Hyperverzweigte Lacton-Copolymere: enzymatische Synthese, Charakterisierung und Darstellung strukturierter Polymernetzwerke = (Hyperbranched lactone copolymers by enzyme catalysis: synthesis, characterization and preparation of structured polymer networks)

Hyperverzweigte Polymere erfuhren in den letzten Jahren immer mehr Beachtung, da sie im Vergleich zu ihren linearen Analoga besondere Eigenschaften besitzen. Im Jahre 2002 wurde die erste enzymkatalysierte Darstellung hyperverzweigter Poly(epsilon-caprolacton)e (hb-PCL) beschrieben. Hier ermöglichte das Konzept der konkurrierenden ringöffnenden Polymerisation und Polykondensation die Kontrolle der Eigenschaften des dargestellten Polymers. Detaillierte Untersuchungen in Hinblick auf Grenzen und Möglichkeiten, aber auch die Synthese im Technikumsmaßstab sind wesentliche Aspekte dieser Arbeit. Außerdem wird ein neues Konzept eingeführt, das Reknitting genannt wurde. Ziel desselben ist das Recycling kommerziellen, linearen PCLs mittels Umesterung zu hb-PCL durch Enzymkatalyse. Diese hb-PCLs zeigen vergleichbare Eigenschaften zu den aus den Comonomeren dargestellten. Ausgehend von hb-PCL sollte eine geeignete Route zu methacrylierten Vernetzerverbindungen entwickelt werden. Aus Mischungen derselben mit 2-Hydroxyethylmethacrylat wurden komplexe Netzwerkarchitekturen durch Copolymerisation erhalten. Diese Netzwerke wurden in Hinblick auf ihre mechanisch physikalischen Eigenschaften untersucht. Zuletzt wurden Screeningexperimente an anderen zyklischen Estern durchgeführt, da ein Transfer des oben vorgestellten Konzepts angestrebt wurde. Zwei neue hyperverzweigte Polymerklassen, hb-Poly(delta-valerolacton) und hb-Polytrimethylencarbonat wurden detaillierter untersucht und in Ihren Eigenschaften mit hb-PCL verglichen.

From amphiphilic block copolymers to ferrocenyl-functionalized polymers for biosensoric applications

The present thesis can be divided in three main parts. In all parts new polymer architecturesrnwere synthesized and characterized concerning their special features.rnThe first part will emphasize the advantage of a polystyrene-block-(hyperbranchedrnpolyglycerol) copolymer in comparison to an analogue polystyrene-block-(linear polyglycerol)rncopolymer. Therefore a synthethic route to prepare linear block copolymersrnhas been developed. Two strategies were examined. One strategy was based on thernclassic, sequential anionic polymerization; the second strategy was based on arn“Click-Chemistry” coupling reaction. In a following step glycidol was hypergraftedrnfrom these block copolymers by applying a hypergrafting reaction with glycidol. Thernbehavior of the amphiphilic block copolymers synthesized was studied in differentrnsolvents. Furthermore the polarity of the solvent was changed to form the correspondingrninverse micelles. DLS, SLS, SEC-MALLS-VISCO, AFM and Cyro TEMrnmeasurements were performed to obtain a visual image from the appearance of thernaggregates. It was found that a linear-hyperbranched architecture is necessary, ifrnwell defined, monodisperse aggregates are required, e.g. for the preparation of orderedrnnanoarrays. Linear-linear block copolymers formed only polydisperse aggregates.rnAdditionally it was found that size distribution could be improved dramaticallyrnby passing the aggregates through a SEC column with large pores. The SEC columnsrnacted like a template in which the aggregates adopt a more stable conformation.rnIn the second part anionic polymerization was employed to synthesize silaneendfunctionalizedrnmacromonomers with different molecular weights based on polybutadienernand polyisoprene. These were polymerized by a hydrosilylation reaction inrnbulk to obtain branched polymers, using Karstedt’s catalyst. Surprisingly the additionrnof monofunctional silanes during the polymerization had only a minimal effect concerningrnthe degree of polymerization. It was possible to introduce silanes without increasingrnthe overall number of reaction steps by a very convenient “pseudo-copolymerization”rnmethod. All branched polymers were analyzed by SEC, SEC-MALLS,rnSEC-viscometry, 1H-NMR-spectroscopy and DSC concerning their branching ratio.rnThe branching parameters for the branched polymers exhibited similar characteristicsrnas hyperbranched polymers based on AB2 monomers. Detailed kinetic study showedrnthat the polymerization occurred very rapidly in comparison to the hydrosilylation polymerizationrnof classical AB2 type carbosilanes monomers.rnThe last part will deal with ferrocenyl-functionalized polymers. On the one hand,rnferrocenyl-functionalized polyglycerols (PG) were studied. Esterification of PGs withrndifferent molecular weight using ferrocenemonocarboxylic acid gave the ferrocenylrnfuntionalized polymers in high yields. On the other hand three different block copolymersrnwere prepared with different ratios of styrene to butadiene units (10:1, 4:1, 2:1).rnThe double bonds of the 1,2-PB block were hydrosilylated using silanes bearing onern(HSiMe2Fc) or two (HSiMeFc2) ferrocene units. High degrees of functionalizationrnwere obtained (up to 83 %). In this manner, six different ferrocenyl-rich block copolymersrnwith different fractions of ferrocene were prepared and analyzed, employingrnNMR-spectroscopy, SEC, SEC/MALLS/viscometry, DLS and cyclic voltammetry. Thernredox properties of the studied polymers varied primarily with the nature of the silanernunit attached. Additionally, the redox properties in solution of the studied polymersrnwere influenced by the block length ratio of the block copolymers. Unexpectedly, withrnincreasing block length of the ferrocenyl block the fraction of active ferrocenes decreased.rnNevertheless, in case of thin monolayer films this behaviour was not observed.rnAll polymers (PG and PS-b-PB based) exhibited good electrochemical propertiesrnin a wide range of solvents, which rendered them very interesting for biosensoricrnapplications.

