Synthesis and characterization of diblock copolymers and triblock terpolymers for nanotechology applications

In this PhD thesis the synthesis and characterization of linear diblock copolymers of the A-b-B type and triblock terpolymers of the A-b-B-b-C type, where A, B and C are blocks consisting of monomeric units that exhibit different chemical composition was conducted. The blocks involved in the different copolymer and terpolymer sequences are the following: PS: polystyrene, PB1,2: poly(butadiene) bearing -1,2 microstructure ≈90-100%, PI1,4: poly(isoprene) bearing -1,4 microstructure ≈90%, PDMS: poly(dimethylsiloxane), PEO: poly(ethylene oxide) and P4VP: poly(4-vinylpyridine).Six (6) different sequences of diblock copolymers were studied, namely: PS-b-PB1,2, PB1,2-b-PDMS, PI1,4-b-PDMS, PS-b-PDMS, PS-b-P4VP and PB1,2-b-PEO. A total of twenty-three (23) samples of linear diblock copolymers were synthesized and their molecular, thermal, morphological and optical characterization was carried out. Three (3) different triblock terpolymer sequences were also studied, namely: PS-b-PB1,2-b-PDMS, PS-b-PB1,2-b-PEO and PS-b-P4VP-b-PEO. The number of triblock terpolymers samples was seven (7) and they were also subjected to molecular, thermal, morphological and optical characterization.All samples were synthesized via anionic polymerization and sequential monomers addition under high vacuum techniques. All experiments were carried out utilizing extremely purified reagents and glassware apparatuses, manufactured through scientific glassblowing, as required for anionic polymerization experiments. For the development of composites containing gold nanoparticles, the copolymers and terpolymers bearing P4VP as one of the blocks, were used as precursors, due to the ability of P4VP to be chemically modified through facile reactions.The thirty (30) samples discussed in this thesis were molecularly characterized through size exclusion chromatography (SEC) and vapor pressure or membrane osmometry (VPO, MO), to determine the dispersity index (Đ) and the total number average molecular weight respectively. By means of size exclusion chromatography the quality control of the samples was also carried out at all stages of the polymerization reactions (two or three reactions in total after the sequential addition of two or three different monomers respectively). The composition of the copolymers and terpolymers in terms of the mass fractions of each block as well as the determination of the microstructures of the poly(diene) blocks were carried out via proton nuclear magnetic resonance spectroscopy (1H-NMR).Utilizing differential scanning thermometry (DSC) all final samples were studied to calculate the temperature transitions (Tg, Tc, Tm) of the different blocks and to study the miscibility or immiscibility of the blocks involved by calculating the glass transition temperature (Tg) and comparing the values with those of the homopolymer segments.Through transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), the samples were morphologically characterized and their microphase separation was confirmed even for samples with very low total number average molecular weight. Also, to justify the different phases using TEM and to draw definite conclusions, the staining of the PB blocks with vapors of osmium tetroxide (OsO4) in aqueous solution (2% w/v) and P4VP blocks with iodine vapors was necessary in order to provide adequate difference on electronic density and to appear as dark phases. Furthermore, the characteristic dimensions of the unit cell in the range of few nanometers were verified.Through atomic force microscopy (AFM) the morphology verification was carried out in the thin films state, including the composite materials containing nanoparticles. In addition, the size of the nanoparticles of the composite materials was calculated. The ability to obtain morphologies in thin film state as well as the successful incorporation of nanoparticles, are very important properties for nanotechnology applications.The spectroscopic ellipsometry technique was used to measure the thickness and roughness of the deposited thin films. Absorption measurements of the composite materials were carried out to determine their response to the wavelengths of the visible spectrum. Finally, the average size of the nanoparticles in solution was calculated using dynamic light scattering (DLS) method.