Molecular weight and concentration are two most important characteristics of polymers synthesized through chemical or microbial processes. However, current methods for characterizing polymer molecular weight such as Multi-Angle Laser Light Scattering (MALLS) or Gel Permeation Chromatography (GPC) require precise information on concentration as well as extensive sample preparation. Additionally, these current methods are also generally expensive, low throughput, and require large sample titers. These limitations prevent dynamic time-point studies of changes in molecular weight, which would be very useful for monitoring synthesis progress in microbes or in chemical synthesis. In this thesis, we designed, fabricated, and tested a rapid, low cost, high throughput, modular microfluidic system for determining polymer molecular weight in samples of unknown concentrations. To assess the accuracy of this system, we first constructed theoretical predictions for its accuracy, and then compared these to the experimental results from our microfluidic system. The system evaluated molecular weight by correlating the behavior of polymers in various solvent conditions to their molecular weights. The system consists of two modules for measuring fluid viscosity, and for controlling solvent conditions. Results of this study will show that this system is able to evaluate the differences in polymer viscosity for varying molecular weights and solvent conditions. For the solvent control module, we show that salt concentrations in small titers of polymer solutions can be rapidly added or subtracted and evaluated compared with current methods. Next, we will show the efficacy of the viscosity module at rapidly and accurately assessing fluid viscosity over a wide range of molecular weights. Finally, we will show the effects of solvent changes on molecular weight viscosity, and thus the efficacy of the system in determining molecular weight from fluid viscosity. This system will be applied to the evaluation of both the biologically produced polymer Hyaluronic Acid (HA) as well as the synthetically produced polymer Poly-ethylene Oxide (PEO).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1942. / Includes bibliographical references (p. 97-99).

The thermal conductivities of polystyrene in benzene solutions at concentrations of 0.l to 15 weight percent were measured at 25° C and atmospheric pressure. Osmotic pressure measurements and information supplied by the manufacturer indicated number average molecular weights (M̅_N) of 21,000, 264,000, and 660,000 for the three polystyrene polymers studied. The following equation was obtained by regression analysis of the results and predicts the measured thermal conductivity within ± 2 percent in the range of variables studied. K = 0.1088 - 0.1311 C + 0.57629 C² - 6.40 x 10⁻⁵ (M̅_N x 10⁻⁵)² - 4.2 x 10⁻³ C(M̅_N x 10⁻⁵) where: K = thermal conductivity of solution, Btu/hr-ft-°F C = weight fraction polymer M̅_N = number average molecular weight The conductivities were measured in a steady-state concentric cylinder apparatus developed for measuring the thermal conductivity of viscous liquids. The annular gap was 0.052 inches and guard heaters were employed to minimize end losses and distortion of the steady-state temperature distribution at the ends. The apparatus was calibrated with three liquids of known thermal conductivity, water, cyclohexanol and ethylene glycol. The calibration factor was found to be constant to within experimental error (± 3 percent) over the range of measurements. / Master of Science

The Suwannee River natural organic matter (SRNOM) was fractionated by preparative size-exclusion chromatography (SEC) into seven molecular weight (MW) fractions. The SRNOM and its MW fractions were subsequently analyzed for their concentrations of acidic functional groups by direct titrations, average MWs and MW distributions by semi-analytical SEC, and charge-to-MW distributions by capillary electrophoresis. Carboxyl concentrations in the MW fractions were inversely proportional to their average MWs. Conversely, the phenolic concentrations, though smaller than the carboxyl concentrations, were proportional to average MWs. Hysteresisthe non-overlap between sequential forward and reverse titrationswas observed for the SRNOM and its MW fractions, where the reverse titrations predicted a greater concentration of carboxylic acid groups than the forward titration. Because hysteresis is thought to be caused by the base-catalyzed hydrolysis of esters, this suggests that ester groups in the SRNOM are distributed over all MWs. Data for direct titrations, MW distributions, and capillary electrophoresis were evaluated by a computational scheme that solves for the most probable distribution of acidic functional groups and charges on solutes in the SRNOM and the MW fractions as a function of pH. Depending on the MW ranges of the samples, solutes in the SRNOM and the MW fractions are predicted to have from one to a maximum of 25 carboxyl groups per solute. Most phenolic groups are predicted to be on solutes that have a minimum of two carboxyl groups. At low pH, all samples have high relative abundances of solutes with the lowest charges. The charges of solutes are predicted to increase with increasing pH due to the sequential ionization of acidic functional groups. Depending on the MW ranges of the samples, the maximum probable charges of solutes in the SRNOM and the fractions at high pH are -12 to -30. By knowing the most probable distribution of charge and abundances of acidic functional groups, researchers will make better estimates of thermodynamic parameters and models that describe equilibria between metals and natural organic matter in the environment.

