Download or read book Complex Macromolecular Architectures written by Nikos Hadjichristidis and published by John Wiley & Sons. This book was released on 2011-04-20 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of CMA (complex macromolecular architecture) stands at the cutting edge of materials science, and has been a locus of intense research activity in recent years. This book gives an extensive description of the synthesis, characterization, and self-assembly of recently-developed advanced architectural materials with a number of potential applications. The architectural polymers, including bio-conjugated hybrid polymers with poly(amino acid)s and gluco-polymers, star-branched and dendrimer-like hyperbranched polymers, cyclic polymers, dendrigraft polymers, rod-coil and helix-coil block copolymers, are introduced chapter by chapter in the book. In particular, the book also emphasizes the topic of synthetic breakthroughs by living/controlled polymerization since 2000. Furthermore, renowned authors contribute on special topics such as helical polyisocyanates, metallopolymers, stereospecific polymers, hydrogen-bonded supramolecular polymers, conjugated polymers, and polyrotaxanes, which have attracted considerable interest as novel polymer materials with potential future applications. In addition, recent advances in reactive blending achieved with well-defined end-functionalized polymers are discussed from an industrial point of view. Topics on polymer-based nanotechnologies, including self-assembled architectures and suprastructures, nano-structured materials and devices, nanofabrication, surface nanostructures, and their AFM imaging analysis of hetero-phased polymers are also included. Provides comprehensive coverage of recently developed advanced architectural materials Covers hot new areas such as: click chemistry; chain walking; polyhomologation; ADMET Edited by highly regarded scientists in the field Contains contributions from 26 leading experts from Europe, North America, and Asia Researchers in academia and industry specializing in polymer chemistry will find this book to be an ideal survey of the most recent advances in the area. The book is also suitable as supplementary reading for students enrolled in Polymer Synthetic Chemistry, Polymer Synthesis, Polymer Design, Advanced Polymer Chemistry, Soft Matter Science, and Materials Science courses. Color versions of selected figures can be found at www.wiley.com/go/hadjichristidis

Download or read book Double Hydrophilic Block Copolymers with Monophosphate Ester Moieties as Crystal Growth Modifiers of CaCO3 written by Jan Rudloff and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Low Dimensional Systems Theory Preparation and Some Applications written by Luis M. Liz-Marzán and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains papers presented at the NATO Advanced Research Workshop (ARW) Dynamic Interactions in Quantum Dot Systems held at Hotel Atrium in Puszczykowo, near Poznan, Poland, May 16-19,2002. The term low-dimensional systems, which is used in the title of this volume, refers to those systems which contain at least one dimension that is intermediate between those characteristic ofatoms/molecules and those ofthe bulk material. Depending on how many dimensions lay within this range, we generally speak of quantum wells, quantum wires, and quantum dots. As such an intermediate state, some properties of low-dimensional systems are very different to those of their molecular and bulk counterparts. These properties generally include optical, electronic, and magnetic properties, and all these are partially covered in this book. The main goal of the workshop was to discuss the actual state of the art in the broad area ofnanotechnology. The initial focus was on the innovative synthesis of nanomaterials and their properties such as: quantum size effects, superparamagnetism, or field emission. These topics lead us into the various field based interactions including plasmon- magnetic spin- and exciton coupling. The newer, more sophisticated methods for characterization of nanomaterials were discussed, as well as the methods for possible industrial applications. In general, chemists and physicists, as well as experts on both theory and experiments on nanosized regime structures were brought together, to discuss the general phenomena underlying their fields ofinterest from different points ofview.

Download or read book Developments in Block Copolymer Science and Technology written by Ian W. Hamley and published by John Wiley & Sons. This book was released on 2004-03-05 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focuses on recent advances in research on block copolymers, covering chemistry (synthesis), physics (phase behaviors, rheology, modeling), and applications (melts and solutions). Written by a team of internationally respected scientists from industry and academia, this text compiles and reviews the expanse of research that has taken place over the last five years into one accessible resource. Ian Hamley is the world-leading scientist in the field of block copolymer research Presents the recent advances in the area, covering chemistry, physics and applications. Provides a broad coverage from synthesis to fundamental physics through to applications Examines the potential of block copolymers in nanotechnology as self-assembling soft materials

Download or read book Block Copolymers in Solution written by Ian W. Hamley and published by Wiley. This book was released on 2005-12-13 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique text discusses the solution self-assembly of block copolymers and covers all aspects from basic physical chemistry to applications in soft nanotechnology. Recent advances have enabled the preparation of new materials with novel self-assembling structures, functionality and responsiveness and there have also been concomitant advances in theory and modelling. The present text covers the principles of self-assembly in both dilute and concentrated solution, for example micellization and mesophase formation, etc., in chapters 2 and 3 respectively. Chapter 4 covers polyelectrolyte block copolymers - these materials are attracting significant attention from researchers and a solid basis for understanding their physical chemistry is emerging, and this is discussed. The next chapter discusses adsorption of block copolymers from solution at liquid and solid interfaces. The concluding chapter presents a discussion of selected applications, focussing on several important new concepts. The book is aimed at researchers in polymer science as well as industrial scientists involved in the polymer and coatings industries. It will also be of interest to scientists working in soft matter self-assembly and self-organizing polymers.

