scholarly journals Oligomeric alkylpyridinium surfactants prepared via ATRP

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Xin Su ◽  
Zonglin Chu ◽  
Ya Shuai ◽  
Zanru Guo ◽  
Yujun Feng
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Surface Tension ◽  
Critical Micelle Concentration ◽  
Aqueous Media ◽  
Degree Of Polymerization ◽  
Surface Activities ◽  
H Nmr ◽  
Molecular Weight Distributions ◽  
Weight Distributions

AbstractA series of oligomeric alkylpyridinium surfactants were prepared directly in aqueous media by atom transfer radical polymerization (ATRP) of a surfmer, 4- vinyl-N-dodecylpyridinium bromide, and their surface activities were examined in comparison with the surfmer. The resulting oligomers have narrow molecular weight distributions, with polydispersity indices in the range of 1.17-1.23. By using 2-morpholinoethyl 2-bromo-2-methylpropanoate as ATRP initiator, the molecular weight of oligomeric surfactants was characterized by 1H NMR and the results were close to those obtained from GPC analysis. It was found that critical micelle concentration (CMC) of the oligomeric alkylpyridinium surfactants shifted to lower concentrations with increasing degree of polymerization (DPn), and their γ-cmc values were smaller by about 4 to 8 mN/m than that of the corresponding surfmer. Among the series of surfactants, the oligomer with highest DPn showed the greatest efficiency in lowering the surface tension in aqueous solution.

The Use of Novel F-RAFT Agents in High Temperature and High Pressure Ethene Polymerization: Can Control be Achieved?

2007 ◽  
Vol 60 (10) ◽  
pp. 788 ◽  
Author(s):  
Markus Busch ◽  
Marion Roth ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
High Temperature ◽  
Degree Of Polymerization ◽  
Molecular Weight Distributions ◽  
High Pressure High Temperature ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Raft Agent ◽  
Initial Results

Simulations are employed to establish the feasibility of achieving controlled/living ethene polymerizations. Such simulations indicate that reversible addition–fragmentation chain transfer (RAFT) agents carrying a fluorine Z group may be suitable to establish control in high-pressure high-temperature ethene polymerizations. Based on these simulations, specific fluorine (F-RAFT) agents have been designed and tested. The initial results are promising and indicate that it may indeed be possible to achieve molecular weight distributions with a polydispersity being significantly lower than that observed in the conventional free radical process. In our initial trials presented here (using the F-RAFT agent isopropylfluorodithioformate), a correlation between the degree of polymerization and conversion can indeed be observed. Both the lowered polydispersity and the linear correlation between molecular weight and conversion indicate that control may in principle be possible.

scholarly journals Tuning the Properties of High Molecular Weight Chitosans to Develop Full Water Solubility Within a Wide pH Range

2020 ◽  
Author(s):  
Anderson Fiamingo ◽  
Sergio Paulo Campana Filho ◽  
Osvaldo Novais Oliveira Junior
Keyword(s):  
Molecular Weight ◽  
Biomedical Applications ◽  
Random Distribution ◽  
Water Solubility ◽  
Aqueous Media ◽  
Degree Of Polymerization ◽  
Molecular Weights ◽  
H Nmr ◽  
Wide Ph Range ◽  
Ph Range

<p>The preparation of chitosans soluble in physiological conditions has been sought for years, but so far solubility in non-acidic aqueous media has only been achieved at the expense of lowering chitosan molecular weight. In this work, we applied the multistep ultrasound-assisted deacetylation process (USAD process) to β-chitin and obtained extensively deacetylated chitosans with high molecular weights (Mw ≥ 1,000,000 g mol<sup>-1</sup>). The homogeneous <i>N</i>-acetylation of a chitosan sample resulting from three consecutive USAD procedures allowed us to produce chitosans with a high weight average degree of polymerization (DPw ≈ 6,000) and tunable degrees of acetylation (DA from 5 to 80%). <i>N</i>-acetylation was carried out under mild conditions to minimize depolymerization, while preserving a predominantly random distribution of 2-amino-2-deoxy-D-glucopyanose (<i>GlcN</i>) and 2-acetamido-2-deoxy-D-glucopyanose (<i>GlcNAc</i>) units. This close to random distribution, inferred with deconvolution of nuclear magnetic resonance (<sup>1</sup>H NMR) spectra, is considered as responsible for the solubility within a wide pH range. Two of the highly <i>N</i>-acetylated chitosans (DA ≈ 60 % and ≈ 70 %) exhibited full water solubility even at neutral pH, which can expand the biomedical applications of chitosans. </p>