Organic π-conjugated Donor-Acceptor copolymers are emerging as potential candidate materials for organic field effect transistor (OFET) and organic photovoltaic (OPV) applications. The electron-deficient benzothiadiazole group coupled with an electron-rich oligothiophene to form donor-acceptor copolymers has attracted significant attention. These low optical band gap materials absorb photons in the range of 400-800 nm and exhibit good thermal stability. In particular, poly(benzothiadiazole-sexithiophene) (PBT6) exhibits excellent performance in optoelectronic devices and high thermal stability. Here, we present the chemical synthesis and characterization of the polymer, PBT6. Three samples of PBT-6 with differing molecular weights in the range of Mn 18000-45000 Da were synthesized. Each polymer was characterized with respect to its photophysical, thermal properties and field-effected mobility was determined. Devices were prepared by drop-casting polymer solutions in 1,2-dichlorobenzene (DCB) onto an OFET (bottom gate/bottom contact) substrate and the devices were used to examine the charge transport properties of each polymer system. The optimal solvent to be used for processing technique was determined and surface techniques using OTS-8 and OTS-18 were compared through contact angle measurements. The measured charge carrier mobilities were in the range of 0.45-0.6 cm² / V.s. Polymer films prepared via drop-casting and which were thermal annealed exhibit mobilities as high as 0.825 cm² / V.s. This work examines the effect of molecular weight on the charge carrier transport properties and demonstrates the correlation of performance with molecular ordering. Drop-casted films of PBT-6 exhibit highly ordered crystalline lamellar structure with high degree of π- π stacking with edge-on orientation on the substrate. The longer conjugation lengths promote intrachain charge transfer. This high degree of molecular ordering in high MW samples of PBT6 improves the interchain and intrachain charge transfer leading to enhanced mobilities. The increased molecular weight (MW) facilitates in forming more uniform thin films which is vital in processing and application of polymer thin film technologies. These results and observations clearly demonstrate the potential of PBT-6 as a semiconducting material for Optoelectronic devices.

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2006. / Michael Bergin, Committee Member ; E. Michael Perdue, Committee Chair ; Ching-Hua Huang, Committee Member ; Ellery Ingall, Committee Member ; Martial Taillefert, Committee Member. Vita. Includes bibliographical references.