Download or read book Handbook of Solid State Chemistry 6 Volume Set written by Richard Dronskowski and published by John Wiley & Sons. This book was released on 2017-10-23 with total page 3912 pages. Available in PDF, EPUB and Kindle. Book excerpt: This most comprehensive and unrivaled compendium in the field provides an up-to-date account of the chemistry of solids, nanoparticles and hybrid materials. Following a valuable introductory chapter reviewing important synthesis techniques, the handbook presents a series of contributions by about 150 international leading experts -- the "Who's Who" of solid state science. Clearly structured, in six volumes it collates the knowledge available on solid state chemistry, starting from the synthesis, and modern methods of structure determination. Understanding and measuring the physical properties of bulk solids and the theoretical basis of modern computational treatments of solids are given ample space, as are such modern trends as nanoparticles, surface properties and heterogeneous catalysis. Emphasis is placed throughout not only on the design and structure of solids but also on practical applications of these novel materials in real chemical situations.

Download or read book Synthesis and Characterization of Stimuli Responsive Block Copolymers Self Assembly Behavior and Applications written by and published by . This book was released on 2005 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi-responsive properties of the pentablock copolymer. Demonstrate potential biomedical applications of these materials with in vitro drug release studies from pentablock copolymer hydrogels. The intent of this work is to contribute to the knowledge necessary for further tailoring of these, and other functional block copolymer materials for biomedical applications.

Download or read book Synthesis and Characterization of Smart Block Copolymers for Biomineralization and Biomedical Applications written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-assembly is a powerful tool in forming structures with nanoscale dimensions. Self-assembly of macromolecules provides an efficient and rapid pathway for the formation of structures from the nanometer to micrometer range that are difficult, if not impossible to obtain by conventional lithographic techniques [1]. Depending on the morphologies obtained (size, shape, periodicity, etc.) these self-assembled systems have already been applied or shown to be useful for a number of applications in nanotechnology [2], biomineralization [3, 4], drug delivery [5, 6] and gene therapy [7]. In this respect, amphiphilic block copolymers that self-organize in solution have been found to be very versatile [1]. In recent years, polymer-micellar systems have been designed that are adaptable to their environment and able to respond in a controlled manner to external stimuli. In short, synthesis of 'nanoscale objects' that exhibit 'stimulus-responsive' properties is a topic gathering momentum, because their behavior is reminiscent of that exhibited by proteins [8]. By integrating environmentally sensitive homopolymers into amphiphilic block copolymers, smart block copolymers with self assembled supramolecular structures that exhibit stimuli or environmentally responsive properties can be obtained [1]. Several synthetic polymers are known to have environmentally responsive properties. Changes in the physical, chemical or biochemical environment of these polymers results in modulation of the solubility or chain conformation of the polymer [9]. There are many common schemes of engineering stimuli responsive properties into materials [8, 9]. Polymers exhibiting lower critical solution temperature (LCST) are soluble in solvent below a specific temperature and phase separate from solvent above that temperature while polymers exhibiting upper critical solution temperatures (UCST) phase separate below a certain temperature. The solubility of polymers with ionizable moieties depends on the pH of the solution. Polymers with polyzwitterions, anions and cations have been shown to exhibit pH responsive self assembly. Other stimuli responsive polymers include glucose sensitive polymers, calcium ion-sensitive polymers and so on. Progress in living radical polymerization (LRP) methods [10] has made it possible for the facile synthesis of these block copolymer systems with controlled molecular weights and well defined architectures. The overall theme of this work is to develop novel smart block copolymers for biomineralization and biomedical applications. Synthesis and characterization of self-assembling thermoreversible ionic block copolymers as templates in biomimetic nanocomposite synthesis using a bottom-up approach is a novel contribution in this respect. Further, we have extended these families of copolymers to include block copolymer-peptide conjugates to enhance biological specificity. Future directions on this work will focus on enhancing the polymer templating properties for biomineralization by expanding the family of block copolymers with organic polypeptides and biological polypeptide scaffolds as well as a detailed understanding of the polymer-inorganic nanocomposites at the molecular level using small angle scattering analysis. Glucose responsive polymer hydrogels for drug delivery, polymer-ligand conjugates for non-viral therapy and thermoresponsive injectable photocrosslinkable hydrogels for posttraumatic arthritis cartilage healing are other applications of these novel copolymers synthesized in our work.

