Neste trabalho foi investigado o processo de relaxação em copolímeros metacrilicos funcionalizados com o grupo cromóforo 4-[N-etil-N-(2-hidroxietil)]amino-2\'-cloro-4\'nitro-azobenzeno (MMADRI3). Os copolímeros sintetizados foram caracterizados por espectrofotometria de visível e infravermelho, calorimetria diferencial de varredura, análise termogravimétrica e elipsometria. O triodo de corona foi utilizado para induzir a orientação dos cromóforos dipolares a temperaturas próximas da transição vítrea. Os valores do coeficiente eletroóptico linear r13 de filmes obtidos por derramento de solução podem alcançar 14 pm/V em amostras funcionalizadas com 43%de cromóforo.O efeito piezoelétricoé significativo para amostras contendo 4% de cromóforo sendo a sua origem atribuída à carga espacial. A relaxação orientacional dos cromóforos foi estudada medindo-se o decaimento do coeficiente eletroóptico e a relaxação dielétrica a diferentes temperaturas. O processo de relaxação foi interpretado utilizando a equação de Kohlraush-Williams-Watts (KWW) aplicada aos domínios do tempo e da freqüência. O tempo de relaxação característico &#964 e o parâmetro b da equação de KWW foram obtidos como função da temperatura desde a temperatura ambiente até acima da temperatura de transição vítrea. O parâmetro b à temperatura de transição vítrea aproxima-se de 0,6 valor que é atribuído a forças de curto alcance. As medidas dielétricas revelaram duas bandas de relaxação &#946 e &#945 respectivamente a baixas e a altas temperaturas. A relaxação a está relacionada com a transição vítrea e à desorientação dos cromóforos. A dependência de &#964 foi fundamentada nas equações de Arrhenius e de Vogel-Fulcher-Tarmnann-Hesse (VFTH), respectivamente a baixas e a altas temperaturas. Os parâmetros de VFTH encontram-se próximos dos considerados universais. O comportamento de &#964 em toda a gama de temperaturas, foi explicado pela equação de Adam-Gibbs, usando-se os parâmetros de VFTH. O resfriamento a taxas lentas após o processo de polarização aumenta substancialmente o tempo de relaxação e a sua energia de ativação. Os expoentes m e n do modelo de Dissado-Hill baseado na interação de multicorpos foram obtidos em função da temperatura. Os valores do parâmetro n ficam dentro do esperado pela teoria / The relaxation process of side-chain methacrylate copolymers functionalized with the nonlinear optical azo chromophore 4-[Nethyl-N-(2-hydroxyethyl)]-amino-2\'-chloro-4-nitroazobenzene (MMADR13) was investigated. The copolymers synthesized were characterized by visible and infrared spectrophotometry, differential scanning calorimetry, thermogravimetric analysis and ellipsometry. The corona triode was employed to induce the orientation of the dipolar chromophore at a temperature near the glass transition. The linear eletrooptic coefficient r13 of cast fllms can reach values as high as 14 pm/V in samples with 43% of chromophore contento The piezoeletric effect attributed to space charge was only significant in the lowest chromophore content samples (4%). Electrostriction was shown to affect to some extent the quadratic electrooptic measurements. The chromophore relaxation at different temperatures was investigated by both electrooptic decay and dielectric measurements. The relaxation process was interpreted using the Kohlraush-Williams-Watts (KWW) equation both in the time and frequency domains. From the KWW equation the characteristic relaxation time &#964 and the stretching parameter b were obtained from room temperature to temperatures above the glass transition. Near the glass transition b is ca 0.6 which is characteristic of short range interactions. Dielectric measurements revealed two relaxation bands, &#946 and &#945, at low and high temperatures, respectively. The &#945 relaxation was attributed to the glass transition and to the 10ss of chromophore orientational order. The temperature behavior of &#964 was interpreted by the Arrhenius and Vogel-Fulcher-Tammann-Hesse (VFTH) equations. at low and high temperatures. respectivelly. The VFTH parameters lie close to the so-called universal values. In addition the overall temperature dependence was explained by the Adam-Gibbs equation using the VFTH parameters. Using a small cooling rate after corona poling increases substantially the relaxation time and the activation energy .The power law exponents m and n. from Dissado-Hill manybody interactions model were obtained as a function of temperature. The n values are in the range of expected values for the many-body interactions model