Orientador: Liliane Maria Ferrareso Lona / Dissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-07T07:49:45Z (GMT). No. of bitstreams: 1 Franco_CileneMeinberg_M.pdf: 1835289 bytes, checksum: 8c7c34fee69d338538caffa2e9546741 (MD5) Previous issue date: 2006 / Resumo: Iniciadores mono funcionais são largamente utilizados em polimerizações VIa radical livre. Muitas vezes, na busca de maiores produtividades, utilizam-se temperaturas de operação mais elevadas e/ou maiores concentrações iniciais de iniciador, que por conseqüência, geram polímeros com pesos moleculares mais baixos. O uso de iniciadores difuncionais permite o aumento da produtividade sem a redução no peso molecular do produto final, o que pode ser urna característica desejável. A pesquisa com iniciadores difuncionais é atual e de grande interesse industrial. O objetivo deste trabalho é analisar o efeito da funcionalidade do iniciador, no caso mono e difuncional, sobre a polimerização via radical livre, considerando corno caso estudo um polímero linear, o poliestireno, e um ramificado, o poli (acetato de vinila). Para isso, foram feitas, experimentalmente, reações de polimerização em ampolas de vidro (polimerização em massa), com o iniciador mono funcional (Luperox TBEC) e o di funcional (Luperox 531). Foram analisados também o efeito da temperatura de polimerização e a concentração de iniciador. Também neste trabalho é apresentado um estudo estatístico através de um Planejamento Fatorial, a fim de analisar o efeito das variáveis temperatura e concentração de iniciador na polimerização do estireno com iniciador difuncional. Observou-se, tanto para o estireno corno para o acetato de vinila, que quando utilizado o iniciador difuncional é possível obter conversões maiores, sem alterar o peso molecular médio mássico e numérico, sendo que em alguns casos pode se até obter um aumento no peso molecular. O uso de iniciador di funcional é também mais viável economicamente, pois apresenta melhores resultados frente ao monofuncional, mesmo quando utilizado em concentrações ou temperaturas menores do que as utilizadas com o iniciador mono funcional. É importante salientar o caráter inovador desta pesquisa, já que não foram encontrados, em literatura aberta, dados experimentais da polimerização do acetato de vinila (ou outro monômero que produza ramificações de cadeia longa) utilizando iniciadores difuncionais / Abstract: Monofunctional initiators are extensively utilized in free radical polymerization. In order to increase productivity, higher temperature or higher initial initiator concentration are used, therefore polymers with lower molecular weights are obtained. Bifunctional initiators increase the polymerization rate without decreasing the average molecular weight and this can be desirable. They are an important issue to be investigated and are of great interest to industries. The objective of this work is to analyze the effect of the functionality of the initiator, by using mono and bifunctional, in free radical polymerization, for linear polymer (poly styrene) and branched polymer (poly(vinyl acetate)). Polymerizations were experimentally performed in glass ampoules (bulk polymerization) using both mono(Luperox TBEC) and bi- (Luperox 531) functional initiators. The effects of temperature and initiator concentration were also analyzed for various polymerization conditions. This work includes a statistical study using the factorial design to analyze the effect of temperature and initiator concentration in styrene polymerization with bifunctional initiator. It is observed in this study, that high conversions with no effect in the molecular weigh of the dead polymer can be achieved using bifunctional initiators in the polymerization of styrene and vinyl acetate. In many cases, it is possible to obtain higher molecular weights. Bifunctional initiator can also be used to provide reduction costs to initiators. They showed better results than the monofunctional initiator when lower concentration or temperature lower were utilized. / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Abstract not available