Download or read book Self Assembly of Double Hydrophilic Block Copolymers written by Jochen Willersinn and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The motivation of this work was to investigate the self-assembly of a block copolymer species that attended little attraction before, double hydrophilic block copolymers (DHBCs). DHBCs consist of two linear hydrophilic polymer blocks. The self-assembly of DHBCs towards suprastructures such as particles and vesicles is determined via a strong difference in hydrophilicity between the corresponding blocks leading to a microphase separation due to immiscibility. The benefits of DHBCs and the corresponding particles and vesicles, such as biocompatibility, high permeability towards water and hydrophilic compounds as well as the large amount of possible functionalizations that can be addressed to the block copolymers make the application of DHBC based structures a viable choice in biomedicine. In order to assess a route towards self-assembled structures from DHBCs that display the potential to act as cargos for future applications, several block copolymers containing two hydrophilic polymer blocks were synthesized. [...]

Download or read book Investigating the Role of Topological Frustration on Morphology of Novel Multiblock Copolymers written by Rohit Gupta and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiblock copolymers have gained considerable attention due to their ability to offer immense potential for designing soft materials with complex architectures for diverse applications. The enlarged parameter space offered by these multiblock copolymers gives access to a wide variety of multiply continuous morphologies which can be used to produce highly ordered nanostructures. The investigation on multiblock copolymers has been subjected to two critical limitations: (i) A suitable synthetic strategy for accessing these structures and (ii) computational tools which can help in application driven design of these molecules. In this dissertation, the goal was to develop methodologies for the synthesis of multiblock copolymers with different architectures and understand how the variations in molecular architecture can influence macromolecular self-assembly. In chapter 2, the concept of single molecule insertion (SMI) for precise insertion of functional molecules is presented. The molecule precisely inserts once within the polymer chain with high chain fidelity and provides functionalities for post-insertion modifications. A series of molecules satisfying the criteria for SMI based on their reactivity ratios with styrene and methyl methacrylate were examined and used to synthesize a series of multiblock polymers with complex architectures. In chapter 3, a highly efficient synthetic methodology for synthesis of graft copolymers which lie along the continuum of a 3-arm star and A-B-C linear triblock copolymer has been described. The morphological characterization of the synthesized continuum graft copolymers is performed using SAXS, TEM, and DPD simulations. Interesting morphologies are observed for these continuum copolymers and projects them as interesting candidates to access new morphologies. Contrary to most of the work done on block copolymers, these structures are novel as their morphologies can be tuned keeping the [phi] and [chi] constant. This study helps in understanding of the effect of polymer architecture on the phase behavior of these graft copolymers and provides a novel pathway to tune the block copolymer morphologies. In chapter 4, a series of PMMA-b-PtBS-b-P2VP and PtBA-b-PtBS-b-P2VP triblock copolymers with extending P2VP arm has been synthesized. The study helps in extending the concept of high [chi]-low N block copolymer system from diblock to triblock copolymers. The morphologies of the synthesized triblock copolymers were characterized using SAXS and TEM and morphologies with multiple domains and smaller feature size were observed. Also, the effect of extending chain length of P2VP arm on the phase diagram on these highly frustrated triblock copolymer systems was studied and the observed morphologies using SAXS and TEM were mapped with the theoretical predictions.

