This dissertation demonstrates the preparation of blocky brominated syndiotactic polystyrene (sPS-co-sPS-Br) copolymers with tailored chain sequences using a simple, post-polymerization functionalization method conducted in the heterogeneous gel state, and investigates the effect of sPS reaction state and sPS/solvent gel morphology on the copolymer microstructure and thermal properties. Gel-state (Blocky) brominated copolymers were prepared from a 10 w/v% sPS/carbon tetrachloride (CCl4) gel and a 10 w/v% sPS/chloroform (CHCl3) gel in a matched set containing 6−32 mol% p-bromostyrene (Br-Sty) units. For comparison, a matched set of randomly brominated copolymers was prepared using a homogeneous solution-state (Random) reaction method and a set of brominated copolymers was prepared using a heterogenous powder-state (Powder) reaction method. The degree of bromination was evaluated using 1H nuclear magnetic resonance (NMR) spectroscopy. Powder-state bromination produced copolymers with a limited degree of functionalization of up to 12 mol% Br and required a threefold longer reaction time than the gel-state method conducted on the sPS/CHCl3 gel, demonstrating that the powder-state method is time-consuming and the dense sPS powder is incapable of producing copolymers with high Br-content. Microstructural characterization provided by 13C NMR spectroscopy, showed that bromination of sPS produces multiple peaks in the quaternary carbon region of the NMR spectrum, signifying through-bond communication between neighboring styrene and Br-Sty monomers. This work provides the first high-resolution comonomer sequencing of brominated sPS copolymers. Characterization of the quaternary carbon spectrum, assisted by band selective gradient heteronuclear multiple bond correlation (bsgHMBC) spectroscopy, electronic structure calculations, and simulated statistically random copolymer chains, revealed that each resonance peak could be assigned to a styrene or Br-Sty unit that exists in the center of a unique sequence of five monomers (i.e., a pentad) along the copolymer chain (e.g., ssssb where s = styrene and b = brominated styrene). Our comonomer sequencing method demonstrated that the Blocky and Powder copolymers have block-like character. Remarkably, the Blocky copolymers exhibit notably higher degrees of blockiness and larger fractions of sssss and bbbbb pentads at low Br contents (i.e., 32 mol% Br), relative to the Powder copolymers, confirming their blocky microstructure. Quenched films of the Blocky copolymers, analyzed using ultra-small-angle (USAXS) and small-angle X ray scattering (SAXS), show micro-phase separated morphologies that are reminiscent of conventional block copolymer phase behavior, supporting that the Blocky copolymers contain distinct segments of pure sPS and segments of randomly brominated sPS. Crystallization behavior of the copolymers, examined using differential scanning calorimetry (DSC), demonstrates that the Blocky copolymers are more crystallizable and crystallize faster at lower supercooling compared to their Random analogs. Simulations of blocky copolymers were developed based on the semicrystalline gel morphology to rationalize the effect of gel-state functionalization on copolymer microstructure and crystallization behavior. The simulations confirm that restricting the accessibility of the brominating reagent to monomers well removed from the crystalline fraction of the gel network produces copolymers with a greater prevalence of long runs of pure sPS that is advantageous for preserving desired crystallizability of the resulting blocky copolymers. To investigate the effect of sPS/solvent gel morphology on copolymer microstructure and crystallization behavior, the sPS/CCl4 and sPS/CHCl3 copolymers were compared directly. Characterization of the sPS/solvent gels using USAXS/SAXS, revealed that the gels exhibit different morphologies and average lamella thicknesses. Microstructural analysis showed that the sPS/CHCl3 copolymers contain larger fractions of sssss pentad and a greater degree of blockiness. The sPS/CHCl3 copolymers contain larger phase domains, supporting that these copolymers contain longer distinct segments of pure sPS and randomly brominated sPS in a multiblock-like microstructure. In addition, the sPS/CHCl3 copolymers are more crystallizable during conditions of rapid cooling and crystallize faster at low supercooling relative to their sPS/CCl4 analogs. Simulated average chains of the Blocky copolymers, generated from the empirical pentad sequence distributions, provide strong evidence that the runs of pure sPS in the Blocky copolymers originate