Controlled radical polymerization of p-(iodomethyl)styrene—a route to branched and star-like structures (original) (raw)
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Radical polymerization of styrene initiated by poly(ethylene oxide) macroinitiators
European Polymer Journal, 1992
The kinetics of the polymerization of styrene in bulk and in dilute systems in the presence of p-acetyi benzylidene triphenylarsonium ylide (p-ABTAY) as radical initiator has been examined at 60+0.1°C for 20 h under N2. The values of the initiator exponent and the monomer exponent showed that the system follows ideal radical kinetics with bimolecular termination. The overall activation energy and average value of k~/k t are 64.6 kJ moi -1 and 0.10 × 10-21 mol -1 s -1, respectively. The ylide dissociates to produce phenyl radical, which brings about polymerization.
Macromolecules, 1998
2-bromopropionyloxy)calix[8]arene (1) which was readily synthesized in one step, was used to initiate the bulk atom transfer radical polymerization (ATRP) of styrene, at 100°C , in the presence of CuBr/2,2′-bipyridyl. Polystyrene (PS) stars of narrow polydispersity with precisely eight arms could be synthesized by restricting the polymerization to low conversion, typically below 15-20%. At higher conversions, irreversible coupling occurred between stars as evidenced by a size exclusion chromatography line equipped with a multiangle laser light scattering detector (MALLS/SEC). Octafunctional stars of molar masses up to 340 000 g mol-1 could be prepared by using high ratios of the monomer to the initiator ([M]/[I]) 12 000). The precise octafunctional structure of the stars was confirmed, on one hand, by studying the kinetics of ATRP of styrene initiated by an equimolar mixture of 1 and its monofunctional equivalent, namely 4-tert-butylphenyl(2-bromopropionate) (2) and, on the other hand, by the characterization of the individual arms obtained upon hydrolysis of the ester link between the core and the branches of the stars.
Journal of Polymer Research
A finely tuned-up and high-performance Monte Carlo simulation, which takes diffusion-controlled and chain-length-dependent bimolecular termination reactions into account, is developed to thoroughly simulate and compare free radical (FRP) and atom transfer radical polymerization (ATRP) of styrene. It is found out that the termination rate constant falls and eventually plateaus upon the increase of the chain length of radicals. In addition, average termination rate constant greatly decreases during ATRP; nonetheless, it remains almost unchanged and smaller in FRP. Moreover, there is an accumulation of CuBr2 in the reactor as the ATRP proceeds, while the concentration of CuBr decreases and finally plateaus. Polymer chains are entirely initiated at the beginning of the ATRP, whereas initiation of chains continues throughout the free radical polymerization up to the end of the reaction. Also, the dead polymers are much lower in concentration (only 20%) in ATRP as compared to FRP (about 50%). In addition, a shift (toward higher molecular weight) in the location of the peaks of molecular weight distributions can easily be seen for the ATRP system, whilst the chain length distribution of free-radically generated polymers remains the same throughout the free radical polymerization. The molecular weight distributions narrow as the atom transfer radical polymerization progresses. Finally, the simulation results correspond closely to the experimental data.
Controlled polymerization of styrene in the presence of Blatter’s radicals
Russian Chemical Bulletin, 2020
Controlled polymerization of styrene (both self-initiated and initiated with azobisisobutyronitrile) in the presence of Blatter´s radical at 125 С was studied. When using the radical initiator, there is no induction period. On the basis of UV spectroscopy and MALDI massspectrometry studies, it was established that the Blatter radical is completely consumed at the initial stage of the polymerization, inserting into almost all macromolecules. The prepared polystyrene exhibits the ability to reinitialization in post-polymerization and the synthesis of block copolymers.
2019
Polystyrene (PSt) has been known as one of the important polymers with a wide range of applications. Ability to synthesize PSt with different but predictable molecular weights for various applications is very important in the laboratories and industries. In this study, using various simple and inexpensive techniques with only free radical mechanism, it was tried to synthesize PSt with different low ( 105 g mol-1) molecular weights. PSts with high and moderate molecular weights (2×104-105 g mol-1) were synthesized using thermal and conventional free radical polymerizations, respectively. Reverse iodine transfer radical polymerization (RITP) was utilized to synthesize PSt with a low and controlled molecular weight. Conversion, molecular weight distribution and PSt structure were analyzed using 1H-NMR spectroscopy and size exclusion chromatography (SEC), respectively. Moreover, ω-iodo poly(dimethylsiloxane), i.e. PDMS-I, was also used as a macrotransfer agent for ITP of styrene. Dibloc...
