@phdthesis{Stahlhut2016,
  author    = {Stahlhut, Frank},
  title     = {Entwicklung neuer triphiler, fluorkohlenstofffreier Blockcopolymere und Untersuchung ihrer Eigenschaften f{\"u}r Multikompartiment-Mizellen},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-96299},
  school      = {Universit{\"a}t Potsdam},
  pages     = {iv, 191},
  year      = {2016},
  abstract  = {Neue Systeme f{\"u}r triphile, fluorkohlenstofffreie Blockcopolymere in Form von Acrylat-basierten thermoresponsiven Blockcopolymeren sowie Acrylat- bzw. Styrol-basierten Terblock-Polyelektrolyten mit unterschiedlich chaotropen Kationen des jeweiligen polyanionischen Blocks wurden entwickelt. Multikompartiment-Mizellen, mizellare Aggregate mit ultrastrukturiertem hydrophobem Mizellkern die biologischen Strukturen wie dem Humanalbumin nachempfunden sind, sollten bei der Selbstorganisation in w{\"a}ssriger Umgebung entstehen. Durch Verwendung apolarer und polarer Kohlenwasserstoff-Dom{\"a}nen anstelle von fluorophilen Fluorkohlenstoff-Dom{\"a}nen sollte erstmals anhand solcher triphilen Systeme nachgewiesen werden, ob diese in der Lage zur selektiven Aufnahme hydrophober Substanzen in unterschiedliche Dom{\"a}nen des Mizellkerns sind. Mit Hilfe von sequentieller RAFT-Polymerisation wurden diese neuen triphilen Systeme hergestellt, die {\"u}ber einen permanent hydrophilen, eine permanent stark hydrophoben und einen dritten Block verf{\"u}gen, der durch externe Einfl{\"u}sse, speziell die Induzierung eines thermischen Coil-to-globule-{\"U}bergangs bzw. die Zugabe von organischen, hydrophoben Gegenionen von einem wasserl{\"o}slichen in einen polar-hydrophoben Block umgewandelt werden kann. Als RAFT-Agens wurde 4-(Trimethylsilyl)benzyl(3-(trimethylsilyl)-propyl)-trithiocarbonat mit zwei unterschiedlichen TMS-Endgruppen verwendet, das kontrollierte Reaktions-bedingungen sowie die molekulare Charakterisierung der komplexen Copolymere erm{\"o}glichte. Die beiden Grundtypen der linearen tern{\"a}ren Blockcopolymere wurden jeweils in zwei 2 Modell-Systeme, die geringf{\"u}gig in ihren chemischen Eigenschaften sowie in dem Blockl{\"a}ngenverh{\"a}ltnis von hydrophilen und hydrophoben Polymersegmenten variierten, realisiert und unterschiedliche Permutation der Bl{\"o}cke aufwiesen. Als ersten Polymertyp wurden amphiphile thermoresponsive Blockcopolymere verwendet. Modell-System 1 bestand aus dem permanent hydrophoben Block Poly(1,3-Bis(butylthio)-prop-2-yl-acrylat), permanent hydrophilen Block Poly(Oligo(ethylenglykol)monomethyletheracrylat) und den thermoresponsiven Block Poly(N,N'-Diethylacrylamid), dessen Homopolymer eine LCST-Phasen{\"u}bergang (LCST, engl.: lower critical solution temperature) bei ca. 36°C aufweist. Das Modell-System 2 bestand aus dem permanent hydrophilen Block Poly(2-(Methylsulfinyl)ethylacrylat), dem permanent hydrophoben Block Poly(2-Ethylhexylacrylat) und wiederum Poly(N,N'-Diethylacrylamid). Im tern{\"a}ren Blockcopolymer erh{\"o}hte sich, je nach Blocksequenz und relativen Blockl{\"a}ngen, der LCST-{\"U}bergang auf 50 - 65°C. Bei der Untersuchung der Selbstorganisation f{\"u}r die Polymer-Systeme dieses Typs wurde die Temperatur variiert, um verschieden mizellare {\"U}berstrukturen in w{\"a}ssriger Umgebung zu erzeugen bzw. oberhalb des LCST-{\"U}bergangs Multikompartiment-Mizellen nachzuweisen. Die Unterschiede in der Hydrophilie bzw. den sterischen Anspr{\"u}che der gew{\"a}hlten hydrophilen Bl{\"o}cke sowie die Variation der jeweiligen Blocksequenzen erm{\"o}glichte dar{\"u}ber hinaus die Bildung verschiedenster Morphologien mizellarer Aggregate. Der zweite Typ basierte auf ein Terblock-Polyelektrolyt-System mit Polyacrylaten bzw. Polystyrolen als Polymerr{\"u}ckgrat. Polymere ionische Fl{\"u}ssigkeiten wurden als Vorlage der Entwicklung zweier Modell-Systeme genommen. Eines der beiden Systeme bestand aus dem permanent hydrophilen Block Poly(Oligo(ethylenglykol)monomethyletheracrylat, dem permanent hydrophoben Block Poly(2-Ethylhexylacrylat) sowie dem Polyanion-Block Poly(3-Sulfopropylacrylat). Die Hydrophobie des