from the crystalline stems within the crystalline lamellae. Thus, the simulations support that semicrystalline blocky brominated copolymers with tailored chain sequences, phase behavior, and crystallization properties and can be prepared simply by changing the gelation solvent. / Doctor of Philosophy / Block copolymers are a class of large molecules (polymers) that are made up of two or more chains (blocks) of different smaller units (monomers) linked together at one of each of the chain ends. When the monomers that make up each block have distinctly different chemical properties, the blocks may be capable of self-assembling into well-ordered physical structures, which give the block copolymer unique material properties that are different, and often better than the properties of the individual blocks alone (homopolymers). Block cop olymers have thus received tremendous attention with respect to controlled preparation, tailored structure development, and customized physical properties, for their potential use in self-assembled, nanostructured materials. Nevertheless, the generally difficult procedures and conditions required to make (polymerize) block copolymers with controlled sequences limits the scope of their commercial application. As an alternative to conventional polymerization methods, this dissertation demonstrates a comparatively simple physical method to make copolymers that contain significantly non-random (blocky) monomer sequences, starting with a homopolymer and using a reagent to modify units along the polymer chain. This post-polymerization method is conducted in the homopolymer’s gel state, in which segments of the homopolymer chains are effectively shielded from the reagent. The homopolymer, syndiotactic polystyrene (sPS), was used as a model to conduct a fundamentical investigation into the effects of the polymer reaction state, i.e., gel, solution, or powder, and the gel structure (morphology) on the copolymer structure and properties. The gel-state was found to produce copolymers with a high degree of modification and a greater degree of blockiness than the solution-state and powder-state. Copolymers prepared from the gel state exhibited properties that are characteristic of conventional block copolymers. Furthermore, using the gel-state method, blocky copolymers with tailored chain sequences and properties were prepared by simply changing the gel morphology. Thus, reaction in the gel-state is demonstrated as a simple physical approach to polymer design and synthesis that will be useful in the development of next-generation functionalized materials through the modification of lowcost commodity polymers. As an advancement to the manner in which nanostructured materials are created, these tailored materials will greatly enhance the convenience of block copolymers for a wide variety of applications including structural and biomechanical materials, and polymeric membranes for energy conversion and water purification systems.

Sulfonated polyaromatic hydrocarbon membranes have emerged as desirable candidates for proton exchange membranes (PEMs) due to their excellent mechanical properties, high thermal and chemical stability, and low cost. Specifically, sulfonated multiblock copolymers are attractive because their phase-separated morphologies aide in facile proton transport. In this work, the functionalization of semicrystalline gels of poly(ether ether ketone) (PEEK) is explored as a novel post-polymerization method to prepared blocky copolymers, and the effect of copolymer architecture on membrane physical properties, structure, and performance is extensively investigated. First, the blocky sulfonation of PEEK was explored to prepare blocky copolymers (SPEEK) with densely sulfonated domains and unfunctionalized, crystallizable domains. Compared to random SPEEK ionomers at similar ion content, blocky SPEEK exhibited enhanced crystallizability, decreased melting point depression, and faster crystallization kinetics. Phase separation between the hydrophilic sulfonated blocks and hydrophobic PEEK blocks, aided by polymer crystallization, resulted in enhanced water uptake, superior proton conductivity, and more closely associated ionic domains than random SPEEK. Furthermore, the random and blocky bromination of PEEK was investigated to prepare PEEK derivatives (BrPEEK) with reactive aryl-bromides. Spectroscopic evidence revealed long domains of unfunctionalized homopolymer for blocky BrPEEK, and this translated to an increased degree of crystallinity, higher melting temperature, and more rapid crystallization kinetics than random BrPEEK at similar degrees