Journal of Ultrafine Grained and Nanostructured Materials, 2019
A novel nano-initiator containing kojic acid moiety, [5-(benzyloxy)-4-oxo-4H-pyran-2-yl)methyl-2-bromo-2-methylpropanoate was synthesized by the reaction of 5-(benzyloxy)-2-(hydroxymethyl)-4H-pyran-4one with 2-bromoisobutyryl bromide in triethylamine and used as initiator in the atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate in the presence of Cu(0)/CuCl 2 and N,N,Nʹ,N″,N″pentamethyl diethylenetriamnie (PMDETA). The characteristics of resulting polymers were verified by proton nuclear magnetic resonance spectroscopy (1 H NMR), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). 1 H NMR spectra were recorded in deuterated chloroform (CDCl 3) with a Fourier transform (FT)-nuclear magnetic (NMR) spectrometer. To investigate the living nature of polymerization, the obtained polymers were subjected to further chain extension reaction. The chain extension of polystyrene (PS) and poly(methyl methacrylate) (PMMA) macroinitiators demonstrated that the chain ends of the obtained PS-Br and PMMA-Br were enable for further functionalization. After chain extension, the GPC curves shifted to high molecular weight. The values of number average molecular weight (M n) of PS and PMMA increased from 37853 to 40808 g/mol and from 107640 to 156310 g/mol, respectively. These results demonstrated that the chain extension reaction was successful and exhibited the living features of the chain end. To the best of our knowledge, the synthesis of ATRP initiator containing kojic acid moiety has not been reported. Herein, we report the synthesis and characterization of an ATRP initiator containing kojic acid moiety, and its application for the polymerzation of styrene and methyl methacrylate.
N,N′-Diaminoethane linked bis-TEMPO-mediated free radical polymerization of styrene
European Polymer Journal, 2010
The N,N 0 -diaminoethane linked bis-TEMPO nitroxide (C2)-mediated free radical polymerization of styrene at 135°C in bulk was studied. It was found that under comparable conditions a single nitroxide group of C2 biradical retards the polymerization more than TEMPO. The results were discussed in terms of through-space interactions between two TEMPO moieties of C2 biradical and diffusion effects. According to experimental results analyzed by means of statistical methods, the polymerization system displays a bimodal molecular-weight distribution (MWD) from the beginning of the polymerization process, most probably by undergoing decomposition side reactions leading to irreversible polymer arm (P) separation from PC2P to PC2 Å and PC2H alkoxyamines. The scale of the decomposition depends rather on the time the system is maintained at the polymerization temperature than on conversion of monomer. Generally, the contribution of low molecular weight chains to overall MWD increases with time of polymerization whereas the contribution of high molecular weight chains to MWD increases for less controlled polymerization systems. For polymers obtained at high [dinitroxide]/[initiator] ratio, the thermal treatment of polystyrene in mass at 135°C unexpectedly revealed an increase of M n , which can probably be ascribed to post-polymerization effects involving polystyrene with unsaturated chains end groups.
Kinetic Studies on Bulk Atom Transfer Radical Polymerization of Styrene
American Journal of Polymer Science and Technology, 2017
The long chain vinyl end-functional polystyrene has been synthesized in bulk polymerization method using atom transfer radical polymerization (ATRP) with Undecenyl-2-Bromopropionate (UnBP) and CuCl/bypyridine catalytic system. The polymerizations demonstrate an increase in molecular weight and conversion in direct proportion to the polymerization time by consumed monomer which exhibited first-order kinetics. This study concludes the simple kinetics of polystyrene synthesized by ATRP using initiator and ligand-to-copper(I) halide was found to be 1:2:1, which tentatively indicates that the coordination sphere of the active copper(I) center contains two bipyridine ligands. The propagation rate has been investigated for long range of time for ensuring that the rate of radical combination or disproportionation is sufficiently less.
Polymer, 2003
The bulk radical polymerizations of styrene (St) at 80 -120 8C in the presence of 6-aza-7,7-dimethyl-9-hydroxyspiro[4.5]decane-6-yloxyl (1) and 1-aza-2,2-dimethyl-4-hydroxy[5.5]undecane-1-yloxyl (2) were studied. At 100 and 120 8C, the polymerizations were well controlled by those nitroxides to give poly(St)s with narrow polydispersities. On the other hand, the polymerization mediated by 2 at 80 8C showed a good 'livingness' of polymerization, but 1 had a poor ability to control the polymerization to give poly(St) with a broad polydispersity of 1.52. The rate constants ðk act Þ for the homolysis of the NO -C bond of the alkoxyamines prepared from 1 and 2 were measured at 333-373 K, and the A act s and E act s values were determined to be 2.8 £ 10 13 s 21 and 128 kJ mol 21 (1) and 4.0 £ 10 13 s 21 and 125 kJ mol 21 (2), respectively, from the Arrhenius plots. These results are compared with those for the structurally related piperidinyl-N-yloxyl radicals including TEMPO. q