Supramolecular polymers azo-containing : photo-responsive block copolymer elastomers and homopolymers

Beaucoup d'efforts dans le domaine des matériaux polymères sont déployés pour développer de nouveaux matériaux fonctionnels pour des applications spécifiques, souvent très sophistiquées, en employant des méthodes simplifiées de synthèse et de préparation. Cette thèse porte sur les polymères photosensibles – i.e. des matériaux fonctionnels qui répondent de diverses manières à la lumière – qui sont préparés à l'aide de la chimie supramoléculaire – i.e. une méthode de préparation qui repose sur l'auto-assemblage spontané de motifs moléculaires plus simples via des interactions non covalentes pour former le matériau final désiré. Deux types de matériaux photosensibles ont été ciblés, à savoir les élastomères thermoplastiques à base de copolymères à blocs (TPE) et les complexes d'homopolymères photosensibles. Les TPEs sont des matériaux bien connus, et même commercialisés, qui sont généralement composés d’un copolymère tribloc, avec un bloc central très flexible et des blocs terminaux rigides qui présentent une séparation de phase menant à des domaines durs isolés, composés des blocs terminaux rigides, dans une matrice molle formée du bloc central flexible, et ils ont l'avantage d'être recyclable. Pour la première fois, au meilleur de notre connaissance, nous avons préparé ces matériaux avec des propriétés photosensibles, basé sur la complexation supramoléculaire entre un copolymère tribloc simple parent et une petite molécule possédant une fonctionnalité photosensible via un groupe azobenzène. Plus précisément, il s’agit de la complexation ionique entre la forme quaternisée d'un copolymère à blocs, le poly(méthacrylate de diméthylaminoéthyle)-poly(acrylate de n-butyle)-poly(méthacrylate de diméthylaminoéthyle) (PDM-PnBA-PDM), synthétisé par polymérisation radicalaire par transfert d’atomes (ATRP), et l'orange de méthyle (MO), un composé azo disponible commercialement comportant un groupement SO3 -. Le PnBA possède une température de transition vitreuse en dessous de la température ambiante (-46 °C) et les blocs terminaux de PDM complexés avec le MO ont une température de transition vitreuse élevée (140-180 °C, en fonction de la masse molaire). Des tests simples d'élasticité montrent que les copolymères à blocs complexés avec des fractions massiques allant de 20 à 30% présentent un caractère élastomère. Des mesures d’AFM et de TEM (microscopie à force atomique et électronique à ii transmission) de films préparés à l’aide de la méthode de la tournette, montrent une corrélation entre le caractère élastomère et les morphologies où les blocs rigides forment une phase minoritaire dispersée (domaines sphériques ou cylindriques courts). Une phase dure continue (morphologie inversée) est observée pour une fraction massique en blocs rigides d'environ 37%, ce qui est beaucoup plus faible que celle observée pour les copolymères à blocs neutres, dû aux interactions ioniques. La réversibilité de la photoisomérisation a été démontrée pour ces matériaux, à la fois en solution et sous forme de film. La synthèse du copolymère à blocs PDM-PnBA-PDM a ensuite été optimisée en utilisant la technique d'échange d'halogène en ATRP, ainsi qu’en apportant d'autres modifications à la recette de polymérisation. Des produits monodisperses ont été obtenus à la fois pour la macroamorceur et le copolymère à blocs. À partir d'un seul copolymère à blocs parent, une série de copolymères à blocs partiellement/complètement quaternisés et complexés ont été préparés. Des tests préliminaires de traction sur les copolymères à blocs complexés avec le MO ont montré que leur élasticité est corrélée avec la fraction massique du bloc dur, qui peut être ajustée par le degré de quaternisation et de complexation. Finalement, une série de complexes d'homopolymères auto-assemblés à partir du PDM et de trois dérivés azobenzènes portant des groupes (OH, COOH et SO3) capables d'interactions directionnelles avec le groupement amino du PDM ont été préparés, où les dérivés azo sont associés avec le PDM, respectivement, via des interactions hydrogène, des liaisons ioniques combinées à une liaison hydrogène à travers un transfert de proton (acidebase), et des interactions purement ioniques. L'influence de la teneur en azo et du type de liaison sur la facilité d’inscription des réseaux de diffraction (SRG) a été étudiée. L’efficacité de diffraction des SRGs et la profondeur des réseaux inscrits à partir de films préparés à la méthode de la tournette montrent que la liaison ionique et une teneur élevée en azo conduit à une formation plus efficace des SRGs.