Η παρούσα διδακτορική διατριβή πραγματεύεται τη σύνθεση και το χαρακτηρισμό γραμμικών δισυσταδικών συμπολυμερών του τύπου A-b-B και τρισυσταδικών τριπολυμερών του τύπου A-b-B-b-C, όπου με A, B και C συμβολίζονται συστάδες διαφορετικής χημικής σύστασης. Οι συστάδες που μελετήθηκαν ήταν οι ακόλουθες: PS: πολυστυρένιο, PB1,2: πολυ(βουταδιένιο) μικροδομής -1,2 σε ποσοστό ≈90-100%, PI1,4: πολυ(ισοπρένιο) μικροδομής 1,4 σε ποσοστό ≈90%, PDMS: πολυ(διμεθυλοσιλοξάνη), ΡΕΟ: πολυ(αιθυλενοξείδιο) και P4VP: πολυ(4-βινυλοπυριδίνη).Συνολικά έξι (6) διαφορετικές αλληλουχίες δισυσταδικών συμπολυμερών και συγκεκριμένα οι: PS-b-PΒ1,2, PB1,2-b-PDMS, PΙ1,4-b-PDMS, PS-b-PDMS, PS-b-P4VP και PB1,2-b-PEO. Συντέθηκαν είκοσι τρία (23) δείγματα γραμμικών δισυσταδικών συμπολυμερών για τα οποία πραγματοποιήθηκε μοριακός, θερμικός, μορφολογικός και οπτικός χαρακτηρισμός τους. Επίσης μελετήθηκαν 3 διαφορετικές αλληλουχίες τρισυσταδικών τριπολυμερών και συγκεκριμένα οι: PS-b-PΒ1,2-b-PDMS, PS-b-PΒ1,2-b-PEO και PS-b-P4VP-b-PEO. Ο αριθμός δειγμάτων τρισυσταδικών τριπολυμερών ήταν εφτά (7) και σε αυτά πραγματοποιήθηκε επίσης μοριακός, θερμικός, μορφολογικός και οπτικός χαρακτηρισμός.Όλα τα δείγματα συντέθηκαν με τη μέθοδο του ανιοντικού πολυμερισμού και τη διαδοχική προσθήκη μονομερών υπό συνθήκες υψηλού κενού. Για τη διεξαγωγή όλων των πειραμάτων χρησιμοποιήθηκαν υπερκάθαρα αντιδραστήρια και υάλινες αυτοσχέδιες συσκευές, οι οποίες κατασκευάστηκαν μέσω επιστημονικής υαλουργίας, όπως προβλέπεται για επιτυχή πειράματα ανιοντικού πολυμερισμού. Για την ανάπτυξη σύνθετων υλικών των δειγμάτων που συντέθηκαν με νανοσωματίδια χρυσού χρησιμοποιήθηκαν αποκλειστικά τα συμπολυμερή και τριπολυμερή που περιείχαν τη συστάδα της P4VP καθώς η συγκεκριμένη μπορεί εύκολα να τροποποιηθεί χημικά. Και τα τριάντα (30) δείγματα που μελέτηθηκαν στην παρούσα διατριβή χαρακτηρίστηκαν μοριακά με χρωματογραφία αποκλεισμού μεγεθών (SEC) και ωσμωμετρία τάσης ατμών ή ωσμωμετρία μεμβράνης (VPO, ΜΟ) για να προσδιοριστούν η κατανομή μέσων μοριακών βαρών (Đ) και τα μέσα μοριακά βάρη κατ’ αριθμό αντίστοιχα. Μέσω της χρωματογραφίας αποκλεισμού μεγεθών πραγματοποιήθηκε επίσης ο ποιοτικός έλεγχος των δειγμάτων σε όλα τα στάδια των αντιδράσεων πολυμερισμού (δύο ή τρεις συνολικά αντιδράσεις αφού έλαβε χώρα η διαδοχική προσθήκη δύο ή τριών διαφορετικών μονομερών αντίστοιχα). Η σύσταση των συμπολυμερών και τριπολυμερών ως προς τα κλάσματα μάζας της κάθε συστάδας όπως και ο προσδιορισμός των μικροδομών των συστάδων των πολυ(διενίων) πραγματοποιήθηκαν μέσω της φασματοσκοπίας πυρηνικού μαγνητικού συντονισμού πρωτονίου (1H-NMR).Με τη χρήση της διαφορικής θερμιδομετρίας σάρωσης (DSC) μελετήθηκαν όλα τα τελικά δείγματα για τον υπολογισμό των θερμοκρασιακών μεταπτώσεων (Tg, Tc, Tm) των διαφορετικών συστάδων και την μελέτη της αναμιξιμότητας ή μη των εμπλεκόμενων συστάδων μέσω του υπολογισμού της θερμοκρασίας υαλώδους μετάπτωσης (Tg) και συγκρίνοντας τις τιμές με αυτές των αντίστοιχων ομοπολυμερών.Με την ηλεκτρονική μικροσκοπία διέλευσης (TEM) και την σκέδαση ακτινών-Χ υπό μικρές γωνίες (SAXS), τα δείγματα χαρακτηρίστηκαν μορφολογικά και επιβεβαιώθηκε ο μικροφασικός τους διαχωρισμός ακόμα και σε περιπτώσεις δειγμάτων με ιδιαίτερα χαμηλό συνολικό μέσο μοριακό βάρος κατ’ αριθμό. Επίσης για την επιβεβαίωση των διαφορετικών φάσεων με ΤΕΜ ήταν απαραίτητη η βαφή των συστάδων ΡΒ με ατμούς υδατικού διαλύματος (2% w/v) τετροξειδίου του οσμίου (OsO4) και της P4VP με ατμούς ιωδίου ώστε να μεταβληθεί η ηλεκτρονιακή τους πυκνότητα, να εμφανίζονται ως σκούρες φάσεις και να εξάγονται σαφέστερα συμπεράσματα. Επίσης, προέκυψε μικροφασικός διαχωρισμός σε δείγματα με πολύ χαμηλό συνολικό μέσο μοριακό βάρος κατ’ αριθμό οδηγώντας σε συμμετρίες με χαρακτηριστική διάσταση της μοναδιαίας κυψελίδας σε εύρος τιμών των λίγων νανομέτρων. Με την χρήση της μικροσκοπίας ατομικής δύναμης (AFM) πραγματοποιήθηκε μορφολογικός έλεγχος σε κατάσταση λεπτών υμενίων για όλα τα δείγματα συμπεριλαμβανομένων και των σύνθετων υλικών με νανοσωματίδια. Με την ίδια μέθοδο πραγματοποιήθηκε και μέτρηση του μεγέθους των νανοσωματιδίων των σύνθετων υλικών. Η ικανότητα λήψης μορφολογιών σε κατάσταση λεπτών υμενίων αλλά και η ενσωμάτωση των νανοσωματιδίων χρυσού αποτελούν επιθυμητές ιδιότητες για εφαρμογές νανοτεχνολογίας. Η τεχνική της ελλειψομετρίας χρησιμοποιήθηκε για τη μέτρηση του πάχους και της τραχύτητας των εναποτιθέμενων λεπτών υμενίων. Τέλος, πραγματοποιήθηκαν μετρήσεις απορρόφησης των σύνθετων υλικών με νανοσωματίδια με σκοπό τη διαπίστωση της απόκρισής τους στα μήκη κύματος του ορατού φάσματος. Τέλος με τη μέθοδο δυναμικής σκέδασης φωτός (DLS) υπολογίστηκε το μέσο μέγεθος των νανοσωματιδίων σε κατάσταση διαλύματος

