scholarly journals Ring-opening polymerization of monosubstituted oxiranes in the presence of potassium hydride: determination of initiation course and structure of macromolecules by MALDI-TOF mass spectrometry

2019 ◽  
Vol 26 (12) ◽  
Author(s):  
Zbigniew Grobelny ◽  
Justyna Jurek-Suliga ◽  
Sylwia Golba
Keyword(s):  
Mass Spectrometry ◽  
Ring Opening ◽  
Glycidyl Ether ◽  
Ring Opening Polymerization ◽  
Size Exclusion ◽  
Oxirane Ring ◽  
Maldi Tof ◽  
Glycidyl Ethers ◽  
Initiation Step ◽  
Potassium Hydride

AbstractSeveral monosubstituted oxiranes were polymerized with suspension of potassium hydride (KH) in tetrahydrofuran (THF) at room temperature. This heterogeneous process resulted in polyethers with various starting groups depending on the kind of monomer. The macromolecules formed in ring-opening polymerization of monosubstituted oxiranes were analyzed by Matrix Assisted Laser Desorption/Ionization - Time of Flight Mass Spectrometry (MALDI-TOF MS). It was stated, that initiation of propylene oxide (PO) polymerization with KH proceeded via three ways, i.e. cleavage of oxirane ring in the β-position, monomer deprotonation and deoxygenation. Potassium isopropoxide, potassium allyloxide and potassium hydroxide were the real initiators. The main reactions, which occur in the initiation step, depend on the type of monomer used. In the case of allyl glycidyl ether (AGE) and phenyl glycidyl ether (PGE) deprotonation of the monomer did not occur. During initiation of glycidyl ethers oxirane ring was opened and also linear ether bond between glycidyl group and oxygen atom was cleaved under influence of KH. Interestingly, formation of new kinds of macromolecules was observed in the systems containing glycidyl ethers, which do not possess mers of the monomers used. Mechanisms of the studied processes were presented and discussed. Carbon-13 Nuclear Magnetic Resonance (13C NMR) was used as supporting technique for analysis of the obtained polymers. Number average molar masses of the polymers (Mn) determined by Size Exclusion Chromatography (SEC) were about two times higher than calculated ones. It indicated that half of used KH did not take part in the initiation step.

Synthesis, characterization, and structures of zircona- and boracyclosiloxanes with ferrocenyl substituents

2002 ◽  
Vol 80 (11) ◽  
pp. 1469-1480 ◽  
Author(s):  
Karena Thieme ◽  
Sara C Bourke ◽  
Juan Zheng ◽  
Mark J MacLachlan ◽  
Fojan Zamanian ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Differential Scanning Calorimetry ◽  
Thermogravimetric Analysis ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
The Novel ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Multinuclear Nmr Spectroscopy

The novel zirconatetraferrocenylcyclotrisiloxane Cp2Zr(OSiFc2)2O (6), dizirconatetraferrocenylcyclotetrasiloxane [Cp2Zr(OSiFc2)O]2 (7), boratetraferrocenylcyclotrisiloxane (C6H5)B(OSiFc2)2O (8), and diboratetraferrocenylcyclotetrasiloxane [(C6H5)B(OSiFc2)O]2 (9) with ferrocenyl (Fc = Fe(η-C5H4)(η-C5H5)) substituents at silicon have been prepared from the reactions of Cp2Zr(NMe2)2 and PhBCl2 with diferrocenylsilanediol Fc2Si(OH)2 (3) and tetraferrocenyldisiloxanediol [Fc2SiOH]2O (5). The compounds were characterized by mass spectrometry, elemental analysis, UV–vis, IR, Raman, and multinuclear NMR spectroscopy, as well as single crystal X-ray diffraction. Thermogravimetric analysis and differential scanning calorimetry investigation of 6–9 showed that the cycles decompose before they can undergo any thermal ring-opening polymerization. In addition, no polymerization was detected in the presence of either KOSiMe3 or HOTf. The bulky ferrocenyl substituents on the Si atoms are likely to be at least partially responsible for the inability of these heterocycles to undergo ring-opening polymerization. Key words: heterocyclosiloxanes, ferrocenyl.

Ring-Opening Polymerization of L-lactide Initiated by Samarium(III) Acetate

2019 ◽  
Vol 3 (2) ◽  
pp. 112-119
Author(s):  
Jesús Miguel Contreras Ramírez ◽  
Dimas Medina ◽  
Francisco López-Carrasquero ◽  
Ricardo Rafael Contreras
Keyword(s):  
1H Nmr ◽  
Ring Opening ◽  
Alkali Metals ◽  
Molar Mass ◽  
Ring Opening Polymerization ◽  
Solvent Free ◽  
Size Exclusion ◽  
Polymerization Process ◽  
Molar Ratio ◽  
Aliphatic Polyesters