of bromination. The subsequent sulfonation of blocky BrPEEK resulted in a hydrophilic-hydrophobic blocky copolymer with clear multi-phase behavior. The phase-separated morphology contributed to decreased water uptake and areal swelling compared to random SPEEK and resulted in considerably higher proton conductivity at much lower hydration levels. Moreover, Ullmann coupling introduced superacidic perfluorosulfonic acid side chains to the BrPEEK backbone, which yielded membranes with less water content and less dimensional swelling than random SPEEK. Superior proton transport than random SPEEK was observed due to the superacid side chain and wider hydrophilic channels within the membranes, resulting in more continuous pathways for proton transport. Overall, this work provided a novel platform for the preparation of functionalized PEEK membranes using a simple post-polymerization functionalization procedure. The established methods produced blocky-type copolymers with properties reminiscent of multiblock copolymers prepared by direct polymerization from monomers/oligomers. / PHD / Block copolymers are an important class of polymers that are composed of two or more blocks of distinct polymeric segments covalently tethered to one another. Dissimilarity in the chemical nature of the blocks leads to self-organization into well-defined structures, and this unique structural order imparts material properties that are different from (and often superior to) the properties of the individual blocks alone. Thus, block copolymers are advantageous for a diverse array of applications including membranes, gas separation, water purification, medical devices, etc. Although considerable synthetic progress has been made towards discovering novel methods to prepare block copolymers, their widespread use is somewhat limited by the complex, energy-intensive procedures necessary to precisely control the block sequencing during polymerization. In this dissertation, a straightforward, inexpensive physical procedure is explored to synthesize blocky copolymers with controlled sequencing from commercially available polymers. This process relies on performing reactions in the gel state, whereby segments of the polymer chain are effectively shielded from the functionalizing chemistry. In particular, the gel state sulfonation and bromination of poly(ether ether ketone), a high performance polymer, is investigated to develop novel, blocky materials for membrane applications. This work not only expands the methodology towards the synthesis of block copolymers, but alaso provides critical insight into the effect of copolymer architecture on membrane physical properties, structure, and performance. Furthermore, this work provides an economically feasible method to prepare blocky copolymers from commercially derived materials, thereby providing a means to progress the widespread use of block copolymers in industry.

This work investigates the influence of microstructure and cooling and heating rates on the physical and chemical properties of fast crystallizing polymers. The primary objectives were to 1) utilize advanced methodologies to accurately determine the fundamental thermodynamic value of equilibrium melting temperature (Tmo) for the semi-crystalline polymer poly(ether ketone ketone) (PEKK), 2) increase understanding of the influence of microstructure (random versus blocky) of functionalized semi-crystalline polymers on physical and chemical properties, and 3) understand the influence of additive manufacturing process parameters on semi-crystalline polymer crystallization and final properties. All objectives utilized the advanced characterization technique of fast scanning calorimetry (FSC) using the Mettler Toledo Flash DSC 1. The first half of this work focuses on the high-performance semi-crystalline aromatic polymer poly(ether ketone ketone) (PEKK) with a copolymerization ratio of terephthalate to isophthalate moieties (i.e., T/I ratio) of 80/20. Due to the fast heating and cooling rates of the Flash DSC, PEKK underwent melt-reorganization upon heating at slow heating rates. This discovery resulted in utilizing a Hoffman-Weeks linear extrapolation of the zero-entropy production temperature to establish a new equilibrium melting temperature of 382 oC. Additionally, a new NMR solvent, dichloroacetic acid, was discovered for PEKK, allowing for comprehensive NMR analysis of PEKK for the first time. Diphenyl acetone (DPA) was discovered as a novel, benign gelation solvent for PEKK, enabling heterogeneous gel-state bromination and sulfonation to afford blocky microstructures. The gel state functionalization