Les synthèses de polymérisation assistées par micro-ondes sont reconnues pour réduire les temps de chauffe et améliorer des rendements en comparaison à celles effectuées sous chauffage conventionnel. Cette technique étant limitée par la profondeur de pénétration des micro-ondes, un dispositif millifluidique en continu couplé à l’irradiation micro-onde a été développé et étudié. Dans ce travail, une étude des réactions de polymérisation et de copolymérisation d’un couple de monomères (acide acrylique et styrène sulfonate de sodium) a été réalisée. Ces polymères ont été synthétisés par polymérisation radicalaire en réacteur discontinu ouvert sous chauffage conventionnel et sous irradiation micro-ondes dans un premier temps. Dans une seconde partie, ces polymères ont été synthétisés dans un dispositif millifluidique sous chauffage conventionnel et sous irradiation micro-onde. Enfin une dernière partie concerne l’étude de ces synthèses en millifluidique micro-ondes, pour cela un nouveau dispositif, associant micro-ondes et procédé fluidique, a été développé. Un nouvel outil de lecture de la température a été mis en place et l’utilisation d’une sonde chimique interne a été validée. Des synthèses de (co)polymères ont été réalisées et les résultats en termes de cinétiques comparés aux systèmes précédents. / Assisted microwave polymerization syntheses are known to reduce heating time and to improve yields as compared to the syntheses conducted under conventional heating methods. Nevertheless, this technique is limited by the penetration depth of microwaves. Within this work, a millifluidic device coupled to the microwaves irradiation has been developed and studied.Polymerization and copolymerization reactions of both monomers, acid acrylic and sulfonated styrene, were carried out. First, these polymers were synthesized by radical polymerization in a batch reactor under conventional heating and under microwaves irradiation. Secondly, these polymers have been synthesized and compared in a millifluidic device under conventional heating and under microwave irradiation. At last, a specific device has been developed to do the polymerization in millifluidic condition and under microwaves irradiation. A new tool for reading the temperature inside this system was implemented and the use of a chemical probe was validated. (Co)polymers have been obtained and the results, especially in terms of kinetics, have been compared to the above systems.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A solubilidade do fÃrmaco em Ãgua à um fator importante para sua eficÃcia. Entretanto, a maioria dos fÃrmacos apresenta baixa solubilidade em Ãgua. Para resolver este problema, copolÃmeros em bloco com propriedades surfactantes tÃm sido bastante investigados. O objetivo deste trabalho à investigar os copolÃmeros F87 (E62P39E62), E43B14E43 e suas misturas 50/50 a 90/10, com proporÃÃo crescente do copolÃmero mais hidrofÃbico (E43B14E43), a sÃrie de diblocos EmBn para carrear o fÃrmaco modelo griseofulvina atravÃs de diferentes mÃtodos de solubilizaÃÃo e estudar a sua liberaÃÃo, bem como o estudo da solubilizaÃÃo dos fÃrmacos quercetina e mangiferina nos copolÃmeros E65G5 e E65G7E65 visando suas aplicaÃÃes no carreamento e liberaÃÃo controlada de fÃrmacos. Utilizou-se a tÃcnica de inversÃo de tubo para o estudo das propriedades geleificantes dos copolÃmeros F87, E43B14E43 e suas misturas 50/50 a 90/10. Para a determinaÃÃo da concentraÃÃo micelar crÃtica (CMC) utilizou-se o mÃtodo de solubilizaÃÃo de corante medida por fluorescÃncia. A solubilidade dos fÃrmacos griseofulvina, quercetina e mangiferina nos sistemas micelares foi medida por espectrofotometria UV-Vis e para os sistemas dos copolÃmeros E65G5 e E65G7E65 utilizou-se a cromatografia lÃquida de alta eficiÃncia (HPLC). Os copolÃmeros puros e os sistemas contendo os fÃrmacos foram caracterizados