Background: The synthesis of the aliphatic polyesters obtained by the ring opening polymerization has been achieved using as initiators a large amount of organometallic compounds derivative from: Alkali metals, alkaline earth metals, transition metals and lanthanide metals. Of all these compounds, the lanthanide derivatives have acquired great importance in the synthesis of aliphatic polyesters, since these show a greater catalytic activity and also can provide polymer with characteristics that will be very useful in the design of biomaterials. Objective: It was proposed the synthesis of poly(L-lactida) (PL-LA) through a ring opening polymerization process of L-lactide initiated with samarium(III) acetate (Sm(OAc)3) under solvent-free melt conditions. The influence of different parameters of reaction, such as temperature, time, molar ratio monomer to initiator, on typical variables of polymers, e.g., conversion, dispersity, and molar mass, were analyzed. Methods: All polymerizations were carried out under solvent-free melt conditions in ampoules-like flasks, equipped with a magnetic stirrer. The obtained polyesters were characterized by size exclusion chromatography (SEC) and 1H-NMR. Results: The Sm(OAc)3 induces the polymerization of L-LA at high conversion, and produce polyesters with number-average molecular weights of 1.00 x 103 to 30.00 x 103 Dalton. The 1H-NMR analysis indicates a typical polymerization mechanism of coordination-insertion, with a breakdown of the acyl-oxygen bond of the L-LA. Conclusion: Sm(OAc)3 was an effective initiator for the ring-opening polymerization of L-LA. SEC chromatography showed that, at high temperatures and prolonged reaction times, the molar mass of the polyester decreases, which is associated with the transesterification collateral reactions that occur during the polymerization process.

Insights into the mechanism for ring-opening polymerization of lactide catalyzed by Zn(C6F5)2/organic superbase Lewis pairs

2016 ◽  
Vol 6 (21) ◽  
pp. 7763-7772 ◽  
Author(s):  
Xiao-Qing Li ◽  
Bin Wang ◽  
He-Yuan Ji ◽  
Yue-Sheng Li
Keyword(s):  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Experimental Results ◽  
Maldi Tof Ms ◽  
Maldi Tof ◽  
Good Consistency ◽  
Plausible Mechanism ◽  
Tof Ms ◽  
Lewis Pairs

A plausible mechanism for ring-opening polymerization of lactide catalyzed by Zn(C6F5)2-based Lewis pairs was proposed based on in situ NMR and MALDI-TOF MS analyses. Several experimental results show very good consistency with the proposed mechanism.

Diol glycidyl ether-bridged low molecular weight PEI as potential gene delivery vehicles

2015 ◽  
Vol 3 (13) ◽  
pp. 2660-2670 ◽  
Author(s):  
Qian Guo ◽  
Yan-Hong Liu ◽  
Miao-Miao Xun ◽  
Ji Zhang ◽  
Zheng Huang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Gene Delivery ◽  
Ring Opening ◽  
Transfection Efficiency ◽  
Glycidyl Ether ◽  
Ring Opening Polymerization ◽  
Low Molecular Weight ◽  
Delivery Vehicles ◽  
Gene Delivery Vehicles

PEI 600-based polymers were synthesized via ring-opening polymerization and exhibited much better transfection efficiency and biocompatibility than PEI 25 kDa.

scholarly journals Synthesis and characterization of poly(1-methyltrimethylene carbonate) (PMTMC) by mean ring-opening polymerization

2020 ◽  
Vol 5 (3) ◽  
pp. 21
Author(s):  
Jesús Miguel Contreras Ramírez ◽  
Meribary Monsalve
Keyword(s):  
Ring Opening ◽  
Molar Mass ◽  
Thermal Polymerization ◽  
Ring Opening Polymerization ◽  
Active Species ◽  
Size Exclusion ◽  
Polymerization Process ◽  
Molar Ratio ◽  
Molecular Characteristics ◽  
Ft Ir