Polyanion-Blocks variierte durch Verwendung großer organischer Gegenionen, n{\"a}mlich Tetrabutylammonium, Tetraphenylphosphonium und Tetraphenylstibonium. Analog wurde in einem weiteren System aus dem permanent hydrophilen Block Poly(4-Vinylbenzyltetrakis(ethylenoxy)methylether), dem permanent hydrophoben Block Poly(para-Methylstyrol) und Poly(4-Styrolsulfonat) mit den entsprechenden Gegenionen gebildet. Aufgrund unterschiedlicher Kettensteifigkeit in beiden Modell-Systemen sollte es bei der Selbstorganisation der mizellarer Aggregate zu unterschiedlichen {\"U}berstrukturen kommen. Mittels DSC-Messungen konnte nachgewiesen werden, dass f{\"u}r alle Modell-Systeme die Bl{\"o}cke in Volumen-Phase miteinander inkompatibel waren, was eine Voraussetzung f{\"u}r Multikompartimentierung von mizellaren Aggregaten ist. Die Gr{\"o}ße mizellarer Aggregate sowie der Einfluss externer Einfl{\"u}sse wie der Ver{\"a}nderung der Temperatur bzw. der Hydrophobie und Gr{\"o}ße von Gegenionen auf den hydrodynamischen Durchmesser mittels DLS-Untersuchungen wurden f{\"u}r alle Modell-Systeme untersucht. Die Ergebnisse zu den thermoresponsiven tern{\"a}ren Blockcopolymeren belegten , dass sich oberhalb der Phasen{\"u}bergangstemperatur des thermoresponsiven Blocks die Struktur der mizellaren Aggregate {\"a}nderte, indem der p(DEAm)-Block scheinbar kollabierte und so zusammen mit den permanent hydrophoben Block den jeweiligen Mizellkern bildete. Nach gewisser Equilibrierungszeit konnten bei Raumtemperatur dir urspr{\"u}nglichen mizellaren Strukturen regeneriert werden. Hingegen konnte f{\"u}r die Terblock-Polyelektrolyt-Systeme bei Verwendung der unterschiedlich hydrophoben Gegenionen kein signifikanter Unterschied in der Gr{\"o}ße der mizellaren Aggregate beobachtet werden. Zur Abbildung der mizellaren Aggregate mittels kryogene Transmissionselektronenmikroskopie (cryo-TEM) der mizellaren Aggregate war mit Poly(1,3-Bis(butylthio)-prop-2-yl-acrylat) ein Modell-System so konzipiert, dass ein erh{\"o}hter Elektronendichtekontrast durch Schwefel-Atome die Visualisierung ultrastrukturierter hydrophober Mizellkerne erm{\"o}glichte. Dieser Effekt sollte in den Terblock-Polyelektrolyt-Systemen auch durch die Gegenionen Tetraphenylphosphonium und Tetraphenylstibonium nachgestellt werden. W{\"a}hrend bei den thermoresponsiven Systemen auch oberhalb des Phasen{\"u}bergangs kein Hinweis auf Ultrastrukturierung beobachtet wurde, waren f{\"u}r die Polyelektrolyt-Systeme, insbesondere im Fall von Tetraphenylstibonium als Gegenion {\"U}berstrukturen zu erkennen. Der Nachweis der Bildung von Multikompartiment-Mizellen war f{\"u}r beide Polymertypen mit dieser abbildenden Methode nicht m{\"o}glich. Die Unterschiede in der Elektronendichte einzelner Bl{\"o}cke m{\"u}sste m{\"o}glicherweise weiter erh{\"o}ht werden um Aussagen diesbez{\"u}glich zu treffen. Die Untersuchung von ortsspezifischen Solubilisierungsexperimenten mit solvatochromen Fluoreszenzfarbstoffen mittels „steady-state"-Fluoreszenzspektroskopie durch Vergleich der Solubilisierungsorte der Terblockcopolymere bzw. -Polyelektrolyte mit den jeweiligen Solubilisierungsorten von Homopolymer- und Diblock-Vorstufen sollten den qualitativen Nachweis der Multikompartimentierung erbringen. Aufgrund der geringen Mengen an Farbstoff, die f{\"u}r die Solubilisierungsexperimente eingesetzt wurden zeigten DLS-Untersuchungen keine st{\"o}renden Effekte der Sonden auf die Gr{\"o}ße der mizellaren Aggregate. Jedoch erschwerten Quench-Effekte im Falle der Polyelektrolyt Modell-Systeme eine klare Interpretation der Daten. Im Falle der Modell-Systeme der thermoresponsiven Blockcopolymere waren dagegen deutliche solvatochrome Effekte zwischen der Solubilisierung in den mizellaren Aggregaten unterhalb und oberhalb des Phasen{\"u}bergangs zu erkennen. Dies k{\"o}nnte ein Hinweis auf Multikompartimentierung oberhalb des LCST-{\"U}bergangs sein. Ohne die Informationen einer Strukturanalyse wie z.B. der R{\"o}ntgen- oder Neutronenkleinwinkelstreuung (SAXS oder SANS), kann nicht abschließend gekl{\"a}rt werden, ob die Solubilisierung in mizellaren hydrophoben Dom{\"a}nen des kollabierten Poly(N,N'-Diethylacrylamid) erfolgt oder in einer Mischform von mizellaren Aggregaten mit gemittelter Polarit{\"a}t.},
