Synthesis and characterization of novel β-cyclodextrin cored poly(α-caprolactone)s by anionic ring opening polymerization

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Yingzhi Guo ◽  
Changjiang Yu ◽  
Zhongwei Gu
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Ring Opening ◽  
Monomer Conversion ◽  
Ring Opening Polymerization ◽  
Molar Ratio ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Anionic Ring ◽  
Feed Molar Ratio

Abstract By anionic ring opening polymerization initiated by cyclodextrin oxyanions generated from NaH and β-cyclodextrin(β-CD), novel biodegradable β- CD cored star-shaped poly(ε-caprolactone)s (s-PCLs) were synthesized and then characterized by means of FTIR, GPC, 1H-NMR. The effects of different feed molar ratios of NaH and β-CD on arm number and on the molecular weight of s-PCLs, and the relationship between the polymerization time and monomer conversion were investigated. Moreover, the physical properties of linear PCL (l-PCL) and s- PCLs with similar molecular weights but different arm number were studied and compared by DSC, SEM and intrinsic viscosity measurement, respectively. It was found that the feed molar ratio of NaH and β-CD is an important factor which influences both the molecular weight and arm number. The melting points and intrinsic viscosities of s-PCLs with similar molecular weights were lower than that of l-PCL, and were found to decrease with increasing arm number. Both SEM and AFM showed that the surface morphology of s-PCL films was different from that of l-PCL. These results indicated that s-PCL with different arms and physical properties could be synthesized using just a β-CD core by adjusting the feed molar ratio of NaH and β-CD

Anionic Ring-Opening Polymerization Simulations for Hyperbranched Polyglycerols with Defined Molecular Weights

2013 ◽  
Vol 46 (21) ◽  
pp. 8458-8466 ◽  
Author(s):  
Florian Paulus ◽  
Maximilian E. R. Weiss ◽  
Dirk Steinhilber ◽  
Anatoly N. Nikitin ◽  
Christof Schütte ◽  
...  
Keyword(s):  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Molecular Weights ◽  
Anionic Ring

scholarly journals A Simplified Method for Formulation of Epoxy Resin Embedding Media

2006 ◽  
Vol 14 (5) ◽  
pp. 50-51 ◽  
Author(s):  
E. Ann Ellis
Keyword(s):  
Molecular Weight ◽  
Epoxy Resin ◽  
Molar Ratio ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Low Viscosity ◽  
Simplified Method ◽  
Beam Stability ◽  
Embedding Medium

In a recent paper on the revised formulation of Spurr low viscosity embedding medium with ERL 4221 the importance of maintaining an appropriate anhydride:epoxide (A:E) ratio was discussed. By understanding a few simple concepts about epoxy resin formulations and setting up a formulation table it is possible to create new resin mixtures with good sectioning properties and other desirable properties such as decreased viscosity and increased beam stability.Before starting a formulation you need to know the molecular weight of the anhydride and the WPE (weight per epoxide equivalent) of the epoxy resin component. The molecular weights and WPEs are usually printed on the bottle or can be obtained from the vendor. An A:E ratio of 0.7:1.0 -1.0:1.0 is used for most biological specimens. Increasing the A:E ratio results in a harder block; decreasing the A:E ratio results in a softer block. Table 1 shows a basic formulation spreadsheet where the molecular weights of the anhydrides and the WPEs of the epoxy resin components can be entered. The A:E ratio is entered under the anhydride for the molar ratio and the molar ratios of the epoxy components are entered under the epoxy components. The calculations are done as shown in each column and row.

Functionalized Polyesters via Stereoselective Electrochemical Ring-Opening Polymerization of O-Carboxyanhydrides

2020 ◽  
Author(s):  
Yongliang Zhong ◽  
quanyou feng ◽  
xiaoqian wang ◽  
jia chen ◽  
wenjun cai ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Catalytic System ◽  
Ring Opening ◽  
Electrical Current ◽  
Ring Opening Polymerization ◽  
Glass Transition Temperatures ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Ring-opening polymerization is used to prepare polyesters with precisely controlled molecular weights, molecular weight distributions, and tacticities. Herein, we report a newly developed Co/Zn catalytic system that can be activated by an electrical current to mediate efficient ring-opening polymerization of enantiopure <i>O</i>-carboxyanhydrides, allowing for the synthesis of isotactic functionalized polyesters with high molecular weights (>140 kDa) and narrow molecular weight distributions (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> < 1.1). We also demonstrate that these catalysts can be used for stereoselective ring-opening polymerization of racemic <i>O</i>-carboxyanhydrides to synthesize syndiotactic or stereoblock copolymers with different glass transition temperatures compared with their atactic counterparts.