  In this work, the activity of samarium (III) acetate (Sm(OAc)3) was evaluated as a possible initiator in the ring opening polymerization (ROP) of 1-methyltrimethylene carbonate (MTMC). The effects of temperature (Tr) and monomer-initiator molar ratio (M/I) on the molecular characteristics (conversion, dispersity, and molar mass) of the polymers obtained were analyzed. The reaction temperature was varied between 90 and 160 °C and the molar ratio M/I between 200 and 1000. The molar mass of the products was obtained by size exclusion chromatography (SEC), while its structure was analyzed using FT-IR and 1H-NMR spectroscopy. Thermal polymerization experiments (in the absence of an initiator) were performed in order to evaluate the effectiveness of the initiator. The comparison between the thermal polymerization of MTMC and its polymerization in the presence of Sm(OAc)3, suggests that acetate has very low catalytic activity as the initiator of the ROP of PMTMC. The molar masses of the polymers obtained ranged between 6000 and 10000 Dalton, and the monomer to polymer conversions varied between 9 and 30 %. SEC chromatograms showed monomodal and symmetric curves, suggesting that only one type of active species participates in the polymerization process. Based on the structural analysis, a polymerization mechanism was proposed in which the water possibly acts as the only active species that initiates the reaction.   Palabra clave: Samarium (III) acetate, ring-opening polymerization, 1-methyltrimethylenecarbonate, poly(1-methyltrimethylenecarbonate).   Abstract En este trabajo se evaluó la actividad del acetato de samario (III) (Sm(OAc)3) como posible iniciador en la polimerización de apertura de anillo (PAA) del carbonato de 1-metiltrimetileno (MTMC). Se analizaron los efectos de la temperatura (Tr) y relación molar monómero-iniciador (M/I) sobre las características moleculares (conversión, dispersidad y masa molar) de los polímeros obtenidos. La temperatura de reacción se varió entre 90 y 160 °C y la relación molar M/I entre 200 y 1000. La masa molar de los productos se obtuvo mediante cromatografía de exclusión por tamaño, mientras que su estructura fue analizada mediante espectroscopia FT-IR y 1H-RMN. Además, se realizaron algunos experimentos de polimerización térmica (en ausencia de iniciador) que sirvieron de referencia para evaluar la efectividad del iniciador. La comparación de los resultados obtenidos en la polimerización térmica y en presencia del Sm(OAc)3 indicó que este último presenta muy poca actividad catalítica como iniciador de la PAA de PMTMC. Las masas molares de los polímeros obtenidos oscilaron entre 6000 y 10000 Dalton, mientras que las conversiones de monómero a polímero variaron entre 9 y 30%. Los cromatogramas SEC mostraron curvas mono-modales y simétricas, indicando que en el proceso de polimerización participa un solo tipo de especie activa. En base al análisis estructural, mediante técnicas espectroscópicas, se propuso un mecanismo de reacción para la polimerización en la que el agua posiblemente actúa como la única especie activa iniciadora de la reacción.   Keywords: Acetato de samario (III), polimerización por apertura de anillo, 1-metiltrimetilencarbonato, poli(1-metiltrimetilencarbonato).  

Σύνθεση γραμμικών και αστεροειδών πολυμερών αποτελούμενα από συστάδες με υψηλή παράμετρο αλληλεπίδρασης Flory-Huggins χ

2020 ◽  
Author(s):  
Μαρία-Μαλβίνα Σταθουράκη
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Size Exclusion ◽  
Resonance Spectroscopy ◽  
X Ray ◽  
X Ray Scattering ◽  
Exclusion Chromatography

Σκοπό της διατριβής αυτής αποτελεί η σύνθεση και η μελέτη της αυτοοργάνωσης γραμμικών και αστεροειδών συμπολυμερών με υψηλή παράμετρο αλληλεπιδρασης Flory-Huggins, χ. Τα πολυμερή αυτά, λόγω της μικρής αναμιξιμότητας που παρουσιάζουν τα συστατικά τους, έχουν την δυνατότητα σε μικρά μοριακά βάρη να μπορούν να σχηματίζουν πολύ μικρές και καλά καθορισμένες δομές κατά το μικροφασικό διαχωρισμό. Αρχικά, πραγματοποιήθηκε η σύνθεση των γραμμικών δισυσταδικών συμπολυμερών πολυ(2-βινυλοπυριδίνης)-b-πολυ(l-λακτιδίου) (P2VP-b-PLLA) και των τρισυσταδικών πολυ(l-λακτιδίου)-b-πολύ(διμεθυλοσιλοξάνη)-b-πολύ(l-λακτιδίου) (PLLA-b-PDMS-b-PLLA), καθώς και γραμμικών και αστεροειδών συμπολυμερών πολύ(στυρένιο)-b-πολυ(μονομεθακρυλική γλυκερόλη), PS-b-PGMA, (πολυστυρένιο)2(πολυ(μονομεθακρυλική γλυκερόλη)), (PS)2(PGMA), και (πολυστυρένιο)3(πολυ(μονομεθακρυλική γλυκερόλη)), (PS)3(PGMA), σε διάφορες αναλογίες μοριακών βαρών των συστατικών τους. Χρησιμοποιήθηκαν τεχνικές ζωντανού ανιοντικού πολυμερισμού για τη σύνθεση της P2VP, καθώς και για τη σύνθεση των αστεροειδών πολυμερών, ενώ η σύνθεση των PLLA πραγματοποιήθηκε με χρήση πολυμερισμού διάνοιξης δακτυλίου (Ring Opening Polymerization, ROP). Ο μοριακός χαρακτηρισμός των πολυμερών έγινε μέσω Χρωματογραφίας Αποκλεισμού Μεγεθών (Size Exclusion Chromatography, SEC) και Φασματοσκοπίας Πυρηνικού Μαγνητικού Συντονισμού Πρωτονίου (Nuclear Magnetic Resonance Spectroscopy, 1H-NMR). Τέλος, τίθενται τα αποτελέσματα που αφορούν τα γεωμετρικά χαρακτηριστικά (μέγεθος, μορφολογία) των περιοδικών νανοδομών που σχηματίζουν στο τήγμα τα συμπολυμερή, μέσω σκέδασης ακτίνων Χ σε μικρές γωνίες (Small-angle X-ray Scattering, SAXS).

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