Exploring the formaldehyde reactivity of tannins with different molecular weight distributions: bayberry tannins and larch tannins

Holzforschung ◽  
2020 ◽  
Vol 74 (7) ◽  
pp. 673-682 ◽  
Author(s):  
Tao Yang ◽  
Mengqi Dong ◽  
Juqing Cui ◽  
Lu Gan ◽  
Shuguang Han
Keyword(s):  
Molecular Weight ◽  
High Performance ◽  
Average Molecular Weight ◽  
Degree Of Polymerization ◽  
Standard Curve ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Curve Method ◽  
Standard Curve Method ◽  
Tannin Degradation

AbstractIn recent years, tannin degradation has been used to obtain tannin materials with an optimal molecular weight distribution (MWD) for synthesizing tannin-formaldehyde (TF) resin with high performance, but the optimal MWD of tannins is still unknown. The excellent formaldehyde reactivity of tannins is the basis for the synthesis of high-performance TF resin. Based on the formaldehyde reactivity of tannins, bayberry tannins and larch tannins were used to explore the optimal MWD of tannins for TF resin synthesis. Progressive solvent precipitation (PSP) was used to obtain tannin fractions with different MWDs. The formaldehyde reactivity of tannins was determined using the modified Stiansy method combined with the standard curve method (GB/T 17657-2013). The bayberry tannin fraction [weight-average molecular weight (Mw) of acetylated tannin: 4115, mean degree of polymerization (mDP): 6.64] and the larch tannin fraction (Mw of acetylated tannin: 3906, mDP: 5.84) had the best formaldehyde reactivity. Furthermore, significant differences in the formaldehyde reactivity of condensed tannins (CTs) with different MWDs were observed. The obtained results can be used to purposefully degrade tannins to achieve an optimal MWD, which is beneficial for the production of TF adhesives with high performance.

Synthesis and characterization of new phenanthrolinetriether copolymers with rotaxane architecture

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Aurica Farcas ◽  
Valeria Harabagiu
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Ethylene Glycol ◽  
Synthesis And Characterization ◽  
Nmr Analysis ◽  
H Nmr ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Different Content

AbstractThis paper is devoted to the preparation and characterization of new phenanthroline-triether copolymers with rotaxane architecture by reaction of complexes of α- or β- cyclodextrin and tri(ethylene glycol) ditosylate with 2,9-di(4-hydroxyphenyl)-1,10- phenanthroline, which is large enough to prevent dethreading of cyclodextrin molecules. Comparative 1H-NMR analysis of tri(ethylene glycol) ditosylate complexes and of rotaxane copolymers evidenced the lower cyclodextrin content in rotaxane copolymers as compared to the calculated values. The rotaxane copolymers present bimodal molecular weight distributions attributed to the separation of the fractions with different content of cyclodextrin threaded on the copolymer chain. As evidenced by thermogravimetric analysis, the rotaxane copolymers show higher thermal stability than its non-complexed homologue.

Synthesis and Characterization of Polythiophene Derivatives with Different Alkyl Substitution Groups

2015 ◽  
Vol 815 ◽  
pp. 477-482
Author(s):  
Wei Xing Chen ◽  
Yong Qiang Gu ◽  
Chun Yan Luo ◽  
Xiao Long Zhang
Keyword(s):  
Molecular Weight ◽  
Synthesis And Characterization ◽  
H Nmr ◽  
Chemical Structures ◽  
Molecular Weight Distributions ◽  
Alkyl Substitution ◽  
Weight Distributions ◽  
Maximum Absorption Wavelength ◽  
Uv Absorption Spectrum

Three kinds of poly (3-alkylthiophene), such as poly (3-butylthiophene) (P3BT), poly (3-hexylthiophene) (P3HT) and poly (3-dodecylthiophene) (P3DDT) were prepared by the Grignard Metathesis Method (GRIM). Their chemical structures are characterized by FTIR,1H-NMR and GPC.1H-NMR result shows that regioregular structure of these polymers is relatively higher. The GPC results show that the molecular weight of the polymers is 8.42×104, 1.06×105and 1.21×104g/mol with molecular weight distributions of 1.41, 2.18 and 1.18, respectively. The DSC result shows that the glass transition temperature of three kinds of polymers is 120.8, 146, 118 °C, respectively. UV absorption spectrum and fluorescence spectroscopy of three polymers in THF solution show that the maximum absorption wavelength is 448 nm, 470 nm, 390 nm, and the maximum emission wavelength is 531, 535, 527 nm with the band gap of 2.06, 1.86, 2.21 eV, respectively.