Tuning the morphology of silicon containing copolymers via macromolecular architecture effect

We demonstrate the successful synthesis of linear and non-linear star block copolymers consisting of the highly segregated polystyrene (PS) and poly(dimethylsiloxane) (PDMS) blocks through sequential anionic polymerization combined with chlorosilane chemistry. To study the macromolecular architecture effect on the adopted morphology star block copolymers with six equivalent diblock arms [(PS-b-PDMS)6] were synthesized and compared with their linear diblock copolymer precursors as well as with the corresponding star block copolymers with smaller arm number (2, 3, 4) but identical molecular characteristics. After verifying the molecular and thermal characteristics, bulk studies were carried out through transmission electron microscopy and small angle X-ray scattering. Well-defined structures with enhanced order and similar domain spacing values, irrespective of the architecture complexity of the samples, were observed. The better order of star block copolymers suggests an alternative way to further reduce the lower limit of repeating period by tuning the architecture which is important for the potential future use of the copolymers for nanotechnology related applications. The findings of the specific study are related to the effects of the increased conformational restriction of the inner block. Herein, we show morphological transformations in the (PS-b-PDMS)6 copolymers having non symmetric volume fraction ratios when compared to their linear diblock precursors and triblock copolymers which has not been observed in previous relevant (PS-b-PDMS)n studies that involved stars with less than six arms. To establish the structure/property relationship as a function of arm number, a series of samples involving the diblock precursor, the triblock, the three-, four- and six- arm star block copolymers was prepared, and a systematic comparison was conducted

Synthesis, Characterization and Structure Properties of Biobased Hybrid Copolymers Consisting of Polydiene and Polypeptide Segments

