Crystalline ZnO photocatalysts with different morphologies prepared at ambient temperature

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Amphiphilic block copolymers based in sucrose methacrylate and methyl methacrylate : synthesis and self-assembly

Orientadores: Maria Isabel Felisberti, Cesar Liberato PetzholdTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuímicaResumo: Copolímeros em bloco e anfifílicos, baseados nos metacrilato de sacarose (SMA) e metacrilato de metila (MMA) foram sintetizados via polimerização controlada por transferência reversível de cadeia adição/fragmentação (RAFT), em duas etapas sequenciais. Copolímeros dibloco foram sintetizados empregando-se o agente de transferência de cadeia (CTA) ditiobenzoato de 2-cianopropila (CPDB), enquanto os copolímeros tribloco foram sintetizados empregando-se o CTA S,S'-Bis(R,R¿ dimetil-R¿¿ ácido acético) -tritiocarbonato (CMP). Nos copolímeros anfifílicos, os blocos hidrofílico e hidrofóbico são o poli(metacrilato de sacarose) (PSMA) e poli(metacrilato de metila) (PMMA), respectivamente. Inicialmente, foram sintetizados homopolímeros, apresentando fragmentos do CTA nas terminações de cadeias, do tipo PMMA-CPDB, PMMA-CMP-PMMA e PSMA-CMP-PSMA, os quais foram empregados como macroCTA para a etapa de copolimerização com SMA ou MMA, dando origem aos copolímeros dibloco P(MMA-b-SMA) e tribloco P(MMA-b-SMA-b-MMA) e P(SMA-b-MMA-b-SMA), respectivamente. O emprego do CTA CMP permitiu a síntese de copolímeros tribloco simétricos em apenas duas etapas de síntese. Os macroCTA se mostraram capazes de promover a extensão da cadeia mesmo após um período de 36 meses de armazenamento a -4°C. MacroCTA e copolímeros foram caracterizados por ressonância magnética nuclear de prótons e carbono (1H e 13C RMN), cromatografia de permeação em gel (GPC), analise calorimétrica diferencial exploratória (DSC), analise termogravimétrica (TGA), difratometria de raios-X (DRX) e solubilidade em diferentes solventes. Os copolímeros apresentaram a capacidade de se organizarem em contato a um solvente seletivo, e também no estado sólido. As estruturas resultantes da organização dos copolímeros no estado sólido e em solução/dispersão foram investigadas por microscopia eletrônica de varredura (SEM), espalhamento dinâmico de luz (DLS), medidas de potencial zeta e espalhamento de raios-X a baixos ângulos (SAXS). Também se mostraram capazes de emulsionar água/óleo e, de encapsular e estabilizar moléculas hidrofóbicas em meio aquoso. Copolímeros contendo fração molar de ~10 mol% de SMA foram solúveis em dimetilformamida (DMF) e apresentaram solubilidade parcial em benzeno, tetrahidrofurano (THF) e água, sendo que nestes solventes os copolímeros se apresentaram na forma de estruturas organizadas dispersas do tipo core-shell vesiculares e com dimensões dependentes da massa molar e configuração dos copolímeros. O caráter anfifílico dos copolímeros foi comprovado por 1H RMN em benzeno e água. As estruturas vesiculares foram observadas por SEM e os diâmetros médios determinados por DLS e SEM. Resultados de SAXS indicaram que os copolímeros dibloco P(MMA-b-SMA) e tribloco P(MMA-b-SMA-b-MMA) e P(SMA-b-MMA-b-SMA) no estado sólido se organizam em estruturas lamelares, cujo período longo aumenta com a massa molar do polímeroAbstract: Amphiphilic block copolymers based on sucrose methacrylate (SMA) and methyl methacrylate (MMA) were synthesized by a two sequential step of reversible addition/fragmentation chain transfer polymerization (RAFT). Diblock and triblock copolymers were synthesized using 2-cyano-2-propyl benzodithioate (CPDB) and S,S'-Bis(R,R'-dimethyl-R"-acetic acid)-trithiocarbonate (CMP) as chain transfer agents (CTA), respectively. The hydrophilic and the hydrophobic blocks of the amphiphilic copolymers are poly(sucrose methacrylate) (PSMA) and poly(methyl methacrylate) (PMMA), respectively. Initially, homopolymers containing fragments of CTA at the chain end PMMA-CPDB, PMMA-CMP-PMMA PSMA-CMP-PSMA, were synthesized and characterized and further used as macroCTA for copolymerization of SMA and MMA, resulting in diblock P(MMA-b-SMA) and triblock P(MMA-b-SMA-b-MMA) and P(SMA-b-MMA-b-SMA) copolymers, respectively. The CTA CMP allowed synthesizing symmetrical triblock copolymers just in two stages. MacroCTA were capable to promote chain extension even after a period of 36 months of storage at -4 ° C MacroCTA and copolymers were characterized by proton and carbon nuclear magnetic resonance (1H and 13C NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and the solubility of the copolymers in different solvents. The copolymers presented the self-assembly capability in contact with a selective solvent, and in solid state. The structures resulting from self-assembly of the copolymers were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential measurements, small angle X-ray scattering (SAXS) and Fourier transform infrared spectroscopy by attenuated total reflectance (FTIR-ATR). In addition, the copolymers were capable to stabilize nonpolar molecules such as benzene, dichloromethane and aromatic dyes in aqueous medium. Copolymers containing ~ 10 mol% of SMA were soluble in dimethylformamide (DMF) and exhibited partial solubility in benzene, tetrahydrofuran (THF) and water. In these solvents, the copolymers presented as dispersed self-assembled structures of the vesicular core-shell type with dimensions dependent on the molar mass and configuration of the copolymers. The amphiphilic feature of the copolymers were demonstrated by 1H NMR in benzene and water. The vesicular structures were observed by SEM and their mean diameters determined by DLS and SEM. SAXS experiments provided evidences of the self-assembly of the diblock copolymers P(MMA-b-SMA) and triblock P(MMA-b-SMA-b-MMA) and P(SMA-b-MMA-b-SMA) in the solid state in lamellar structures with long period dependent on the molar mass of the polymers determined by SAXSDoutoradoFísico-QuímicaDoutor em CiênciasCAPE

