Os processos de separação com membranas estão presentes nas mais diversas aplicações industriais. Em especial, a microfiltração e a ultrafiltração vêm sendo extensivamente utilizadas no tratamento de água e de efluentes. Com o aumento da demanda, muitos estudos têm sido feitos para melhorar o desempenho dos processos com membranas, porém a escolha apropriada da membrana é um fator crucial para atingir esse objetivo. As membranas à base de polietersulfona (PES) estão entre as mais utilizadas industrialmente para esse tipo de aplicação devido às suas excelentes propriedades mecânicas, estabilidade térmica e resistência química. No entanto, por serem pouco hidrofílicas, essas membranas apresentam baixos fluxos de água e elevada tendência ao fouling e ao biofouling. A fim de melhorar essas propriedades, muitos autores têm proposto modificações nas membranas para torná-las mais hidrofílicas e, portanto, aumentar o fluxo de água e diminuir o fouling. Dentro desse contexto, o presente trabalho teve como objetivo preparar membranas de ultrafiltração de PES, utilizando a ftaloil-quitosana (FQ) como aditivo, a fim de se obter membranas com propriedade antifouling. Membranas de PES e PES/FQ foram preparadas pelo processo de inversão de fases e caracterizadas quanto à morfologia, à estrutura química, à estabilidade térmica, ao caráter hidrofílico, à permeância hidráulica, à massa molar de corte (MMC) e ao desempenho em ultrafiltração de solução proteica. As membranas modificadas com o aditivo apresentaram estrutura mais heterogênea e com macrovazios maiores, maior caráter hidrofílico e maior permeância hidráulica. Os resultados de MMC não foram conclusivos. No teste de ultrafiltração, essas membranas apresentaram maiores fluxos e menor tendência ao fouling, indicando que o aditivo utilizado foi adequado na melhoria das propriedades desejadas. A retenção proteica, a perda de fluxo e a recuperação de fluxo após limpezas não apresentaram diferenças significativas. / In recent years, membrane separation processes have been widely used in all kinds of industries and applications. Particularly microfiltration and ultrafiltration have been extensively used for drinking water and wastewater treatments. With the increasing demand, many efforts have been done in order to enhance the process performance, but the choice of the appropriate membrane is a crucial factor to achieve this goal. Polyethersulfone (PES) based membranes are among the most commonly used for such applications due to their excellent chemical resistance, thermal stability and mechanical properties. However, because of its low hydrophilicity, these membranes have low water flux and high fouling and biofouling tendency. In order to improve these properties, many authors have proposed membrane modifications to make them more hydrophilic and thus increase the water flux and reduce fouling. Within this context, this work aimed to prepare PES ultrafiltration membranes using phthaloyl-chitosan (FQ) as an additive in order to obtain membranes with antifouling property. PES and PES/FQ membranes were prepared by phase inversion process and their morphology, chemical structure, thermal stability, hydrophilicity, hydraulic permeance, molecular weight cutoff (MWCO) and performance in ultrafiltration of protein solution were characterized. The membranes modified with additives showed more heterogeneous structure with larger macrovoids, higher hydrophilicity and higher hydraulic permeance. The MWCO results were inconclusive. In the ultrafiltration test, these membranes exhibited higher fluxes and lower fouling tendency, indicating that the additive used was adequate in improving the desired properties. The protein retention, flux reduction and flux recovery after cleaning showed no significant differences.