Controlled Self-assembly of p-Phenyleneethynylene Derivatives to Diverse Supramolecular Architectures

Regional Research Laboratory

Oligo(p-Phenylenevinylene) Derived Organogels: A Novel Class of Functional Supramolecular Materials

The main objective of the present study is to have a detailed investigation on the gelation properties, morphology and optical properties of small π-conjugated oligomers. For this purpose we have chosen oligo(p-phenylenevinylene)s (OPVs), a class of molecules which have received considerable attention due to their unique optical and electronic properties. Though a large number of reports are available in the literature on the self-assembly properties of tailor made OPVs, none of them pertain to the design of nanostructures based on organogels. In view of this, we aimed at the creation of functional chromophoric assemblies of π-conjugated OPVs through the formation of organogels, with the objective of crafting nanoscopic assemblies of different size and shape thereby modulating their optical and electronic properties.In order to fulfill the above objectives, the design and synthesis of a variety of OPVs with appropriate structural variations were planned. The design principle involves the derivatization of OPVs with weak H-bonding hydroxymethyl end groups and with long aliphatic hydrocarbon side chains. The noncovalent interactions in these molecules were expected to lead the formation of supramolecular assembly and gels in hydrocarbon solvents. In such an event, detailed study of gelation and extensive analysis of the morphology of the gel structures were planned using advanced microscopic techniques. Since OPVs are strongly fluorescent molecules, gelation is expected to perturb the optical properties. Therefore, detailed study on the gelation induced optical properties as a way to probe the nature and stability of the selfassembly was planned. Apart from this, the potential use of the modulation of the optical properties for the purpose of light harvesting was aimed. The approach to this problem was to entrap an appropriate energy trap to the OPV gel matrix which may lead to the efficient energy transfer from the OPV gel based donor to the entrapped acceptor. The final question that we wanted to address in this investigation was the creation of helical nanostructures through proper modification of the OPV backbone With chiral handles.The present thesis is a detailed and systematic approach to the realization of the above objectives which are presented in different chapters of the thesis.

Supramolecular Organization of Metal Nanoparticles in Solution and of Phenyleneethynylenes on Surfaces

Most of the procedures reported for the synthesis of metal nanoparticles involve the use of strong reducing agents or elevated temperatures. This limits the possibility of developing metal nanoparticle based sensors for the in situ detection of analytes. One of the objectives of the present investigations is to (i) develop newer methodologies for the synthesis of metal nanoparticles in aqueous medium at ambient conditions and (ii) their use in the detection of metal cations by taking advantage of the unique coordination ability. Ideally, biocompatible molecules which possess both the reducing and stabilizing groups are desirable for such applications. Formation of stable supramolecular assembly, by bringing metal nanoparticles close to each other, results in plasmon coupling and this strategy can be effectively utilized for the development of metal nanoparticle based sensors.Another objective of the present study is to understand the supramolecular organization of molecules on surfaces. Various noncovalent interactions between the molecules and with surface play a decisive role in their organizations. An in-depth understanding of these interactions is essential for device fabrications. Recent photophysical studies have revealed that phenyleneethynylene based molecular systems are ideal for device application. The second objective of the thesis focuses on understanding the (i) organization of phenyleneethynylenes on highly oriented pyrolytic graphite (HOPG) surface with atomic level precision and (ii) weak intermolecular interactions which drive their organization.

Chemistry of molecular and supramolecular structures of vanadium(IV) and dioxygen-bridged V(V) complexes incorporating tridentate hydrazone ligands

Four hydrazone ligands: 2-benzoylpyridine benzoyl hydrazone (HBPB), di-2-pyridyl ketone nicotinoyl hydrazone (HDKN), quinoline-2-carbaldehyde benzoyl hydrazone (HQCB), and quinoline-2-carbaldehyde nicotinoyl hydrazone (HQCN) and four of their complexes with vanadyl salts have been synthesized and characterized. Single crystals of HBPB and complexes [VO(BPB)(l2-O)]2 (1) and [VO(DKN)(l2-O)]2 ½H2O (2) were isolated and characterized by X-ray crystallography. Each of the complexes exhibits a binuclear structure where two vanadium(V) atoms are bridged by two oxygen atoms to form distorted octahedral structures within cis-N2O4 donor sets. In most complexes, the uninegative anions function as tridentate ligands, coordinating through the pyridyl- and azomethine-nitrogen atoms and enolic oxygen whereas in complex [VO(HQCN)(SO4)]SO4 4H2O (4) the ligand is coordinated in the keto form. Complexes [VO(QCB)( OMe)] 1.5H2O (3) and 4 are found to be EPR active and showed well-resolved axial anisotropy with two sets of eight line pattern

