focuses on synthesis and application development of O2 and CO2 switchable polymers. The thesis starts from investigating O2-switchable thermo-responsive fluorinated monomers and their linear random copolymers, which undergo LCST shifting induced by O2 treatment. It provides good insight and general guidance for design and screening of monomer candidates for the synthesis of O2-switchable polymers. The second part of the thesis presents development of the first O2 and CO2 dual gas-switchable microgel system and building of the microgel-colloidosomes with O2 and CO2 tailored shell permeability. The latter is evaluated as microcapsules for hierarchical control-release of water-soluble cargo molecules upon respective O2 and CO2 treatment. The last part of the thesis explores preparation of various porous polymer systems from high internal phase emulsion (HIPE) templates. In particular, a highly porous polyHIPE membrane with "open-cell" structure exhibiting CO2-switchable surface wettability is promising for smart separation applications. This thesis represents a significant progress and a solid step forward in the development of gas-switchable polymers from monomer design, polymer preparation, and advanced application of polymer systems. / Thesis / Doctor of Philosophy (PhD) / Polymer materials are used in every aspect of our daily life, from clothing, furniture to construction. This thesis work is to develop functional polymers that can feel variations in environment (e.g. pH, thermo, light, magnetic, etc) and give out changes in properties. Such materials are smart for stimuli-responsive applications. The first report of carbon dioxide (CO2)-switchable polymers in 2006 was marked as the start of gas-responsive polymers. Gas triggers interact with specific functionalities in polymer chains and change their physicochemical properties such as chain structure, architecture, hydrophilicity and polarity. Oxygen (O2) and CO2 are explored in this work to reversibly trigger changes in volume, shell permeability and surface wettability, of different polymer systems. Potential applications include drug control-release, smart oil/water separation, and so on. This work presents a systematic study on the development of O2 and/or CO2-switchable polymers from monomer design, polymer preparation, and advanced application of polymer systems. It represents a significant progress and a solid step forward in the study of gas-switchable polymers.

Thesis advisor: Jeffery A. Byers / This dissertation discusses the development of a family of iron complexes and their role in the synthesis of degradable polymers. Chapter one will introduce the different areas of redox-switchable polymerization. In chapter two the synthesis of block copolymers containing a polyester and polyether block is presented. The application redox-switchable polymerization to form a copolymer with two fundamentally distinct backbone functionalities and their characterization is discussed. In chapter three the synthesis of a degradable cross-linked polymer through a novel redox-triggered cross linking event is summarized. In chapter four, a detailed mechanistic study of iron-complex catalyzed epoxide polymerization is examined and a unique mechanistic scheme is proposed. Lastly, in chapter five the synthesis and characterization of a formally iron(I) complex is presented. This complex shows remarkable catalytic activity towards ring-opening polymerization. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Jeffery A. Byers / This dissertation covers the development of redox-switchable ring-opening polymerizations for the synthesis of copolymers of underutilized monomers. In Chapter one, the progress in the development of switchable methods for ring-opening polymerization and ring-opening copolymerizations. Chapter two describes a method for the redox-switchable copolymerization of L-lactide, propylene oxide and carbon dioxide. The benefits of this method are demonstrated through the facile synthesis of blocky and statistical copolymers of the three monomers. In Chapter three, a method for the redox-switchable polymerization of N-carboxyanhydrides is presented. A mechanistic analysis and copolymerizations of N-carboxyanhydrides and either lactones or epoxides follow the initial findings. Chapter four further expands the uses of N-carboxyanhydride redox-switchable polymerizations by immobilizing the catalysts onto semiconductor surfaces for the synthesis of surface bound polyamides. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

This work showcases the utility of switchable materials. Included are a switchable room-temperature ionic liquid, a switchable solvent, a switchable heterogeneous catalyst system, and a switchable gel. First, the switchable ionic liquid 2-butyl-1,1,3,3-tetramethylguanidium methylcarbonate is fully investigated. Its use in a complete chemical process (including reaction, separation, reformation, and recycle) is demonstrated with several reactions. Furthermore, its potential use for bitumen separation and purification and SO2 capture/isolation are discussed, and preliminary data is presented. Next, piperylene sulfone (PS), a switchable solvent, is synthesized and fully characterized. Anionic nucleophilic substitution reactions were performed in PS, the products were isolated in high yields, and then the PS was reformed for reuse. Then, we designed an immobilized fluorous microphase system that uses F-MonoPhos to induce high enantioselectivities as a switchable heterogeneous catalyst system. Finally, stable reversible polyethyleimine-CO2 gels have been synthesized with 1-octanol. Our findings indicate that PEI-1200/octanol/CO2 gels have potential as a possible drug carrier matrix for transdermal delivery applications.

