Alternating Gyroid Network Structure in an ABC Miktoarm Terpolymer Comprised of Polystyrene and Two Polydienes

The synthesis, molecular and morphological characterization of a 3-miktoarm star terpolymer of polystyrene (PS, M¯¯¯¯n = 61.0 kg/mol), polybutadiene (PB, M¯¯¯¯n = 38.2 kg/mol) and polyisoprene (PI, M¯¯¯¯n = 29.2 kg/mol), corresponding to volume fractions (φ) of 0.46, 0.31 and 0.23 respectively, was studied. The major difference of the present material from previous ABC miktoarm stars (which is a star architecture bearing three different segments, all connected to a single junction point) with the same block components is the high 3,4-microstructure (55%) of the PI chains. The interaction parameter and the degree of polymerization of the two polydienes is sufficiently positive to create a three-phase microdomain structure as evidenced by differential scanning calorimetry and transmission electron microscopy (TEM). These results in combination with small-angle X-ray scattering (SAXS) and birefringence experiments suggest a cubic tricontinuous network structure, based on the I4132 space group never reported previously for such an architecture

Μακρομοριακή αρχιτεκτονική: σύνθεση, χαρακτηρισμός και ιδιότητες γραμμικών και μη γραμμικών συμπολυμερών πολυστυρενίου και πολυ (διμεθυλοσιλοξάνης) για εφαρμογές στη νανοτεχνολογία