Functionalization of hyperbranched polycarbosilanes - block copolymers and electrochemistry

Polycarbosilanes are a class of polymers at the interface between organic and inorganic chemistry. They are characterized by a high thermal and chemical inertness and high flexibility, especially pronounced for branched structures. Linear polycarbosilanes are well known as precursors for the preparation of SiCx ceramics. Additionally, more sophisticated architectures like dendrimers, hyperbranched polymers or block copolymers have been the subject of research for more than a decade. The scope of this work was to expand the properties and fields of application for polycarbosilane-containing structures. Thus, the work is divided in two major parts. The first part covers the synthesis and characterization of hyperbranched polycarbosilanes containing organometallic moieties. Hyperbranched poly-carbosilanes were synthesized using hydrosilylation of diallylmethylsilane and methyldiundecenylsilane. The degree of branching for polydiallymethylsilane was determined using standard 1H-NMR spectroscopy. The functional building blocks ferrocenyldimethylsilane and diferrocenylmethylsilane were synthesized which contain an isolated ferrocene unit or two ferrocenes bridged by silicon, respectively. Hyperbranched polycarbosilanes functionalized with ferrocenyl moieties were synthesized by modification of preformed polymers or by copolymerization of AB2 carbosilane monomers with AX-type ferrocenylsilanes. Polymers with Mn = 2500-9000g/mol and ferrocene contents of up to 67wt% were obtained. Electrochemical characterization by cyclic voltammetry revealed that polymers functionalized with isolated ferrocene units showed a single reversible oxidation wave, while voltammograms for polymers functionalized with diferrocenyl silane exhibited two well-separated reversible oxidation-reduction waves. This shows that the polymer bound ferrocenes bridged by silicon are electronically communicating and thus oxidation of the first ferrocene shifts the oxidation potential for the adjacent one. The polymers were utilized successfully for the preparation of modified electrodes with persistent and reproducible electrochemical response in organic solvents as well as in aqueous solution. The presented work has proven that ferrocenyl-functionalized hyperbranched polymers exhibit similar electrochemical properties as the analogous dendrimers. In a further approach it was shown that hyperbranched polymers containing organometallic moieties can be synthesized by polymerization of a new ferrocene-containing AB2 monomer - diallylferrocenylsilane. The second part of this work is dedicated to the preparation of core-functional hyperbranched polycarbosilanes. Low molecular weight ambifunctional molecules were synthesized that contain double bonds for the attachment of a polycarbosilane polymer as well as a second functionality available for further reaction and modification. Reactive vinyl groups in the core molecule allow an efficient attachment of hyperbranched polycarbosilane which was proven by MALDI-ToF and GPC. In combination with slow monomer addition techniques molecular weight and polydispersity of the polymers were controlled successfully. Core-functional polymers were characterized by NMR-spectroscopy, MALDI-ToF and GPC. Polymers with polydispersities <2 and molecular weights up to 5300g/mol were obtained. Transformation of the double bonds of the carbosilane was demonstrated with various silanes using hydrosilylation reaction or hydrogenation. Additionally, the core-functionality was varied resulting in polymers with bromo-, phthalimide-, amine- or azide moieties. Thus, a versatile synthetic strategy was developed that allows the synthesis of tailor-made polymers.A promising approach is the application of the polymer building blocks in copolymer synthesis. Bisglycidolization of amine-functional polycarbosilanes produces macro-initiators that are suitable for the multibranching-ring opening polymerization of glycidol. This experiments lead to the first example of hyperbranched-hyperbranched amphiphilic block copolymers, hb-PG-b-hb-PCS. Furthermore, the implementation of copper-catalyzed cycloaddition between azide-functional polycarbosilane and alkyne-functional poly(ethoxyethyl glycidylether) resulted in linear-hyperbranched block copolymers. The facile removal of acetal protecting groups provided convenient access to lin-PG-b-hb-PCS.