International audienceNovel hybrid materials of the PB-b-P(o-Bn-L-Tyr) and PI-b-P(o-Bn-L-Tyr) type (where PB: 1,4/1,2-poly(butadiene), PI: 3,4/1,2/1,4-poly(isoprene) and P(o-Bn-L-Tyr): poly(ortho-benzyl-L-tyrosine)) were synthesized through anionic and ring-opening polymerization under high-vacuum techniques. All final materials were molecularly characterized through infrared spectroscopy (IR) and proton and carbon nuclear magnetic resonance (1H-NMR, 13C-NMR) in order to confirm the successful synthesis and the polydiene microstructure content. The stereochemical behavior of secondary structures (α-helices and β-sheets) of the polypeptide segments combined with the different polydiene microstructures was also studied. The influence of the α-helices and β-sheets, as well as the polydiene chain conformations on the thermal properties (glass transition temperatures, thermal stability, α- and β-relaxation) of the present biobased hybrid copolymers, was investigated through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dielectric spectroscopy (DS). The obtained morphologies in thin films for all the synthesized materials via atomic force microscopy (AFM) indicated the formation of polypeptide fibrils in the polydiene matrix

Dendrons and Dendritic Terpolymers: Synthesis, Characterization and Self-Assembly Comparison

International audienceTo the best of our knowledge, this is the very first time that a thorough study of the synthetic procedures, molecular and thermal characterization, followed by structure/properties relationship for symmetric and non-symmetric second generation (2-G) dendritic terpolymers is reported. Actually, the synthesis of the non-symmetric materials is reported for the first time in the literature. Anionic polymerization enables the synthesis of well-defined polymers that, despite the architecture complexity, absolute control over the average molecular weight, as well as block composition, is achieved. The dendritic type macromolecular architecture affects the microphase separation, because different morphologies are obtained, which do not exhibit long range order, and various defects or dislocations are evident attributed to the increased number of junction points of the final material despite the satisfactory thermal annealing at temperatures above the highest glass transition temperature of all blocks. For comparison reasons, the initial dendrons (miktoarm star terpolymer precursors) which are connected to each other in order to synthesize the final dendritic terpolymers are characterized in solution and in bulk and their self-assembly is also studied. A major conclusion is that specific structures are adopted which depend on the type of the core connection between the ligand and the active sites of the dendrons

Synthesis, characterization and self-assembly of linear and miktoarm star copolymers of exclusively immiscible polydienes

International audienceLinear and non-linear copolymers of the PB-b-PI sequence [PB: polybutadiene of high 1,4-microstructure (∼92%) and PI: polyisoprene of high 3,4-microstructure (∼55–60%)] and their corresponding miktoarm star copolymers of the PB(PI3,4)2 and PB(PI3,4)3 type were synthesized by combining anionic polymerization and selective chlorosilane chemistry. Molecular characteristics, thermal properties and structure/properties relationship are reported for the specific copolymers and especially the self-assembly is of major importance and interest due to the nature of the blocks. The identical electron densities between the two polydienes led to impossible morphological characterization through small angle X-ray scattering (SAXS) and only transmission electron microscopy results verify the adopted morphology for each copolymer, justifying the assumption that the segment–segment interaction parameter between the two polydienes of high 1,4-microstructure (∼92%) for the PB and ∼55–60% 3,4-microstructure for the PI is well above zero. The consistency of the bulk morphology results of this study compared with those of the extensively studied system of the PS(PI)n=1,2,3 type (PS: polystyrene), were unexpectedly coherent. High chain flexibility provided by the two polydiene segments, leads to promising properties unattainable from corresponding thermoplastic triblock copolymers of these polydienes with PS (PS-b-PI-b-PS, PS-b-PB-b-PS), especially for rheological studies

Structure/Properties Relationship of Anionically Synthesized Diblock Copolymers “Grafted to” Chemically Modified Graphene

International audiencenovel approach to obtaining nanocomposite materials using anionic sequential polymerization and post-synthetic esterification reactions with chemically modified graphene sheets (CMGs) is reported. The anionically synthesized diblock copolymer precursors of the PS-b-PI-OH type were grafted to the chemically modified –COOH groups of the CMGs, giving rise to the final composite materials, namely polystyrene-b-poly(isoprene)-g-CMGs, which exhibited enhanced physicochemical properties. The successful synthesis was determined through multiple molecular characterization techniques together with thermogravimetric analysis for the verification of increased thermal stability, and the structure/properties relationship was justified through transmission electron microscopy. Furthermore, the arrangement of CMGs utilizing lamellar and cylindrical morphologies was studied in order to determine the effect of the loaded CMGs in the adopted topologie

Thermal and Bulk Properties of Triblock Terpolymers and Modified Derivatives towards Novel Polymer Brushes