por tÃcnicas de espectroscopia de absorÃÃo na regiÃo do infravermelho (FT-IR), espectroscopia RAMAN (FT-RAMAN), raios-X, tamanho de partÃcula por espalhamento de luz dinÃmico (Zetasizer), e experimentos de liberaÃÃo in vitro foram realizados para alguns dos sistemas. Os copolÃmeros F87, E43B14E43, suas misturas, os diblocos da sÃrie EmBn e os copolÃmeros E65G5 e E65G7E65 sÃo promissores para administraÃÃo de fÃrmacos hidrofÃbicos, pois apresentaram bons valores de capacidade de solubilizaÃÃo (Scp). Os copolÃmeros E65G5 e E65G7E65 foram os que mais se destacaram na solubilizaÃÃo da quercetina (HPLC): seu sistema micelar aumentou a solubilidade aquosa da quercetina em 264 vezes a 25 ÂC em ambos os copolÃmeros e 118 e 135 vezes a 37ÂC, no dibloco e tribloco, respectivamente, e suas partÃculas apresentaram total eficiÃncia de encapsulaÃÃo da quercetina. Portanto, o dibloco de glicidil (E65G5) à o melhor copolÃmero para encapsulamento de fÃrmaco. / Most drug candidates fail to progress in their formulations due to its low solubility in water. To resolve this issue, block copolymers with surfactant properties have been well investigated. The objective of this study was to investigate the copolymers F87 (E62P39E62), and mixtures thereof E43B14E43 50/50 to 90/10, with increasing proportion of the more hydrophobic copolymer (E43B14E43), the series of diblock EmBn to carry the model drug through different griseofulvin solubilization methods and study their release, and the study of drug solubilization of quercetin and mangiferin E65G5 the copolymers and their applications in order E65G7E65 Entrainment and controlled release of drugs. We used the technique of inversion of the tube for the study of gelling properties of copolymers F87, and mixtures thereof E43B14E43 50/50 to 90/10. To determine the critical micelle concentration (CMC) used the dye solubilization method measured by fluorescence. The solubility of drugs griseofulvin, quercetin and mangiferin in micellar systems was measured by UV-Vis spectrophotometry and systems of copolymers E65G5 E65G7E65 and used the high performance liquid chromatography (HPLC). The pure copolymers and the systems containing the drugs were characterized by infrared spectroscopy (FT-IR), Raman spectroscopy (FT-Raman), X-rays, particle size by dynamic light scattering (Zetasizer), and experiments in vitro release were carried out for some systems. The copolymers F87, E43B14E43, their mixtures, the number of diblock copolymers and EmBn E65G5 E65G7E65 and are promising for administration of hydrophobic drugs, because they showed good solubilising capacity values ​​(Scp). The copolymers were E65G7E65 E65G5 and those who stood out in solubilization of quercetin (HPLC): its micellar system increased the aqueous solubility of quercetin in 253 times at 25  C for both copolymers and 124 and 142 times at 37  C for the diblock and triblock, respectively, and its particles showed complete encapsulation efficiency of quercetin

L’encapsulation et le relargage à la demande de principes actifs présentent de nombreux avantages et trouvent leur place dans de nombreuses applications, au sein de formulations complexes. Dans cette thèse, nous montrons que la chimie supramoléculaire permet de réaliser des copolymères amphiphiles capables d’encapsuler des composés lipophiles, dispersés en solution aqueuse.L’objectif de ces travaux a été d’élaborer et de caractériser les édifices encapsulants formés par des copolymères amphiphiles supramoléculaires, inspirés des émulsifiants non ioniques commerciaux, les Pluronics®.Dans un premier temps, nous avons synthétisé des copolymères supramoléculaires amphiphiles. Les unités associatives et complémentaires thymine (Thy) et diaminotriazine (DAT), très étudiées dans le domaine des matériaux supramoléculaires, ont été greffées en une étape au(x) extrémité(s) de chaines poly(éthylène) glycol, hydrophiles, et poly(propylène) glycol, hydrophobes, commerciales (Jeffamine®). Les deux unités supramoléculaires s’associent sélectivement par trois liaisons hydrogène parallèles, permettant de former des copolymères amphiphiles. Leur auto-assemblage en solvant sélectif, notamment dans l’eau ou dans des mélanges biphasiques