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1.
Mitsuo Sawamoto Masami Kamigaito Kazushige Kojima Toshinobu Higashimura 《Polymer Bulletin》1988,19(4):359-363
Summary Trimethylsilyl iodide in conjunction with zinc iodide (Me3SiI/ZnI2) as an initiating system led to living cationic polymerization of isobutyl vinyl ether in toluene at 0 or –40°C or in methylene chloride at –40°C (ZnI2 was dissolved in acetone). The number-average molecular weight of the polymers was directly proportional to monomer conversion and in excellent agreement with the calculated value assuming that one polymer chain forms per unit trimethylsilyl iodide. At room temperature (+25°C), however, the polymerization failed to give perfectly living polymers; the polymer molecular weight was smaller than the calculated value. On addition of a fresh feed of monomer at the end of the polymerization at –40°C, the added feed was smoothly polymerized at nearly the same rate as in the first stage, and the polymer molecular weight continued to increase in direct proportion to monomer conversion. Throughout the reaction, the molecular weight distribution of the polymers stayed very narrow (Mw/Mn< 1.1).Living cationic polymerization of vinyl ethers by electrophile/Lewis acid initiating systems, part 2. For part 1 see ref. 2 相似文献
2.
Summary Living cationic polymerization of isobutul vinyl ether (IBVE), initiated by1-iodo-1-(2-methyl propyloxy)-ethane (1) and tetraalkylammonium perchlorate yields polymers of well defined molar masses and end groups. The controlled introduction of end groups was confirmed by a model reaction and was then applied to introduce and azo initiator function. The resulting polymeric initiator was used for the synthesis of a blockcopolymer. 相似文献
3.
Summary A new iodine-free initiating system, MeCH(Oi-Bu)Cl/n-Bu4NTiCl5, was found to induce the living carbocationic polymerization (LCPzn) of isobutyl vinyl ether (IBuVE) at-20 °C in CH2Cl2. Using this system, poly(isobutyl vinyl ether) (PIBuVE) with the theoretical molecular weights (up toca. 45,000) calculated from the initiator/monomer input and narrow molecular weight distribution (Mw/Mn < 1.1) can be readily obtained. The polymerization is first order in the monomer. The coinitiating function ofn-Bu4NTiCl5 may be due to a salt effect or to its Lewis acid character. An attempt for the synthesis of the polyisobutylene (PIB)-PIBuVE block copolymer has failed most likely becausen-Bu4NTiCl5 is unable to activate the C(CH3)2-Cl bond of the PIB termini. 相似文献
4.
Summary Cationic polymerization of p-methoxystyrene initiated by HI/ZnI2 in toluene afforded living polymers not only at low temperature (–15°C) but at room temperature (+25°C) as well. The number-average molecular weight of the polymers was directly proportional to monomer conversion and in excellent agreement with the calculated value assuming that one polymer chain forms per unit hydrogen iodide. On addition of a fresh feed of monomer at the end of the first-stage polymerization, the added feed was smoothly polymerized at nearly the same rate as in the first stage; the polymer molecular weight further increased in direct proportion to monomer conversion and was close to the calculated value for living polymer. Throughout these reactions, the molecular weight distribution of the polymers stayed very narrow (¯Mw/¯Mn<1.1). This is the first example of living cationic polymerizations of styrene derivatives that proceed even at room temperature. 相似文献
5.
The cationic polymerization of isobutyl vinyl ether initiated by triphenyl methyl and tropylium hexachloroantimonates, and by triphenyl methyl tetrafluoroborate, has been studied in detail. Initiation was rapid and complete, termination was shown to be insignificant, polymerization half lives were of the order of 5–10 s and reaction rates were measured by an adiabatic calorimetric technique. Catalyst concentrations employed were sufficiently low that essentially complete dissociation into free ions is indicated by ion-pair dissociation constants, and this permits estimation of the rate coefficient for propagation by free cations (kp). At 0°C in methylene dichloride kp ∼ 5 × 103 M−1 s−1, in substantial agreement with values obtained by radiation induced polymeirzation of bulk monomer. Molecular weights of the poly(isobutyl vinyl ether) samples fell in the range 2000–5000 on account of monomer transfer processes. Detailed mechanisms for initiation, propagation, transfer and termination reactions are considered. 相似文献
6.
The absolute rate constants for the cationic polymerization of ethyl and isobutyl vinyl ethers have been determined in methylene chloride solution. Under the conditions used, the polymerization proceeded by ‘free ions’. Extremely rigorous drying procedures were used and the values obtained were somewhat higher than those reported in the literature. The values were in reasonable agreement with the ‘free cation’ values obtained by a combination of rate and conductivity measurements of bulk polymerizations, initiated with gamma radiation under ‘super dry’ conditions. The activation energies were also in good agreement. 相似文献
7.