This thesis describes the covalent modification of carbon electrodes with a monolayer of polymerisation initiators and the growth of polymer brushes by surface initiated atom transfer radical polymerisation (SI-ATRP). Monolayer modification was sought to preserve the underlying electrode properties and topography and to produce a well-organised layer from which the polymer brushes can be grown. This work investigated two approaches for immobilising a monolayer of polymerisation initiators. Firstly, the electrochemical grafting of protected aryl diazonium salts produced a covalently anchored monolayer of tether groups that can participate in subsequent amide coupling and click reactions, to covalently anchor the polymerisation initiator. Secondly, specific reactions between the electrode surface and appropriate polymerisation initiator derivatives have been used to covalently anchor the initiators. For most systems, electro-active ferrocene (Fc) groups were reacted with modified surfaces as model reactants to enable the electrochemical estimation of the surface concentration of the polymer initiator groups. Film thickness measurements of the ethynylaryl (Ar-Eth) monolayer were carried out using atomic force microscopy confirming a monolayer. XPS analysis confirmed the presence of bromine on most of the polymerisation initiator modified samples. Modification of surfaces with polymer brushes can introduce new surface properties, such as switchable wettability, while maintaining the underlying bulk substrate properties. This work focused on examining SI-ATRP at each of the polymerisation initiator monolayers, with the aim to identify the most promising system(s) for further investigation. Polymer brushes of poly(3-(methacryloylamino)propyl)-N,N’-dimethyl(3-sulfopropyl)-ammonium hydroxide) (PMPDSAH) were grown from initiators tethered through the aryl diazonium salts modification procedure. Redox probe voltammetry and XPS analysis indicated that the grafting from polymerisation by the copper catalysed SI-ATRP was successful. Polymer brushes of poly(methyl methacrylate) PMMA were grown from the Ar-Eth modified monolayer by three SI-ATRP procedures: a standard procedure, an electrochemically mediated SI-ATRP method and a one-pot copper catalysed azide-alkyne click (CuAAC) reaction and SI-ATRP reaction from the Ar-Eth monolayer. Redox probe voltammetry and AFM images provided evidence for the growth of polymer brushes by these three methods. The successful one-pot CuAAC/SI-ATRP reaction for simultaneous coupling of the polymerisation initiator to the surface and polymerisation is a new approach for the production of polymer brushes and it minimises the number of surface modification steps needed. This method appears most promising for further development.

Photochromism has been investigated extensively during recent years. The large interest for information storage in memory applications is associated with the bi-stable character of the photochromism phenomena. In molecular photochromics, two isomers with different absorption spectrum can be obtained according to the specific wavelength of the light exposure. This reversible transformation process can be considered as optical writing/erasing step of a memory. Here we first report the absorption spectra of solid-state films based on the blends consisting of PC molecules, the spirooxazine 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3’-[3H]phenanthr[9,10-b](1,4)oxazine] (PIII, Sigma-Aldrich, 32,256-3) and a polymer matrix host, poly(2-methoxy-5(2’-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The bi-stability in conjugated polymer matrix is studied by following the time evolution of the optical properties of the blends. Thereafter, the electrical performance of PC-polymer diodes is characterized and reported. While the PIII molecules in the blend bulks are switched to their low energy gap state, forming external energy levels above the valence band of MEH-PPV, the injected charges (hole-dominated) will be trapped by the low energy gap isomer of PIII and that leads to current modulation. PIII molecules can be switched between two energy gap states upon the photo-stimulation, and the I-V characteristics of the device can also be controlled reversibly via the photoisomerization. The retention time of the diode’s electrical switching fits quite well with the absorption characteristics of the blend films; this correspondence builds a good link between the film property and the device behavior. Furthermore, we observed a two-trap system in the blend diodes from the I-V curves, and a model is proposed which can explain the schematic concept of the trap-limited current modulation. To combine the knowledge and information from the investigations above, we tested a novel device design based on a bi-layer of the PC and polymer materials, and the promising result for future work is presented in the end.

Solid phase extraction is one of the most widely used techniques to trap and release compounds in a solution. A hydrophobic substance will stick efficiently to a hydrophobic surface (the “like dissolves like” principle). With an introduced response (i.e. pH change), a responsive surface can change from hydrophobic to hydrophilic, weakening the hydrophobic substance’s attraction and thus facilitate in an easy removal. A surface has been prepared having a terminal anthranilic acid (AA) moiety on silica gel particles, microscope slides, and TLC plates in three steps. First, a vinyl group was attached to the surface. Then, this vinyl group was reacted to form a surface carboxylic acid group. Finally, the carboxylic acid group was converted to an amide group that linked to the silica surface. FT-IR, and elemental analysis were used to confirm each step of the synthesis. At low pHs the –COOH group on the AA moiety is neutral and intrahydrogen bonding keeps this moiety’s phenyl (hydrophobic) portion exposed to the surface. The effect has been investigated by measuring contact angles at various pH values. At higher pHs the AA’s carboxylic acid group becomes the charged carboxylate, rendering the surface hydrophilic. Substances can be trapped and released using this unique switching approach. 2-naphthol, for example, is hydrophobic and thus was trapped at lower pHs (pH 4) (hydrophobic surface) and released at higher pHs (pH 10) (hydrophilic surface) on this responsive surface