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.

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 Molecular weight distributions of polysaccharides and lignin extracted from plant biomass with a polar ionic liquid analysed without a derivatisation process

2015 ◽  
Vol 7 (5) ◽  
pp. 1719-1726 ◽  
Author(s):  
Kosuke Kuroda ◽  
Yukinobu Fukaya ◽  
Tatsuhiko Yamada ◽  
Hiroyuki Ohno
Keyword(s):  
Molecular Weight ◽  
Ionic Liquid ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
High Performance ◽  
Plant Biomass ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Polysaccharides and lignin, extracted from biomass with 1-ethyl-3-methylimidazolium methylphosphonate, were directly analysed with high-performance liquid chromatography with the aid of ionic liquid as an eluent (HPILC).

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.

scholarly journals Determination of the Correction Factor for Dinalmefene Hydrochloride in Nalmefene Hydrochloride Injection

2019 ◽  
Vol 267 ◽  
pp. 03001
Author(s):  
Tianyi Zhao ◽  
Ziqing Liu ◽  
Furao Guo ◽  
Peiyu He ◽  
Hongyu Zhang ◽  
...  
Keyword(s):  
High Performance Liquid Chromatography ◽  
Correction Factor ◽  
High Performance ◽  
Limit Of Quantification ◽  
Sample Concentration ◽  
Standard Curve ◽  
Curve Method ◽  
Standard Curve Method ◽  
Impurity Detection

Objective: To calculate the detection correction factor for the impurity, that is, the dinalmefene hydrochloride in nalmefene hydrochloride injection. Methods: High performance liquid chromatography (HPLC) is used to analyze the impurities of nalmefene hydrochloride easily produced during storage, and the impurity is determined and correction factor is calculated for the known the dinalmefene hydrochloride. According to the standard curve method, the sample concentration is selected between the detection limit and the limit of quantification, and the standard curve is prepared. The correction factor is then calculated according to the slope of the standard curve. Results: finally, the correction factor for dinalmefene hydrochloride is 0.22. Conclusions: the correction factor calculated by the standard curve method is accurate and reliable, and can be used for impurity detection of nalmefene hydrochloride injection.

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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