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.

Molecular Weight Determinations Of Low Molecular Weight (LMW) Heparins By Ultracentrifugation And High Pressure Liquid Chromatography

1981 ◽  
Author(s):  
Grant Barlow ◽  
N Sugisaka ◽  
F J Petracek
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
Liquid Chromatography ◽  
High Pressure Liquid Chromatography ◽  
Low Molecular Weight ◽  
Analytical Ultracentrifuge ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Heparin Fractions

Molecular weights were independently determined on nitrous acid depolymerized LMW heparin fractions ranging from 2-15 daltons using the analytical ultracentrifuge and high pressure liquid chromatography (HPLC).Sedimentation-diffusion equilibria were obtained in the analytical ultracentrifuge using speeds ranging from 20,000 to 56,000 rpm. Near theta conditions were obtained using 0.5M NaCl as the solvent. Calculations of molecular weight distributions and, from those figures, weight average molecular weights were made using the method described by Scholte (N.Y. Acad Sci. 164, 156, 1969). The results show that weight average values as low as 2,000 daltons can be determined.Sedimentation-diffusion equilibria were obtained in the analytical ultracentrifuge using speeds ranging from 20,000 to 56,000 rpm. Near theta conditions were obtained using 0.5M NaCl as the solvent. Calculations of molecular weight distributions and, from those figures, weight average molecular weights were made using the method described by Scholte (N.Y. Acad Sci. 164, 156, 1969). The results show that weight average values as low as 2,000 daltons can be determined.The HPLC results were obtained using previously described methods (Fed Proc. 36, 89, 1977) and a new highly efficient gel column (TSK gels). Fractionated dextrans were used as reference standards.

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.

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.

High pressure water-initiated ring opening polymerization for the synthesis of well-defined α-hydroxy-ω-(carboxylic acid) polycaprolactones

2017 ◽  
Vol 19 (15) ◽  
pp. 3618-3627 ◽  
Author(s):  
A. Dzienia ◽  
P. Maksym ◽  
M. Tarnacka ◽  
I. Grudzka-Flak ◽  
S. Golba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
Carboxylic Acid ◽  
Ring Opening ◽  
Chemical Structure ◽  
Ring Opening Polymerization ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Pressure Water ◽  
Novel Method

A novel method to produce polyesters of a well-defined chemical structure, and narrow molecular weight distributions by using a combination of high pressure, temperature and water was proposed.

Reversible-deactivation radical polymerization of chloroprene and the synthesis of novel polychloroprene-based block copolymers by the RAFT approach

RSC Advances ◽  
2014 ◽  
Vol 4 (98) ◽  
pp. 55529-55538 ◽  
Author(s):  
Jia Hui ◽  
Zhijiao Dong ◽  
Yan Shi ◽  
Zhifeng Fu ◽  
Wantai Yang
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Radical Polymerization ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Reversible Deactivation ◽  
Raft Agent ◽  
Reversible Deactivation Radical Polymerization

Novel, well-defined PCP-based block copolymers (PSt-b-PCP and PMMA-b-PCP) with controlled number averaged molecular weights and molecular weight distributions can be prepared, employing EPDTB and CPDB, respectively, as the initial RAFT agent.

Synthesis and Characterization of well Defined Polychloroprene by RAFT Polymerization

2013 ◽  
Vol 787 ◽  
pp. 241-244
Author(s):  
Jia Hui ◽  
Yan Shi ◽  
Zhi Feng Fu
Keyword(s):  
Molecular Weight ◽  
Raft Polymerization ◽  
Average Molecular Weight ◽  
Reaction Times ◽  
Monomer Conversion ◽  
H Nmr ◽  
Molecular Weight Distributions ◽  
Reversible Addition ◽  
Raft Agent ◽  
Active Nature

Well defined polychloroprene has been synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization with 2-(ethoxycarbonyl) prop-2-yl dithiobenzoate (EPDTB) as RAFT agent, AIBN as initiator, Chloroprene as monomer. Polymerization with two different feed ratios of monomer to RAFT agent were carried out. The sampling products at different reaction times were characterized using GPC and 1H-NMR. The GPC results demonstrated the molecular weight distributions (Mw/Mn) were narrow, and the number average molecular weight (Mn) was developed linearly with monomer conversion. All the characteristic signals of polychloroprene with the EPDTB as terminal groups were clearly observed in the 1H-NMR spectrum. In addition, the chain-extended polymers were also obtained successfully using the macro-RAFT agent, which indicated the active nature of the chain end.

Mechanism of CPDB-Mediated RAFT Polymerization of Methyl Methacrylate: Influence of Pressure and RAFT Agent Concentration

2009 ◽  
Vol 62 (11) ◽  
pp. 1484 ◽  
Author(s):  
Michael Buback ◽  
Wibke Meiser ◽  
Philipp Vana
Keyword(s):  
Methyl Methacrylate ◽  
Raft Polymerization ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Reversible Addition ◽  
Rate Of Polymerization ◽  
Weight Distributions ◽  
Raft Agent ◽  
Successful Control ◽  
Mma Polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerizations of methyl methacrylate (MMA) in bulk at 60°C were performed at five pressures up to 200 MPa using 2-(2′-cyanopropyl)dithiobenzoate (CPDB) as RAFT agent at concentrations between 1.5 × 10–3 and 2.0 × 10–2 mol L–1. Applying high pressure during polymerization increases the rate of polymerization, but no effect on polydispersity was observed. Molecular weight distributions and average molecular weights of the final polymer indicated the successful control of MMA polymerization even at low CPDB concentrations. The slight retardation observed is adequately described by the dependence the termination rate coefficient, kt, on the chain-length.

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.

scholarly journals Tailoring Polymer Dispersity by Controlled Radical Polymerization: A Versatile Approach

2020 ◽  
Author(s):  
Richard Whitfield ◽  
Kostas Parkatzidis ◽  
Nghia Truong ◽  
Tanja Junkers ◽  
Athina Anastasaki
Keyword(s):  
Molecular Weight ◽  
Kinetic Modelling ◽  
Raft Polymerization ◽  
Good Control ◽  
Chain Extension ◽  
Molecular Weight Distributions ◽  
Polymer Properties ◽  
Reversible Addition ◽  
Wide Range ◽  
Weight Distributions

<p>Dispersity (<i>Ɖ</i>) can significantly affect polymer properties and is a key parameter in materials design; however, current methods do not allow for the comprehensive control of dispersity. They are limited in monomer scope, may require the use of flow-based systems and/or additional reagents (<i>e.g.</i> termination agents or co-monomers), and are often accompanied by multimodal molecular weight distributions, low initiator efficiencies or poor end-group fidelity. Herein, we report a straightforward and versatile batch method based on reversible addition-fragmentation chain transfer (RAFT) polymerization which enables good control over <i>Ɖ</i> of a wide range of monomer classes, including acrylates, acrylamides, methacrylates and styrene. In addition, our methodology is compatible with more challenging monomers such as methacrylic acid, vinyl ketone and vinyl acetate. Control over <i>Ɖ</i> is achieved by mixing two RAFT agents with sufficiently different transfer activities in various ratios, affording polymers with monomodal molecular weight distributions over a broad dispersity range (<i>Ɖ</i> ~ 1.09-2.10). Our findings were further supported by simulations through the use of deterministic kinetic modelling which was fully in line with our experimental data, further confirming the power of our methodology. The robustness of the concept is further demonstrated by the preparation of well-defined block copolymers via chain extension of all polymers regardless of the initial <i>Ɖ</i>.</p>

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