Hyperbranched polyglycerols as building blocks for complex amphiphilic structures: synthesis, characterization and applications

Among hyperbranched polymers, polyglycerol is one of the most promising and commonly used macromolecules due to its biocompatibility and versatility. However, the synthesis of high molecular weight polyglycerols still involves many intricacies and has only been understood to a limited extent. Furthermore, only few complex structures like star or block copolymers incorporating polyglycerol have been realized so far. Particularly biocompatible block copolymers are considered promising candidates for biomedical applications.rnThe scope of this thesis was the enhancement of the synthetic process leading to polyglycerol derivatives which implies improved molecular weight control for a broad molecular weight range as well as the assembly of more complex structures like amphiphilic block copolymers. Further insight into the relation between reaction solvent, degree of deprotonation during the ring-opening multibranching polymerization of glycidol and the characteristics of the obtained polymers were achieved within the scope of this work. Based on these results, a novel concept for the preparation of hyperbranched polyglycerols with molecular weights up to 20,000 g/mol was developed, applying a two step synthesis pathway. Starting from a partially deprotonated TMP core, low molecular weight hb-PGs were prepared using the known synthetic protocol that has been established since the late 1990ies. In a subsequent reaction sequence, these well defined polymers were used as hyperbranched macroinitiator cores in order to obtain high molecular weight hb-PGs with remarkably low polydispersity (Mw/Mn < 1.8). Molecular weight control was shown to be excellent and undesired low molecular weight side products were absent. Furthermore, the technique of continuous spin fractionation has been discovered as an efficient method for polyglycerol work-up to remove quantitatively residual monomer- and oligomer traces from hb-PG compositions to result in samples with significantly reduced polydispersities. Based on these results the synthesis of amphiphilic block copolymers containing hydrophilic hyperbranched polyglycerol blocks and linear, apolar poly(propylene oxide) blocks has been significantly improved and augmented to hb-PG-b-l-PPO-b-hb-PG ABA block copolymers. The influence of different polyglycerol-based amphiphiles on the fibril formation was studied by Thioflavin T Fluorescence showing remarkable increasing lag times which is promising in order to enhance the stability of this protein. In addition the first synthesis of poly(glyceryl glycerols) (PGG), introducing a new solketyl glycidyl ether monomer (IGG) was shown. It was furthermore demonstrated that core-functional carbosilane wedges allow application in block copolymer synthesis. Bisglycidolized amine functional polymers were successfully employed as macroinitiators for glycidol polymerization. This resulted in the first example of amphiphilic hyperbranched-hyperbranched polymer structures. Finally, it has been shown that the previously reported synthetic pathway to carboxylated hyperbranched polyglycerol polyelectrolytes can also be applied for the amphiphilic linear-hyperbranched block copolymers. These novel biocompatible and highly amphiphilic polyelectrolytes offer great potential for further investigations. rnrn

Hyperverzweigte Polyphenylene und redoxaktive Dendrimere

Die Doktorarbeit gliedert sich in zwei Abschnitte. Das erste Kapitel beschäftigt sich mit den hyperverzweigten Polyphenylenen. Es wurden Untersuchungen des Molekulargewichts in Abhängigkeit von der Monomerkonzentration und der Reaktionszeit durchgeführt. Die synthetisierten Polymere haben große Polydispersitäten, die durch fraktioniertes Fällen herabgesetzt werden können. Die Funktionalisierung der hyperverzweigten Polyphenylene mit unterschiedlichen Methoden führt zu verschiedenen Funktionen auf der Oberfläche der Polymere. Die chlormethylierten hyperverzweigen Polymere können als Makroinitiator für den Aufbau von Kern-Schale-Systemen genutzt werden. Mit Hilfe der ATRP-Polymerisation wurde Methylmethacrylat anpolymerisiert. Als Charakterisierungsmethode zur Bestimmung des freien Volumens findet die Positronenauslöschungsspektroskopie Anwendung. Im zweiten Teil der Arbeit stehen die Synthese und Charakterisierung von redoxaktiven Dendrimeren mit Triphenylamin- bzw. Naphthalinkern im Mittelpunkt. Den Einfluß der Dendrimerhülle auf die Redoxaktivität zeigen cyclovoltammetrische Untersuchungen. Die Zunahme der dendritischen Hülle führt zu einer Abschirmung des Redoxzentrums gegen die Elektrode und damit zu einer Inhibierung des Elektronentransfers. Das spiegelt sich in der Abnahme der Geschwindigkeitskonstanten sowie in der Ausdehnung der cyclovoltammetrischen Kurve wieder. Die Funktionalisierung der Triphenylamin-Dendrimere mit Chromophoren auf der Oberfläche führt zu einer Änderung der optische Eigenschaften, die mit Hilfe von Absorptions- und Emissionsmessungen untersucht wurden.