Solvent-assisted anionic ring opening polymerization of glycidol: Toward medium and high molecular weight hyperbranched polyglycerols

2013 ◽  
Vol 51 (12) ◽  
pp. 2614-2621 ◽  
Author(s):  
Muhammad Imran ul-haq ◽  
Rajesh A. Shenoi ◽  
Donald E. Brooks ◽  
Jayachandran N. Kizhakkedathu
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Anionic Ring

Synthesis and Properties of Biodegradable ABA Triblock Copolymers of Polylactide (A) and Polyethylene Glycol (B)

2006 ◽  
Vol 11-12 ◽  
pp. 469-472 ◽  
Author(s):  
Shu Xian Shi ◽  
Yu Zheng Xia ◽  
Xiao Yan Ma ◽  
Shu Ke Jiao ◽  
Xiao Yu Li
Keyword(s):  
Molecular Weight ◽  
Ethylene Glycol ◽  
Ring Opening ◽  
Average Molecular Weight ◽  
Analytical Techniques ◽  
Normal Pressure ◽  
Molar Ratio ◽  
Poly Ethylene Glycol ◽  
Molar Ratios ◽  
Poly Ethylene

The triblock ABA copolymers of poly (D,L-lactide)-b-poly (ethylene glycol)-b-poly (D,L-lactide) (PDLLA-PEG-PDLLA) were synthesized by bulk ring-opening polymerization in the presence of N2 under normal pressure, using the D,L-lactide (DLLA) as monomer, hydroxyl endgroups of poly(ethylene glycol) (PEG) as initiator and the stannous octoate as the catalyst. The resulting copolymers were characterized by various analytical techniques. Effects of molar ratios of lactide to PEG and the chain length of PEG on the viscosity-average molecular weight of the copolymers, the biodegradation behaviors and hydrophilicity of the copolymers were investigated in detail. The results showed that the viscosity-average molecular weight and the contact angle of the copolymers increased with the molar ratio of lactide to PEG, but water uptake and degradability decreased.

Chemical synthesis of novel biodegradable polyesters

1995 ◽  
Vol 41 (13) ◽  
pp. 282-288 ◽  
Author(s):  
Y. Hori ◽  
Y. Takahashi ◽  
A. Yamaguchi ◽  
T. Hagiwara
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Lactone Ring ◽  
Ring Opening Polymerization ◽  
Optically Active ◽  
Bond Breaking ◽  
Carbonyl Carbon ◽  
Biodegradable Polyesters ◽  
Molecular Weights ◽  
High Molecular Weight Poly

Distannoxane complexes catalyze the ring-opening polymerization of optically active β-butyrolactone (β-BL) to afford a high molecular weight poly(3-hydroxybutyrate). When 1-ethoxy-3-chlorotetrabutyldistannoxane was used as a catalyst (catalyst/(R)-β-BL = 1/8000 at 100 °C for 4 h), poly((R)-3-hydroxybutyrate) was obtained from (R)-β-BL in a yield of 99%. The copolymerizations of (R)-β-BL with racemic β-BL in several ratios gave corresponding stereocopolymers. The copolymerizations of (R)-β-BL with ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, and L-lactide afforded novel optically active and biodegradable polyesters of high molecular weights, comprising (R)-3-hydroxybutyrate (3HB). The polymerization of (R)-β-BL catalyzed by the distannoxane complexes proceeded by bond breaking between the carbonyl carbon and oxygen atom of the lactone ring (acyl cleavage) with retention of the configuration and little or no racemization. Polymers that have over 80 mol% of the (R)-3HB unit were found to have almost the same degree of biodegradability as the copolyester of 3-hydroxybutyrate and 11% 3-hydroxyvalerate produced by the microbial method.Key words: distannoxane, ring-opening polymerization, poly(3-hydroxybutyrate), poly(3-hydroxyalkanoates), biodegradable polymer.