8.
Muhammet U. Kahveci 《Polymer》2007,48(8):2199-2202
A new photoinitiating system for living cationic polymerization of vinyl ethers such as isobutyl vinyl ether (IBVE) has been reported. The photoinitiating system comprises free radical photoinitiators such as 2,2-dimethoxy-2-phenyl acetophenone (DMPA), benzophenone or thioxanthone, together with an onium salt, such as diphenyliodonium chloride and zinc bromide. In the first step, photochemically generated free radicals are oxidized to the corresponding carbocations which subsequently react with vinyl ether monomer to yield an adduct. In the presence of zinc salt, this adduct initiates living cationic polymerization of IBVE. 相似文献
9.
Summary A series of end-functionalized polymers (4), carrying a hydroxyl, carboxyl, or primary amino terminal group Y, were obtained by living cationic polymerization of isobutyl vinyl ether. The initiating systems of choice consisted of EtAlCl2 and the trifluoroacetate [2; X-CH2CH2OCH(CH3)OOCCF3; X = OOCCH3, CH(COOC2H5)2, N(COOC(CH3)3)2] obtained from a vinyl ether with a protected functional pendant group. In the presence of 1,4-dioxane, the 2/EtAlCl2 systems invariably induced a well-defined living polymerization of isobutyl vinyl ether in n-hexane at 0 to +40°C to give polymers, the -end group (X) of which was derived from the initiator 2. Subsequent de-protection of X of these polymers led to 4, all of which were shown to have a very narrow molecular weight distribution (¯MW/¯Mn = 1.07–1.18), a number-average molecular weight (¯Mn = 103-104) controllable by the monomer/2 molar feed ratio, and one terminal function Y per chain. 相似文献
10.
Summary Amphiphilic or polar-nonpolar AB block copolymers of p-methoxystyrene (pMOS) and vinyl ethers (VE; methyl or isobutyl) were synthesized by the sequential living cationic polymerization
initiated with the hydrogen iodide/zinc iodide (HI/ZnI2) system in toluene at -15 and +25 °C. pMOS-VE block copolymers of narrow molecular weight distributions (
= 1.05−1.25;
= 6000−16000) were obtained in nearly quantitative blocking efficiency, when methyl or isobutyl VE was polymerized first
by HI/ZnI2, followed by addition of pMOS to the resulting living polymer solutions; an additional amount of ZnI2 was required to accelerate the second-phase living polymerization of the less reactive styrenic monomer. Similar block polymerizations
in an opposite monomer-addition sequence (from pMOS to VE), in contrast, resulted in mixtures of the desired block polymer
and homopolymer of pMOS. 相似文献
11.
Summary Cationic polymerization of CH2=CH-O-CH2CH2C(COOC2H5)3, a vinyl ether with three pendent esters, initiated by the HI/I2 system in toluene at –40 °C afforded living polymers with a controlled molecular weight (
= 103–104) and a narrow molecular weight distribution (
= 1.1–1.2). The number-average molecular weight of the polymers was directly proportional to monomer conversion and the monomer-to-initiator (HI) feed ratio. The polymers obtained with BF3O(C2H5)2 had a fairly high molecular weight (
105,
5 × 104) and a broad molecular weight distribution. The triester vinyl ether was similar in reactivity to alkyl counterparts and one order of magnitude more reactive than the corresponding mono- and diester vinyl ethers. 相似文献
12.
Summary Living cationic polymerization of isobutyl vinyl ether was achieved by EtAlCl2 in the presence of ethyl acetate at rather high temperatures up to +25°C in toluene. In the absence of the ester additives, neither living nor long-lived propagating species were formed under these conditions. Similarly, living propagating species of vinyl ethers with an ester unit in the pendant (2-vinyloxyethyl benzoate and methacrylate) were obtained with EtAlCl2 alone. The obtained polymers showed a very narrow molecular weight distribution (¯Mw/¯Mn<1.2) and the ¯Mn was directly proportional to the monomer conversion. 相似文献
13.
Summary Well-defined living polymers of isobutyl vinyl ether were obtained in the polymerization initiated with ethylaluminum dichloride (EtAlCl2) in conjunction with a stoichiometric excess of dioxane (5–10 vol%) in n-hexane at 0°C. Under these conditions, the number-average molecular weight of the polymers increased in direct proportion to monomer conversion, while the molecular weight distribution stayed narrow (Mw/Mn = 1.1–1.25). In sharp contrast, the EtAlCl2-initiated polymerization in the absence of dioxane led to non-living polymers with a broad molecular weight distribution. It was concluded that the propagating carbocation is stabilized not by the counteranion but by an externally added basic compound (dioxane) that strongly interacts with the active end. 相似文献
14.