Struktur-Eigenschafts-Beziehungen flüssigkristalliner hyperverzweigter Polymere

Auf dem Gebiet der polymeren Flüssigkristallforschung sind definierte Systeme unerlässlich. Im Gegensatz zu Dendrimeren und linearen Polymeren, standen hyperverzweigte Materialien mit enger Molekulargewichtsverteilung lange Zeit nicht zur Verfügung. Hyperverzweigte Polymere besitzen die gleichen Vorteile wie Dendrimere; hohe Endgruppendichte und niedrige Viskositäten, jedoch sind hyperverzweigte Polymere einfacher und in größeren Mengen zugänglich, was sie für industrielle Anwendungen interessant macht. Mit der Entwicklung der Synthese von hyperverzweigten Polymeren enger Molekulargewichtsverteilung durch Frey et al. wurde der Grundstein für hyperverzweigte LC-Materialien gelegt. Im Rahmen diese Dissertation wurden Synthesewege zur Darstellung hyperverzweigter LC-Materialien entwickelt und ihr Phasenverhalten sowie die Überstrukturbildung in Abhängigkeit verschiedener struktureller Parameter untersucht. Die erarbeiteten Struktur-Eigenschafts-Beziehungen ermöglichen die Synthese flüssigkristalliner hyperverzweigter Polymere mit spezifischen Eigenschaften für Anwendungen in der Display-Technologie oder auf dem Gebiet selbstorganisierender Systeme.

Electrostatic supramolecular assembly of charged dendritic polymers and their biological application

The aim of this study was the development of functional multilayer films through electrostatic layer by layer (LbL) assembly of dendritic macromolecules, the investigation of the fundamental properties of these multilalyered films and the study of their biological applications. rnThe synthesis of the anionic hyperbranched polyglycerols (hbPG) and the preparation of multilayers made of hbPG/phosphorus dendrimer as well as the influences of deposition conditions on multilayers were reported. The thicknesses of multilayer films increase with a decrease of molecular weight of anionic hbPGs. The multilayer films fabricated by low molecular weight hbPGs grow less regularly due to the less charged carboxylic acid groups providing the relative weaker electrostatic forces for the deposition. The thicknesses of multilayer films are reduced with increasing pH values and decreasing the concentration of NaCl. The observed changes of multilayer thickness and surface morphology could be interpreted with the aid of theories regarding the charge density and conformation of the anionic hbPG chains in solution. rnBesides the study of fundamental properties of hbPG/phosphorus multilayer films, antifouling thin films derived from hbPG layers were developed. The antifouling properties of hbPG layers were found to correlate with factors of the molecular weight of anionic hbPG and the film thickness. It was demonstrated that anionic hbPG single layer with highest molecular weight can reduce non specific protein adsorption more efficiently than single layer with lower molecular weight and all the hbPG bilayers possessed excellent property of antifouling. rnPhosphorus dendrimer multilayers were successfully prepared as the platforms to detect DNA immobilization and hybridization. The effect of NaCl concentration on the multilayer film thickness was evaluated to obtain the optimized film thickness. Making use of the multilayer deposited at the optimized condition as a substrate, a high loading of DNA probes was achieved through covalent coupling of probe DNA with the as-formed multilayer films. The hybridization of target DNA with immobilized probe DNA was then carried out and studied by SPFS. The limit of detection upon hybridization was estimated on various dendrimer multilayer platforms. The minimum detection concentration for DNA hybridization is in the same order of magnitude compared with other neutral phosphorus dendrimer systems. Furthermore, the LbL deposition of phosphorus dendrimer multilayers provided a mild and simple way to prepare platforms as DNA microarrays. rnBased on the phosphorus dendrimer multilayer systems, dendritic star polymers were employed which have more reactive groups than that phosphorus dendrimers. The as-assembled dendritic star polymer multilayer films exhibited such distinct morphology characteristics that they underwent extensive structural reorganization upon post-treatment under different pH conditions. Kinetic binding of probe DNA molecules on the outermost negatively charged dendritic surface was studied by SPR as well. The binding capacities of probe DNA on the multilayer surfaces fabricated from the first-generation and the second-generation of dendritic star polymers were compared. The improved binding capacity was achieved from the second-generation of dendritic star polymer multilayer films due to their more reactive groups. DNA hybridization reaction on dendritic multilayer films was investigated by SPFS. The similar hybridization behaviors were found on both multilayer surfaces. Meanwhile, the hybridization kinetic affinities were compared with that of phosphorus dendrimer multilayer surfaces and showed improved detection sensitivity than phosphorus dendrimer multilayer films.rn

Hyperbranched polyether polyols as building blocks for complex macromolecular architectures

