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Tay JH, Lim YH, Zheng M, Zhao Y, Tan WS, Xu C, Ramamurty U, Song J. Development of hyaluronic acid-silica composites via in situ precipitation for improved penetration efficiency in fast-dissolving microneedle systems. Acta Biomater 2023; 172:175-187. [PMID: 37865280 DOI: 10.1016/j.actbio.2023.10.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 09/13/2023] [Accepted: 10/11/2023] [Indexed: 10/23/2023]
Abstract
Fast-dissolving microneedles (DMNs) hold significant promise for transdermal drug delivery, offering improved patient compliance, biocompatibility, and functional adaptability for various therapeutic purposes. However, the mechanical strength of the biodegradable polymers used in DMNs often proves insufficient for effective penetration into human skin, especially under high humidity conditions. While many composite strategies have been developed to reinforce polymer-based DMNs, simple mixing of the reinforcements with polymers often results in ineffective penetration due to inhomogeneous dispersion of the reinforcements and the formation of undesired micropores. In response to this challenge, this study aimed to enhance the mechanical performance of hyaluronic acid (HA)-based microneedles (MNs), one of the most commonly used DMN systems. We introduced in situ precipitation of silica nanoparticles (Si) into the HA matrix in conjunction with conventional micromolding. The precipitated silica nanoparticles were uniformly distributed, forming an interconnected network within the HA matrix. Experimental results demonstrated that the mechanical properties of the HA-Si composite MNs with up to 20 vol% Si significantly improved, leading to higher penetration efficiency compared to pure HA MNs, while maintaining structural integrity without any critical defects. The composite MNs also showed reduced degradation rates and preserved their drug delivery capabilities and biocompatibility. Thus, the developed HA-Si composite MNs present a promising solution for efficient transdermal drug delivery and address the mechanical limitations inherent in DMN systems. STATEMENT OF SIGNIFICANCE: HA-Si composite dissolving microneedle (DMN) systems were successfully fabricated through in situ precipitation and conventional micromolding processes. The precipitated silica nanoparticles formed an interconnected network within the HA matrix, ranging in size from 25 to 230 nm. The optimal silica content for HA-Si composite MN systems should be up to 20 % by volume to maintain structural integrity and mechanical properties. HA-Si composite MNs with up to 20 % Si showed improved penetration efficiency and reduced degradation rates compared to pure HA MNs, thereby expanding the operational window. The HA-Si composite MNs retained good drug delivery capabilities and biocompatibility.
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Affiliation(s)
- Jie Hao Tay
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 639798, Singapore
| | - Yu Han Lim
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 639798, Singapore
| | - Mengjia Zheng
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong SAR, China
| | - Yakai Zhao
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 138634, Singapore
| | - Wen See Tan
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 639798, Singapore; Singapore Centre for 3D Printing, Nanyang Technological University, Singapore, 639798, Singapore
| | - Chenjie Xu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong SAR, China
| | - Upadrasta Ramamurty
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 138634, Singapore; Singapore Centre for 3D Printing, Nanyang Technological University, Singapore, 639798, Singapore; School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798, Singapore
| | - Juha Song
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 639798, Singapore; Singapore Centre for 3D Printing, Nanyang Technological University, Singapore, 639798, Singapore.