Download or read book Synthesis Self assembly and Applications of Amorphous Polyferrocenylsilane Block Copolymers written by David Allen Rider and published by . This book was released on 2007 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of well-defined polystyrene-block-poly(ferrocenylethylmethylsilane) (PS-b-PFEMS) diblock copolymers was synthesized. Both PFEMS and PS- b-PFEMS were shown to be amorphous due to the atactic nature of the PFEMS. As a result, PS- b-PFEMS readily undergo solid-state self-assembly in the bulk producing a spectrum of ordered nanometer sized iron-rich morphologies. When cylinder-forming PS-b-PFEMSs were studied in thin films, well-ordered arrays of hexagonally packed iron-rich cylindrical microdomains oriented either parallel to or normal to the substrate were produced. The orientation was found to depend strongly on the film thickness and/or the conditions of annealing. The etching of these films using (i) reactive plasmas, and (ii) an oxidative chemical wet etch technique were investigated. Using (i), surface-patterned magnetic ceramics were produced as well as a nanotextured silver metal film. The latter was found to dramatically enhance the Raman spectroscopy of an adsorbed analyte molecule. Using (ii), nanoporous polystyrene films were generated by the quantitative elimination of PFEMS domains by exposure to a nucleophilic non-solvent under oxidizing conditions.Thin films of PS-b-PFEMS generated efficient iron nanoparticle catalysts for single-walled carbon nanotube (SWNT) growth via a chemical vapor deposition growth process. The kinetics of the formation of iron catalysts from PS- b-PFEMS and PFEMS were compared. Despite the lower iron content for PS-b -PFEMS films, more active iron sites were produced. Additionally, the tube diameter and density were tunable by adjusting the chain lengths of polyferrocenylsilane- block-polysiloxanes in thin films. Lastly, high-throughput field-effect SWNT transistors have been fabricated with more than 160 individually addressable devices on a chip.The influence of strong 3D confinement on the self-assembly of PS-b-PFEMS was studied. Both silica colloidal crystals and silica inverse colloidal crystals were used for directing the self-assembly. Unusual morphologies, such as concentric shells and branched lamellae, resulted from the interaction of the lamellar-forming PS-b-PFEMS with the high surface area templates. In addition, the control of the 3D confined morphology of cylinder-forming PS-b-PFEMS was demonstrated through mediation of the interfacial interactions within the colloidal crystal.For solution state self-assembly, PS-b -PFEMSs and polystyrene-block-poly(ferrocenylmethylphenylsilanes) (PS-b-PFEMSs) were stoichiometrically oxidized in solution. Due to a redox-induced polarity change for the PFEMS and PFMPS blocks, self-assembly into well-defined spherical micelles occurred. The micelles, composed of a core of partially oxidized PFS segments and a corona of PS, disassembled when treated with a reducing agent and regenerated unassociated free chains.Lastly, the photochemical treatment of metal-containing ferrocenophane monomers with low energy Pyrex-filtered light from a mercury lamp (lambda > 310 nm) or bright sunlight in the presence of an anionic initiator led to living polymerizations in which the conversion and molecular weight of the resulting polymer was controlled by irradiation time. The polymerization proceeded via attack of the initiator or propagating anion on the iron atom of the photoexcited monomer. The formation of functional block copolymer architectures was possible when the light is alternately switched on and off in between the sequential addition of different monomers.

Download or read book Synthesis and Characterisation of Novel Ionic Block Copolymers written by Andrew Brian Lowe and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Self assembly Behavior in Hydrophilic Block Copolymers written by Clara Valverde Serrano and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Block copolymers are receiving increasing attention in the literature. Reports on amphiphilic block copolymers have now established the basis of their self-assembly behavior: aggregate sizes, morphologies and stability can be explained from the absolute and relative block lengths, the nature of the blocks, the architecture and also solvent selectiveness. In water, self-assembly of amphiphilic block copolymers is assumed to be driven by the hydrophobic. The motivation of this thesis is to study the influence on the self-assembly in water of A b B type block copolymers (with A hydrophilic) of the variation of the hydrophilicity of B from non-soluble (hydrophobic) to totally soluble (hydrophilic). Glucose-modified polybutadiene-block-poly(N-isopropylacrylamide) copolymers were prepared and their self-assembly behavior in water studied. The copolymers formed vesicles with an asymmetric membrane with a glycosylated exterior and poly(N-isopropylacrylamide) on the inside. Above the low critical solution temperature (LCST) of poly(N-isopropylacrylamide), the structure collapsed into micelles with a hydrophobic PNIPAM core and glycosylated exterior. This collapse was found to be reversible. As a result, the structures showed a temperature-dependent interaction with L-lectin proteins and were shown to be able to encapsulate organic molecules. Several families of double hydrophilic block copolymers (DHBC) were prepared. The blocks of these copolymers were biopolymers or polymer chimeras used in aqueous two-phase partition systems. Copolymers based on dextran and poly(ethylene glycol) blocks were able to form aggregates in water. Dex6500-b-PEG5500 copolymer spontaneously formed vesicles with PEG as the "less hydrophilic" barrier and dextran as the solubilizing block. The aggregates were found to be insensitive to the polymer's architecture and concentration (in the dilute range) and only mildly sensitive to temperature. Variation of the block length, yielded different morphologies. A longer PEG chain seemed to promote more curved aggregates following the inverse trend usually observed in amphiphilic block copolymers. A shorter dextran promoted vesicular structures as usually observed for the amphiphilic counterparts. The linking function was shown to have an influence of the morphology but not on the self-assembly capability in itself. The vesicles formed by dex6500-b-PEG5500 showed slow kinetics of clustering in the presence of Con A lectin. In addition both dex6500-b-PEG5500 and its crosslinked derivative were able to encapsulate fluorescent dyes. Two additional dextran-based copolymers were synthesized, dextran-b-poly(vinyl alcohol) and dextran-b-poly(vinyl pyrrolidone). The study of their self-assembly allowed to conclude that aqueous two-phase systems (ATPS) is a valid source of inspiration to conceive DHBCs capable of self-assembling. In the second part the principle was extended to polypeptide systems with the synthesis of a poly(N-hydroxyethylglutamine)-block-poly(ethylene glycol) copolymer. The copolymer that had been previously reported to have emulsifying properties was able to form vesicles by direct dissolution of the solid in water. Last, a series of thermoresponsive copolymers were prepared, dextran-b-PNIPAMm. These polymers formed aggregates below the LCST. Their structure could not be unambiguously elucidated but seemed to correspond to vesicles. Above the LCST, the collapse of the PNIPAM chains induced the formation of stable objects of several hundreds of nanometers in radius that evolved with increasing temperature. The cooling of these solution below LCST restored the initial aggregates. This self-assembly of DHBC outside any stimuli of pH, ionic strength, or temperature has only rarely been described in the literature. This work constituted the first formal attempt to frame the phenomenon. Two reasons were accounted for the self-assembly of such systems: incompatibility of the polymer pairs forming the two blocks (enthalpic) and a considerable solubility difference (enthalpic and entropic). The entropic contribution to the positive Gibbs free energy of mixing is believed to arise from the same loss of conformational entropy that is responsible for "the hydrophobic effect" but driven by a competition for water of the two blocks. In that sense this phenomenon should be described as the "hydrophilic effect".