  language  = {de}
}
@phdthesis{Kristen2011,
  author    = {Kristen, Juliane Ute},
  title     = {Amphiphilic BAB-triblock copolymers bearing fluorocarbon groups : synthesis and self-organization in aqueous media},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-61782},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {In this work new fluorinated and non-fluorinated mono- and bifunctional trithiocarbonates of the structure Z-C(=S)-S-R and Z-C(=S)-S-R-S-C(=S)-Z were synthesized for the use as chain transfer agents (CTAs) in the RAFT-process. All newly synthesized CTAs were tested for their efficiency to moderate the free radical polymerization process by polymerizing styrene (M3). Besides characterization of the homopolymers by GPC measurements, end- group analysis of the synthesized block copolymers via 1H-, 19F-NMR, and in some cases also UV-vis spectroscopy, were performed attaching suitable fluorinated moieties to the Z- and/or R-groups of the CTAs. Symmetric triblock copolymers of type BAB and non-symmetric fluorine end- capped polymers were accessible using the RAFT process in just two or one polymerization step. In particular, the RAFT-process enabled the controlled polymerization of hydrophilic monomers such as N-isopropylacrylamide (NIPAM) (M1) as well as N-acryloylpyrrolidine (NAP) (M2) for the A-blocks and of the hydrophobic monomers styrene (M3), 2-fluorostyrene (M4), 3-fluorostyrene (M5), 4-fluorostyrene (M6) and 2,3,4,5,6-pentafluorostyrene (M7) for the B-blocks. The properties of the BAB-triblock copolymers were investigated in dilute, concentrated and highly concentrated aqueous solutions using DLS, turbidimetry, 1H- and 19F-NMR, rheology, determination of the CMC, foam height- and surface tension measurements and microscopy. Furthermore, their ability to stabilize emulsions and microemulsions and the wetting behaviour of their aqueous solutions on different substrates was investigated. The behaviour of the fluorine end-functionalized polymers to form micelles was studied applying DLS measurements in diluted organic solution. All investigated BAB-triblock copolymers were able to form micelles and show surface activity at room temperature in dilute aqueous solution. The aqueous solutions displayed moderate foam formation. With different types and concentrations of oils, the formation of emulsions could be detected using a light microscope. A boosting effect in microemulsions could not be found adding BAB-triblock copolymers. At elevated polymer concentrations, the formation of hydrogels was proved applying rheology measurements.},
  language  = {en}
}
@phdthesis{Miasnikova2012,
  author    = {Miasnikova, Anna},
  title     = {New hydrogel forming thermo-responsive block copolymers of increasing structural complexity},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-59953},
  school      = {Universit{\"a}t Potsdam},
  year      = {2012},
  abstract  = {This work describes the synthesis and characterization of stimuli-responsive polymers made by reversible addition-fragmentation chain transfer (RAFT) polymerization and the investigation of their self-assembly into "smart" hydrogels. In particular the hydrogels were designed to swell at low temperature and could be reversibly switched to a collapsed hydrophobic state by rising the temperature. Starting from two constituents, a short permanently hydrophobic polystyrene (PS) block and a thermo-responsive poly(methoxy diethylene glycol acrylate) (PMDEGA) block, various gelation behaviors and switching temperatures were achieved. New RAFT agents bearing tert-butyl benzoate or benzoic acid groups, were developed for the synthesis of diblock, symmetrical triblock and 3-arm star block copolymers. Thus, specific end groups were attached to the polymers that facilitate efficient macromolecular characterization, e.g by routine 1H-NMR