Linear and non-linear copolymers consisting of polystyrene (PS) and poly(dimethylsiloxane) (PDMS) demonstrate significant scientific and technological interest. These systems showcase high Flory-Huggins interaction parameter (χ), leading to enhanced microphase separation, even for low average molecular weights (able to approach the molecular weight values in which entanglements are formed). Furthermore, the polysiloxane segment renders the materials quite promising for nanotechnology applications due to the etch contrast capability.The selection of the (PS-b-PDMS)n system where n = 1 or 2 or 3 or 4 or 6 is attributed to several factors. Specifically, the high molecular and compositional homogeneity of the copolymers imparts exquisite properties. The well-defined macromolecular architecture and the desired molecular characteristics are allocated to the synthetic protocol followed, and in particular to anionic polymerization and chlorosilane chemistry. In addition, the microphase separation in bulk state constitutes an important tool for the fabrication of nanostructures without the implementation of sophisticated processing steps. It should be mentioned that, tuning the environmental conditions (pressure and temperature) for the linear diblock copolymers or changing the overall entropy of the system for the triblock and/or the star block copolymers during thin films studies, the perpendicular orientation of the nanodomains can be adopted.The above-mentioned considerations led to the synthesis of: twenty three (23) linear diblock copolymers of the PS-b-PDMS type, six (6) triblock copolymers or (PS-b-PDMS)2, nine (9) three-arm star block copolymers or (PS-b-PDMS)3, six (6) four-arm star block copolymers or (PS-b-PDMS)4 and five (5) six-arm star block copolymers or (PS-b-PDMS)6. The synthesis was realized through anionic polymerization and sequential addition of the two monomers under high vacuum conditions. The synthesis of linear and non-linear copolymers was conducted through chlorosilane chemistry using the appropriate coupling agent including dichlorodimethylsilane, trichloromethylsilane, silicon tetrachloride and 1,2-bis(trichlorosilyl)ethane) respectively. The process involves the reaction of the living copolymer chain ends (PS-b-PDMSLi+) with the proper chlorosilane and therefore fifteen (15) linear diblock copolymers were used as precursors for the synthesis of the complex architecture copolymers.The molecular characterization of the samples in this PhD thesis was carried out through size exclusion chromatography (SEC), vapor pressure and membrane osmometry (VPO, MO) to determine the dispersity indices (Đ) and the number average molecular weights , respectively. The mass composition in all samples was calculated through proton nuclear magnetic resonance spectroscopy (1H-NMR) and appropriate equation was used for the calculation of the volume fraction. The thermal characterization for the determination of the thermal transitions was conducted through differential scanning calorimetry (DSC).The structure/property relationship in bulk state was carried out through transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) for all copolymer sequences (linear and non-linear architectures). Some linear diblock copolymers were studied through field emission scanning electron microscopy (FESEM) and three dimensional TEM (3D TEM). The order-disorder transition of specific linear and non-linear copolymers was estimated through in-situ SAXS experiments. The surface morphology in specific copolymers was determined through scanning probe microscopy (SPM).The majority of the morphological characterizations was conducted through the collaboration with the research group of Professor Rong-Ming Ho (Chemical Engineering Department at National Tsing Hua University, Hsinchu, Taiwan) leading to quite significant results.