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2
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Nifant'ev I, Tavtorkin A, Komarov P, Kretov E, Korchagina S, Chinova M, Gavrilov D, Ivchenko P. Dispersant and Protective Roles of Amphiphilic Poly(ethylene phosphate) Block Copolymers in Polyester/Bone Mineral Composites. Int J Mol Sci 2023; 24:11175. [PMID: 37446347 DOI: 10.3390/ijms241311175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/02/2023] [Accepted: 07/04/2023] [Indexed: 07/15/2023] Open
Abstract
Composites of synthetic bone mineral substitutes (BMS) and biodegradable polyesters are of particular interest for bone surgery and orthopedics. Manufacturing of composite scaffolds commonly uses mixing of the BMS with polymer melts. Melt processing requires a high homogeneity of the mixing, and is complicated by BMS-promoted thermal degradation of polymers. In our work, poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites reinforced by commercial β-tricalcium phosphate (βTCP) or synthesized carbonated hydroxyapatite with hexagonal and plate-like crystallite shapes (hCAp and pCAp, respectively) were fabricated using injection molding. pCAp-based composites showed advanced mechanical and thermal characteristics, and the best set of mechanical characteristics was observed for the PLLA-based composite containing 25 wt% of pCAp. To achieve compatibility of polyesters and pCAp, reactive block copolymers of PLLA or PCL with poly(tert-butyl ethylene phosphate) (C1 and C2, respectively) were introduced to the composite. The formation of a polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer during composite preparation, followed by chemical binding of PEPA with pCAp, have been proved experimentally. The presence of 5 wt% of the compatibilizer provided deeper homogenization of the composite, resulting in a marked increase in strength and moduli as well as a more pronounced nucleation effect during isothermal crystallization. The use of C1 increased the thermal stability of the PLLA-based composite, containing 25 wt% of pCAp. In view of positive impacts of polyester-b-PEPA on composite homogeneity, mechanical characteristics, and thermal stability, polyester-b-PEPA will find application in the further development of composite materials for bone surgery and orthopedics.
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Affiliation(s)
- Ilya Nifant'ev
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Chemistry Department, M.V. Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow, Russia
- Faculty of Chemistry, National Research University Higher School of Economics, Myasnitskaya St. 20, 101100 Moscow, Russia
| | - Alexander Tavtorkin
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
| | - Pavel Komarov
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
| | - Egor Kretov
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Faculty of Chemistry, National Research University Higher School of Economics, Myasnitskaya St. 20, 101100 Moscow, Russia
| | - Sofia Korchagina
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
| | - Maria Chinova
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
| | - Dmitry Gavrilov
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Chemistry Department, M.V. Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow, Russia
| | - Pavel Ivchenko
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Chemistry Department, M.V. Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow, Russia
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3
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Design Strategies and Biomimetic Approaches for Calcium Phosphate Scaffolds in Bone Tissue Regeneration. Biomimetics (Basel) 2022; 7:biomimetics7030112. [PMID: 35997432 PMCID: PMC9397031 DOI: 10.3390/biomimetics7030112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/05/2022] [Accepted: 08/07/2022] [Indexed: 11/16/2022] Open
Abstract
Bone is a complex biologic tissue, which is extremely relevant for various physiological functions, in addition to movement, organ protection, and weight bearing. The repair of critical size bone defects is a still unmet clinical need, and over the past decades, material scientists have been expending efforts to find effective technological solutions, based on the use of scaffolds. In this context, biomimetics which is intended as the ability of a scaffold to reproduce compositional and structural features of the host tissues, is increasingly considered as a guide for this purpose. However, the achievement of implants that mimic the very complex bone composition, multi-scale structure, and mechanics is still an open challenge. Indeed, despite the fact that calcium phosphates are widely recognized as elective biomaterials to fabricate regenerative bone scaffolds, their processing into 3D devices with suitable cell-instructing features is still prevented by insurmountable drawbacks. With respect to biomaterials science, new approaches maybe conceived to gain ground and promise for a substantial leap forward in this field. The present review provides an overview of physicochemical and structural features of bone tissue that are responsible for its biologic behavior. Moreover, relevant and recent technological approaches, also inspired by natural processes and structures, are described, which can be considered as a leverage for future development of next generation bioactive medical devices.
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Urtaza U, Guaresti O, Gorroñogoitia I, Zubiarrain-Laserna A, Muiños-López E, Granero-Moltó F, Lamo de Espinosa JM, López-Martinez T, Mazo M, Prósper F, Zaldua AM, Anakabe J. 3D printed bioresorbable scaffolds for articular cartilage tissue engineering: a comparative study between neat polycaprolactone (PCL) and poly(lactide-b-ethylene glycol) (PLA-PEG) block copolymer. Biomed Mater 2022; 17. [PMID: 35700720 DOI: 10.1088/1748-605x/ac78b7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 06/14/2022] [Indexed: 11/11/2022]
Abstract
This work identifies and describes different material-scaffold geometry combinations for cartilage tissue engineering (CTE). Previously reported potentially interesting scaffold geometries were tuned and printed using bioresorbable polycaprolactone and poly(lactide-b-ethylene) block copolymer. Medical grades of both polymers were 3D printed with fused filament fabrication technology within an ISO 7 classified cleanroom. Resulting scaffolds were then optically, mechanically and biologically tested. Results indicated that a few material-scaffold geometry combinations present potential for excellent cell viability as well as for an enhance of the chondrogenic properties of the cells, hence suggesting their suitability for CTE applications.