Download or read book Copolymerization of Dienes from Mechanistic Insights Towards Material Properties of Multiblock Copolymers written by Ramona Denise Barent and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the groundbreaking work of Hermann Staudinger in 1920, polymer science has evolved tremendously for more than 100 years into manifold directions, impacting countless parts of life. Naming only a few disciplines, polymers find an omnipresent application in the automotive and the construction sector. Their insulating or semiconducting properties are pivotal for electric and electronic devices, whereas membrane technologies rely on their separation capability, and both the medical and the agricultural sector benefit from advanced polymer structures for controlled drug release. Yet, macromolecules played a crucial role long before they were recognized, studied in depth and specialized for targeted applications. For instance, natural rubber has been commercialized for almost the past two centuries, with Charles Goodyear's and Thomas Hancock's vulcanization process providing the basis for stable elastomeric materials. The introduction of synthetic thermoplastic elastomers (TPEs) in the 20th century, possessing the processability of thermoplastics and the elasticity of vulcanized rubber, and progress in understanding the chemical nature and the resulting material properties allows for envisioning versatile characteristics. With the living anionic polymerization technique at hand, which is the method of choice for the synthesis of complex but well-defined polymer architectures, new challenges designing materials with tailored physical properties can be met. The first part of this thesis aspires to elucidate the influence of an (IS)nI multiblock architecture on the materials' properties in bulk, whereas the second part evaluates their solution characteristics. At the end of this work a fundamental framework for the living anionic polymerizability in non-polar media is outlined. Chapter 1 gives a general introduction to the versatile toolbox of living anionic polymerization against the background of their use as thermoplastic elastomers (TPEs). After a brief outline of the historical background of elastomers and current application fields of TPEs, this review focuses on synthetic approaches tailoring the polymers' and in turn the materials ́ properties. In particular, inherent mechanical properties are discussed with respect to the phase segregation strength and the resulting microdomain morphologies. The highlighted synthetic strategies focus on lithium initiated living anionic (co)polymerizations of different styrenic and 1,3-diene monomers in hydrocarbons, further emphasizing the influence of modifiers on the block profile in statistical copolymers. In this regard, not only the block profile, but also the influence of the block sequence, the block number, and the polymer chain architecture are elaborated. Furthermore, the benefit of in situ monitoring techniques to determine kinetic parameters is demonstrated and expanded on kinetic Monte Carlo simulations, which allow for the calculation of reaction times, greatly facilitating the workflow of multiblock syntheses. Chapter 2 reviews the use of plasticized poly(vinyl chloride) for medical devices. In the first part health concerns related to the commonly used plasticizer are discussed within the framework of human exposure and its metabolism. The second and third part evaluate potential solutions by the introduction of different plasticizers and by the replacement of PVC by alternative polymer materials, respectively. For the latter, a project funded by the European Commission addressing the implementation of polyolefins for medical bags and the use of styrenic thermoplastic elastomers for healthcare applications are considered in greater detail. Chapter 3 highlights the structural and mechanical investigation of polyisoprene-polystyrene multiblock copolymers with two polyisoprene end blocks. These structures are of interest due to the potential internal plasticizer effect of the flexible end blocks, probably rendering a soft but resilient material. Temperature-dependent small-angle x-ray scattering experiments were implemented to investigate the phase separated morphologies of both sequential and tapered (IS)nI multiblock copolymers covering a wide range of molar masses and block numbers. A strong decrease in the segregation strength and hence of the order-disorder temperature was proven, comparing sequential block copolymers with a defined transition between the adjacent blocks with tapered block-like copolymers with a sharp, but gradual comonomer transition in each polyisoprene-polystyrene diblock sequence. This is caused by the reduced enthalpic incompatibility in tapered structures. While the sequential multiblock copolymers exhibited well-ordered lamellar morphologies, the tapered counterparts showed weakly- ordered perforated layers. The viscoelastic responses measured by tensile tests evidenced superior resilience for the sequential structures, while the tapered structures revealed a higher softness and flexibility. The concomitant decrease of the block size by increasing the block number at a given overall molar mass is accompanied by an increased domain bridging, but at the same time a weakened microphase separation. Due to this trade-off, the higher molar mass tapered pentablocks and sequential heptablocks were found to best balance these opposite effects, resulting in a significant mechanical toughness. Interestingly, polymers with the same molar mass per block exhibited comparable domain spacings