Τα γραμμικά και μη γραμμικά συμπολυμερή που αποτελούνται από πολυστυρένιο (PS) και πολυ(διμεθυλοσιλοξάνη) (PDMS) παρουσιάζουν τεράστιο επιστημονικό και τεχνολογικό ενδιαφέρον. Τα συστήματα αυτά εμφανίζουν υψηλή παράμετρο αλληλεπίδρασης Flory-Huggins (χ), γεγονός που οδηγεί σε μικροφασικό διαχωρισμό μεταξύ των δύο συστάδων ακόμα και σε περιπτώσεις μικρών μέσων μοριακών βαρών (που δύναται να προσεγγίζουν και τις τιμές μοριακών βαρών που σχηματίζονται οι ενδοεμπλοκές μεταξύ των μακρομοριακών αλυσίδων). Επιπλέον η πολυσιλοξανική συστάδα τα καθιστά αρκετά υποσχόμενα υλικά για νανοτεχνολογικές εφαρμογές λόγω της αντοχής στην εγχάραξη που εμφανίζει. Η επιλογή του συστήματος (PS-b-PDMS)n όπου n = 1 ή 2 ή 3 ή 4 ή 6 αποδίδεται σε αρκετές παραμέτρους. Συγκεκριμένα, η υψηλή ομοιογένεια ως προς τη σύσταση και το μοριακό βάρος που εμφανίζουν τα συμπολυμερή τους προσδίδει σημαντικές ιδιότητες. Η αυστηρά καθορισμένη μακρομοριακή αρχιτεκτονική και τα επιθυμητά μοριακά χαρακτηριστικά απορρέουν από τη συνθετική πορεία που ακολουθείται και συγκεκριμένα λόγω του ανιοντικού πολυμερισμού και της χημείας χλωροσιλανίων. Επιπλέον, ο διαχωρισμός μικροφάσεων σε κατάσταση τήγματος (bulk) αποτελεί σημαντικό μέσο για την κατασκευή νανοδομών χωρίς την εφαρμογή πολύπλοκων σταδίων επεξεργασίας για τα συγκεκριμένα υλικά. Αξιοσημείωτο είναι να αναφερθεί ότι ελέγχοντας περιβαλλοντολογικές συνθήκες (πίεση και θερμοκρασία) για τα γραμμικά δισυσταδικά συμπολυμερή ή μεταβάλλοντας τη συνολική εντροπία του συστήματος για τα τρισυσταδικά ή/και αστεροειδή συμπολυμερή κατά τη μελέτη τους υπό μορφή λεπτών υμενίων (thin films), ο κάθετος προσανατολισμός των νανοδομών δύναται να υιοθετηθεί.Οι παραπάνω λόγοι οδήγησαν στη σύνθεση: εικοσιτριών (23) γραμμικών δισυσταδικών συμπολυμερών του τύπου PS-b-PDMS, έξι (6) τρισυσταδικών συμπολυμερών ή (PS-b-PDMS)2, εννέα (9) αστεροειδών συμπολυμερών με τρεις κλάδους ή (PS-b-PDMS)3, έξι (6) αστεροειδών συμπολυμερών με τέσσερις κλάδους ή (PS-b-PDMS)4 και πέντε (5) αστεροειδών συμπολυμερών με έξι κλάδους ή (PS-b-PDMS)6. Η σύνθεση πραγματοποιήθηκε μέσω του ανιοντικού πολυμερισμού και της διαδοχικής προσθήκης μονομερών σε συνθήκες υψηλού κενού. Η σύνθεση των γραμμικών και μη γραμμικών συμπολυμερών πραγματοποιήθηκε μέσω της χημείας των χλωροσιλανίων και των κατάλληλων αντιδραστηρίων σύζευξης τα οποία περιλαμβάνουν το διχλωροδιμεθυλοσιλάνιο, το τριχλωρομεθυλοσιλάνιο, το τετραχλωροσιλάνιο και το 1,2-δις(τριχλωροσιλυλο)αιθάνιο. Η διαδικασία περιλαμβάνει την αντίδραση των ενεργών αλυσίδων του συμπολυμερούς (PS-b-PDMSLi+) με το εκάστοτε αντιδραστήριο και για το λόγο αυτό δεκαπέντε (15) από τα δισυσταδικά συμπολυμερή χρησιμοποιήθηκαν ως πρόδρομα υλικά για τη σύνθεση των πολύπλοκης αρχιτεκτονικής δειγμάτων.Ο μοριακός χαρακτηρισμός των δειγμάτων της παρούσας διατριβής πραγματοποιήθηκε μέσω χρωματογραφίας αποκλεισμού μεγεθών (SEC), οσμωμετρίας τάσης ατμών ή μεμβράνης (VPO, ΜΟ) για να προσδιοριστούν η κατανομή μέσων μοριακών βαρών (Đ) και τα μέσα μοριακά βάρη κατ’ αριθμό αντίστοιχα. Η κατά βάρος και κατ’ όγκο σύσταση σε όλα τα δείγματα υπολογίστηκε μέσω φασματοσκοπίας πυρηνικού μαγνητικού συντονισμού πρωτονίου (1H-NMR). Ο θερμικός χαρακτηρισμός έλαβε χώρα για τον προσδιορισμό των θερμικών μεταπτώσεων των συστημάτων και διεξήχθει μέσω της διαφορικής θερμιδομετρίας σάρωσης (DSC). Η μελέτη της σχέσης δομής/ιδιοτήτων σε κατάσταση τήγματος για όλες τις αλληλουχίες δειγμάτων (γραμμικά και μη γραμμικά συμπολυμερή) πραγματοποιήθηκε μέσω ηλεκτρονικής μικροσκοπίας διέλευσης (TEM) και σκέδασης ακτίνων-Χ υπό μικρές γωνίες (SAXS). Μερικά εκ των συντεθειμένων γραμμικών συμπολυμερών μελετήθηκαν μέσω ηλεκτρονικής μικροσκοπίας σάρωσης πεδίου (FESEM) και μέσω ηλεκτρονικής μικροσκοπίας διέλευσης τριών διαστάσεων (3D TEM). Η μελέτη της θερμοκρασίας μετάπτωσης από την τάξη στην αταξία μερικών γραμμικών και μη γραμμικών συμπολυμερών κατέστη δυνατή μέσω in-situ πειραμάτων σκέδασης ακτίνων-Χ υπό μικρές γωνίες. H μελέτη επιφάνειας ορισμένων δειγμάτων πραγματοποιήθηκε μέσω μικροσκοπίας σάρωσης με ακίδα (SPM).Η πλειοψηφία των μετρήσεων του μορφολογικού χαρακτηρισμού πραγματοποιήθηκε μέσω της συνεργασίας με την ερευνητική ομάδα του Καθηγητή Rong-Ming Ho (Chemical Engineering Department at National Tsing Hua University, Hsinchu, Taiwan) οδηγώντας σε ενδιαφέροντα αποτελέσματα

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

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 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

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

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

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

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