scholarly journals Unsymmetrical Growth Synthesis of Nontraditional Dendrimers

2021 ◽  
Author(s):  
Shengtao Ding ◽  
Lijiao Niu ◽  
Xueyan Zhang
Keyword(s):  
Molecular Weight ◽  
Functional Groups ◽  
1H Nmr ◽  
Science And Technology ◽  
Complex Molecules ◽  
Organic Azides ◽  
Dendritic Macromolecules ◽  
Interior Layers

Developing highly complex molecules is of great significance in science and technology. Here we present an unprecedented type of dendrimer assembled from linear ABB-type monomer. The construction of this nontraditional ramified architecture was facilely achieved through one simple convergent strategy established on the iridium-catalyzed cycloaddition of organic azides with internal 1-thioalkynes (IrAAC). By virtue of the unsymmetrically growing fashion in this process, diverse functional groups could be conveniently distributed on both of its exterior and interior layers. Syntheses of two dendrons from the cooperation of one linear alkyne motif with different azides were presented to demonstrate the efficiency and fidelity of this protocol. Post-modifications on their core or periphery were further conducted, resulting in diverse newly functionalized dendrimers with up to ~16.0 kDa molecular weight. The identity and purity of these unsymmetrical dendritic macromolecules were well confirmed by 1H NMR, MS and SEC analysis.

Visible Light-Mediated Oxidative Debenzylation

2020 ◽  
Author(s):  
Cristian Cavedon ◽  
Eric T. Sletten ◽  
Amiera Madani ◽  
Olaf Niemeyer ◽  
Peter H. Seeberger ◽  
...  
Keyword(s):  
Reaction Time ◽  
Visible Light ◽  
Functional Groups ◽  
Continuous Flow ◽  
Protecting Groups ◽  
Benzyl Ether ◽  
Complex Molecules ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

scholarly journals Synthesis of polylactic acid-diol (PLA-diol) from lactic acid and 1,4-butanediol

2016 ◽  
Vol 19 (4) ◽  
pp. 58-65
Author(s):  
Ha Thi Thai La
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Polyethylene Glycol ◽  
1H Nmr ◽  
Biodegradable Polymer ◽  
Average Molecular Weight ◽  
Chain Extension ◽  
Structure And Properties ◽  
Chain Reaction ◽  
A Chain

In this research, the PLA-diol were synthesized from lactic acid (LA) and 1.4 butanediols (BD) with a tin octoate Sn(Oct)2 catalyst at a temperature of 180 °C and the pressure 5 mmHg. The structure and properties of PLA-diol are analyzed by the following methods: GPC, 1H-NMR and DSC. As a result, with the change in the content of Sn (Oct)2 from 0.1 to 1.0%, the molecular weight Mn of PLA - diol increased gradually from 4.119,2 to 7.359,6 g / mol . In addition, the BD content increased from 2.0% to 5.0%, the average molecular weight of the product decreased gradually from 7.536,9 g / mol to 4.735 g / mol, respectively. This change will affect the ability to use PLA-diol in the next denaturation research to apply in the field of biodegradable polymer such as copolymer with polyurethane, copolymer with polyethylene glycol diacid, or chain extension with other polymer in a chain reaction,...

scholarly journals Water soluble metal-polymeric complexes of gallium and triple co-polymer of N-vinylpyrrolidone with N-vinylformamide and N-vinylminodiacetic acid

2019 ◽  
Vol 485 (3) ◽  
pp. 306-310
Author(s):  
N. I. Gorshkov ◽  
A. Yu. Murko ◽  
I. I. Gavrilova ◽  
I. I. Malakhova ◽  
V. D. Krasikov ◽  
...  
Keyword(s):  
Molecular Weight ◽  
1H Nmr ◽  
Metal Ion ◽  
Water Soluble ◽  
Polymer Complex ◽  
Nmr Data ◽  
Exclusion Chromatography ◽  
Polymeric Complexes ◽  
Metal Polymer

A terpolymer with a molecular weight of 45 kDa containing 7 mol.% of vinylamine units, 80 mol.% of vinylpyrrolidone, and 3 mol.% of vinyliminodiacetic acid units has been synthesized. Its complexation with Ga3+ ion has been studied by HPLC. The resulting metal–polymer complex has been characterized by exclusion chromatography and spectral (IR, 1H NMR) data. The complex has a monomolecular structure where the metal ion acts as an anchor fragment between vinyliminodiacetic acid units and is stable in the reaction of interligand exchange with histidine.

Molecular Structure and Macroscopic Properties of Synthetic Cis-Poly(Isoprene)

1974 ◽  
Vol 47 (2) ◽  
pp. 342-356 ◽  
Author(s):  
V. A. Grechanovskii ◽  
I. Ya Poddubnyi ◽  
L. S. Ivanova
Keyword(s):  
Molecular Weight ◽  
Functional Groups ◽  
Chemical Structure ◽  
Sol Gel ◽  
Average Molecular Weight ◽  
Dense Network ◽  
Green Strength ◽  
Gel Fraction ◽  
Rubber Compounds ◽  
Processing Properties

Abstract By changing the sol-gel ratio and the structure of the gel fraction it is possible to obtain various grades of synthetic cis-poly(isoprene) which show promise for different applications in the tire and mechanical rubber goods industries. The processability of commercial SKI-3 rubber (at a given average molecular weight of sol) depends mainly on the structure of the gel fraction. Thus, for example, inferior processing properties of rubber compounds is associated primarily with the presence of tight gel. The content and structure of the gel fraction also significantly affect plasto-elastic properties of raw rubbers, e.g. a low plasticity of raw rubbers owes to the increased content of gel fraction. The reduced green strength of compounds based on SKI—3 rubber is accounted for by its chemical structure. Conventional methods used to change the properties of rubbers (including the variation in molecular weight, molecular weight distribution, branching degree, and variation in the content and structure of gel fraction) cannot be considered to be adequate to tackle the problem of the green strength of SKI—3 black stocks. The way to solve the problem appears to be the introduction of functional groups into the polymer chain at the stage of synthesis or processing. These functional groups should be active as to the formation of labile rubber—carbon black—rubber and/or rubber—rubber bonds. High purity of microstructure is necessary but not sufficient for obtaining the required level of green strength of compounded SKI—3. The gel fractions of SKI—3 rubber yield vulcanizates with a more dense network than the corresponding sol vulcanizates. The temperature dependence of the tensile strength is controlled by the network density of vulcanizates from high cis-1,4 poly(isoprene).

Properties of Hyperbranched Polyglycidol’s Derivatives

2020 ◽  
Vol 869 ◽  
pp. 190-195
Author(s):  
Yuri Mikhailov ◽  
Ludmila Romanova ◽  
Anna Darovskikh ◽  
Nilson Garifullin
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Functional Groups ◽  
Enthalpy Of Formation ◽  
Rheological Parameters ◽  
Weight Composition ◽  
Composition And Structure

Some properties (enthalpy of formation, glass transition temperature and rheological parameters) of hyperbranched polyglycidol derivatives containing nitrate and azide functional groups were investigated. The dependence of the found properties on the molecular weight, composition and structure of the investigated substances was determined.

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