spectroscopy. Further, the carboxyl end-groups allowed functionalizing the various polymers by a fluorophore. Because reports on PMDEGA have been extremely rare, at first, the thermo-responsive behavior of the polymer was investigated and the influence of factors such as molar mass, nature of the end-groups, and architecture, was studied. The use of special RAFT agents enabled the design of polymer with specific hydrophobic and hydrophilic end-groups. Cloud points (CP) of the polymers proved to be sensitive to all molecular variables studied, namely molar mass, nature and number of the end-groups, up to relatively high molar masses. Thus, by changing molecular parameters, CPs of the PMDEGA could be easily adjusted within the physiological interesting range of 20 to 40°C. A second responsivity, namely to light, was added to the PMDEGA system via random copolymerization of MDEGA with a specifically designed photo-switchable azobenzene acrylate. The composition of the copolymers was varied in order to determine the optimal conditions for an isothermal cloud point variation triggered by light. Though reversible light-induced solubility changes were achieved, the differences between the cloud points before and after the irradiation were small. Remarkably, the response to light differed from common observations for azobenzene-based systems, as CPs decreased after UV-irradiation, i.e with increasing content of cis-azobenzene units. The viscosifying and gelling abilities of the various block copolymers made from PS and PMDEGA blocks were studied by rheology. Important differences were observed between diblock copolymers, containing one hydrophobic PS block only, the telechelic symmetrical triblock copolymers made of two associating PS termini, and the star block copolymers having three associating end blocks. Regardless of their hydrophilic block length, diblock copolymers PS11 PMDEGAn were freely flowing even at concentrations as high as 40 wt. \%. In contrast, all studied symmetrical triblock copolymers PS8-PMDEGAn-PS8 formed gels at low temperatures and at concentrations as low as 3.5 wt. \% at best. When heated, these gels underwent a gel-sol transition at intermediate temperatures, well below the cloud point where phase separation occurs. The gel-sol transition shifted to markedly higher transition temperatures with increasing length of the hydrophilic inner block. This effect increased also with the number of arms, and with the length of the hydrophobic end blocks. The mechanical properties of the gels were significantly altered at the cloud point and liquid-like dispersions were formed. These could be reversibly transformed into hydrogels by cooling. This thesis demonstrates that high molar mass PMDEGA is an easily accessible, presumably also biocompatible and at ambient temperature well water-soluble, non-ionic thermo-responsive polymer. PMDEGA can be easily molecularly engineered via the RAFT method, implementing defined end-groups, and producing different, also complex, architectures, such as amphiphilic triblock and star block copolymers, having an analogous structure to associative telechelics. With appropriate design, such amphiphilic copolymers give way to efficient, "smart" viscosifiers and gelators displaying tunable gelling and mechanical properties.},
  language  = {en}
}
@phdthesis{Weiss2011,
  author    = {Weiß, Jan},
  title     = {Synthesis and self-assembly of multiple thermoresponsive amphiphilic block copolymers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53360},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.},
  language  = {en}
}
@phdthesis{BivigouKoumba2009,
  author    = {Bivigou Koumba, Achille Mayelle},
  title     = {Design, Synthesis and Characterisation of Amphiphilic Symmetrical triblock copolymers by the RAFT process : their self-organisation in dilute and concentrated aqueous solutions},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-39549},
  school      = {Universit{\"a}t Potsdam},
  year      = {2009},
  abstract  = {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.},