Nitric oxide releasing crosslinked poly(vinyl alcohol) films for the increase of dermal vasodilation

Orientador: Marcelo Ganzarolli de OliveiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de QuímicaResumo: Condições fisiológicas associadas à diminuição do nível de óxido nítrico (NO) na vasculatura, como na síndrome de Raynaud e na angiopatia diabética, têm estimulado o desenvolvimento de novos biomateriais capazes de liberar NO topicamente. Neste trabalho efetuamos a modificação do poli(álcool vinílico), PVA, pela sua reticulação química através da esterificação com o ácido mercaptosuccínico. Esta reação permitiu a moldagem de filmes de PVA sulfidrilados (PVA-SH). A calorimetria diferencial de varredura e a difratometria de raios X mostraram que a reação de reticulação suprimiu a cristalização do PVA, levando a um material sem poros, com uma distribuição homogênea de grupos sulfidrila(-SH). Os grupos hidroxila remanescentes na rede de PVA-SH conferiram hidrofilicidade parcial ao material, associada a um grau de intumescimento de 80 a 120 % em meio aquoso. Os filmes de PVA-SH, foram submetidos a uma reação de S-nitrosação dos grupos ¿SH produzindo um PVA contendo grupos S-nitrosotióis (PVA-SNO). Medidas amperométricas e por quimiluminescência mostraram que os filmes de PVA-SNO contém ca. 6 nmols de NO/mg de filme e são capazes de liberar NO espontaneamente após imersão em meio fisiológico. A fluxometria por laser Doppler, usada para medir o fluxo sanguíneo na microcirculação dérmica, permite verificar que a aplicação tópica dos filmes de PVA-SNO hidratados sobre a pele saudável leva a um aumento dependente da dose e do tempo de mais de 5 vezes no fluxo sanguíneo basal em menos de 10 min de aplicação com uma ação prolongada de mais de 4 h durante a aplicação contínua. Estes resultados mostram que os filmes de PVA-SNO podem representar um novo material com potencial para o tratamento tópico no tratamento de desordens microvasculares da peleAbstract: Pathological conditions associated with the impairment of nitric oxide (NO) production in the vasculature, like Raynaud¿s syndrome and diabetic angiopathy, have stimulated the development of new biomaterials capable of delivering NO topically. In this work, we have modified poly(vinyl-alcohol) (PVA) by chemically crosslinking it via esterification with mercaptosuccinic acid. This reaction allowed the casting of sulfhydrylated PVA (PVA-SH) films. Differential scanning calorimetry and X-ray diffractometry showed that the crosslinking reaction suppressed the crystallization of PVA, leading to a non-porous material with a homogeneous distribution of -SH groups. The remaining hydroxyl groups in the PVA-SH network confered partial hydrophylicity to the material, associated with a swelling degree of 80 to 120 % in aqueous medium. The PVA-SH films were subjected to an S-nitrosation reaction of the SH groups yielding a PVA containing S-nitrosothiol groups (PVA-SNO). Amperometric and chemiluminescence measurements showed that the PVA-SNO films contain ca. 6 nmol NO/mg of film and are capable of releasing NO spontaneously after immersion in physiological medium. Laser Doppler-flowmetry, used to assess the blood flow in the dermal microcirculation, showed that the topical application of hydrated PVA-SNO films on the health skin leads to a dose and time dependent increase of more than 5-fold in the dermal baseline blood flow in less than 10 min with a prolonged action of more than 4 h during continuous application. These results show that the PVA-SNO films may represent a new material with potential for the topical treatment of microvascular skin disordersMestradoFísico-QuímicaMestre em Químic