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2017-11-30T10:57:51Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Douglas Tomachewski.pdf: 4287227 bytes, checksum: 4ee4e1b519755860efa6f01d55b3569f (MD5) / Made available in DSpace on 2017-11-30T10:57:51Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Douglas Tomachewski.pdf: 4287227 bytes, checksum: 4ee4e1b519755860efa6f01d55b3569f (MD5) Previous issue date: 2017-09-04 / A identificação de microrganismos, nas áreas da saúde e agricultura, é essencial para compreender a composição e o desenvolvimento do meio. Novas técnicas estão buscando identificar estes microrganismos com mais acurácia, rapidez e com menor custo. Uma técnica cada vez mais estudada e utilizada atualmente é a identificação de microrganismos através de espectros de massa, gerados por uma espectrometria de massa. Os espectros de massa são capazes de gerar um perfil para reconhecimento de um microrganismo, utilizando os picos referentes às mais abundantes massas moleculares registradas nos espectros. Analisando os picos pode-se designar um padrão, como uma impressão digital, para reconhecer um microrganismo, esta técnica é conhecida como PMF, do inglês Peptide Mass Fingerprint. Outra forma de identificar um espectro de massa, é através dos picos que são esperados que se apresentem no espectro, modelo qual este trabalho utilizou. Para prever os picos esperados no espectro, foram calculados os pesos moleculares estimados de proteínas ribossomais. Essas proteínas são denominadas house keeping, ou seja são presentes para o próprio funcionamento celular. Além de apresentarem grande abundância no conteúdo procariótico, elas são altamente conservadas, não alterando sua fisiologia para diferentes meios ou estágios celulares. Os pesos estimados formaram uma base de dados presumida, contendo todas as informações obtidas do repositório do NCBI. Esta base de dados presumida foi generalizada para taxonomia a nível de espécie, e posteriormente submetida à um aprendizado de máquina. Com isso foi possível obter um modelo classificatório de microrganismos baseado em valores de proteínas ribossomais. Utilizando o modelo gerado pelo aprendizado de máquina, foi desenvolvido um software chamado Ribopeaks, capaz classificar os microrganismos a nível de espécie com acurácia de 94.83%, considerando as espécies correlatas. Também foram observados os resultados a nível taxonômico de gênero, que obteve 98.69% de assertividade. Valores de massas moleculares ribossomais biológicas retiradas da literatura também foram testadas no modelo obtido, obtendo uma assertividade total de 84,48% para acertos em nível de espécie, e 90,51% de acerto em nível de gênero. / Identification of microorganisms in health and agriculture areas is essential to understand the composition and development of the environment. New techniques are seeking to identify these microorganisms with more accuracy, speed and at a lower cost. Nowadays, a technique that is increasingly studied and used is the identification of microorganisms through mass spectra, generated by mass spectrometry. The mass spectra are able to generate a recognition profile from a microorganism, using the referring peaks to the most abundant molecular masses recorded in the spectrum. By analyzing the peaks, it is possible to designate a pattern, such as a fingerprint, to recognize a microorganism; this technique is known as the Peptide Mass Fingerprint (PMF). Another way to identify a mass spectrum is through the peaks that are expected to appear in the spectrum, which model this work used. To predict the expected peaks in the spectrum, the estimated molecular weights of ribosomal proteins were calculated. These proteins are responsible for the cellular functioning itself, so-called housekeeping. Besides they being abundant in the prokaryotic content, they are highly conserved, not altering their physiology to different environments or cell stage. The estimated weights formed a presumed database, containing all the information obtained from the NCBI’s repository. This presumed database was generalized at the specie level and later submitted to a machine learning algorithm. With this, it was possible to obtain a microorganism’s classificatory model based on ribosomal proteins values. Using the generated model by the machine learning, a software called Ribopeaks was developed to classify the microorganisms at the specie level with an accuracy of 94.83%, considering the related species. It was also observed the results at genus level, which obtained 98.69% of assertiveness. Values of biological ribosomal molecular masses from the literature were also tested in the acquihired model, obtaining a total assertiveness of 84.48% at the specie level, and 90.51% at the genus level.

This research addresses and illuminates a little understood region of miscible polymer mixtures and demonstrates a new means of separating wax from such blends. The method, termed Deformation Induced Phase Segregation potentially eliminates need of toxic processing solvents for wax removal or recovery in these types of blends. Previous theories of polymer combinations address them exclusively as solutions or as blends, two independent classes having very different behaviors. This study provides bridge connecting these two classes by identifying crossover points between them and the behaviors exhibited therein. The blends of this form were found to be semi-miscible, forming a homogenous phase in the melt but a two-phase system in the solid, with the rheological behavior influenced by the polymer's molecular weight and architecture. It also demonstrates practical promise of this regime by introducing a mechanical compression process to separate the wax phase from such a type of blend. This process potentially permits production of ultra-high molecular weight polyethylene (UHMwPE) films and fibers by melt processing, thereby obviating need of otherwise essential but expensive and environmentally unfriendly toxic solvents.