aqueux, conduit à la formation d’objets encapsulants, destinés à des applications cosmétiques.La force et la stabilité de la liaison supramoléculaire Thy/DAT ont été étudiées dans l’eau et dans différents solvants organiques. Les objets formés par l’auto-assemblage des copolymères supramoléculaires ont également été caractérisé par différentes techniques physico-chimiques. L’utilisation des copolymères amphiphiles supramoléculaires s’est révélée concluante pour la stabilisation d’émulsions directes préparées par émulsification spontanée (effet Ouzo). Ainsi, la preuve de concept de l’encapsulation a été établie, les émulsions obtenues s’apparentant à l’encapsulation d’un composé lipophile en phase aqueuse (dispersion liquide-liquide). / The encapsulation and triggerable release of actives display numerous benefits and are used in complex formulations designed for various applications. In this thesis, we show that supramolecular chemistry enables the design of amphiphilic copolymers, capable to encapsulate lipophilic compounds, dispersed in aqueous solution.The goal of this work was to develop and characterize encapsulating objects formed by amphiphilic supramolecular copolymers, inspired by non ionic, commercially available emulsifiers, Pluronics®.As a first step, we synthesized amphiphilic supramolecular copolymers. Associative and complementary units thymine (Thy) and diaminotriazine (DAT), which are largely studied in supramolecular materials subjects, were grafted by a one-step reaction, at the end(s) of poly(ethylene) glycol chains, hydrophilic, and poly(propylene) glycol chains, hydrophobic. Both initial chains are commercially available (Jeffamine®). The two supramolecular units associate selectively by 3 parallel hydrogen bonds, enabling the formation of amphiphilic copolymers. Their self-assembly in a selective solvent, like water, or in a aqueous biphasic mixture, lead to the formation of encapsulating objects, which are designed for a cosmetic application.Strength and stability of Thy/DAT supramolecular bon was investigated in water and in different organic solvents. Objects formed by the self-assembly of the supramolecular copolymers were also characterized by the mean of several techniques. Use of amphiphilic supramolecular copolymers was found conclusive for the stabilization of direct emulsions, formed by spontaneous emulsification (Ouzo effect). Thus, proof on concept was established, emulsions being seen as the encapsulation of a lipophilic compound in an aqueous phase (liquid-liquid dispersion).

The first polysulfenamides were synthesized with S-N and N-S-N bonds along the backbone. We demonstrated that sulfenamides were stable in polar protic and aprotic solvents, but degraded rapidly when exposed to acidic conditions. Microparticles were fabricated from polysulfenamides with S-N bonds, their surfaces were readily functionalized, and they were internalized by cells allowing for intracellular delivery of their cargo. These microparticles were also stable at physiological pH, degraded under acidic conditions, and possessed minimal toxicity towards cells. This work demonstrated that polysulfenamides form the basis for a new set of polymers for drug delivery that greatly differ from prior work in this field. New biodegradable polymers with N-S-N bonds along the backbone were synthesized. These were the first polymers with these bonds and possessed many of the same characteristics as polymers synthesized with S-N bonds. The synthesis and characterization of comb block copolymers with arms composed of poly(lactic acid), poly(butyl acrylate), and poly(styrene-b-vinylpyridine) were described. The self-assembled morphologies in the solid state of comb tri- and tetrablock copolymers with poly(styrene) were also described. These assemblies demonstrated that well-ordered and complex morphologies were assembled from these polymers. The steric effect of substitutions on oxanorbornenes in ring opening metathesis polymerization (ROMP) was investigated. Oxanorbornenes substituted with methyls at the bridgehead positions showed limited reactivity with the Grubbs first and second generation catalysts and the Grubbs first generation methylidene catalyst.

