Hidrótropos são uma classe de compostos, que em alta concentração, aumentam a solubilidade de uma variedade de compostos hidrofóbicos em água. A principal propriedade dos hidrótropos está relacionada a MHC (concentração hidrotrópica mínima) na qual os hidrótopos começam a agregar. Neste trabalho, uma série de compostos aromáticos que mostram o efeito hidrotrópico foram usados: xileno sulfonato de sódio, salicilato de sódio, p-tolueno sulfonato de sódio, benzoato de sódio e estireno sulfonato de sódio. Diferentes técnicas foram utilizadas para avaliar a MHC, tais como, condutividade, tensão superficial, espalhamento de luz, viscosidade e fluorescência. A espectroscopia de fluorescência foi utilizada para determinar por sonda interna e externa , o grupo fenil do anel dos compostos, é utilizada como uma sonda fluorescente interna. A contribuição da intensidade dos monômeros e excímeros (Iaggr/Imonomol) foram determinados e o pireno foi utilizado como uma sonda externa determinando as intesidades relativas I1/I3. Foi observado que os valores de MHC determinados pelos diferentes métodos são concordantes entre si. O método baseado na intensidade de emissão agregado / monomol, apresentou vantagens quando comparado com outros métodos, pois não requer o uso de sondas ou aditivos, que proporcionariam a desagregação dos hidrótropos. / Hydrotropes are a class of compounds that, at a high concentration, enhance the solubility of a variety of hydrophobic compounds in water. The main property of the hydrotropes is related to the MCH (minimum hydrotropic concentration) at which hydrotropes start to aggregate. In this work, a series of aromatics compounds that showed hydrotropic effects is used: sodium xylenesulfonate, sodium salicylate, sodium p-toluenesulfonate, sodium benzoate and sodium styrenesulfonate. Different techniques were used to evaluate the MHC, like as: conductivity, surface tension, light scattering, viscosity and fluorescence. The fluorescence spectroscopy was used to determine the MHC by external and internal probe; the moiety phenyl of compounds ring served as the internal fluorescence probe. Intensities of the monomer and excimer contributions (Iaggr/Imonomol) were determined and the pyrene was used as external probe measuring the ratio of intensities I1/I3. It is shown that MHC values determined by different methods agree well. The method based on the aggregate to monomol emission ratio showed advantages when compared to the other method, because it doesn\'t require the use of probes or other additives, which might disrupt the aggregation process.

Hidrótropos são uma classe de compostos, que em alta concentração, aumentam a solubilidade de uma variedade de compostos hidrofóbicos em água. A principal propriedade dos hidrótropos está relacionada a MHC (concentração hidrotrópica mínima) na qual os hidrótopos começam a agregar. Neste trabalho, uma série de compostos aromáticos que mostram o efeito hidrotrópico foram usados: xileno sulfonato de sódio, salicilato de sódio, p-tolueno sulfonato de sódio, benzoato de sódio e estireno sulfonato de sódio. Diferentes técnicas foram utilizadas para avaliar a MHC, tais como, condutividade, tensão superficial, espalhamento de luz, viscosidade e fluorescência. A espectroscopia de fluorescência foi utilizada para determinar por sonda interna e externa , o grupo fenil do anel dos compostos, é utilizada como uma sonda fluorescente interna. A contribuição da intensidade dos monômeros e excímeros (Iaggr/Imonomol) foram determinados e o pireno foi utilizado como uma sonda externa determinando as intesidades relativas I1/I3. Foi observado que os valores de MHC determinados pelos diferentes métodos são concordantes entre si. O método baseado na intensidade de emissão agregado / monomol, apresentou vantagens quando comparado com outros métodos, pois não requer o uso de sondas ou aditivos, que proporcionariam a desagregação dos hidrótropos. / Hydrotropes are a class of compounds that, at a high concentration, enhance the solubility of a variety of hydrophobic compounds in water. The main property of the hydrotropes is related to the MCH (minimum hydrotropic concentration) at which hydrotropes start to aggregate. In this work, a series of aromatics compounds that showed hydrotropic effects is used: sodium xylenesulfonate, sodium salicylate, sodium p-toluenesulfonate, sodium benzoate and sodium styrenesulfonate. Different techniques were used to evaluate the MHC, like as: conductivity, surface tension, light scattering, viscosity and fluorescence. The fluorescence spectroscopy was used to determine the MHC by external and internal probe; the moiety phenyl of compounds ring served as the internal fluorescence probe. Intensities of the monomer and excimer contributions (Iaggr/Imonomol) were determined and the pyrene was used as external probe measuring the ratio of intensities I1/I3. It is shown that MHC values determined by different methods agree well. The method based on the aggregate to monomol emission ratio showed advantages when compared to the other method, because it doesn\'t require the use of probes or other additives, which might disrupt the aggregation process.