and hence softness, while the ultimate deformability was found to increase with the extension by a diblock sequence due to an enhanced domain bridging. Comparison with a literature-known analogous structure with two polystyrene end blocks revealed an easier deformability of the structure with two polyisoprene end blocks reasoned in a smaller domain size. Chapter 4 further elaborates the mechanical properties of polyisoprene-polystyrene multiblock copolymers with different architectures in terms of chain connectivity. This fundamental research is intriguing due to the potential to minimize the issue of permanent sets upon large deformation while preserving the advantage of easily processable and reprocessable materials. Uniaxial tensile tests as well as recovery measurements were performed comparing linear tapered SIS triblock copolymers with linear (SIS)2 pentablock and star-shaped (SIS)4 multiblock copolymers featuring vitrifying core and end blocks. The advanced architectures were synthesized by an “arm-first” approach coupling the (SIS) arms. For small molar masses per arm, the star-shaped multiblock architectures showed superior ultimate stress and strain at break reflected in a higher toughness, which can be ascribed to their higher bridging fraction. For higher molar masses, the ultimate mechanical properties of the linear pentablock copolymers and the star-shaped structures approached each other reaching a plateau value, showing that at this point the covalent linkage of the star architecture does not provide further resilience. Yet, they still outperformed the simple triblock structure, further emphasizing the importance of large fractions of bridged chain conformations. For polymers with the same overall molar mass, the star-shaped multiblock copolymers could not compete with the linear pentablock copolymers due to an inferior phase segregation and hence facilitated chain pull-out. For three counterparts of equal molar mass per arm, which showed decent phase segregation and comparable ultimate properties, the cyclic strain experiments evidenced striking differences in their recovery behavior. While the star-shaped (SIS)4 multiblock copolymer showed unprecedented final recovery after 5 minutes of rest, they exhibited poor initial recovery during receding. In contrast, the linear structures feature superior rapid recovery but smaller final recoveries after resting. These phenomena prove the higher chain flexibility of the linear architectures being responsible for fast restoring, while the even stress distribution in star-shaped architectures with a covalent core junction generates improved shape memory. However, at high stress levels all specimens experienced a permanent set due to substantial restructuring, resulting in converging restoring properties. Chapter 5 examines the three most decisive tribological parameters dictating the performance of viscosity modifiers in lubricating oils relating to not only commonly implemented, but also novel polymer classes. Moving metal parts have to be lubricated in order to prevent friction. However, lubricating fluids face a rapid viscosity decrease upon increasing temperature. Therefore, viscosity modifiers are added to attenuate the adverse effects of asperity contact. Yet, optimum performance in all of the three key metrics, i.e., a beneficial viscosity-temperature relationship, thickening efficiency, and shear stability has not been achieved so far. Since these tribological parameters are complexly intercorrelated, their balancing is challenging, which is the reason for the demand for novel lubricant additives. The influence of key polymer characteristics such as molar mass, dispersity, chain composition, and architecture on the hydrodynamic volume and by this on the tribological parameters are accentuated. Furthermore, the chemical nature of the commonly implemented polymer classes comprising poly(alkyl methacrylates), olefinic copolymers, and hydrogenated styrene- diene copolymers is reviewed with respect to their polymerization mechanism and the inherent thickening mechanisms for viscosity improvement. The latter include the coil expansion mechanism prominent in poly(alkyl methacrylate) formulations and association phenomena featured by hydrogenated styrene-diene copolymers. Beyond this, advanced structures aiming at exceeding the current performance limits are discussed. Here, blending approaches and new polymer classes like poly(2-oxazolines) and poly(2-oxazines), but also sophisticated architectures like brush-like, comb-like or linear (tapered) multiblock copolymer structures are emphasized. This promising combination of several benefits gives food for further investigations. Chapter 6 addresses the self-organization of multiblock copolymers with both a defined and a gradual block profile in the polyisoprene-selective solvent heptane. Conclusions on the aggregate structures are drawn based on the diffusion behavior at varying concentrations. For this purpose, dilute and concentrated polymer solutions are examined by dynamic light scattering using a cross-correlation approach, which allows to study diffusion processes even in the presence of multiple scattering events. Diverging diffusion coefficients for the triblock and multiblock copolymers at a polymer concentration above 1 wt% proved the formation of non-ergodic systems, i.e., polymer networks, in case of the structures with several solvophobic polystyrene blocks. Complementary fluorescence correlation spectroscopy measurements permitted insights into the self-diffusion of unimers through these polymer networks. These processes were found to be most