Macrocycles in dual role: ancillary ligands in metal complexes and organocatalysts for the ring-opening polymerization of lactide

2021 ◽  
Author(s):  
Sourav Singha Roy ◽  
Sriparna Sarkar ◽  
Debashis Chakraborty
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
First Century ◽  
Environmentally Benign ◽  
Catalytic Systems ◽  
Ancillary Ligands ◽  
Central Focus ◽  
Polymer Research ◽  
Review Reports

AbstractIn the twenty-first century, one of the central focus of polymer research in academia and industries is directed towards the design of environmentally-benign materials produced from reagents that have minimal deleterious effects on our environment. The aliphatic polyester PLA is one such example. Due to its biodegradable, biorenewable and biocompatible nature, PLA finds diverse applications, especially in the biomedical field. PLA is exclusively synthesized by the ring-opening polymerization of lactide (cyclic dimer of lactic acid) in the presence of a catalyst. The macrocycles and macrocyclic metal moieties can act as effective catalysts for the polymerization resulting in the formation of PLA with controlled tacticity and predetermined molecular weight. This review reports metal-based catalytic systems supported by porphyrin, calixarene and bispyrrolidine- salan as ancillary ligand and metal-free organocatalyst sparteine for the ROP of LA. The variation in catalytic activity, tacticity of PLA, and PLA's molecular weight distribution by substitutional changes in the catalyst framework have been discussed in detail. Graphic abstract

Influence of Different Initiators Against the Mechanical Properties of Poly(e-caprolactone) used for Biodegradable Bone Implants

2008 ◽  
Vol 59 (11) ◽  
Author(s):  
Adriana Lungu ◽  
Teodora Zecheru ◽  
Stanca Comsa ◽  
Horia Iovu
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Hydrolysis Rate ◽  
Reaction Conditions ◽  
Structures And Properties ◽  
Polymer Research ◽  
Industrial Use ◽  
Improved Characteristics

The ability of a strict control for the advanced macromolecular structures synthesis has been an important objective in our research. The development of polymers with defined structures and properties, aimed at biomedical applications, leads to complex and advanced architecture and diversity of the biodegradable polymers. Ring-opening polymerization is one of the most common methods for the synthesis of polymers with improved characteristics. Poly e-(caprolactone) (PCL) is prepared by ring-opening polymerization of the monomer e-caprolactone. The main factors which influence the ring-opening polymerization are the reaction conditions, such as the nature of the initiator, type and concentration of catalyst, reaction temperature and time. Stannous (II) 2-ethylhexanoate is used to catalyze the polymerization and alcohols are used as initiators. The initiators are also used to control the polymers molecular weight. Despite the long use of this catalyst in both industrial use and polymer research, several questions about the properties of the final product still remain. Our study describes the polymerization of e-caprolactone performed in the presence of catalyst (stannous (II) 2-ethylhexanoate) and initiator (1, 6 hexandiol or trimethylol propane) at moderate temperature (110�C). The polymerization of e-caprolactone was also performed in the presence of catalyst alone in order to evaluate the effect of the initiator against the polymers molecular weight. The obtained polymers were characterized by FTIR, GPC and TGA with respect to their mechanical properties. It is crucial to control the molecular weight of PCL for biomedical and pharmaceutical applications, because its molecular weight determines the hydrolysis rate. Several ratios among monomer, catalyst and initiator were studied, and we chose an optimum composition, in order to control the mechanical properties, degradation profiles respectively, and to avoid the cytotoxicity given by the reagents used.

Catalytic Ring-Opening Polymerization of Renewable Macrolactones to High Molecular Weight Polyethylene-like Polymers

2011 ◽  
Vol 44 (11) ◽  
pp. 4301-4305 ◽  
Author(s):  
Inge van der Meulen ◽  
Erik Gubbels ◽  
Saskia Huijser ◽  
Rafaël Sablong ◽  
Cor E. Koning ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization

The synthesis and polymerization behaviour of silicon-bridged [1]- and [2]ferrocenophanes with sterically demanding trimethylsilyl substituents attached to the cyclopentadienyl rings

1995 ◽  
Vol 73 (11) ◽  
pp. 2069-2078 ◽  
Author(s):  
Timothy J. Peckham ◽  
Daniel A. Foucher ◽  
Alan J. Lough ◽  
Ian Manners
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Monoclinic Space Group ◽  
Organometallic Polymers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cyclopentadienyl Ligands ◽  
Sterically Demanding ◽  
High Molecular Weight Poly