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Affiliation(s)
| | | | | | | | - Emma Muiños-López
- Department of Orthopaedic Surgery and Traumatology, Clínica Universidad de Navarra, Pamplona, Spain
| | - Froilán Granero-Moltó
- Department of Orthopaedic Surgery and Traumatology, Clínica Universidad de Navarra, Pamplona, Spain.,Cell Therapy Area, Clínica Universidad de Navarra, Pamplona, Spain
| | - J M Lamo de Espinosa
- Department of Orthopaedic Surgery and Traumatology, Clínica Universidad de Navarra, Pamplona, Spain
| | | | - Manuel Mazo
- Hematology and Cell Therapy Area, Clínica Universidad de Navarra, Pamplona, Spain.,Regenerative Medicine Program, Cima Universidad de Navarra, Foundation for Applied Medical Research, Pamplona, Spain
| | - Felipe Prósper
- Hematology and Cell Therapy Area, Clínica Universidad de Navarra, Pamplona, Spain.,Regenerative Medicine Program, Cima Universidad de Navarra, Foundation for Applied Medical Research, Pamplona, Spain
| | | | - Jon Anakabe
- Leartiker S. Coop., Markina-Xemein 48270, Spain
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5
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Cheng K, Lu S, Wang K, Luo G. Green and sustainable synthesis of poly(δ-valerolactone) with a TBD catalyzed ring-opening polymerization reaction. REACT CHEM ENG 2022. [DOI: 10.1039/d1re00434d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A green and sustainable method is proposed for the TBD catalyzed ring-opening polymerization of δ-valerolactone.
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Affiliation(s)
- Kai Cheng
- The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Shiyao Lu
- The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Kai Wang
- The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Guangsheng Luo
- The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
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6
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Karava A, Lazaridou M, Nanaki S, Michailidou G, Christodoulou E, Kostoglou M, Iatrou H, Bikiaris DN. Chitosan Derivatives with Mucoadhesive and Antimicrobial Properties for Simultaneous Nanoencapsulation and Extended Ocular Release Formulations of Dexamethasone and Chloramphenicol Drugs. Pharmaceutics 2020; 12:pharmaceutics12060594. [PMID: 32604758 PMCID: PMC7356116 DOI: 10.3390/pharmaceutics12060594] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 06/23/2020] [Accepted: 06/24/2020] [Indexed: 01/31/2023] Open
Abstract
The aim of this work was to evaluate the effectiveness of neat chitosan (CS) and its derivatives with 2-acrylamido-2-methyl-1-propanesulfonic acid (AAMPS) and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (MEDSP) as appropriate nanocarriers for the simultaneous ocular administration of dexamethasone sodium phosphate (DxP) and chloramphenicol (CHL). The derivatives CS-AAMPS and CS-MEDSP have been synthesized by free-radical polymerization and their structure has been proved by Fourier-Transformed Infrared Spectroscopy (FT-IR) spectroscopy. Both derivatives exhibited low cytotoxicity, enhanced mucoadhesive properties and antimicrobial activity against Staphylococcus aureus (S.aureus) and Escherichia coli (E. coli). Encapsulation was performed via ionic crosslinking gelation using sodium tripolyphosphate (TPP) as the crosslinking agent. Dynamic light scattering measurements (DLS) showed that the prepared nanoparticles had bimodal distribution and sizes ranging from 50–200 nm and 300–800 nm. Drugs were encapsulated in their crystalline (CHL) or amorphous (DexSP) form inside nanoparticles and their release rate was dependent on the used polymer. The CHL dissolution rate was substantially enhanced compared to the neat drug and the release time was extended up to 7 days. The release rate of DexSP was much faster than that of CHL and was prolonged up to 3 days. Drug release modeling unveiled that diffusion is the main release mechanism for both drugs. Both prepared derivatives and their drug-loaded nanoparticles could be used for extended and simultaneous ocular release formulations of DexSP and CHL drugs.