restricted in networks of sequential multiblock copolymers, which is the consequence of a denser network due to a higher bridging fraction in combination with larger unimer dimensions. The unimer dimensions themselves were studied in highly diluted polymer solutions, where no aggregation phenomena are present. Furthermore, micellar aggregates and their fraction increased going from dilute solutions to higher concentrations, finally adapting the discussed transient polymer networks. In order to enable fluorescence correlation spectroscopy investigations, a novel post-polymerization protocol for fluorescent dye attachment was established, which stands out by only a marginal alteration in the chemical nature of the labeled polymer. Chapter 7 emphasizes the concentration-dependent viscosity-temperature relationship of the (non)-hydrogenated tapered multiblock copolymers in the polyisoprene-selective solvents squalane and a highly isoparaffinic hydrocarbon lubricating oil against the background of the self-assembled structures discussed in Chapter 6. Combining temperature- and frequency- dependent dynamic viscosity measurements with temperature-dependent kinematic viscosity measurements at 40 °C and 100 °C, a clear correlation between the self-organized polymer aggregate structure and the performance as viscosity modifier could be established. At comparably low polymer concentrations, an enhanced viscosity-temperature relationship with increasing overall molar mass, block number, and isoprene content was identified. As an explanation, the formation of loose aggregates with several polystyrene cores and hence extended hydrodynamic volumes in case of multiblock architectures was deduced. Yet at high concentrations, the structures with the shortest individual solvophobic polystyrene blocks faced a deterioration in the investigated tribological key parameters, i.e., the viscosity- temperature relationship and the thickening efficiency. This is explained by the formation of large transient networks, which are more prone to partial disassembly upon shearing. This effect is further intensified by the migration of solvent molecules into the aggregate's cores, which is most pronounced for short polystyrene blocks. The resulting weakened van-der-Waals interactions promote chain pull-out and by this partial disassembly. Comparison of the investigated styrene-diene multiblock copolymers to a commercialized comb-like poly(alkyl methacrylate) displayed a superior performance of the presented structures at low polymer treat rates. This demonstrates the enormous potential of tapered multiblock architectures as advanced viscosity modifiers. Chapter 8 aims at understanding the structure-property relationships of multiblock copolymers with a defined or a gradual, albeit sharp block profile in dilute non-selective solution. For this purpose, series of sequential and tapered multiblock copolymers (IS)nI with molar masses ranging from 40-400 kg·mol-1 and block numbers of 3-13 were comprehensively characterized by complementary approaches. Subsequently, dilute solutions in toluene were systematically investigated, implementing classical scaling relationships between the hydrodynamic characteristics derived from analytical ultracentrifugation, intrinsic viscosity, and related experiments. Both rotational and translational diffusion experiments showed subtle differences in the polymer coil dimension and hence rigidity for polymer series with equal block number. For these homologous polymer series, a more rigid and hence expanded chain conformation for the sequential structures was deducible compared to their tapered analogues. Interestingly, the polymer series with different molar masses and block number, whose polymers featured equal degrees of polymerization per polystyrene block, did not comply with the classical scaling relationships. This demonstrates the influence of the block number on the solution properties even in non-selective solvents. Chapter 9 studies the polymerizability of rotationally constrained 1,3-dienes with a fixed cisoid or transoid geometry of the double bonds. Particularly, the reactivity in living anionic polymerization approaches in non-polar media is examined, whose mechanism is proposed to proceed via a coordinative mechanism. Theoretical simulation approaches of two new 1,3-diene monomers with a rigid, prescribed cisoid or transoid geometry in cyclohexane as a typical non-polar solvent are combined with synthetic and kinetic studies. Experimental observations correlated with the predicted reactivities and simulated reaction pathways, which showed that a cisoid geometry with in-plane double bonds is mandatory for propagation. Indeed, the cisoid diene was homo- as well as copolymerizable with isoprene, whereas the transoid diene lacked reactivity. The required ring distortion in case of the cyclic cisoid diene resulted in higher simulated activation barriers for the propagation step in comparison to the addition of the unrestricted common monomer isoprene. This was experimentally confirmed by real-time 1H NMR spectroscopic kinetic investigations, which evinced a gradient formation in statistical copolymerization experiments of the cisoid diene with isoprene, whose steepness became flattened upon temperature increase. Additionally, thermal characterization of the statistical copolymers revealed a weakened segregation strength for the tapered diblock copolymers with a smoother gradual distribution of the comonomers along the polymer chain. Chapter A1 comprises a complementary examination of the ultimate mechanical properties of the tapered star-shaped polyisoprene-polystyrene