Three substituted 4-pyrazolylbenzoates: hydrogen-bonded supramolecular structures in one, two and three dimensions

The molecules of ethyl 4-(5-amino-3-methyl-1H-pyrazol-1yl) benzoate, C13H15N3O2, are linked by two independent N-H center dot center dot center dot O hydrogen bonds into a chain of edge-fused and alternating R-4(2)(8) and R-2(2)(20) rings. A combination of N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds links the molecules of methyl 4-(5-amino-3-tert-butyl-1H-pyrazol-1-yl) benzoate, C15H19N3O2, into sheets of alternating R-2(2)(20) and R-6(6)(32) rings. In 4-(5-amino-3-methyl-1H-pyrazol-1-yl) benzoic acid monohydrate, C11H11N3O2 center dot H2O, the molecular components are linked into a three-dimensional framework structure by a combination of five independent hydrogen bonds, two of O-H center dot center dot center dot N type and one each of O-H center dot center dot center dot O, N-H center dot center dot center dot O and N-H center dot center dot center dot N types

A healable supramolecular polymer blend based on aromatic π-π stacking and hydrogen bonding interactions

An elastomeric, supramolecular healable polymer blend, comprising a chain-folding polyimide and a telechelic polyurethane with pyrenyl endgroups, is compatibilised by aromatic π−π stacking between the π-electron-deficient diimide groups and the π-electron-rich pyrenyl units. This inter-polymer interaction is key to forming a tough, healable, elastomeric material. Variable temperature FTIR analysis of the bulk material also conclusively demonstrates the presence of hydrogen bonding, which complements the π–π stacking interactions. Variable temperature SAXS analysis shows that the healable polymeric blend has a nanophase-separated morphology, and that the X-ray contrast between the two types of domain increases with increasing temperature, a feature that is repeatable over several heating and cooling cycles. A fractured sample of this material reproducibly regains more than 95% of the tensile modulus, 91% of the elongation to break, and 77% of the modulus of toughness of the pristine material.

Bis(hydroxy-isoindolinone)s: synthesis, stereochemistry, polymer chemistry, and supramolecular assembly

Pseudoacid chlorides of 2,5-bis(4-fluorobenzoyl) terephthalic acid and 4,6-bis(4-fluorobenzoyl) isophthalic acid condense with primary amines to afford diastereomeric bis(hydroxyindolinone)s in good isolated yields and with diamines to give high molecular weight poly(hydroxyindolinone)s. Bis-N-pyrenemethyl bis(hydroxyindolinone)s assemble, even in dipolar solvents such as DMSO, with macrocyclic diimide-sulfones to give [3]pseudorotaxanes stabilized by electronically complementary aromatic π−π-stacking and shape-complementary van der Waals interactions.

Thermo-responsive microphase separated supramolecular polyurethanes

The ability to generate very stable assemblies via non-covalent interactions has enabled materials to be constructed that were not feasible via traditional covalent bond formation processes. A series of low molecular mass bisurethane and bisurea polymers have been developed that form stable self-assembled networks through hydrogen bonding interactions. Thermo-responsive polymers were generated by end-capping poly(ethylene-co-butylene) or polybutadiene chains with the bisurethane or bisurea motif. Microphase separation is observed via TEM and small-angle X-ray scattering (SAXS) for the modified pseudo polymers and significant differences in the temperature dependence of microphase separation are analysed via SAXS. The importance of the polarity of the end groups is manifested in distinct temperature-dependent microphase separation behaviour. Information on the local hydrogen bonding structure is provided by wide-angle X-ray scattering and variable temperature FTI

Supramolecular parallel beta-sheet and amyloid-like fibril forming peptides using delta-aminovaleric acid residue

Four terminally blocked tripeptides containing delta-aminovaleric acid residue self-assemble to form supramolecular beta-sheet structures as are revealed from their FT-IR data. Single crystal X-ray diffraction studies of two representative peptides also show that they form parallel beta-sheet structures. Self-aggregation of these beta-sheet forming peptides leads to the formation of fibrillar structures, as is evident from scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images. These peptide fibrils bind to a physiological dye, Congo red and exhibit a typical green-gold birefringence under polarized light, showing close resemblance to neurodegenerative disease causing amyloid fibrils. (c) 2005 Elsevier Ltd. All rights reserved.