We report the synthesis of three (3) linear triblock terpolymers, two (2) of the ABC type and one (1) of the BAC type, where A, B and C correspond to three chemically incompatible blocks such as polystyrene (PS), poly(butadiene) of exclusively (~100% vinyl-type) -1,2 microstructure (PB1,2) and poly(dimethylsiloxane) (PDMS) respectively. Living anionic polymerization enabled the synthesis of narrowly dispersed terpolymers with low average molecular weights and different composition ratios, as verified by multiple molecular characterization techniques. To evaluate their self-assembly behavior, transmission electron microscopy and small-angle X-ray scattering experiments were conducted, indicating the effect of asymmetric compositions and interactions as well as inversed segment sequence on the adopted morphologies. Furthermore, post-polymerization chemical modification reactions such as hydroboration and oxidation were carried out on the extremely low molecular weight PB1,2 in all three terpolymer samples. To justify the successful incorporation of –OH groups in the polydiene segments and the preparation of polymeric brushes, various molecular, thermal, and surface analysis measurements were carried out. The synthesis and chemical modification reactions on such triblock terpolymers are performed for the first time to the best of our knowledge and constitute a promising route to design polymers for nanotechnology applications

Molecular and Structure-Properties Comparison of an Anionically Synthesized Diblock Copolymer of the PS-b-PI Sequence and Its Hydrogenated or Sulfonated Derivatives

International audienceAn approach to obtaining various nanostructures utilizing a well-studied polystyrene-bpoly(isoprene) or PS-b-PI diblock copolymer system through chemical modification reactions is reported. The complete hydrogenation and partial sulfonation to the susceptible carbon double bonds of the PI segment led to the preparation of [polystyrene-b-poly(ethylene-alt-propylene)] as well as [polystyrene-b-poly(sulfonated isoprene-co-isoprene)], respectively. The hydrogenation of the polyisoprene block results in enhanced segmental immiscibility, whereas the relative sulfonation induces an amphiphilic character in the final modified material. The successful synthesis of the pristine diblock copolymer through anionic polymerization and the relative chemical modification reactions were verified using several molecular and structural characterization techniques. The thin film structure-properties relationship was investigated using atomic force microscopy under various conditions such as different solvents and annealing temperatures. Small-angle X-ray scattering was employed to identify the different observed nanostructures and their evolution upon thermal annealing

Thermal and Bulk Properties of Triblock Terpolymers and Modified Derivatives towards Novel Polymer Brushes

We report the synthesis of three (3) linear triblock terpolymers, two (2) of the ABC type and one (1) of the BAC type, where A, B and C correspond to three chemically incompatible blocks such as polystyrene (PS), poly(butadiene) of exclusively (~100% vinyl-type) -1,2 microstructure (PB1,2) and poly(dimethylsiloxane) (PDMS) respectively. Living anionic polymerization enabled the synthesis of narrowly dispersed terpolymers with low average molecular weights and different composition ratios, as verified by multiple molecular characterization techniques. To evaluate their self-assembly behavior, transmission electron microscopy and small-angle X-ray scattering experiments were conducted, indicating the effect of asymmetric compositions and interactions as well as inversed segment sequence on the adopted morphologies. Furthermore, post-polymerization chemical modification reactions such as hydroboration and oxidation were carried out on the extremely low molecular weight PB1,2 in all three terpolymer samples. To justify the successful incorporation of –OH groups in the polydiene segments and the preparation of polymeric brushes, various molecular, thermal, and surface analysis measurements were carried out. The synthesis and chemical modification reactions on such triblock terpolymers are performed for the first time to the best of our knowledge and constitute a promising route to design polymers for nanotechnology applications

Self-Assembly of Low-Molecular-Weight Asymmetric Linear Triblock Terpolymers: How Low Can We Go?

International audienceThe synthesis of two (2) novel triblock terpolymers of the ABC type and one (1) of the BAC type, where A, B and C are chemically different segments, such as polystyrene (PS), poly(butadiene) (PB 1,4) and poly(dimethylsiloxane) (PDMS), is reported; moreover, their corresponding molecular and bulk characterizations were performed. Very low dimensions are evident from the characterization in bulk from transmission electron microscopy studies, verified by small-angle X-ray data, since sub-16 nm domains are evident in all three cases. The self-assembly results justify the assumptions that the high Flory-Huggins parameter, χ, even in low molecular weights, leads to significantly well-ordered structures, despite the complexity of the systems studied. Furthermore, it is the first time that a structure/properties relationship was studied for such systems in bulk, potentially leading to prominent applications in nanotechnology and nanopatterning, for as low as sub-10 nm thin-film manipulations