TERTIARY MERCAPTANS AS MODIFIERS IN GR-S POLYMERIZATIONS

1947 ◽  
Vol 25b (2) ◽  
pp. 159-182 ◽  
Author(s):  
Maurice Morton ◽  
R. V. V. Nicholls
Keyword(s):  
Molecular Weight ◽  
Rate Equation ◽  
Slow Rate ◽  
Chain Transfer ◽  
Transfer Reactions ◽  
Molecular Weight Polymer ◽  
First Order ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Order Rate Equation

Tertiary octyl, decyl, dodecyl, and hexadecyl mercaptans were investigated as modifiers in GR-S polymerizations.The rate of disappearance of these modifiers followed a first-order rate equation during the first half of the polymerization, in accordance with the theory of chain-transfer reactions. During the latter part of the reaction, an increased rate of disappearance generally occurred. A mechanism is suggested.The rate of disappearance increased with decreasing chain-length of the mercaptan. The intrinsic viscosities and molecular weight distributions of the polymers obtained at different conversions were related to the activity of each mercaptan as a modifier. Values for the regulating index of each mercaptan were calculated.The slow rate of disappearance of tertiary hexadecyl mercaptan leads to the formation of polymer that is relatively homogeneous in molecular weight, and this mercaptan is therefore a desirable modifier. However, after 50% polymerization, the regulator action shows a marked acceleration, leading to the formation of progressively lower molecular weight polymer and resulting in a spread in the molecular weight distribution.

scholarly journals Further Effects of Chain-Length-Dependent Reactivities on Radical Polymerization Kinetics

2007 ◽  
Vol 60 (10) ◽  
pp. 754 ◽  
Author(s):  
Johan P. A. Heuts ◽  
Gregory T. Russell ◽  
Gregory B. Smith
Keyword(s):  
Molecular Weight ◽  
Radical Polymerization ◽  
Chain Length ◽  
Chain Transfer ◽  
Transfer Constant ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
A Chain ◽  
Chain Transfer Constant ◽  
Independent Chain

In the present paper, we finalize some threads in our investigations into the effects of chain-length-dependent propagation (CLDP) on radical polymerization kinetics, confirming all our previous conclusions. Additionally, and more significantly, we uncover some unexpected and striking effects of chain-length-dependent chain transfer (CLDTr). It is found that the observed overall rate coefficients for propagation and termination (and therefore the rate of polymerization) are not significantly affected by whether or not chain transfer is chain-length dependent. However, this situation is different when considering the molecular weight distributions of the resulting polymers. In the case of chain-length-independent chain transfer, CLDP results in a considerable narrowing of the distribution at the low molecular weight side of the distribution in a chain-transfer controlled system. However, the inclusion of both CLDP and CLDTr yields identical results to classical kinetics – in these latter two cases, the molecular weight distribution is governed by the same chain-length-independent chain transfer constant, whereas in the case of CLDP only, it is governed by a chain-length-dependent chain transfer constant that decreases with decreasing chain length, thus enhancing the probability of propagation for short radicals. Furthermore, it is shown that the inclusion of a very slow first addition step has tremendous effects on the observed kinetics, increasing the primary radical concentration and thereby the overall termination rate coefficient dramatically. However, including possible penultimate unit effects does not significantly affect the overall picture and can be ignored for the time being. Lastly, we explore the prospects of using molecular weight distributions to probe the phenomena of CLDP and CLDTr. Again, some interesting insights follow.

scholarly journals Synthesis and Characterization of Well-Defined SolubleAlq3- andZnq2-Functionalized Polymers via RAFT Copolymerization

2010 ◽  
Vol 2010 ◽  
pp. 1-7
Author(s):  
Chengchao Wang ◽  
Wei Zhang ◽  
Nianchen Zhou ◽  
Yansheng Qiu ◽  
Zhengping Cheng ◽  
...  
Keyword(s):  
Chain Transfer ◽  
Chain Extension ◽  
Aluminium Isopropoxide ◽  
Soluble Polymers ◽  
First Order ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Reversible Addition ◽  
Weight Distributions