Os processos de separação com membranas estão presentes nas mais diversas aplicações industriais. Em especial, a microfiltração e a ultrafiltração vêm sendo extensivamente utilizadas no tratamento de água e de efluentes. Com o aumento da demanda, muitos estudos têm sido feitos para melhorar o desempenho dos processos com membranas, porém a escolha apropriada da membrana é um fator crucial para atingir esse objetivo. As membranas à base de polietersulfona (PES) estão entre as mais utilizadas industrialmente para esse tipo de aplicação devido às suas excelentes propriedades mecânicas, estabilidade térmica e resistência química. No entanto, por serem pouco hidrofílicas, essas membranas apresentam baixos fluxos de água e elevada tendência ao fouling e ao biofouling. A fim de melhorar essas propriedades, muitos autores têm proposto modificações nas membranas para torná-las mais hidrofílicas e, portanto, aumentar o fluxo de água e diminuir o fouling. Dentro desse contexto, o presente trabalho teve como objetivo preparar membranas de ultrafiltração de PES, utilizando a ftaloil-quitosana (FQ) como aditivo, a fim de se obter membranas com propriedade antifouling. Membranas de PES e PES/FQ foram preparadas pelo processo de inversão de fases e caracterizadas quanto à morfologia, à estrutura química, à estabilidade térmica, ao caráter hidrofílico, à permeância hidráulica, à massa molar de corte (MMC) e ao desempenho em ultrafiltração de solução proteica. As membranas modificadas com o aditivo apresentaram estrutura mais heterogênea e com macrovazios maiores, maior caráter hidrofílico e maior permeância hidráulica. Os resultados de MMC não foram conclusivos. No teste de ultrafiltração, essas membranas apresentaram maiores fluxos e menor tendência ao fouling, indicando que o aditivo utilizado foi adequado na melhoria das propriedades desejadas. A retenção proteica, a perda de fluxo e a recuperação de fluxo após limpezas não apresentaram diferenças significativas. / In recent years, membrane separation processes have been widely used in all kinds of industries and applications. Particularly microfiltration and ultrafiltration have been extensively used for drinking water and wastewater treatments. With the increasing demand, many efforts have been done in order to enhance the process performance, but the choice of the appropriate membrane is a crucial factor to achieve this goal. Polyethersulfone (PES) based membranes are among the most commonly used for such applications due to their excellent chemical resistance, thermal stability and mechanical properties. However, because of its low hydrophilicity, these membranes have low water flux and high fouling and biofouling tendency. In order to improve these properties, many authors have proposed membrane modifications to make them more hydrophilic and thus increase the water flux and reduce fouling. Within this context, this work aimed to prepare PES ultrafiltration membranes using phthaloyl-chitosan (FQ) as an additive in order to obtain membranes with antifouling property. PES and PES/FQ membranes were prepared by phase inversion process and their morphology, chemical structure, thermal stability, hydrophilicity, hydraulic permeance, molecular weight cutoff (MWCO) and performance in ultrafiltration of protein solution were characterized. The membranes modified with additives showed more heterogeneous structure with larger macrovoids, higher hydrophilicity and higher hydraulic permeance. The MWCO results were inconclusive. In the ultrafiltration test, these membranes exhibited higher fluxes and lower fouling tendency, indicating that the additive used was adequate in improving the desired properties. The protein retention, flux reduction and flux recovery after cleaning showed no significant differences.

Marine biofouling is the accumulation of organisms onto surfaces immersed in sea water. Fouling of ships causes an increase in hydrodynamic drag which leads to performance issues such as increased fuel consumption and a reduced top operating speed. Fouling-release (FR) coatings are one way that paints have been used in combating biofouling by allowing for the easy removal of settled organisms. Traditional FR coatings are silicone elastomers which are soft, easily damaged, and require a tie coat for adhesion to marine primers. Siloxanepolyurethane FR coatings have shown promise as FR coatings, providing enhanced durability and toughness, better adhesion to marine primers, and comparable FR performance to commercial coatings. Preliminary studies were conducted to explore the use of PDMS macromers in the preparation of siloxane-polyurethane FR coatings. Attachment and removal of fouling organisms on the siloxane-polyurethane coatings based on PDMS macromers was comparable to commercial FR coatings. Extended water aging was also carried out to determine effects of extended water immersion on the fouling-release performance of the coatings. At up to four weeks of aging, the FR performance of the coatings was not affected. Static immersion marine field testing was performed to determine the fouling-release performance of siloxane-polyurethane coatings prepared with PDMS macromers. The performance was found to be comparable to commercial FR coatings for up to one year, including water jet removal of slimes, barnacle push-off removal, and soft sponging. The coatings showed good fouling-release performance until extremely heavy fouling was allowed to settle. Underwater hull cleaning was conducted for one siloxane-polyurethane composition identified as a top performer from static field testing. The coating was easily cleaned of fouling with rotating brushes for six months. The cleaning capability of the coating was reduced when large barnacles and other extremely heavy fouling was present. A commercial FR coating became heavily damaged with brush cleaning while the siloxane-polyurethane coating remained mostly undamaged. With more frequent cleaning, it is suspected that siloxanepolyurethane coatings would show cleaning capability for longer periods of time. Pigmentation of siloxane-polyurethane coatings based on difunctional PDMS and PDMS macromers was explored to investigate the effect on FR performance. Pigmentation with titanium dioxide caused a slight decrease in FR performance in some cases, but this was easily overcome by the addition of slightly more PDMS in the coating binder, thus illustrating the feasibility of siloxane-polyurethane coatings as effective, pigmented FR coatings. Finally, the exploration of unique PDMS polymer architectures has been explored for the development of additional, novel, fouling-release coatings. The incorporation of end-functional PDMS homopolymer molecular brushes and branched PDMS macromers into siloxane-polyurethane fouling-release coatings shows promise for the development of unique coatings where improved FR performance may be obtained. / Office of Naval Research (U.S.)