O meio hidrotrópico tem sido intensamente explorado pela indústria a fim de melhorar a solubilização de substâncias pouco solúveis em água. Os hidrótropos são compostos anfifílicos, como os surfactantes, mas os microdomínios formados não têm estruturas bem organizadas como as micelas. O mecanismo de solubilização hidrotrópica não está completamente elucidado. Muitos esforços têm sido feitos nesse sentido tanto em nosso grupo quanto por outros pesquisadores. Os alginatos também formam microdomínios em solução e tem sido bastante estudados devido a suas aplicações na agricultura, farmácia, medicina, dentre outras. Sabe-se que as propriedades fotofísicas de corantes são sensíveis ao meio no qual eles se encontram. Neste trabalho as propriedades fotofísicas do corante pseudoisocianina (PIC) foram determinadas em soluções hidrotrópicas de toluenossulfonato de sódio (TSS) e estirenossulfonato de sódio (ESS), em soluções de metanol, etanol, butanol e etilenoglicol, bem como em solução aquosa de alginato de sódio. Estes estudos também agregam informações para a compreensão do comportamento dos hidrótropos em solução aquosa, usando-se o corante PIC como sonda fotofísica. / Hydrotropic media have been intensively explored by industry to improve the solubilization of poorly water-soluble substances. Hydrotropes are amphiphilic compounds, such as surfactants, that form microdomains that are not as wellorganized as micelles. The mechanism of hydrotropic solubilization is not completely elucidated. Much effort has been done towards this end, in our group and by other researchers. Alginates also form microdomains in solution and have been largely studied due to their applications in agriculture, pharmacy, medicine, among others. It is well-known that the photophysical properties of dyes depend on the environment in which they are placed. In this work, photophysical properties of the dye pseudoisocyanine (PIC) have been determined in hydrotropic solutions of sodium toluenesulphonate (TSS) and sodium styrenesulphonate (ESS), in solutions of methanol, ethanol, butanol and etileneglycol, as well as in sodium alginate aqueous solution. This study also adds information to the understanding of hydrotrope behaviour in aqueous solution by using PIC as a photophysical probe.