multiblock copolymers treated in Chapter 4. Two series of (SIS)4 multiblock copolymers varying in their comonomer ratio were compared to the linear SIS triblock copolymers representing the corresponding arm structures. While the star-shaped polymers with a lower isoprene content ordered into lamellae and therefore were stiffer and less elastic, the series with a higher isoprene content possessed morphologies with a continuous polyisoprene phase. Irrespective of the formed morphology, the star-shaped (SIS)4 architectures outperformed the corresponding linear SIS polymers with respect to their toughness and strain at break. Furthermore, selective catalytic hydrogenation of the PI blocks was exemplified for one star-shaped multiblock copolymer and its linear counterpart, this way increasing the segregation strength and decreasing the entanglement molecular weight of the polydiene segments. Interestingly, the influence of hydrogenation on the ultimate properties varied with the polymer architecture. While the linear tapered triblock copolymer experienced a substantial increase in its ultimate properties, the star-shaped multiblock copolymer faced a deteriorated performance. This is explained by differences in the magnitude of strain- hardening improvement in combination with higher amounts of entanglements. Chapter A2 focuses on the impact of solvents on the copolymerization kinetics of epoxides via an anionic ring-opening polymerization mechanism. For this purpose, the copolymerization kinetics of ethylene oxide (EO) with glycidyl ethers with varying coordination sites were monitored by in situ 1H NMR spectroscopy both in tetrahydrofuran (THF) and the highly polar solvent dimethyl sulfoxide (DMSO). The experiments revealed slightly higher reactivities of the glycidyl ethers compared to EO, which lacks in any side group, emphasizing a pronounced chelation effect of the potassium counterion by the side groups of the glycidyl ether monomers about to be added. With allyl glycidyl ether (AGE) featuring one and ethoxy vinyl glycidyl ether (EVGE) possessing two ether-type coordination sites per side group, EVGE showed slightly stronger incorporation preference than AGE. An increase in the disparity of the relative reactivities was found with decreasing solvent polarity, which relies on the degree of solvation of the propagating chain end and its counterion. Density functional theoretical simulation approaches were implemented to illustrate and further justify the pivotal role of the complexation capability of the ether-containing side groups.

Download or read book Synthesis of Novel Hydrophilic Methacrylate based Block Copolymers written by Kay Louise Robinson and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Self Healing Polymers written by Wolfgang H. Binder and published by John Wiley & Sons. This book was released on 2013-03-29 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-healing is a well-known phenomenon in nature: a broken bone merges after some time and if skin is damaged, the wound will stop bleeding and heals again. This concept can be mimicked in order to create polymeric materials with the ability to regenerate after they have suffered degradation or wear. Already realized applications are used in aerospace engineering, and current research in this fascinating field shows how different self-healing mechanisms proven successful by nature can be adapted to produce even more versatile materials. The book combines the knowledge of an international panel of experts in the field and provides the reader with chemical and physical concepts for self-healing polymers, including aspects of biomimetic processes of healing in nature. It shows how to design self-healing polymers and explains the dynamics in these systems. Different self-healing concepts such as encapsulated systems and supramolecular systems are detailed. Chapters on analysis and friction detection in self-healing polymers and on applications round off the book.

Download or read book The Synthesis of Modular Block Copolymers written by Mary Nell Higley and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel methodology has been developed for the formation of block copolymers that combines ring-opening metathesis polymerization (ROMP) with functional chain-transfer agents (CTAs), functional chain-terminators (CTs) and self-assembly. Telechelic homopolymers of cyclooctene derivatives that are end-functionalized with hydrogen-bonding or metal-coordination sites are formed via the combination of ROMP with a corresponding functional CTA. These telechelic homopolymers are fashioned with a high control over molecular weight and without the need for post-polymerization procedures. The homopolymers undergo fast and efficient self-assembly with their complement homopolymer or small molecule analogues to form block copolymer architectures. The block copolymers have similar association constants to small molecule analogues described in the literature, regardless of size or the nature of the complementary unit or the polymer side-chain. The ROMP of side-chain functionalized norbornene polymers is coupled with functional CTs to produce block copolymer with main- and side-chain self-assembly sites. Combinations of these norbornene polymers with their complement polymer via self-assembly produce non-covalent AB type block copolymers fast and efficiently. ABA type block copolymers are realized by combining the difunctional homopolymer formed via the CTA pathway with the CT synthesized mono-functional polymer. These polymers show similar association constants regardless of the sequence of polymer formation.