The present thesis deals with the development of new branched polymer architectures containing hyperbranched polyglycerol. Materials investigated include hyperbranched oligomers, hyperbranched polyglycerols containing functional initiator-cores at the focal point, well-defined linear-hyperbranched block copolymers and also negatively charged hyperbranched polyelectrolytes.rnHyperbranched oligoglycerols (DPn = 7 and 14) have been synthesized for the first time. The materials show narrow polydispersity (Mw/Mn ca. 1.45) and a very low content in cyclic homopolymers. 13C NMR evidences the dendritic structure of the oligomers and the DB could be calculated (44% and 52%). These new oligoglycerols were compared with the industrial products obtained by polycondensation which exhibit narrow polydispersity (Mw/Mn<1.3) butrnmultimodal distribution in SEC. Detailed 13C NMR and Maldi-ToF studies reveal the presence of branched units and cyclic compounds. In comparison, the hyperbranched oligoglycerols comprise a very low proportion of cyclic homopolymer which render them very interesting materials for biomedical applications for example.rnThe site isolation of the core moiety in dendritic structure offers intriguing potential with respect to peculiar electro-optical properties. Various initiator-cores (n-alkyl amines, UVabsorbing amines and benzophenone) for the ROMBP of glycidol have been tested. The bisglycidolized amine initiator-cores show the best control over the molecular weight and the molecular weight distribution. The photochemical analyses of the naphthalene containingrnhyperbranched polyglycerols show a slight red shift, a pronounced hypochromic effect (decrease of the intensity of the band) compared with the parent model compound and the formation of a relative compact structure. The benzophenone containing polymers adopt an open structure in polar solvents. The fluorescence measurements show a clear “dendritic effect” on the fluorescence intensities and the quantum yield of the encapsulated benzophenone.rnA convenient 3-step strategy has been developed for the preparation of well-defined amphiphilic, linear-hyperbranched block copolymers via hypergrafting. The procedure represents a combination of carbanionic polymerization with the alkoxide-based, controlled ring-opening multibranching polymerization of glycidol. Materials consisting of a polystyrene linear block and a hyperbranched polyglycerol block exhibit narrow polydispersity (1.01-1.02rnfor 5.4% to 27% wt. PG and 1.74 for 52% wt. PG) with a high grafting efficiency. The strategy was also extended to materials with a linear polyisoprene block.rnDetailed investigations of the solution properties of the block copolymers with linear polystyrene blocks show that block copolymer micelles are stabilized by the highly branched block. The morphology of the aggregates is depending on the solvent: in chloroform monodisperse spherical shape aggregates and in toluene ellipsoidal aggregates are formed. On graphite these aggregates show interesting features, giving promising potential applications with respect to the presence of a very dense, functional and stable hyperbranched block.rnThe bulk morphology of the linear-hyperbranched block copolymers has been investigated. The materials with a linear polyisoprene block only behave like complex liquids due to the low Tg and the disordered nature of both components. For the materials with polystyrene, only the sample with 27% wt. hyperbranched polyglycerol forms some domains showing lamellae.rnThe preparation of hyperbranched polyelectrolytes was achieved by post-modification of the hydroxyl groups via Michael addition of acrylonitrile, followed by hydrolysis. In aqueous solution materials form large aggregates with size depending on the pH value. After deposition on mica the structures observed by AFM show the coexistence of aggregates andrnunimers. For the low molecular weight sample (PG 520 g·mol-1) extended and highly ordered terrace structures were observed. Materials were also successfully employed for the fabrication of composite organic-inorganic multilayer thin films, using electrostatic layer-bylayer self-assembly coupled with chemical vapor deposition.

Poly(lactide): from hyperbranched copolyesters to new block copolymers with functional methacrylates

The prologue of this thesis (Chapter 1.0) gives a general overview on lactone based poly(ester) chemistry with a focus on advanced synthetic strategies for ring-opening polymerization, including the emerging field of organo catalysis. This section is followed by a presentation of the state-of the art regarding the two central fields of the thesis: (i) polyfunctional and branched poly(ester)s in Chapter 1.1 as well as (ii) the development of new poly(ester) based block copolymers with functional methacrylates (Chapter 1.2). Chapter 2 deals with the synthesis of new, non-linear poly(ester) structures. In Chapter 2.1, the synthesis of poly(lactide)-based multiarm stars, prepared via a grafting-from method, is described. The hyperbranched poly(ether)-poly(ol) poly(glycerol) is employed as a hydrophilic core molecule. The resulting star block copolymers exhibit potential as phase transfer agents and can stabilize hydrophilic dyes in a hydrophobic environment. In Chapter 2.2, this approach is expanded to poly(glycolide) multiarm star polymers. The problem of the poor solubility of linear poly(glycolide)s in common organic solvents combined with an improvement of the thermal properties has been approached by the reduction of the total chain length. In Chapter 2.3, the first successful synthesis of hyperbranched poly(lactide)s is presented. The ring-opening, multibranching copolymerization of lactide with the “inimer” 5HDON (a hydroxyl-functional lactone monomer) was carefully examined. Besides a precise molecular characterization involving the determination of the degree of branching, we were able to put forward a reaction model for the formation of branching during polymerization. Several innovative approaches to amphiphilic poly(ester)/poly(methacrylate)-based block copolymers are presented in the third part of the thesis (Chapter 3). Block copolymer build-up especially relies on the combination of ring-opening and living radical polymerization. Atom transfer radical polymerization has been successfully combined with lactide ring-opening, using a “double headed” initiator. This strategy allowed for the realization of poly(lactide)-block-poly(2-hydroxyethyl methacrylate) copolymers, which represent promising materials for tissue engineering scaffolds with anti-fouling properties (Chapter 3.1). The two-step/one-pot approach forgoes the use of protecting groups for HEMA by a careful selection of the reaction conditions. A series of potentially biocompatible and partially biodegradable homo- and block copolymers is described in Chapter 3.2. In order to create a block copolymer with a comparably strong hydrophilic character, a new acetal-protected glycerol monomethacrylate monomer (cis-1,3- benzylidene glycerol methacrylate/BGMA) was designed. The hydrophobic poly(BGMA) could be readily transformed into the hydrophilic and water-soluble poly(iso-glycerol methacrylate) (PIGMA) by mild acidic hydrolysis. Block copolymers of PIGMA and poly(lactide) exhibited interesting spherical aggregates in aqueous environment which could be significantly influenced by variation of the poly(lactide)s stereo-structure. In Chapter 3.3, pH-sensitive poly(ethylene glycol)-b-PBGMA copolymers are described. At slightly acidic pH values (pH 4/37°C), they decompose due to a polarity change of the BGMA block caused by progressing acetal cleavage. This stimuli-responsive behavior renders the system highly attractive for the targeted delivery of anti-cancer drugs. In Chapter 3.4, which was realized in cooperation, the concept of biocompatible, amphiphilic poly(lactide) based polymer drug conjugates, was pursued. This was accomplished in the form of fluorescently labeled poly(HPMA)-b-poly(lactide) copolymers. Fluorescence correlation spectroscopy (FCS) of partially biodegradable block copolymer aggregates exhibited fast cellular uptake by human cervix adenocarcinoma cells without showing toxic effects in the examined concentration range (Chapter 4.1). The current state of further projects which will be pursued in future studies is addressed in Chapter 4. This covers the synthesis of biocompatible star block copolymers (Chapter 4.2) and the development of new methacrylate monomers for biomedical applications (Chapters 4.3 and 4.4). Finally, the further investigation of hydroxyl-functional lactones and carbonates which are promising candidates for the synthesis of new hydrophilic linear or hyperbranched biopolymers, is addressed in Chapter 4.5.