Triblock copolymers based on sucrose methacrylate and methyl methacrylate: RAFT polymerization and self‐assembly

ABA and BAB triblock amphiphilic copolymers based on sucrose methacrylate and methyl methacrylate are synthesized by sequential reversible addition–fragmentation chain transfer polymerization using S ,S ′‐bis(R ,R ′‐dimethyl‐R ′′‐acetic acid)‐trithiocarbonate as a chain transfer agent. The copolymers present narrow molar mass dispersity, controlled molar mass and architecture as determined by gel permeation chromatography and 1H and 13C nuclear magnetic resonance. The copolymers with molar and mass fractions of poly(sucrose methacrylate) block ranging from 1 to 22 mol% and 3 to 52 wt%, respectively, and different molar masses present characteristics of a surfactant such as self‐assembly. The self‐assembly of the triblock copolymers in water, N ,N ‐dimethylformamide (DMF), dichloromethane, tetrahydrofuran, or benzene results mostly in vesicles as confirmed by scanning electron microscopy images and small‐angle X‐ray of the dispersions. Moreover, the copolymers present the capability to stabilize aromatic molecules (Nile Red dye) and nonpolar solvents in an aqueous phase and polar ionic molecules (methylene blue) and water in a nonpolar medium, suggesting the potential for application in drug encapsulation, environmental remediation systems, and molecular extraction in liquid–liquid immiscible systems, for example. Films prepared by casting from copolymer solutions in DMF present a lamellar structure with the lamellar thickness varying according to the copolymer molar mass22110CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP444392/2014‐90012010/17804‐7; 2015/25406‐5; 2016/03394‐

Amphiphilic diblock copolymers based on sucrose methacrylate : RAFT polymerization and self-assembly