The reversible addition-fragmentation chain transfer (RAFT) copolymerizations of 2-((8-hydroxyquinolin-5-yl)methoxy)ethyl methacrylate (HQHEMA) with styrene (St) or methyl methacrylate (MMA) were successfully carried out in the presence of 2-cyanoprop-2-yl dithionaphthalenoate (CPDN). The polymerization behaviors showed the typical living natures by the first-order polymerization kinetics, the linear dependence of molecular weights of the polymers on the monomer conversions with the relatively narrow molecular weight distributions(Mw/Mn), and the successful chain extension experiments. The soluble polymers having tris(8-hydroxyquinoline)aluminum (Alq3) and bis(8-hydroxyquinoline) znic(II) (Znq2) side chains were obtained via complexation of the polymers with aluminium isopropoxide or zinc acetate in the presence of monomeric 8-hydroxyquinoline, which had strong fluorescent emission at 520 nm. The obtained polymers were characterized by GPC, NMR, UV-vis, and fluorescent spectra.

Nitroxide-mediated polymerization of styrene in the presence of a novel trinitroxide

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Jieai Li ◽  
Zhengbiao Zhang ◽  
Xiulin Zhu ◽  
Jian Zhu ◽  
Zhenping Cheng
Keyword(s):  
Molecular Weight ◽  
Ascorbic Acid ◽  
Linear Structure ◽  
Controlled Polymerization ◽  
First Order ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
First Order Kinetics ◽  
Weight Distributions ◽  
Nitroxide Mediated Polymerization

AbstractThe bulk polymerizations of styrene were performed in the presence of a novel trinitroxide, 2,4,6-tri(4’-oxy-2’,2’,6’,6’-tetramethyl-1’-piperidinyloxy)-1,3,5- triazine (TTPT). Typical features of controlled polymerization were observed, such as the first-order kinetics, the molecular weights (Mn) linearly increased with the conversion, and relatively narrow molecular weight distributions (Mw/Mn). The 1H NMR was used to characterize the obtained polystyrene. The most of obtained polymers at 110 °C were the polymer with two-arm linear structure, not the expected three-arm structure, which was confirmed by the analysis of degradation of obtained polymer by ascorbic acid. A proposed polymerization route of styrene mediated by TTPT was also discussed.

Endogenous Denitrification in Biofilm

1992 ◽  
Vol 26 (3-4) ◽  
pp. 523-534 ◽  
Author(s):  
G. H. Chen ◽  
H. Ozaki ◽  
Y. Terashima
Keyword(s):  
Molecular Weight ◽  
Production Rate ◽  
Order Type ◽  
Denitrification Rate ◽  
Experimental Results ◽  
First Order ◽  
Bench Scale ◽  
Metabolic Characteristics ◽  
Molecular Weight Distributions ◽  
Weight Distributions

The model on endogenous denitrification in a biofilm, previously presented by the authors, was verified well with bench scale experiments. Production of the secondary substrate due to lysis of microorganisms, which is necessary for the progress of endogenous denitrification, was experimentally proved. In order to investigate metabolic characteristics of the substrate, molecular weight distributions of the substrate on CODcr or carbohydrate bases were measured. The percentage of the secondary substrate with molecular weight less than 10,000, was more than 50% on both bases. The experimental results demonstrated that the production rate of the substrate can be expressed by the first order type expression with respect to the concentration of biomass. The specific constants for microorganisms lysis and maximum endogenous denitrification rate were determined (0.45 day−1 and 0.141 day−1, respectively).

Polymerization of styrene using 1,1,2,2-tetraphenyl-1,2- ethanediol as initiator in the presence of 2,2,6,6-tetramethyl- 1-piperidinyloxy

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Gang Wang ◽  
Xiulin Zhu ◽  
Dijun Hu ◽  
Zhengping Cheng ◽  
Jian Zhu
Keyword(s):  
Molecular Weight ◽  
Monomer Concentration ◽  
Bulk Polymerization ◽  
Polymerization Rate ◽  
First Order ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
End Groups

Abstract The bulk polymerization of styrene using 1,1,2,2-tetraphenyl-1,2-ethanediol as initiator in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) was investigated. The results show that polymerization proceeded in a controlled/ ’living’ way, i.e., polymerization rate is first order with respect to monomer concentration. Molecular weights increase linearly with conversion and molecular weight distributions are relatively low (Mw/Mn = 1.10 - 1.35). Well-defined polystyrenes with α-hydrogen and TEMPO end groups were obtained.

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