Influence of chain stiffness on structure and dynamics of polymers in the melt

Die vorliegende Arbeit beschaeftigt sich mit der Untersuchung vonPolymeren mit intrinsischer Steifigkeit. Es werden vor allem lokale statische unddynamische Eigenschaften anhand zweier verschiedener Simulationsmodellebetrachtet: Ein generisches Polymermodell, bei dem nur dieSteifigkeit als ein das spezifische Polymer charakterisierenden Parametereingeht und ein atomistisches Modell fuer trans-Polyisopren. Mit Hilfe des ersten Modells koennen Statik und Dynamik wurmartiger Kettenbeobachtet werden. Das Blob-Konzept ist eine angemessene statischeBeschreibung. Lokale Orientierungen haengen schwach von derSteifigkeit ab. Das Reptationsmodell kann die beobachtete Dynamik fuer lange Kettennicht mehr angemessen beschreiben. Lange Ketten bewegen sich, als obsie in Roehren gezwaengt waeren; jedoch ist die Bewegung starkabhaengig von der Steifigkeit. Fuer Ketten dieser Art konntequalitativ das Verhalten reproduziert werden, das in NMR-Experimentenbeobachtet wird. Eine Verhakungslaenge laesst sich fuer solche Kettenkaum mehr definieren. Dynamische Strukturfunktionen und insbesonderedie direkte Visualisierung der Ketten verdeutlichen die effektiv aufeine Roehre beschraenkte Bewegung. Das atomistische Polyisoprenmodell wurde mit verschiedenen Experimenten,verglichen. In den Simulationen bei konnten qualitativ undsemiquantitativ experimentelle Ergebnisse reproduziert werden. Zuletzt wurden die Laengen- und Zeitskalen der beiden Modelleerfolgreich aufeinander abgebildet.