<p>Medical devices are at risk of biofouling within seconds after implantation, which can lead to thrombus formation and bacterial contamination. These issues can negatively impact the performance and reliability of the device. Poly(vinyl chloride) (PVC) and polyurethane (PU) are popular synthetic polymers used in biomedical applications, but their hydrophobic nature makes them susceptible to biofouling. To improve their biocompatibility, their surfaces must be modified to be antifouling. However, achieving a thoroughly coated surface through homogeneous activation and effective modification with antifouling polymers remains a challenge, despite recent advancements in polymer surface modification. In this dissertation, we modified the surfaces of medical-grade PVC and PU using hydrophilic and biocompatible polymer brushes via wet chemistry approaches in an aqueous medium. Specifically, we activated the PVC surface with amino groups and then modified it with either modified or synthesized hydrophilic polymers end-capped with reactive groups. Additionally, we coupled a functionalized surface initiator to the activated PVC surface to allow the grafting of different hydrophilic polymers via conventional <em>in situ</em> free-radical polymerization. We followed a similar process to activate the PU surface with amino groups and then coupled a co-initiator derivative to allow the grafting of different hydrophilic polymers via conventional <em>in situ</em> free radical polymerization as a redox initiation system. All the modified surfaces of PVC and PU have exhibited a significant increase in wettability, as well as extremely effective antifouling effects against cell and bacterial adhesion. Overall, the findings of this work demonstrate the applicability of wet chemistry surface modification for PVC- or PU-based medical devices and supplies in biofouling-resistant applications. </p>

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Marine biofouling has troubled mankind, both environmentally and economically, since they set sail, resulting in many undesired consequences such as increased drag, reduced maneuverability, increased fuel consumption and greenhouse gas emissions, and heightened maintenance costs. This problem is highly complex as it involves more than 4000 marine organisms with varying modes of adhesion and surface preferences as well as many aquatic environments. The common state-of-the-art approaches to contend with marine biofouling on the submerged surfaces of ships in seawater has antifouling (AF) and fouling-release (FR) surfaces. As AF coating systems utilize biocides which are often toxic to the environment to prevent settlement of biofoulants, the endeavors have been shifted towards non-toxic FR marine system. Many FR systems take advantage of low surface energy and modulus polydimethylsiloxane (PDMS) on their surface, while the recent attempts explored the simultaneous effect of PDMS and hydrophilic moieties (i.e. polyethylene glycol (PEG) or zwitterionic polymers) on an FR surface, known as amphiphilic surfaces. Thus, the work in this dissertation focused on attaining amphiphilic surfaces with desirable FR performance. The studies in this dissertation were investigated to deliver two goals: 1) Enhancing the (FR) fouling-release performance of previously developed coating systems; 2) Introducing novel fouling-release marine coatings with set criteria. To address the former, a series of amphiphilic additives containing PDMS and hydrophilic polymers (zwitterionic-based or PEG) were prepared in chapters two-five. These additives were incorporated in several previously developed FR coating systems in order to modify their surfaces and enhance their FR performance. To address the latter, two amphiphilic marine coating systems were explored for accessing durable, non-toxic, and effective FR surfaces using epoxy-amine crosslinking chemistry. Overall, the studies in this dissertation not only demonstrated viable FR surfaces with desirable performance against several representative marine organisms such as N. incerta, U. linza, C. lytica, barnacles, and mussels but also contributed a deeper understanding about the effect of amphiphilicity concentration/balance on surface and FR properties.

Barnacles are dominant hard–fouling organisms in marine waters. They attach to substrates by secreting a complex proteinaceous adhesive. Understanding the chemical composition of this multi–protein underwater adhesive and how it is affected by environmental variables, such as oceanic temperatures, is critical for developing nontoxic solutions to control biofouling. Previous experiments in our lab revealed an inverse relationship between critical removal stress (CRS) and temperatures at which barnacles were reared. Further investigations showed that this correlation is not attributed to differences in physical properties such as barnacle size or short–term changes in the viscosity of adhesive. Therefore, the observed effects may be influenced by a physiological response to temperature during initial growth and development. We hypothesized that rearing temperature affects the expression of proteins found in the adhesive matrix. To elucidate the underlying mechanisms responsible for the temperature effect, we analyzed uncured barnacle adhesive using two-dimensional gel electrophoresis (2DGE) and matrix-assisted laser desorption/ionization-tandem time-of-flight (MALDI-TOF/TOF) mass spectrometry (MS). In our analysis, we 1) detected differences in protein expression at two experimental temperatures (15°C and 25°C) and 2) identified several proteins that may serve functional roles in the process of adhesion. Our data are also consistent with a model that the curing process of barnacle adhesive may be analogous to the process of wound healing in animals.