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Affiliation(s)
- Aikaterini Karava
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece;
| | - Maria Lazaridou
- Laboratory of Chemistry and Technology of Polymers and Dyes, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece; (M.L.); (S.N.); (G.M.); (E.C.)
| | - Stavroula Nanaki
- Laboratory of Chemistry and Technology of Polymers and Dyes, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece; (M.L.); (S.N.); (G.M.); (E.C.)
| | - Georgia Michailidou
- Laboratory of Chemistry and Technology of Polymers and Dyes, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece; (M.L.); (S.N.); (G.M.); (E.C.)
| | - Evi Christodoulou
- Laboratory of Chemistry and Technology of Polymers and Dyes, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece; (M.L.); (S.N.); (G.M.); (E.C.)
| | - Margaritis Kostoglou
- Laboratory of Chemical and Environmental Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece;
| | - Hermis Iatrou
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece;
- Correspondence: (H.I.); (D.N.B.); Tel.: +30-210-7274056 (H.I.); +30-2310-997812 (D.N.B.)
| | - Dimitrios N. Bikiaris
- Laboratory of Chemistry and Technology of Polymers and Dyes, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece; (M.L.); (S.N.); (G.M.); (E.C.)
- Correspondence: (H.I.); (D.N.B.); Tel.: +30-210-7274056 (H.I.); +30-2310-997812 (D.N.B.)
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7
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Schmidt BVKJ. Trends in Polymers 2017/2018: Polymer Synthesis. Polymers (Basel) 2019; 12:E39. [PMID: 31881763 PMCID: PMC7023566 DOI: 10.3390/polym12010039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 12/22/2019] [Indexed: 12/25/2022] Open
Abstract
Polymer synthesis is a substantial area in polymer science and marks the starting point for all sorts of polymer materials that have a plethora of applications in everyday life but also in academic research [...].
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8
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Anbarasan R, Kailash S, Meenarathi B. Synthesis, characterization and sustainable drug release activity of drug bridged diblock copolymer. SN APPLIED SCIENCES 2019. [DOI: 10.1007/s42452-019-1623-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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9
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Terzopoulou Z, Baciu D, Gounari E, Steriotis T, Charalambopoulou G, Tzetzis D, Bikiaris D. Composite Membranes of Poly(ε-caprolactone) with Bisphosphonate-Loaded Bioactive Glasses for Potential Bone Tissue Engineering Applications. Molecules 2019; 24:E3067. [PMID: 31450742 PMCID: PMC6749304 DOI: 10.3390/molecules24173067] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 08/16/2019] [Accepted: 08/21/2019] [Indexed: 12/11/2022] Open
Abstract
Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester with numerous biomedical applications. PCL membranes show great potential in guided tissue regeneration because they are biocompatible, occlusive and space maintaining, but lack osteoconductivity. Therefore, two different types of mesoporous bioactive glasses (SiO2-CaO-P2O5 and SiO2-SrO-P2O5) were synthesized and incorporated in PCL thin membranes by spin coating. To enhance the osteogenic effect of resulting membranes, the bioglasses were loaded with the bisphosphonate drug ibandronate prior to their incorporation in the polymeric matrix. The effect of the composition of the bioglasses as well as the presence of absorbed ibandronate on the physicochemical, cell attachment and differentiation properties of the PCL membranes was evaluated. Both fillers led to a decrease of the crystallinity of PCL, along with an increase in its hydrophilicity and a noticeable increase in its bioactivity. Bioactivity was further increased in the presence of a Sr substituted bioglass loaded with ibandronate. The membranes exhibited excellent biocompatibility upon estimation of their cytotoxicity on Wharton's Jelly Mesenchymal Stromal Cells (WJ-SCs), while they presented higher osteogenic potential in comparison with neat PCL after WJ-SCs induced differentiation towards bone cells, which was enhanced by a possible synergistic effect of Sr and ibandronate.