Synthesis and characterization of polymers containing oligothiophenes

In the present work a series of thiophene oligomers of three and six thiophene units were synthesized, starting from thiophene, and characterized. Polymers containing these electroative side groups were then prepared by two strategies. The oligomers were attached to existing polymer systems and were connected to a polymerizable unit leading to monomer containing the oligothiophenes as side groups. Subsequently the properties of the monomers and the polymers were investigated. A butylcellulose derivative carrying terthienyl side chains (BCTTE, 26) was synthesized starting from cellulose acetate and 5-(2-chloroethyl)-2,2':5',2'-terthiophene (4). The polymer had a degree of substitution (DS) of the butyl and terthienyl side chains of DSbutyl = 1.9 and DSterth = 0.35, respectively. It was successfully spread on a Langmuir-Blodgett (LB) trough and then transferred to several solid substrates. X-rays reflectometry showed an ordered architecture of the cellulose backbones. However, the terthiophene side groups were found as isotropically aligned by polarized UV-Vis spectroscopy. When used as anode material in the electropolymerization of 3-pentylthiophene (28), polythiophene was grafted onto the cellulose backbone through the terthienyl side groups. The polythiophene chains showed an average anisotropic alignment of 20 % along the LB dipping direction, calculated by means of polarized UV-Vis spectroscopy. A second butylcellulose derivative carrying sexithienyl side chains (BCST) was synthesized and investigated, starting from butylcellulose and 2-[b ', b ''-dipentyl-5'''-(2-hydroxyethyl)-2,2': 5',2':5',2'':5'',2'':5'',2'''-sexithiophen-5-yl]-ethyl p-toluensulfonate (7). The polymer showed formation of stable LB monolayers at the air-water interface, but its transfer onto solid substrates was not successful. A poly(p-phenylene-ethynylene) bearing sexithienyl side chains (BzAcST, 31) was prepared by reaction of the two monomers 2-[b ', b ''-dipentyl-5'''-(2-hydroxyethyl)-2,2': 5',2':5',2'':5'',2'':5'',2'''-sexithiophen-5-yl]-ethyl 2,5-diiodobenzoate (15) and 2-[b', b ''-dipentyl-5'''-(2-hydroxyethyl)-2,2':5',2':5',2'':5'',2'':5'',2'''-sexithiophen-5-yl]-ethyl 2,5-diethynylbenzoate (18). The polymer was obtained as insoluble product. Upon oxidation with FeCl3 (doping) of the polymer suspension, BzAcST showed an electrical conductivity of ó = 2.5 . 10 -6 S/cm, a typical value for semiconductors. The IR spectrum of the doped polymer presented the diagnostic bands of oxidized sexithiophene in good agreement with literature results. Along with the monomer and polymer synthesis, an a,a '-disubstituted sexithiophene, b ', b ''-dipentyl-5,5'''-bis-(2-hydroxyethyl)-2,2':5',2':5',2'':5'',2'':5'',2'''-sexithiophene (6a),was synthesized and characterized. The UV-Vis absorption of the chromophore wasinvestigated as a function of temperature and different solvents, showing a blue-shift of the absorption maximum with increasing temperature and a red-shift changing the solvent from hexane to ethanol to toluene. Monitoring the change of the UV-Vis spectrum upon electrochemical oxidation, the oxidized chromophore showed a new broad absorption band, red shifted with respect to the p -p* transition of the neutral state. Upon reduction, the new band disappeared and the UV-Vis spectrum of the chromophore was restored. Such oxidation-reduction cycles were totally reversible. This feature, together with the absorption maximum falling in the visible region, makes this chromophore a suitable compound for the development of an electrochemical sensor.Attempts to polymerize acrylic monomers carrying sexythienyl side chains both via radical polymerization, as in the case of 2-[b ', b ''-dipentyl-5'''-(2-hydroxyethyl)-2,2': 5',2':5',2'':5'',2'':5'',2'''-sexithiophen-5-yl]-ethyl acrylate (8), and anionic polymerization, as in the case of 2-{b ', b ''-dipentyl-5'''-[2-(tertbutyldimethylsiloxy)ethyl]-2,2':5',2':5',2'':5'',2'': 5'',2''' -sexithiophen-5-yl}-ethylacrylate (29), were not successful, probably due to the steric hindrance of the oligothiophene side group. However, due to the time consuming and therefore restricted availability of the monomers, a screening of the polymerization conditions towards the formation of polymeric material was not possible.

Synthese funktionalisierter Phenolpolymere durch HRP-katalysierte Polyrekombination

ZUSAMMENFASSUNG: Die durch das Enzym Horseradish Peroxidase katalysierte oxidative Polymerisation substituierter Phenole gewährt einen bequemen Zugang zu funktionalisierten Phenolpolymeren, deren Anwendung als Ersatz für konventionelle Phenol-Formaldehyd-Harze zur Zeit intensiv erforscht wird. Zur Zeit werden Polymerisation dieser Art in Mischungen aus organischen Lösungsmitteln (z.B. 1,4-Dioxan) und Puffer durchgeführt. Im Rahmen dieser Arbeit wurde eine HRP-katalysierte Phenolpolymerisation von wasserunlöslichen Methacryloyl- und Maleinimid-substituierten Phenolen in 100% Pufferlösung durch die Verwendung von 2,6-methylierten Cyclodextrinen als carrier erreicht. Die so hergestellten Oligomere wurden mit Styrol und MMA copolymerisiert. Weitere Untersuchungen hatten die Synthese photoreaktiver Phenolpolymere mit Zimtsäure- oder Nitrongruppen in der Seitenkette, die Synthese thermisch vernetzbarer Phenolcopolymere aus Furan-2-carboxylsäure-(4-hydroxy-phenyl)-amid und N-methacryloyl-11-aminoundecanoyl-4-hydroxyanilid sowie die Synthese eines Redoxpolymeren ausgehend von 4-Aminophenol zum Ziel. Daneben wurden Strategien zur enzymatisch katalysierten Synthese von Poly[para-phenylenen], hyperverzweigten Phenolpolymeren und biologisch aktiven Phenolpolymeren entwickelt, und detaillierte Untersuchungen zum Polymerisationsmechanismus und zur Struktur der entstehenden Phenolpolymere vorgestellt. Die vorgestellten Phenolpolymere bestehen hoechstwahrscheinlich aus polyaromatischen Helices, da diese p-substituierten Phenole während des Rekombinationsprozesses bevorzugt an den ortho-Positionen rekombinieren.