The silicon-bridged [1]ferrocenophane Fe(η-C5H3SiMe3)2(SiMe2) (5) was synthesized via the reaction of Li2[Fe(η-C5H3SiMe3)2]•tmeda (tmeda = tetramethylethylenediamine) with Me2SiCl2 in hexanes. The disilane-bridged [2]ferrocenophane Fe(η-C5H3SiMe3)2(Si2Me4) (7) was prepared using a similar route from the disilane ClMe2SiSiMe2Cl. Despite the presence of sterically demanding SiMe3 substituents on the cyclopentadienyl rings, compound 5 was found to undergo thermal ring-opening polymerization at 170 °C to produce very soluble, high molecular weight poly(ferrocenylsilane) 6 with Mw = 1.4 × 105, Mn = 8.4 × 104. However, the [2]ferrocenophane 7 was found to be resistant to thermal ring-opening polymerization even at 350 °C and decomposed above 380 °C. A single-crystal X-ray diffraction study of 7 revealed that the steric interactions between the bulky SiMe3 groups are relieved by a significant twisting of the disilane bridge with respect to the plane defined by the centroids of the cyclopentadienyl ligands and the metal atom. The angle between the planes of the cyclopentadienyl rings in 7 was found to be 5.4(6)°, slightly greater than that in the non-silylated analogue Fe(η-C5H4)2(Si2Me4) (4a) (4.19(2)°), and dramatically less than the corresponding tilt angle of the strained, polymerizable, silicon-bridged [1]ferrocenophane Fe(η-C5H4)2(SiMe2) (1) (20.8(5)°). The length of the Si—Si bond in 7 (2.342(3) Å) was found to be close to the sum of the covalent radii (2.34 Å). Crystals of 7 are monoclinic, space group C2/c, with a = 23.689(3) Å, b = 11.174(1) Å, c = 31.027(3) Å, β = 109.16(1)°, V = 7758(2) Å3, and Z = 12. Keywords: ring-opening polymerization, ferrocenophane, organometallic polymers.

Biodegradable Polymers Derived from Amino Acids for Biological Applications

2010 ◽  
Vol 76 ◽  
pp. 30-35 ◽  
Author(s):  
Naomi Cohen-Arazi ◽  
Ilanit Hagag ◽  
Michal Kolitz ◽  
Abraham J. Domb ◽  
Jeoshua Katzhendler
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Ring Opening ◽  
Building Blocks ◽  
Ring Opening Polymerization ◽  
Microwave Assisted Synthesis ◽  
Hydroxy Acids ◽  
Natural Amino Acids ◽  
Direct Condensation ◽  
Positively Charged

Optically active α-hydroxy acids derived from amino acids have been synthesized and polymerized into new biodegradable polyesters. The variety of functional side chains enables the design of positively charged, negatively charged, hydrophobic and hydrophilic chiral building blocks or any combination of these constituents. Hydroxy acids of 15 natural amino acids were prepared with retention of configuration using a straightforward and reliable method of diazotization of α-amino acids. Polyesters were synthesized from these hydroxy acids by a number of methods: direct condensation in bulk, microwave assisted synthesis and ring opening polymerization. The molecular weight of the prepared polymers ranges between 2000 to 5000Da for the direct condensation and the microwave methods, whereas the ring opening polymerization results in high molecular weight polymers (20000 to 30000Da). The polymers were analyzed for their optical activity (Circular Dichroism Spectroscopy), thermal properties (DSC), solubility, molecular weight and polydispersity (GPC), and aqueous degradation. These polymers were tested for their compatibility to neuronal cells growth and differentiation.

Organophosphate-catalyzed bulk ring-opening polymerization as an environmentally benign route leading to block copolyesters, end-functionalized polyesters, and polyester-based polyurethane

2015 ◽  
Vol 6 (24) ◽  
pp. 4374-4384 ◽  
Author(s):  
Tatsuya Saito ◽  
Yusuke Aizawa ◽  
Kenji Tajima ◽  
Takuya Isono ◽  
Toshifumi Satoh
Keyword(s):  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Cyclic Carbonate ◽  
Environmentally Benign ◽  
Cyclic Ester ◽  
Cyclic Esters

To expand the potential of an organophosphate catalyst, ring-opening polymerization of cyclic esters, cyclic ester-ether, and cyclic carbonate was demonstrated under bulk conditions.

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