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Affiliation(s)
- Zoi Terzopoulou
- Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Central Macedonia, Greece.
| | - Diana Baciu
- National Center for Scientific Research "Demokritos", GR15341 Athens, Ag. Paraskevi Attikis, Greece
| | - Eleni Gounari
- Biohellenika Biotechnology Company, Leoforos Georgikis Scholis 65, GR57001 Thessaloniki, Central Macedonia, Greece
| | - Theodore Steriotis
- National Center for Scientific Research "Demokritos", GR15341 Athens, Ag. Paraskevi Attikis, Greece
| | - Georgia Charalambopoulou
- National Center for Scientific Research "Demokritos", GR15341 Athens, Ag. Paraskevi Attikis, Greece
| | - Dimitrios Tzetzis
- School of Science and Technology, International Hellenic University, GR57001 Thermi, Central Macedonia, Greece
| | - Dimitrios Bikiaris
- Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Central Macedonia, Greece
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Lu S, Wang K. Kinetic study of TBD catalyzed δ-valerolactone polymerization using a gas-driven droplet flow reactor. REACT CHEM ENG 2019. [DOI: 10.1039/c9re00046a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction kinetics of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyzed δ-valerolactone polymerization was determined using a gas-driven droplet reactor.
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Affiliation(s)
- Shiyao Lu
- The State Key Lab of Chemical Engineering
- Department of Chemical Engineering
- Tsinghua University
- Beijing 100084
- China
| | - Kai Wang
- The State Key Lab of Chemical Engineering
- Department of Chemical Engineering
- Tsinghua University
- Beijing 100084
- China
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11
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Zhang Q, Zhang W, Solan GA, Liang T, Sun WH. Bimetallic Aluminum 5,6-Dihydro-7,7-dimethyl quinolin-8-olates as Pro-Initiators for the ROP of ε-CL; Probing the Nuclearity of the Active Initiator. Polymers (Basel) 2018; 10:E764. [PMID: 30960689 PMCID: PMC6403881 DOI: 10.3390/polym10070764] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 07/10/2018] [Accepted: 07/10/2018] [Indexed: 11/16/2022] Open
Abstract
Six examples of aluminum 5,6-dihydro-7,7-dimethylquinolin-8-olates, [{2-R¹-7,7-Me₂-8-R²C₉H₆N-8-O}AlR³₂]₂ (R¹ = R² = H, R³ = Me C1; R¹ = R² = H, R³ = Et C2; R¹ = R² = H, R³ = i-Bu C3; R¹ = Cl, R² = H, R³ = Me C4; R¹ = H, R² = R³ = Me C5; R¹ = Cl, R² = R³ = Me C6), have been prepared by treating the corresponding pro-ligand (L1⁻L4) with either AlMe₃, AlEt₃ or Al(i-Bu)₃. All complexes have been characterized by ¹H and 13C NMR spectroscopy and in the case of C1 and C4 by single crystal X-ray diffraction; dimeric species are a feature of their molecular structures. In the presence of PhCH₂OH (BnOH), C1⁻C6 displayed good control and efficiency for the ROP of ε-CL with almost 100% conversion achievable in 10 min at 90 °C; the chloro-substituted C4 and C6 notably exhibited the lowest activity of the series. However, in the absence of BnOH, C1 showed only low activity with 15% conversion achieved in 30 min forming a linear polymer capped with either a methyl or a L1 group. By contrast, when one or more equivalents of BnOH was employed in combination with C1, the resulting catalyst was not only more active but gave linear polymers capped with BnO end-groups. By using ¹H and 27Al NMR spectroscopy to monitor solutions of C1, C1/BnOH and C1/BnOH/10 ε-CL over a range of temperatures, some support for a monomeric species being the active initiator at the operational temperature is presented.
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Affiliation(s)
- Qiurui Zhang
- Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China.
- Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Wenjuan Zhang
- Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China.
- Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Gregory A Solan
- Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
- Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK.
| | - Tongling Liang
- Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Wen-Hua Sun
- Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
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