Charge transfer (CT) complexes have been used in a number of radiation polymerisation processes including grafting and curing. The complexes studied include donor (D) monomers like vinyl ethers and vinyl acetate (VA) with acceptor (A) monomers such as maleic anhydride (MA). Both UV and EB have been utilised as radiation sources. The complexes are directly grafted to these substrates in the presence of radiation. The complexes yield novel copolymers when radiation cured with concurrent grafting improving the properties of the finished product. The term cure grafting has been proposed for this concurrent grafting process. Studies in basic photografting work to complement the cure grafting have been proposed. The role of solvent in grafting is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio (DBMR) of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation (EB) systems, is discussed. EB curing and cure grafting of charge transfer (CT) monomer complexes is investigated. The EB results are compared with UV curing and cure grafting of the same complexes. The work has been extended to include EB/UV curing and cure grafting of thiolene systems. The significance of these results in the potential commercial application of these complexes is discussed. Variables affecting the UV/EB curing and cure grafting of thiolenes on cellulose have been studied. These include effect of varying the type of olefin, increasing the functionality of the thiol, use of acrylate monomers and oligomers in hybrid systems, altering the surface structure of the cellulose and finally the role of air in these processes particularly with EB. Photopolymerisation of the thiol-enes in bulk has also been investigated. The thesis content is based on the published work of 14 research papers over the course of the project. / Doctor of Philosophy (PhD)

<p>This thesis describes syntheses and characterization of star-like amphiphilic block copolymers consisting of poly(ethylene glycol) (PEG) as the hydrophilic block,polycarbonate as the hydrophobic block and an amine-containing dendrimer as the core molecule. The macromolecules were synthesized by either a convergent or adivergent approach that includes tandem click reactions and ring opening polymerizations (ROP) of methyl trimethyl carbonates (MTC) with differentfunctionalities. The ROP of MTC monomers was performed using organocatalysts that allow mild reaction condition and reasonable molecular weight distribution(PDI~1.3). These synthetic approaches provide the resultant polymers with three different conformations, which are; mikto-arm type, comb-block with short PEGbrushes, and linear block with long PEG chain. The star-like polymers that were synthesized were all water soluble and most of them formed nano aggregates inwater. Different morphologies were observed in AFM study depending on the polymer conformation. Interestingly, some of them had indications pointing towards alower critical solution temperature.</p>

Poly(acrylic acid) (PAA) was grafted onto both termini of Pluronic F87 (PEO₆₇-PPO₃₉-PEO₆₇) via atom transfer radical polymerization to produce a novel muco-adhesive block copolymer PAA₈₀-b-F₈₇-b-PAA₈₀. It was observed that PAA₈₀-F₈₇-PAA₈₀ forms stable complexes with weakly basic anti-cancer drug, Doxorubicin. Thermodynamic changes due to the drug binding to the copolymer were assessed at different pH by isothermal titration calorimetry (ITC). The formation of the polymer/drug complexes was studied by turbidimetric titration and dynamic light scattering. Doxorubicin and PAA-b-F87-b-PAA block copolymer are found to interact strongly in aqueous solution via non-covalent interactions over a wide pH range. At pH>4.35, drug binding is due to electrostatic interactions. Hydrogen-bond also plays a role in the stabilization of the PAA₈₀-F₈₇-PAA₈₀/DOX complex. At pH 7.4 (α=0.8), the size and stability of polymer/drug complex depend strongly on the doxorubicin concentration. When CDOX <0.13mM, the PAA₈₀-F₈₇-PAA₈₀ copolymer forms stable inter-chain complexes with DOX (110 ~ 150 nm). When CDOX >0.13mM, as suggested by the light scattering result, the reorganization of the polymer/drug complex is believed to occur. With further addition of DOX (CDOX >0.34mM), sharp increase in the turbidity indicates the formation of large aggregates, followed by phase separation. The onset of a sharp enthalpy increase corresponds to the formation of a stoichiometric complex. / Singapore-MIT Alliance (SMA)