O meio hidrotrópico tem sido intensamente explorado pela indústria a fim de melhorar a solubilização de substâncias pouco solúveis em água. Os hidrótropos são compostos anfifílicos, como os surfactantes, mas os microdomínios formados não têm estruturas bem organizadas como as micelas. O mecanismo de solubilização hidrotrópica não está completamente elucidado. Muitos esforços têm sido feitos nesse sentido tanto em nosso grupo quanto por outros pesquisadores. Os alginatos também formam microdomínios em solução e tem sido bastante estudados devido a suas aplicações na agricultura, farmácia, medicina, dentre outras. Sabe-se que as propriedades fotofísicas de corantes são sensíveis ao meio no qual eles se encontram. Neste trabalho as propriedades fotofísicas do corante pseudoisocianina (PIC) foram determinadas em soluções hidrotrópicas de toluenossulfonato de sódio (TSS) e estirenossulfonato de sódio (ESS), em soluções de metanol, etanol, butanol e etilenoglicol, bem como em solução aquosa de alginato de sódio. Estes estudos também agregam informações para a compreensão do comportamento dos hidrótropos em solução aquosa, usando-se o corante PIC como sonda fotofísica. / Hydrotropic media have been intensively explored by industry to improve the solubilization of poorly water-soluble substances. Hydrotropes are amphiphilic compounds, such as surfactants, that form microdomains that are not as wellorganized as micelles. The mechanism of hydrotropic solubilization is not completely elucidated. Much effort has been done towards this end, in our group and by other researchers. Alginates also form microdomains in solution and have been largely studied due to their applications in agriculture, pharmacy, medicine, among others. It is well-known that the photophysical properties of dyes depend on the environment in which they are placed. In this work, photophysical properties of the dye pseudoisocyanine (PIC) have been determined in hydrotropic solutions of sodium toluenesulphonate (TSS) and sodium styrenesulphonate (ESS), in solutions of methanol, ethanol, butanol and etileneglycol, as well as in sodium alginate aqueous solution. This study also adds information to the understanding of hydrotrope behaviour in aqueous solution by using PIC as a photophysical probe.

The properties of a series of well-defined new surfactant oligomers (dimers to tetramers)were examined. From a molecular point of view, these oligomeric surfactants consist of simple monomeric cationic surfactant fragments coupled via the hydrophilic ammonium chloride head groups by spacer groups (different in nature and length). Properties of these cationic surfactant oligomers in aqueous solution such as solubility, micellization and surface activity, micellar size and aggregation number were discussed with respect to the two new molecular variables introduced, i.e. degree of oligomerization and spacer group, in order to establish structure – property relationships. Thus, increasing the degree of oligomerization results in a pronounced decrease of the critical micellization concentration (CMC). Both reduced spacer length and increased spacer hydrophobicity lead to a decrease of the CMC, but to a lesser extent. For these particular compounds, the formed micelles are relatively small and their aggregation number decreases with increasing the degree of oligomerization, increasing spacer length and sterical hindrance. In addition, pseudo-phase diagrams were established for the dimeric surfactants in more complex systems, namely inverse microemulsions, demonstrating again the important influence of the spacer group on the surfactant behaviour. Furthermore, the influence of additives on the property profile of the dimeric compounds was examined, in order to see if the solution properties can be improved while using less material. Strong synergistic effects were observed by adding special organic salts (e.g. sodium salicylate, sodium vinyl benzoate, etc.) to the surfactant dimers in stoichiometric amounts. For such mixtures, the critical aggregation concentration is strongly shifted to lower concentration, the effect being more pronounced for dimers than for analogous monomers. A sharp decrease of the surface tension can also be attained. Many of the organic anions produce viscoelastic solutions when added to the relatively short-chain dimers in aqueous solution, as