  language  = {en}
}
@phdthesis{Hentschel2008,
  author    = {Hentschel, Jens},
  title     = {Synthese und kontrollierte Mikrostrukturbildung funktionaler Peptid-Polymerkonjugate in organischen L{\"o}sungsmitteln},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-19840},
  school      = {Universit{\"a}t Potsdam},
  year      = {2008},
  abstract  = {In der vorliegenden Arbeit wurde ein Ansatz verfolgt, die besonderen Eigenschaften der Strukturbildung sequenzdefinierter Peptide mit den vielseitigen Materialeigenschaften synthetischer Blockcopolymere zu kombinieren. Dazu wurde ein synthetisches Polymer kovalent mit einer definierten Peptidsequenz verkn{\"u}pft. Der Peptidblock (die Organisationseinheit) wurde speziell designt, um sp{\"a}ter die Strukturbildung des Peptid-Polymerkonjugates induzieren und leiten zu k{\"o}nnen. Als Organisationsmotiv diente hierbei das aus der Natur bekannte β-Faltblatt Strukturmotiv. Das Peptidsegment wurde in einer festphasengebundenen Synthese aufgebaut. Dabei wurden tempor{\"a}re St{\"o}r-Segmente (Switch-Segmente) in die Peptidsequenz integriert. Diese Segmente unterdr{\"u}cken die Aggregationstendenz w{\"a}hrend der Synthese und k{\"o}nnen durch einen pH-abh{\"a}ngigen Schaltvorgang in das nat{\"u}rliche Peptidr{\"u}ckgrat {\"u}berf{\"u}hrt werden. Zus{\"a}tzlich zu der verbesserten Ausbeute und Reinheit der entsprechenden Peptide war auf diese Weise eine kontrollierte Aktivierung der Mikrostrukturbildung m{\"o}glich. Mit Hilfe zwei verschiedener Synthesestrategien (Kupplungs- bzw. Polymerisationsstrategie) wurde ein Satz von definierten Peptid-Polymerkonjugaten mit unterschiedlich großen Polymersegmenten synthetisiert. Diese wurden anschließend im Hinblick auf ihre Strukturbildungseigenschaften in organischen L{\"o}sungsmitteln untersucht. Durch mikroskopische Verfahren (AFM, TEM), konnte f{\"u}r alle Konjugate, die Bildung faserartiger Aggregate mit Dimensionen im Nano- bis Mikrometerbereich beobachtet werden. Genauere Untersuchungen zeigten, dass die Peptidsegmente in diesen Faserstrukturen ein β-Faltblatt ausbilden. Dies ist ein deutlicher Hinweis darauf, dass die Strukturbildung der Konjugate tats{\"a}chlich durch den Peptidblock gesteuert und kontrolliert wurde.},
  language  = {de}
}
@phdthesis{Rettig2006,
  author    = {Rettig, Hartmut Arnim},
  title     = {Methoden zur Synthese von definierten bioorganisch-synthetischen Blockcopolymeren},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10293},
  school      = {Universit{\"a}t Potsdam},
  year      = {2006},
  abstract  = {Bioorganisch-synthetische Blockcopolymere sind sowohl f{\"u}r die Materialwissenschaft als auch f{\"u}r die Medizin hochinteressant. Diese Arbeit besch{\"a}ftigte sich mit neuen Synthesewegen f{\"u}r die Herstellung dieser Blockcopolymere. Zun{\"a}chst wurde der klassische Ansatz zur Herstellung eines Blockcopolymers {\"u}ber die Kupplung der beiden Segmente aufgegriffen. Hierzu wurde eine Methode zur Synthese von selektiv s{\"a}ureendfunktionalisierten Polyacrylaten mittels einer terminalen Benzylesterschutzgruppe vorgestellt. F{\"u}r die Herstellung von bioorganisch-synthetischen Blockcopolymeren mit einem gr{\"o}ßeren Polymersegment wurde daher ein anderer Syntheseansatz entwickelt. Dieser geht von einem funktionalisierten Oligopeptid aus, an dem durch Polymerisation das synthetische Segment aufgebaut wird. Der Aufbau erfolgte durch kontrolliert radikalische Polymerisation, um ein m{\"o}glichst definiertes Segment zu erhalten. Zun{\"a}chst wurde eine Synthese von Oligopeptid-Makroinitiatoren f{\"u}r die ATRP-Polymerisation durchgef{\"u}hrt. Es konnte gezeigt werden, dass in geeigneten polaren L{\"o}sungsmitteln (DMSO, DMF) eine Polymerisation mit dem ATRP-Oligopeptid-Makroinitiator erfolgreich ist. Allerdings treten w{\"a}hrend der Polymerisation Wechselwirkungen zwischen dem Katalysator und dem Oligopeptid auf. Eine Alternative bietet die RAFT-Polymerisation, da sie ohne einen Katalysator durchgef{\"u}hrt wird. Es gelang ausgehend von dem Oligopeptid-ATRP-Makroinitiator den {\"U}bertr{\"a}ger herzustellen. Die RAFT-Polymerisation mit einem Oligopeptid{\"u}bertr{\"a}ger stellt eine wichtige Methode f{\"u}r die Herstellung von bioorganisch-synthetischen Blockcopolymeren dar. Sie besitzt eine hohe Toleranz gegen{\"u}ber funktionellen Gruppen. Die so hergestellten Blockcopolymere sind frei von Verunreinigungen, wie z.B. {\"U}bergangsmetallen. Dabei l{\"a}ßt sich das Molekulargewicht des synthetischen Blocks bei einer Polydispersit{\"a}t um 1,2 gut kontrollieren.},