scholarly journals Tuning the Properties of High Molecular Weight Chitosans to Develop Full Water Solubility Within a Wide pH Range

2020 ◽  
Author(s):  
Anderson Fiamingo ◽  
Sergio Paulo Campana Filho ◽  
Osvaldo Novais Oliveira Junior
Keyword(s):  
Molecular Weight ◽  
Biomedical Applications ◽  
Random Distribution ◽  
Water Solubility ◽  
Aqueous Media ◽  
Degree Of Polymerization ◽  
Molecular Weights ◽  
H Nmr ◽  
Wide Ph Range ◽  
Ph Range

<p>The preparation of chitosans soluble in physiological conditions has been sought for years, but so far solubility in non-acidic aqueous media has only been achieved at the expense of lowering chitosan molecular weight. In this work, we applied the multistep ultrasound-assisted deacetylation process (USAD process) to β-chitin and obtained extensively deacetylated chitosans with high molecular weights (Mw ≥ 1,000,000 g mol<sup>-1</sup>). The homogeneous <i>N</i>-acetylation of a chitosan sample resulting from three consecutive USAD procedures allowed us to produce chitosans with a high weight average degree of polymerization (DPw ≈ 6,000) and tunable degrees of acetylation (DA from 5 to 80%). <i>N</i>-acetylation was carried out under mild conditions to minimize depolymerization, while preserving a predominantly random distribution of 2-amino-2-deoxy-D-glucopyanose (<i>GlcN</i>) and 2-acetamido-2-deoxy-D-glucopyanose (<i>GlcNAc</i>) units. This close to random distribution, inferred with deconvolution of nuclear magnetic resonance (<sup>1</sup>H NMR) spectra, is considered as responsible for the solubility within a wide pH range. Two of the highly <i>N</i>-acetylated chitosans (DA ≈ 60 % and ≈ 70 %) exhibited full water solubility even at neutral pH, which can expand the biomedical applications of chitosans. </p>

scholarly journals Evaluation of the Degree of Polymerization of the Proanthocyanidins in Cranberry by Molecular Sieving and Characterization of the Low Molecular Weight Fractions by UHPLC-Orbitrap Mass Spectrometry

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1504 ◽  
Author(s):  
Claudio Gardana ◽  
Paolo Simonetti
Keyword(s):  
Molecular Weight ◽  
Molecular Sieves ◽  
Degree Of Polymerization ◽  
Low Molecular Weight ◽  
Molecular Weight Distributions ◽  
Orbitrap Mass Spectrometry ◽  
Weight Distributions ◽  
Molecular Weight Fractions ◽  
Molecular Sieving

4-dimethylammino-cinnamaldehyde (DMAC) assays quantify total proanthocyanidins (PACs) but do not provide qualitative PAC molecular weight distribution information and cannot discriminate between A- and B-type PACs. We developed an efficient method for assessing PAC molecular weight distributions. The PACs from three commercial cranberry extracts (A1–A3) were fractionated by molecular sieves with cut-offs of 3, 10, 30, 50, and 100 kDa, and each fraction was analyzed by DMAC assays. A1, A2, and A3 contained 27%, 33%, and 15% PACs, respectively. Approximately 28 PACs, 20 flavonols, and 15 phenolic acids were identified by UHPLC-DAD-Orbitrap MS in A1 and A3, while A2 contained only flavan-3-ols. Epicatechin was the main monomer in A1 and A3, and catechin was the main in A2. Procyanidin A2 was the main dimer in A1 and A3, representing more than 85% of the total dimers, while it constituted approximately only 24% of A2. A1 and A3 contained quercetin, isorhamnetin, myricetin, and their glycosides, which were totally absent in A2. In A1 and A3 the PACs were mainly distributed in the fractions 30–3 and <3 kDa, while in A2 more than 70% were present in the fraction less than 3 kDa. Overall, obtained data strongly suggests that A2 is not cranberry-derived, or is adulterated with another source of PACs.

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