The Reversible Addition Fragmentation Chain Transfer (RAFT) process using the new RAFT agent benzyldithiophenyl acetate is shown to be a powerful polymerization tool to synthesize novel well-defined amphiphilic diblock copolymers composed of the constant hydrophobic block poly(butyl acrylate) and of 6 different hydrophilic blocks with various polarities, namely a series of non-ionic, non-ionic comb-like, anionic and cationic hydrophilic blocks. The controlled character of the polymerizations was supported by the linear increase of the molar masses with conversion, monomodal molar mass distributions with low polydispersities and high degrees of end-group functionalization. <br><br> The new macro-surfactants form micelles in water, whose size and geometry strongly depend on their composition, according to dynamic and static light scattering measurements. The micellization is shown to be thermodynamically favored, due to the high incompatibility of the blocks as indicated by thermal analysis of the block copolymers in bulk. The thermodynamic state in solution is found to be in the strong or super strong segregation limit. Nevertheless, due to the low glass transition temperature of the core-forming block, unimer exchange occurs between the micelles. Despite the dynamic character of the polymeric micellar systems, the aggregation behavior is strongly dependent on the history of the sample, i.e., on the preparation conditions. The aqueous micelles exhibit high stability upon temperature cycles, except for an irreversibly precipitating block copolymer containing a hydrophilic block exhibiting a lower critical solution temperature (LCST). Their exceptional stability upon dilution indicates very low critical micelle concentrations (CMC) (below 4∙10^-4 g∙L^-1). All non-ionic copolymers with sufficiently long solvophobic blocks aggregated into direct micelles in DMSO, too. Additionally, a new low-toxic highly hydrophilic sulfoxide block enables the formation of inverse micelles in organic solvents. <br><br> The high potential of the new polymeric surfactants for many applications is demonstrated, in comparison to reference surfactants. The diblock copolymers are weakly surface-active, as indicated by the graduate decrease of the surface tension of their aqueous solutions with increasing concentration. No CMC could be detected. Their surface properties at the air/water interface confer anti-foaming properties. The macro-surfactants synthesized are surface-active at the interface between two liquid phases, too, since they are able to stabilize emulsions. The polymeric micelles are shown to exhibit a high ability to solubilize hydrophobic substances in water. / Amphiphile sind Moleküle, die aus einem hydrophilen und einem hydrophoben Molekülteil aufgebaut sind. Beispiele für Amphiphile sind Tenside, deren makromolekulares Pendant amphiphile Block-Copolymere sind, die häufig auch als Makro-Tenside bezeichnet sind. Ihre Lösungseigenschaften in einem selektiven Lösungsmittel, i.e., ein für einen Block gutes und für den anderen schlechtes Lösungsmittel, sind analog zu denen von Tensiden. Die Unverträglichkeit der Polymersegmente führt zu einer von hydrophoben Wechselwirkungen getriebenen Mikrophasenseparation, d.h. zur Selbstorganisation der amphiphilen Makromoleküle zu Mizellen unterschiedlichster Form, während die kovalente Bindung zwischen den Blöcken eine Makrophasenseparation verhindert. Aufgrund ihres besonderen strukturellen Aufbaus adsorbieren Makro-Tenside an Grenzflächen, was zahlreiche Anwendungen, z.B. zur (elektro)sterischen Stabilisierung von Emulsionen und Dispersionen findet. <br><br> Die vorliegende Arbeit demonstriert, dass die neuen kontrollierten radikalischen Polymerisationen wie die RAFT-Methode („Reversible Addition Fragmentation Chain Transfer“) für die Synthese von neuen wohldefinierten amphiphilen Diblock-Copolymerstrukturen sehr gut geeignet sind. Eine Reihe von neuen amphiphilen Diblock-Copolymeren wurde mittels RAFT synthetisiert, mit einem konstanten hydrophoben Block und verschiedenen hydrophilen Blöcken unterschiedlichster Polaritäten. Die engen Molmassenverteilungen und der lineare Aufstieg der Molmassen mit dem Umsatz belegen den kontrollierten Charakter der Polymerisation. <br><br> Die thermodynamisch favorisierte Selbstorganisation der synthetisierten Blockcopolymere in Wasser führt zur Bildung von Mizellen, deren Eigenschaften aber von der Präparationsmethode stark abhängig sind. Korrelationen zwischen den Mizelleigenschaften und der Blockcopolymerstruktur zeigen, dass die Mizellgröße vor allem von der Länge des hydrophoben Blocks kontrolliert wird, wohindagegen die Natur des hydrophilen Blocks der entscheidende Faktor für die Mizellgeometrie ist. Die gebildeten Mizellen sind besonders stabil gegenüber Verdünnung und Temperaturzyklen, was ein großer Vorteil für eventuelle Anwendungen ist. Wegen der niedrigen Glasübergangstemperatur des hydrophoben Blocks findet ein Austausch von Makromolekülen zwischen den Mizellen statt, d.h. es handelt sich um dynamische Mizellsysteme. <br><br> Das Potential der neuen Makrotenside für Anwendungen wurde untersucht. Die Polymermizellen zeigen eine hohe Kapazität wasserunlösliche Substanzen in Wasser zu solubilisieren. Die Blockcopolymere sind grenzflächenaktiv, d.h. sie adsorbieren an Wasser / Luft oder Wasser / Öl Grenzflächen. Entsprechend sind die Blockcopolymere in der Lage, Emulsionen zu stabilisieren oder als Antischaumsubstanzen zu wirken.

This work presents the synthesis and the self-assembly of symmetrical amphiphilic ABA and BAB triblock copolymers in dilute, semi-concentrated and highly concentrated aqueous solution. A series of new bifunctional bistrithiocarbonates as RAFT agents was used to synthesise these triblock copolymers, which are characterised by a long hydrophilic middle block and relatively small, but strongly hydrophobic end blocks. As hydrophilic A blocks, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA) were employed, while as hydrophobic B blocks, poly(4-tert-butyl styrene), polystyrene, poly(3,5-dibromo benzyl acrylate), poly(2-ethylhexyl acrylate), and poly(octadecyl acrylate) were explored as building blocks with different hydrophobicities and glass transition temperatures. The five bifunctional trithiocarbonates synthesised belong to two classes: the first are RAFT agents, which position the active group of the growing polymer chain at the outer ends of the polymer (Z-C(=S)-S-R-S-C(=S)-Z, type I). The second class places the active groups in the middle of the growing polymer chain (R-S-C(=S)-Z-C(=S)-S-R, type II). These RAFT agents enable the straightforward synthesis of amphiphilic triblock copolymers in only two steps, allowing to vary the nature of the hydrophobic blocks as well as the length of the hydrophobic and hydrophilic blocks broadly with good molar mass control and narrow polydispersities. Specific side reactions were observed among some RAFT agents including the elimination of ethylenetrithiocarbonate in the early stage of the polymerisation of styrene mediated by certain agents of the type II, while the use of the RAFT agents of type I resulted in retardation of the chain extension of PNIPAM with styrene. These results underline the need of a careful choice of RAFT agents for a given task. The various copolymers self-assemble in dilute and semi-concentrated aqueous solution into small flower-like micelles. No indication for the formation of micellar clusters was found, while only at high concentration, physical hydrogels are formed. The reversible thermoresponsive