evidenced by rheological measurements. This behaviour reflects the formation of entangled wormlike micelles due to strong interactions of the anions with the cationic surfactants, decreasing the curvature of the micellar aggregates. It is found that the associative behaviour is enhanced by dimerization. For a given counterion, the spacer group may also induce a stronger viscosifying effect depending on its length and hydrophobicity. Oppositely charged surfactants were combined with the cationic dimers, too. First, some mixtures with the conventional anionic surfactant SDS revealed vesicular aggregates in solution. Also, in view of these catanionic mixtures, a novel anionic dimeric surfactant based on EDTA was synthesized and studied. The synthesis route is relatively simple and the compound exhibits particularly appealing properties such as low CMC and σCMC values, good solubilization capacity of hydrophobic probes and high tolerance to hard water. Noteworthy, mixtures with particular cationic dimers gave rise to viscous solutions, reflecting the micelle growth. / Die Eigenschaften einer Reihe gut definierter neuer oligomerer Tenside (von Dimeren bis zu Tetrameren) wurden untersucht. Strukturell bestehen diese oligomeren Tenside aus einfachen monomeren kationischen Tensidfragmenten, die über die hydrophile Kopfgruppe (Tetraalkyl-Ammoniumchlorid) durch „Spacer“-Gruppen unterschiedlicher Natur und Länge miteinander verbunden/gekoppelt sind. Die Eigenschaften dieser kationischen oligomeren Tenside in wässriger Lösung wie Löslichkeit, kritische Mizellbildungskonzentration und Oberflächenaktivität, Mizellgröße und Aggregationszahl werden in Bezug auf die zwei neuen molekularen Variabeln (d.h. dem Oligomerisationsgrad und der Spacer-Gruppe) untersucht, um Struktur-Eigenschafts-Beziehungen abzuleiten. Die Erhöhung des Oligomerizationsgrads verringert stark die kritische Mizellbildungskonzentration (CMC). Eine kurze Spacer-Länge oder ein erhöhte Hydrophobie des Spacers erniedrigt die CMC ebenfalls, aber in einem geringeren Umfang. Die gebildeten Mizellen sind relativ klein und ihre Aggregationszahl nimmt mit zunehmendem Oligomerisationsgrad ab, genau wie mit zunehmender Spacerlänge oder sterischer Behinderung. Außerdem wurden Pseudo-Phasendiagramme für die Gemini-Tenside in komplexen Systemen, nämlich in inversen Mikroemulsionen untersucht. Auch hier zeigt die Spacer-Gruppe einen großen Einfluß auf das Tensidverhalten. Weiterhin wurde der Einfluss von Zusätzen auf das Eigenschaftsprofil der dimeren Tenside untersucht. Starke Synergien wurden beobachtet, wenn man spezielle organische Anionen (z.B. Natriumsalicylat, Natriumvinylbenzoat, etc.) zu den dimeren Tensiden in stöchiometrischen Mengen hinzugibt. Für solche Mischungen wird die Mizellbildungskonzentration stark zu niedrigen Konzentrationen verschoben, wobei der Effekt für die Dimere ausgeprägter als für die analogen Monomere ist. Eine Verringerung der Oberflächenspannung wird ebenfalls erreicht. Gemini-Tenside mit geeigneten Spacer-Gruppen bilden nach Zugabe ausgewählter organischer Anionen viskoelastische Lösungen, selbst wenn die dimeren Tenside nur über relativ kurz Alkylketten verfügen. Dies wurde mittels rheologischer Messungen gezeigt. Dieses Verhalten resultiert aus der Bildung langer Zylinder-Mizellen aufgrund der starken Wechselwirkung der Anionen mit den kationischen Tensiden, die die Krümmung der mizellaren Strukturen verringern. Es wurde auch festgestellt, dass das assoziative Verhalten durch die Dimerisation erhöht wird. Für ein gegebenes Gegenion kann die Spacer-Gruppe den verdickenden Effekt verstärken, in Abhängichkeit von seiner Länge und Hydrophobie. Als weitere Zusätze wurden entgegengesetzt geladene Tenside wurden mit den kationischen Dimeren kombiniert. Einige Mischungen mit dem käuflichen anionischen Tensid SDS bilden Vesikel in Lösung. Mit Blick auf diese katanionischen Mischungen wurde ein neues anionisches Gemini-Tensid, das auf EDTA basiert ist, synthetisiert und charakterisiert. Der Syntheseweg ist relativ einfach und das Tensid zeigt interessante Eigenschaften wie niedrige CMC- und scmc-Werte, gute Solubilisierungskapazität von hydrophoben Substanzen und hohe Toleranz gegen hartes Wasser. Mischungen dieses anionischen Tensids mit bestimmten kationischen Dimeren bilden visköse Lösungen, was ein starkes Mizell-Wachstum widerspiegelt.