Amyloid-like fibril-forming supramolecular beta-sheets from a beta-turn forming tripeptide containing non-coded amino acids: the crystallographic signature

The crystal structure of a terminally protected tripeptide Boc-Leu-Aib-beta-Ala-OMe 1 containing non-coded amino acids reveals that it adopts a beta-turn structure, which sell-assembles to form a supramolecular beta-sheet via non-covalent interactions. The SEM image of peptide 1 exhibits amyloid-like fibrillar morphology in the solid state. (C) 2002 Elsevier Science Ltd. All rights reserved.

Supramolecular peptide helix from a novel double turn forming peptide containing a beta-amino acid

A single-crystal X-ray diffraction study of the terminally protected tetrapeptide Boc-beta-Ala-Aib-Leu-Aib-OMe 1 (Aib: alpha-aminoisobutyric acid; beta-Ala: beta-Alanine) reveals that it adopts a new type of double turn structure which self-associates to form a unique supramolecular helix through intermolecular hydrogen bonds. Scanning electron microscopic studies show that peptide 1 exhibits amyloid-like fibrillar morphology in the solid state. (C) 2003 Elsevier Science Ltd. All rights reserved.

An amyloid-like fibril forming antiparallel supramolecular beta-sheet from a synthetic tripeptide: a crystallographic signature

Single crystal X-ray diffraction studies of a terminally blocked tripeptide Boc-Leu(1)-Aib(2)-Leu(3)-OMe 1 demonstrates that it adopts a bend structure without any intramolecular hydrogen bond. Peptide 1 self-assembles to form a supramolecular antiparallel beta-sheet structure by various non-covalent interactions including intermolecular hydrogen bonds in the crystal and it exhibits amyloid-like fibrillar morphology in the solid state. (C) 2003 Elsevier Ltd. All rights reserved.

Hydrogen-bonded dimer can mediate supramolecular beta-sheet formation and subsequent amyloid-like fibril formation: a model study

FT-IR data of six terminally blocked tripeptides containing Acp (epsilon-aminocaproic acid) reveals that all of them form supramolecular beta-sheets in the solid state. Single crystal X-ray diffraction studies of two peptides not only support this data but also disclose the fact that the supramolecular beta-sheet formation is initiated via dimer formation. The Scanning Electron Microscopic images of all peptides exhibit amyloid-like fibrils that show green birefringence after binding with Congo red, which is a characteristic feature of many neurodegenerative disease causing amyloid fibrils. (C) 2004 Elsevier Ltd. All rights reserved.

Copper(II) complexes of mono-anionic glutamate: anionic influence in the variations of molecular and supramolecular structures

Three new polynuclear copper(II) complexes of singly deprotonated L-glutamic acid (L-glu), {[Cu(bipy)(2)][Cu(bipy)(L-glu)H2O](2)(BF4)(4)center dot(H2O)(3)}(n) (1), {[Cu(bipy)(L-glu)H2O][Cu(bipy)(L-glu)(ClO4)]( ClO4)center dot(H2O)(2)}(n) ((2)) and [Cu(phen)(L-glu)H2O](2)(NO3)(2)center dot(H2O)(4) (3) (bipy = 2,2-bipyridine, phen = 1,10-phenanthroline), were synthesized in acidic pH (ca. 2.5) and characterized structurally. In all the complexes, L-glutamic acid acts as a bidentate chelating ligand, leaving the protonated carboxylic acid free. Both in 1 and 2, two different types of species [Cu(bipy)(2)](BF4)(2) and [Cu(bipy)(L-glu)H2O] BF4 for 1 and [Cu(bipy)(L-glu)H2O]ClO4 and [Cu(bipy)(L-glu)(ClO4)] for 2 coexist in the solid state. In complex 1, the [C( bipy)(L-glu)H2O]+ units are joined together by syn-anti carboxylate bridges to form an enantiopure (M) helical chain and the [Cu(bipy)(2)](2+) presents a very rare example of the four-coordinate distorted tetrahedral geometry of Cu(II). In complex 2, the [Cu(bipy)(L gluClO(4))] units are joined together by weakly coordinating perchlorate ions to form a 1D polymeric chain while the [Cu(bipy)(L-glu)H2O]+ units remain as mononuclear species. The different coordinating ability of the two counter anions along with their involvement in the H-bonding network seems likely to be responsible for the difference in the final polymeric structures in the two compounds. Variable-temperature (2-300 K) magnetic susceptibility measurements show negligible coupling for both the complexes. The structure of 3 consists of two independent monomeric [Cu(phen)(L-glu)H2O]+ cations, two nitrate anions and four water molecules. The copper atom occupies a five-coordinate square pyramidal environment with a water molecule in the axial position.