behaviour of the ABA and BAB type copolymer solutions in water with A made of PNIPAM was examined by turbidimetry and dynamic light scattering (DLS). The cloud point of the copolymers was nearly identical to the cloud point of the homopolymer and varied between 28-32 °C with concentrations from 0.01 to 50 wt%. This is attributed to the formation of micelles where the hydrophobic blocks are shielded from a direct contact with water, so that the hydrophobic interactions of the copolymers are nearly the same as for pure PNIPAM. Dynamic light scattering measurements showed the presence of small micelles at ambient temperature. The aggregate size dramatically increased above the cloud point, indicating a change of aggregate morphology into clusters due to the thermosensitivity of the PNIPAM block. The rheological behaviour of the amphiphilic BAB triblock copolymers demonstrated the formation of hydrogels at high concentrations, typically above 30-35 wt%. The minimum concentration to induce hydrogels decreased with the increasing glass transition temperatures and increasing length of the end blocks. The weak tendency to form hydrogels was attributed to a small share of bridged micelles only, due to the strong segregation regime occurring. In order to learn about the role of the nature of the thermoresponsive block for the aggregation, a new BAB triblock copolymer consisting of short polystyrene end blocks and PMDEGA as stimuli-responsive middle block was prepared and investigated. Contrary to PNIPAM, dilute aqueous solutions of PMDEGA and of its block copolymers showed reversible phase transition temperatures characterised by a strong dependence on the polymer composition. Moreover, the PMDEGA block copolymer allowed the formation of physical hydrogels at lower concentration, i.e. from 20 wt%. This result suggests that PMDEGA has a higher degree of water-swellability than PNIPAM. / Die Arbeit behandelt die Synthese und das Selbstorganisationsverhalten von neuen funktionellen symmetrischen "stimuli-responsiven" Triblockcopolymeren ABA und BAB in wässrigen verdünnten und höher konzentrierten Lösungen. Neue symmetrische, bifunktionelle Bistrithiocarbonate wurden als RAFT-Agentien benutzt, um Triblockcopolymere mit langen hydrophilen (A) Innen- und kurzen hydrophoben (B) Außenblöcken zu synthetisieren. Als hydrophile A Blöcke wurden Poly(N-isopropylacrylamid) PNIPAM und Poly(methoxy diethylene glykol acrylat) PMDEGA benutzt, während als hydrophobe Blöcke B Poly(4-tert-butyl styrol), Polystyrol, Poly(3,5-dibromo benzyl acrylat), Poly(2-ethylhexyl acrylat), und Poly(octadecyl acrylat) als Bausteine mit unterschiedlicher Glasübergangstemperatur untersucht wurden. Die Selbstorganisation von ABA und BAB Copolymeren in Wasser mit A Blöcken aus PNIPAM wurde anhand von Trübungsphotometrie, dynamischer Lichtstreuung (DLS) und Rheologie untersucht. Die amphiphilen Blockcopolymere sind direkt wasserlöslich. Bei Konzentrationen von 0.01 bis 50 wt% zeigen Trübungsmessungen bei den Blockcopolymeren wie bei den Homopolymeren eine Übergangstemperatur bei 28-32 °C. Zurückzuführen ist dies auf die Bildung von Mizellen, bei der die hydrophoben Blöcke von einem direkten Kontakt mit Wasser abgeschirmt werden. DLS zeigt kleine Mizellen bei niedrigen Temperaturen und Aggregate mit großem hydrodynamischem Durchmesser bei Temperaturen oberhalb der Übergangstemperatur. Die rheologische Untersuchung von BAB Polymeren zeigt die Bildung von Hydrogelen bei höheren Konzentrationen (über 30-35 wt%). Die minimal benötigte Konzentration, bei der die von Hydrogelen auftreten, nimmt mit wachsender Glasübergangstemperatur ab, und nimmt mit der Länge der hydrophoben Blöcke B zu. Im Unterschied zu PNIPAM zeigen wässrige Lösungen von PMDEGA und seinen Blockcopolymeren reversible Übergangstemperaturen abhängig von der chemischen Struktur. Außerdem bilden PMDEGA Blockcopolymere Hydrogele bei niedriger Konzentration (ab 20 wt%). Dieses Ergebnis deutet darauf hin, dass PMDEGA stärker Wasser bindet als PNIPAM.