scholarly journals Functionalized Polyesters via Stereoselective Electrochemical Ring-Opening Polymerization of O-Carboxyanhydrides

2020 ◽  
Author(s):  
Yongliang Zhong ◽  
quanyou feng ◽  
xiaoqian wang ◽  
jia chen ◽  
wenjun cai ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Catalytic System ◽  
Ring Opening ◽  
Electrical Current ◽  
Ring Opening Polymerization ◽  
Glass Transition Temperatures ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Ring-opening polymerization is used to prepare polyesters with precisely controlled molecular weights, molecular weight distributions, and tacticities. Herein, we report a newly developed Co/Zn catalytic system that can be activated by an electrical current to mediate efficient ring-opening polymerization of enantiopure <i>O</i>-carboxyanhydrides, allowing for the synthesis of isotactic functionalized polyesters with high molecular weights (>140 kDa) and narrow molecular weight distributions (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> < 1.1). We also demonstrate that these catalysts can be used for stereoselective ring-opening polymerization of racemic <i>O</i>-carboxyanhydrides to synthesize syndiotactic or stereoblock copolymers with different glass transition temperatures compared with their atactic counterparts.

scholarly journals Photocatalyst-Independent Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides: Stereocontrol and Mechanism

2021 ◽  
Author(s):  
Yongliang Zhong ◽  
quanyou feng ◽  
xiaoqian wang ◽  
Lei Yang ◽  
Rong Tong
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Precious Metal ◽  
Ring Opening Polymerization ◽  
Oxidative Status ◽  
Mechanistic Studies ◽  
Glass Transition Temperatures ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Photoredox ring-opening polymerization of <i>O</i>-carboxyanhydrides allows for the synthesis of polyesters with precisely controlled molecular weights, molecular weight distributions, and tacticities. While powerful, obviating the use of precious metal-based photocatalysts would be attractive from the perspective of simplifying the protocol and enabling unexpected reactivity. Herein, we report the Co and Zn catalysts that are activated by external light to mediate efficient ring-opening polymerization of <i>O</i>-carboxyanhydrides, without the use of exogenous precious metal-based photocatalysts. Our methods allow for the synthesis of isotactic polyesters with high molecular weights (>200 kDa) and narrow molecular weight distributions (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> < 1.1). Mechanistic studies indicate that light activates the oxidative status of Co<sup>III</sup> intermediate that is generated from the regioselective ring-opening of the <i>O</i>-carboxyanhydride. We also demonstrate that the use of Zn or Hf complexes together with Co can allow for stereoselective photoredox ring-opening polymerizations of multiple racemic <i>O</i>-carboxyanhydrides to synthesize syndiotactic and stereoblock copolymers, which vary widely in their glass transition temperatures.

scholarly journals Chiral 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)-Catalyzed Stereoselective Ring-Opening Polymerization of rac-Lactide: High Reactivity for Isotactic Enriched Polylactides (PLAs)

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2365 ◽  
Author(s):  
Qaiser Mahmood ◽  
Guangqiang Xu ◽  
Li Zhou ◽  
Xuanhua Guo ◽  
Qinggang Wang
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Kinetic Studies ◽  
Monomer Conversion ◽  
Ring Opening Polymerization ◽  
High Reactivity ◽  
Chiral Hplc ◽  
Nmr Spectrum ◽  
Molecular Weight Distributions ◽  
A Chain

Chiral 4,8-diphenyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (DiPh-TBD) was synthesized and applied to a ring-opening polymerization of rac-lactide (rac-LA). The chiral DiPh-TBD promoted the synthesis of isotactic enriched polylactides (PLAs) with controlled molecular weight and narrow molecular weight distributions under mild, metal-free conditions. When the [rac-LA]/[Cat.] ratio was 100/1, full monomer conversion was achieved within only 1 min and a moderate probability of 0.67 meso dyads (Pm) was obtained at room temperature. A chain-end control mechanism (CEC) was found to be responsible for the isoselectivity based on the homodecoupled 1H NMR spectrum, the chiral HPLC measurement, and kinetic studies.

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