process resulted in a blocky microstructure with runs of pristine crystallizable PEKK retained within the crystalline domains, and amorphous domains containing the functionalized PEKK monomers. The preservation of the pristine crystalline domains resulted in enhanced physical and chemical properties compared to the randomly functionalized analogs. Additionally, heterogeneous gel state functionalization of PEKK gels prepared from different solvents and gelation temperatures resulted in differences in crystallization behavior between blocky microstructures of the same degree of functionalization. This result demonstrates that the blocky microstructure can be tuned through controlling the starting gel morphology. The second half of this work focuses on understanding the influence of cooling and heating rates on the melting, crystal morphology, and crystallization kinetics on isotactic polypropylene (iPP), iPP-polyethylene copolymers (iPP-PE), and iPP/iPP-PE blends and using this information to gain understanding of how these polymers crystallize during the additive manufacturing processes of powder bed fusion (PBF) and material extrusion (MatEx). The crystallization kinetics of iPP, iPP-PE copolymers, and iPP/iPP-PE blends exhibited bimodal parabolic-like behavior attributed to crystallization of the mesomorphic crystal polymorph at low temperatures and the α-form crystal at high temperatures. Incorporation of non-crystallizable polyethylene fractions both covalently and blended as a secondary component, resulted in decreasing crystallization rates, inhibition of crystallization, and decreased crystallizability. Additionally, the non-isothermal crystallization behavior of these systems shows that the non-crystallizable fractions influence the crystal nucleation density and temperature at which polymorphic crystallization occurs. Utilizing in-situ IR thermography in the PBF system, the heating and cooling rates observed for a single-layer PBF print were used to mimic the PBF process by FSC. Partial melting in the printing process leads to self-seeding and increased crystallization onset temperatures upon cooling, which influences the final part melting morphology. Nucleation from surrounding powder and partially melted crystals greatly influences the crystallization kinetics and crystal morphology of the final part. Utilizing rheological experiments and process-relevant cooling rates observed in the MatEx process, the miscibility of iPP/iPP-PE blends influenced the nucleation behavior and crystallization rates, subsequently leading to differences in printed part properties. / Doctor of Philosophy / The crystalline morphology of semi-crystalline polymers depends on their microstructure and thermal history. The resultant crystalline morphology greatly affects the physical and chemical properties. In the first part of this work, the effect of microstructure on material properties is explored. Block copolymer microstructures consist of two or more blocks of distinct polymer segments covalently bonded to one another. This leads to self-organization of the components into unique structural order that would not be attainable if the polymer segments were randomly bonded together. This structural order enhances material properties; thus, block copolymers are advantageous for many applications. However, synthesis of block copolymers can be tedious and expensive. Thus, additional methodologies for block copolymer synthesis are desired. In this work blocky (i.e., statistically non-random) copolymers are synthesized through a facile post-polymerization functionalization method. These blocky copolymers result in enhanced physical and chemical properties compared to the randomly synthesized analogs. This work shows blocky functionalization of a new polymer under new post-polymerization conditions and expands upon the synthesis methodology for block copolymers. In the second part of this work, the effect of heating and cooling rates on the formation of crystals during additive manufacturing is explored. Additive manufacturing modalities of powder bed fusion and material extrusion consist of rapid heating and cooling processes, which can affect how crystals form and ultimately affect the final printed part properties. Using a technique called fast scanning calorimetry, the different heating and cooling rates that the polymer witnesses during printing can be mimicked, and the formation of crystals under these different conditions can be replicated. This mimicking analysis can be related to the printing process and be used to help guide printing processes to enhance printed part properties.