Summary A kinetic study of the cationic polymerization of chloroethyl vinyl ether initiated by the system hydrogen iodide — iodine has been performed in order to understand some particular characteristics of the system. As previously reported by Higashimura the polymerization shows a living character at low temperature in toluene. A polymerization process with a first order in iodine and 0.3 order with respect to monomer, has been observed. These results are consistent with the existence of reversible elementary processes involving iodine and monomer.Unité associée CNRS et ENSCPB 相似文献
15.
16.
Summary Living cationic polymerization of styrene was achieved by the methanesulfonic acid/tin tetrachloride (CH3SO3H/SnCl4) initiating system in the presence of tetra-n-butylammonium chloride (nBu4NCl) in methylene chloride solvent below 0 °C. The typical reagent concentrations of this initiating system were as follows: CH3SO3H/SnCl4/nBu4NCl=20/100/40 mM; [Styrene]0=1.0 M. The number-average molecular weights of the product polymers increased in direct proportion to monomer conversion, and their molecular weight distributions (MWDs) were fairly narrow
throughout the reaction. On addition of a fresh feed of styrene at the end of the polymerization, the added feed was smoothly polymerized at the same rate as in the first stage; the polymer molecular weight further increased in direct proportion to monomer conversion; and their molecular weight distributions stayed narrow
. On the other hand, in the absence of nBu4NCl, the polymerization initiated by CH3SO3H/SnCl4 in CH2Cl2 at -15 °C led to non-living polymers with a broad molecular weight distribution. This indicates that nBu4NCl is essential to this living system. 相似文献
17.
Summary -Methyl styrène polymerization was carried out using t-BuCl/Et2AlCl/CH2Cl2 system in the temperature range of 0° to –63.5°C. The effect of temperature on yield and molecular weights of Poly -Methyl styrene was determined. Based on Arrhenius plots, average activation energies of molecular weights were determined to be –9.2 ± 1.0 K cal/mole. (0° to 40°C) and 0 ± 0.5 K cal/mole (–40° to –63.5°C). These were postulated to reflect the molecular weight governing mechanisms such as transfer to monomer and termination respectively. 相似文献
18.
Cationic copolymerization of octadecyl vinyl ether (ODVE) with isobutyl vinyl ether (IBVE) under reaction conditions leading to living vinyl ether polymerization has been studied. The experimental results show that, under such conditions, the living nature of the copolymerization can be retained. The copolymerization parameters were found to be rIBVE = 2.2 and rODVE = 0.30. Incorporation of up to 50% of IBVE units has only a small effect on the crystallinity of ODVE units. This is ascribed to the fact that the crystallinity is due to the octadecyl side‐chains and not to the main chain, and that the copolymers have a gradient‐like (tapered) structure. © 2000 Society of Chemical Industry 相似文献
19.
Summary An initiating system, consisting of 1-phenylethyl chloride, tin tetrachloride, and tetra-n-butylammonium chloride [CH3CH(Ph)C1/SnCl4/nBu4NCl], led to living cationic polymerization of styrene in CH2Cl2 solvent at-15°C; typically, CH3CH(Ph)Cl/SnCl4/nBu4NCl=20/100/40 mM for 1.0 M of styrene. The living nature of the process was confirmed by an increase in the number-average
molecular weight (
) of the polymers in direct proportion to monomer conversion and its continuation on supplying a fresh feed of styrene after
the polymerization; the observed
was close to the calculated value assuming that one molecule of CH3CH(Ph)Cl yields one living polymer. Throughout these reactions, the polymer's molecular weight distribution (MWD) stayed very
narrow (
), though slightly broadening after the second monomer addition. In the absence of nBu4NCl, the CH3CH(Ph)Cl/SnCl4 system yielded polystyrene with a bimodal MWD where the lower polymer fraction alone was apparently of a long lifetime. Styrene
polymerization with the H2O/SnCl4 system was also examined, both with and without added nBu4NCl, and a long-lived propagating species was obtained in the presence of nBu4NCl. 相似文献
20.
Prakash D. Trivedi 《Polymer Bulletin》1979,1(6):433-436
Summary Cationic copolymerination of -MS and IBVE was successfully carried out using H2O/EtAlCl2 initiator system and CH2Cl2 solvent at –50°C. The effect of monomer feed concentration on the copolymer yield and composition was studied. Small concentrations of IBVE had significant effect on the copolymer yield and composition, while that of -MS had only marginal effect. Tg of the copolymers was linearly dependent on the -MS content strongly indicating that the copolymerization was of random nature. 相似文献