  subject      = {ATRP},
  language  = {de}
}
@phdthesis{Nozari2005,
  author    = {Nozari, Samira},
  title     = {Towards understanding RAFT aqueous heterophase polymerization},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5801},
  school      = {Universit{\"a}t Potsdam},
  year      = {2005},
  abstract  = {Reversible addition-fragmentation transfer (RAFT) was used as a controlling technique for studying the aqueous heterophase polymerization. The polymerization rates obtained by calorimetric investigation of ab initio emulsion polymerization of styrene revealed the strong influence of the type and combination of the RAFT agent and initiator on the polymerization rate and its profile. The studies in all-glass reactors on the evolution of the characteristic data such as average molecular weight, molecular weight distribution, and average particle size during the polymerization revealed the importance of the peculiarities of the heterophase system such as compartmentalization, swelling, and phase transfer. These results illustrated the important role of the water solubility of the initiator in determining the main loci of polymerization and the crucial role of the hydrophobicity of the RAFT agent for efficient transportation to the polymer particles. For an optimum control during ab-initio batch heterophase polymerization of styrene with RAFT, the RAFT agent must have certain hydrophilicity and the initiator must be water soluble in order to minimize reactions in the monomer phase. An analytical method was developed for the quantitative measurements of the sorption of the RAFT agents to the polymer particles based on the absorption of the visible light by the RAFT agent. Polymer nanoparticles, temperature, and stirring were employed to simulate the conditions of a typical aqueous heterophase polymerization system. The results confirmed the role of the hydrophilicity of the RAFT agent on the effectiveness of the control due to its fast transportation to the polymer particles during the initial period of polymerization after particle nucleation. As the presence of the polymer particles were essential for the transportation of the RAFT agents into the polymer dispersion, it was concluded that in an ab initio emulsion polymerization the transport of the hydrophobic RAFT agent only takes place after the nucleation and formation of the polymer particles. While the polymerization proceeds and the particles grow the rate of the transportation of the RAFT agent increases with conversion until the free monomer phase disappears. The degradation of the RAFT agent by addition of KPS initiator revealed unambigueous evidence on the mechanism of entry in heterophase polymerization. These results showed that even extremely hydrophilic primary radicals, such as sulfate ion radical stemming from the KPS initiator, can enter the polymer particles without necessarily having propagated and reached a certain chain length. Moreover, these results recommend the employment of azo-initiators instead of persulfates for the application in seeded heterophase polymerization with RAFT agents. The significant slower rate of transportation of the RAFT agent to the polymer particles when its solvent (styrene) was replaced with a more hydrophilic monomer (methyl methacrylate) lead to the conclusion that a complicated cooperative and competitive interplay of solubility parameters and interaction parameter with the particles exist, determining an effective transportation of the organic molecules to the polymer particles through the aqueous phase. The