Decay of imprinted surface waves in polymers

CONCLUSIONS The focus of this work was the investigation ofanomalies in Tg and dynamics at polymer surfaces. Thethermally induced decay of hot-embossed polymer gratings isstudied using laser-diffraction and atomic force microscopy(AFM). Monodisperse PMMA and PS are selected in the Mwranges of 4.2 to 65.0 kg/mol and 3.47 to 65.0 kg/mol,respectively. Two different modes of measurement were used:the one mode uses temperature ramps to obtain an estimate ofthe near-surface glass temperature, Tdec,0; the other modeinvestigates the dynamics at a constant temperature aboveTg. The temperature-ramp experiments reveal Tdec,0 valuesvery close to the Tg,bulk values, as determined bydifferential scanning calorimetry (DSC). The PMMA of65.0 kg/mol shows a decreased value of Tg, while the PS samples of 3.47 and 10.3 kg/mol (Mwpolymers. Non-Arrhenius behavior allowsone to fit the shift factors to the William-Landel-Ferry(WLF) equation. The WLF parameters for the varying molecular weights ofPMMA and PS were extracted and compared to the values frombulk rheology measurements. Assuming cg1=16+/-2 at Tg, assuggested by Angell, the glass temperature was determinedfrom the dynamic decay experiments. Within the experimentalerrors, the values for Tg,surf(c1=16) and T_g,bulk(c1=16)tend to be smaller than Tdec,0 and Tg,bulk fromtemperature-ramp and DSC measurements, but confirm thecourse of the values with increasing Mw. The comparison of the fragilities (temperaturedependence of the polymer properties at Tg) near the surfaceand in the bulk shows a higher fragility for PS near thesurface, a lower one for PMMA with molecular weights of 4.2and 65.0 kg/mol. The different surface behavior of PS istraced back to a lower degree of cooperation and a largerfree volume fraction.

Electronic energy transfer processes in pi-conjugated polymers

Currently pi-conjugated polymers are considered as technologically interesting materials to be used as functional building elements for the development of the new generation of optoelectronic devices. More specifically during the last few years, poly-p-phenylene materials have attracted considerable attention for their blue photoluminescence properties. This Thesis deals with the optical properties of the most representative blue light poly-p-phenylene emitters such as poly(fluorene), oligo(fluorene), poly(indenofluorene) and ladder-type penta(phenylene) derivatives. In the present work, laser induced photoluminescence spectroscopy is used as a major tool for the study of the interdependence between the dynamics of the probed photoluminescence, the molecular structures of the prepared polymeric films and the presence of chemical defects. Complementary results obtained by two-dimensional wide-angle X-ray diffraction are reported. These findings show that the different optical properties observed are influenced by the intermolecular solid-state interactions that in turn are controlled by the pendant groups of the polymer backbone. A significant feedback is delivered regarding the positive impact of a new synthetic route for the preparation of a poly(indenofluorene) derivative on the spectral purity of the compound. The energy transfer mechanisms that operate in the studied systems are addressed by doping experiments. After the evaluation of the structure/property interdependence, a new optical excitation pathway is presented. An efficient photon low-energy up-conversion that sensitises the blue emission of poly(fluorene) is demonstrated. The observed phenomenon takes place in poly(fluorene) derivatives hosts doped with metallated octaethyl porphyrins, after quasi-CW photoexcitation of intensities in the order of kW/cm2. The up-conversion process is parameterised in terms of temperature, wavelength excitation and central metal cation in the porphyrin ring. Additionally the observation of the up-conversion is extended in a broad range of poly-p-phenylene blue light emitting hosts. The dependence of the detected up-conversion intensity on the excitation intensity and doping concentration is reported. Furthermore the dynamics of the up-conversion intensity are monitored as a function of the doping concentration. These experimental results strongly suggest the existence of triplet-triplet annihilation events into the porphyrin molecules that are subsequently followed by energy transfer to the host. After confirming the occurrence of the up-conversion in solutions, cyclic voltammetry is used in order to show that the up-conversion efficiency is partially determined from the energetic alignment between the HOMO levels of the host and the dopant.

Dendritische Copolymere auf der Basis von Milchsäure

In der vorliegenden Arbeit wurden verzweigte Copolymerstrukturen auf der Basis von Milchsäure synthetisiert. Über die Kombination der AB-Ringöffnungspolymerisation (ROP) des Dilactids mit der AB2-Polykondensation symmetrischer Bishydroxy-Carbonsäuren waren langketten- und hyperverzweigte Polylactidcopolyester zugänglich, wobei der Verzweigungsgrad über das Verhältnis der Monomere gezielt variiert werden konnte. Weiterhin wurde ausgehend von hyperverzweigtem Polyglycerin in einer „core-first“ Strategie erstmals PLA-Multiarmsterne aufgebaut. Es zeigte sich, daß die Hydrophobisierung der hydrophilen Polyglycerinstruktur durch Anbindung der Lactidarme zur Ausbildung amphiphiler Kern-Schale-Strukturen führt.