This dissertation presents a discussion of blocky and randomly functionalized sulfonated syndiotactic polystyrene copolymers. These copolymers have been prepared over a range of functionalization (from 2% to 10%) in order to assess the effect of the incorporation of these polar side groups on both the thermal behavior and morphology of these polymer systems. The two different architectures are achieved by conducting the reaction in both the heterogeneous gel-state to obtain blocky copolymers and in the homogeneous solution state to obtain randomly functionalized copolymers. In order to compare both the thermal properties and morphology of these two systems several sets of samples were prepared at comparable levels of sulfonation. Thermal analysis of these two systems proved that the blocky functionalized copolymers provided superior properties with regard to the speed and total amount of the crystalline component of sulfonated syndiotactic polystyrene. Above 3% functionalizion the randomly functionalized copolymer was no longer able to crystallize, whereas, the blocky functionalized copolymer is able to crystallize even at a functionalization level of 10.5% sulfonate groups. When considering the morphology of these systems even at low percentages of sulfonation it is clear that the distribution of these groups is different based on the amplitude of the signal measured by small angle x-ray scattering. Additionally, methods were developed to describe both the distribution of ionic multiplets, which varies between blocky and randomly functionalized systems, but also the distribution of crystals. At a larger scale ultra-small angle x-ray scattering was employed to attempt to understand the clustering of ionic multiplets in these systems. Randomly functionalized polymers should a peak that is attributed to ion clusters, whereas blocky polymers show no such peak. Additional studies have also been done to look at the analysis of crystallite sizes in these systems when there are multiplet polymorphs present, it was observed the polymorphic composition is drastically different. All of these studies support that these systems bear vastly different thermal behavior and possess significantly different morphologies. This supports the hypothesis that this gel-state heterogeneous functionalization procedure produces a much different chain architecture compared to homogeneous functionalization in the solution-state. / Doctor of Philosophy / Polymers are a class of chemicals that are defined by having a very large set of molecules that are chemically linked together where each unit (monomer) is repeated within the chemical structure. In particular, this dissertation focuses on the construction what are termed as "blocky" copolymers, which are defined by having two chemically different monomers that are incorporated in the polymer chain. The "blocky" characteristic of these polymers means that these two different monomers are physically segregated from each other on the polymer chain, where long portions of the chain that are of one type, followed by another section of the polymer that has the other type of monomer. The goal of creating this type of structure is to try to take advantage of the properties of both types of monomers, which can create materials with superior synergistic properties. In this case a hydrophobic (water hating) monomer is combined with a hydrophilic (water loving) chain. This hydrophobic component in the polymer is able to crystallize, which provides mechanical and thermal stability in the material by acting as a physical tether to hold neighboring chains together. With the other set of hydrophilic monomers, which in this case have an ionic component incorporated, we can now take advantage of this chemical components ability to aide in the transportation of ions. Transportation of ions is useful in a variety of commercially relevant applications, two of the most important applications of these ionic materials is in membranes that can be used to purify water or membrane materials in fuel cell technologies, specifically for proton exchange membranes. The focus of this research in particular was to create a simple synthesis technique that can create these blocky polymer chain architectures, which is done by performing the reaction while the polymer is made into a gel. The key to this is that the crystals within the gel act as a barrier to chemical reactions, creating conditions where we have substantial portions of the material that are able to be functionalized and the crystals within the material that are protected from being functionalized. By looking at the thermal characteristics, such as melting temperatures and amount of crystals within these systems we have seen that functionalizing these polymers in the heterogeneous gel state gives substantially better properties than functionalizing these materials randomly. Much like oil and water, incompatible polymer chains will phase separate from each other. In this case the hydrophobic and ionic components will phase separate from each other. The shape and distribution of these phase separated structure will dictate many of the material properties, which can be described by modeling the data collected from x-ray scattering experiments. All of this information will tell us based on the initial conditions that these polymers were created in, what properties should be expected based on the morphology and thermal behavior. This gives a better understanding of how to fine tune these properties based on the structure of the gel and chemical reaction conditions.

This masters project describes properties and primary parameters of active function blocks (OPA, VCA, OTA, CFA, CC) usable in construction of harmonic oscillators. Basic principles of harmonic generators, especially feedback oscillators, are introduced. In next section are presented five particular schematics of harmonic tuned oscillators. For this oscillators are indicated basic formulas, essential qualities performed by simulations and results of sensitivity and tolerance analysis. In the last part of diploma thesis there are selected three circuits which are made and their features are measured.