choice of proper solutions of even the most hydrophobic organic molecules can provide the opportunity of their sorption into the polymer particles. Examples to support this idea were given by loading the extremely stiff fluorescent molecule, pentacene, and very hydrophobic dye, Sudan IV, into the polymer particles. Finally, the first application of RAFT at room temperature heterophase polymerization is reported. The results show that the RAFT process is effective at ambient temperature; however, the rate of fragmentation is significantly slower. The elevation of the reaction temperature in the presence of the RAFT agent resulted in faster polymerization and higher molar mass, suggesting that the fragmentation rate coefficient and its dependence on the temperature is responsible for the observed retardation.},
  subject      = {Heterophasenpolymerisation},
  language  = {en}
}
@phdthesis{Mertoglu2004,
  author    = {Mertoglu, Murat},
  title     = {The synthesis of well-defined functional homo- and block copolymers in aqueous media via Reversible Addition-Fragmentation Chain Transfer (RAFT) Polymerization},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-2338},
  school      = {Universit{\"a}t Potsdam},
  year      = {2004},
  abstract  = {New chain transfer agents based on dithiobenzoate and trithiocarbonate for free radical polymerization via Reversible Addition-Fragmentation chain Transfer (RAFT) were synthesized. The new compounds bear permanently hydrophilic sulfonate moieties which provide solubility in water independent of the pH. One of them bears a fluorophore, enabling unsymmetrical double end group labelling as well as the preparation of fluorescent labeled polymers. Their stability against hydrolysis in water was studied, and compared with the most frequently employed water-soluble RAFT agent 4-cyano-4-thiobenzoylsulfanylpentanoic acid dithiobenzoate, using UV-Vis and 1H-NMR spectroscopy. An improved resistance to hydrolysis was found for the new RAFT agents, providing good stabilities in the pH range between 1 and 8, and up to temperatures of 70°C. Subsequently, a series of non-ionic, anionic and cationic water-soluble monomers were polymerized via RAFT in water. In these experiments, polymerizations were conducted either at 48°C or 55°C, that are lower than the conventionally employed temperatures (>60°C) for RAFT in organic solvents, in order to minimize hydrolysis of the active chain ends (e.g. dithioester and trithiocarbonate), and thus to obtain good control over the polymerization. Under these conditions, controlled polymerization in aqueous solution was possible with styrenic, acrylic and methacrylic monomers: molar masses increase with conversion, polydispersities are low, and the degree of end group functionalization is high. But polymerizations of methacrylamides were slow at temperatures below 60°C, and showed only moderate control. The RAFT process in water was also proved to be a powerful method to synthesize di- and triblock copolymers including the preparation of functional polymers with complex structure, such as amphiphilic and stimuli-sensitive block copolymers. These include polymers containing one or even two stimuli-sensitive hydrophilic blocks. The hydrophilic character of a single or of several blocks was switched by changing the pH, the temperature or the salt content, to demonstrate the variability of the molecular designs suited for stimuli-sensitive polymeric amphiphiles, and to exemplify the concept of multiple-sensitive systems. Furthermore, stable colloidal block ionomer complexes were prepared by mixing anionic surfactants in aqueous media with a double hydrophilic block copolymer synthesized via RAFT in water. The block copolymer is composed of a noncharged hydrophilic block based on polyethyleneglycol and a cationic block. The complexes prepared with perfluoro decanoate were found so stable that they even withstand dialysis; notably they do not denaturate proteins. So, they are potentially useful for biomedical applications in vivo.},
  language  = {en}
}