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Industries (food, beverage, petrochemical, etc.) normally use various gravitational separation echniques in their processes. Such separation processes often suffer from the deposition of undesirable material on the active surfaces of the process equipment, e.g. a high-speed separator or decanter, causing a slew of problems with the process or product quality. To restore operational efficiencies, additional cleaning steps using both water and chemicals are required, making the process more expensive and less environmentally friendly. Other than operating time and concentration of the process fluid there are several factors such as surface nature, surface roughness, type of material, surface charge, etc which influence the fouling deposition of surfaces. Fouling on the surfaces can grow following different mechanisms. The goal of this research work is to learn more about the nature of foulant interactions with stainless steel surfaces and eventually design some antifouling methodology. It is too difficult to study foulingfor all kinds of solutions and industries, so we tried to investigate the organic deposition in dairy and brewery industries by using lab-scale synthesized milk and beer solutions, For quantitative and statistical examination of these characteristics, several experimental approaches (FTIR, percent weight change, surface roughness, surface energy) were used. It was confirmed that fouling grows on the surfaces in a non-linear fashion irrespective of the time and concentration of the solution. The fouling of surfaces can be improved by producing more hydrophilic surfaces or by reducing surface roughness. Steric hindrance, electrostatic charge, and water barrier or hydration layer theories can be used to modify the surface nature and hence the fouling deposition. For antifouling purposes, PMMA (organic) and tungsten oxide (inorganic) coatings were employed. The PMMA was deposited using a dip-coating technique using (6%,10%, and 12%) PMMA solution, and the tungsten oxide coating was carried out by using a standard two electrode electrochemical system under different voltage (3.5V and 4.5V) and time (5min, 10 min, and 20 min) conditions. The coatings were characterized by using different techniques and their antifouling effects were studied in model milk and model beer solutions / Vid industriella processer (livsmedel, petrokemisk etc.) används ofta olika tekniker för separation med hjälp av gravitation. Sådana separationsprocesser drabbas ofta av oönskade beläggningar och påväxt på processutrustningens aktiva ytor så som t.ex. i en separator eller en dekanter, vilket orsakar problem med processen eller produktkvaliteten. För att återställa driftseffektivitet krävs särskilda rengöringssteg med både vatten och kemikalier vilket gör processen dyrare och mindre miljövänlig. Förutom drifttid och processvätskans sammansättning finns det flera faktorer såsom ytbeskaffenhet, ytjämnhet, materialtyp, ytladdning m.m. som påverkar mängden oönskade beläggningar på ytor. Föroreningarna på ytor kan tillväxa med olika mekanismer. Målet med detta forskningsarbete är att studera interaktionen mellan olika former av påväxt och ytan på rostfritt stål och senare utforma metoder för att förhindra bildandet av sådana oönskade beläggningar. Det är en stor utmaning att studera olika typer av påväxt för alla typer av flöden och industrier. I studien undersöktes organisk påväxt inom mejeri- och bryggeriindustrin genom att använda syntetiserade mjölk- och ölprodukter i laboratorieskala, för kvantitativa och statistiska undersökningar av dessa egenskaper. Flera olika experimentella metoder användes (FTIR, viktförändring, ytjämnhet, ytenergi). Det bekräftades att tillväxten på ytorna var olinjärt oavsett tid och lösningens koncentration. Bildandet och tillväxt av oönskade beläggningar kan minskas med hjälp av mera hydrofila ytor eller genom att minska ytans ojämnhet. Steriska hinder, elektrostatisk laddning och vattenbarriär eller hydratiseringsskal kan användas för att modifiera ytan och därmed fördröja bildandet av oönskade beläggningar. För att förhindra påväxt belades ytan med PMMA (organisk) och volframoxid (oorganisk). PMMA deponerades genom en doppbeläggningsteknik med användning av (6%, 10% och 12%) PMMA-lösning och volframoxidbeläggningen utfördes med ett elektrokemiskt tvåelektrodssystem med olika spänningar (3,5V och 4,5V) och tider (5min, 10min och 20min). Ytbeläggningarna karakteriserades genom att använda olika tekniker och deras förmåga att förhindra snabb påväxt studerades i modellösningar av mjölk och öl.

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