Diblock copolymers based on methyl methacrylate and sucrose methacrylate were synthesized by Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization and characterized by 13C and 1H nuclear magnetic resonance and size exclusion chromatography. The copolymers solutions were investigated in terms of solubility, swelling tests and dynamic light scattering in different solvents. Copolymers containing from 5 to 35 mol% of hydrophilic monomer present a typical solubility behavior of amphiphilic polymers and self-assemble capability in solution. While poly(sucrose methacrylate) is water soluble, copolymers self-assemble in water and the highest molar mass copolymers swell, achieving a maximum water swelling ratio of 250%. SEM images of the aggregates formed in water after freeze-drying reveal the presence of monomodal and spherical particles, some of them exhibiting a vesicular structure. The copolymers efficiently promote emulsification of aromatic solvents in water, enabling the transference and stabilization of the aromatic solvent and an aromatic dye in the aqueous phase, suggesting a possible application as delivery systems. Moreover, films of the copolymers prepared by casting from solutions in different solvents are also capable to self-assemble forming mainly lamellar structures, as verified by SAXS. The morphology of dispersed spheres of poly(sucrose methacrylate) throughout a poly(methyl methacrylate) matrix is also observed by AFM and TEM266628639CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP444392/2014-9Não tem2010/17804-7; 2015/25406–5; 2016/03394-8The authors acknowledge CAPES for the scholarship, FAPESP (processes nos. 2010/17804-7, 2015/25406–5 and 2016/03394-8) and CNPq (process no. 444392/2014–9) for the financial support, LNLS for the SAXS beam line time (Proposal 20160505) and LNNano for AFM images (Prop. AFM15635

Eco-Friendly Colloidal Aqueous Sol-Gel Process for TiO2 Synthesis: The Peptization Method to Obtain Crystalline and Photoactive Materials at Low Temperature

This work reviews an eco-friendly process for producing TiO2 via colloidal aqueous sol–gel synthesis, resulting in crystalline materials without a calcination step. Three types of colloidal aqueous TiO2 are reviewed: the as-synthesized type obtained directly after synthesis, without any specific treatment; the calcined, obtained after a subsequent calcination step; and the hydrothermal, obtained after a specific autoclave treatment. This eco-friendly process is based on the hydrolysis of a Ti precursor in excess of water, followed by the peptization of the precipitated TiO2. Compared to classical TiO2 synthesis, this method results in crystalline TiO2 nanoparticles without any thermal treatment and uses only small amounts of organic chemicals. Depending on the synthesis parameters, the three crystalline phases of TiO2 (anatase, brookite, and rutile) can be obtained. The morphology of the nanoparticles can also be tailored by the synthesis parameters. The most important parameter is the peptizing agent. Indeed, depending on its acidic or basic character and also on its amount, it can modulate the crystallinity and morphology of TiO2. Colloidal aqueous TiO2 photocatalysts are mainly being used in various photocatalytic reactions for organic pollutant degradation. The as-synthesized materials seem to have equivalent photocatalytic efficiency to the photocatalysts post-treated with thermal treatments and the commercial Evonik Aeroxide P25, which is produced by a high-temperature process. Indeed, as-prepared, the TiO2 photocatalysts present a high specific surface area and crystalline phases. Emerging applications are also referenced, such as elaborating catalysts for fuel cells, nanocomposite drug delivery systems, or the inkjet printing of microstructures. Only a few works have explored these new properties, giving a lot of potential avenues for studying this eco-friendly TiO2 synthesis method for innovative implementations

Crystalline ZnO Photocatalysts Prepared at Ambient Temperature: Influence of Morphology on p-Nitrophenol Degradation in Water

Since the Industrial Revolution, technological advances have generated enormous emissions of various pollutants affecting all ecosystems. The detection and degradation of pollutants has therefore become a critical issue. More than 59 different remediation technologies have already been developed, such as biological remediation, and physicochemical and electrochemical methods. Among these techniques, advanced oxidation processes (AOPs) have been popularized in the treatment of wastewater. The use of ZnO as a photocatalyst for water remediation has been developing fast in recent years. In this work, the goals are to produce ZnO photocatalysts with different morphologies, by using a green sol-gel process, and to study both the influence of the synthesis parameters on the resulting morphology, and the influence of these different morphologies on the photocatalytic activity, for the degradation of an organic pollutant in water. Multiple morphologies were produced (nanotubes, nanorods, nanospheres), with the same crystalline phase (wurtzite). The most important parameter controlling the shape and size was found to be pH. The photoactivity study on a model of pollutant degradation shows that the resulting activity is mainly governed by the specific surface area of the material. A comparison with a commercial TiO2 photocatalyst (Evonik P25) showed that the best ZnO produced with this green process can reach similar photoactivity without a calcination step