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1.
The low-temperature polymerization of methyl methacrylate initiated with butyllithium–diethylzinc has been studied in toluene and in toluene–tetrahydrofuran and toluene–dioxane mixtures in various proportions. The polymerization process is typically anionic; it is characterized by a very rapid initiation reaction, and the absence of termination and chain transfer reactions, the molecular weight increasing proportionally with the degree of conversion. With toluene as a solvent, the polymer chains are associated, as is shown by viscometric measurements; moreover the polymers produced are highly polydisperse (Mv/Mn = 5.4). The kinetics are very complicated and vary with the range of the catalyst and monomer concentrations. In pure toluene in the presence of the organometallic complex, butyllithium–diethylzinc, the monomer addition is more stereospecific than when butyllithium alone is used as catalyst. By adding tetrahydrofuran to the reaction mixture, the polymer chain association disappears; concomitantly the stereochemical structure of the polymer changes from an isotactic to a mainly syndiotactic configuration. In toluene–tetrahydrofuran mixtures containing from 1 to 10 vol.-% tetrahydrofuran, the kinetics of polymerization can easily be interpreted by assuming the presence of two propagating reactive species which are in equilibrium with each other: the ion pair and the THF-solvated ion pair. The energy of activation of propagation for the free ion pair is equal to 7.5 kcal./mole; for the solvated ion pair a value of 5.5 kcal./mole was found, including the solvation enthalpy of the organometal with tetrahydrofuran. The existence of any relation between the reactivity of the propagating species and the tactic incorporation of the monomeric units has been discussed. The polymerization in mixtures of toluene–dioxane is intermediate between that in pure toluene and that in toluene–HF mixtures; the reaction mechanism however cannot be interpreted with the usual kinetic scheme. The experimental data concerning the rate dependence on catalyst and monomer concentrations are briefly summarized. 相似文献
2.
Y. Amerik W. F. Reynolds J. E. Guillet 《Journal of polymer science. Part A, Polymer chemistry》1971,9(2):531-541
The polymerization of methyl methacrylate has been studied in toluene and tetrahydrofuran solution at ?78°C using butyllithium as catalyst. The structure of the polymer produced was determined by analysis of the α-methyl groups using 100 MHz NMR. It is shown that in a noncomplexing solvent such as toluene, the number of isotactic triads increases from 70% to 93% as the monomer concentration during polymerization is reduced from 5 mole/l. to approximately zero. The value of Pss/Pis depends strongly on monomer concentration, and hence any calculations regarding penultimate effects in such systems should be made at close to zero monomer concentration. In the THF solution the penultimate effect is nearly independent of monomer concentration, and both Pii/Psi and Pss/Pis are close to unity. The results may be explained in terms of a mechanism of the polymerization process in which toluene does not complex with the active site, while monomer and THF are weak and strong complexing agents, respectively. 相似文献
3.
The anionic polymerization of 2-ethylhexyl acrylate (EtHA) initiated with the complex butyllithium/lithium-tert-butoxide (BuLi/t-BuOLi) was investigated at ?60°C in a medium of various solvating power, i.e., in mixtures of toluene and tetrahydrofuran and in neat tetrahydrofuran. With increasing amount of THF in the mixture the attainable limiting conversion of polymerization decreases; the monomer can be polymerized quantitatively only in a toluene/THF mixture (9/1). Molecular weights of the polymers thus obtained, their distribution, and initiator efficiency are not appreciably affected by the polymerization medium. The molecular weight distribution of the products is medium-broad (Mw/Mn = 2–2.4), with a hint of bimodality. The 1H-13C-NMR, and IR spectra suggest that during the polymerization there is neither any perceptible reesterification of the polymer with the alkoxide nor transmetalation of the monomer with the initiator. In a suitable medium, autotermination of propagation proceeds to a limited extent only, predominantly via intramolecular cyclization of propagating chains; in a medium with a higher content of polar THF, it prevails and terminates propagation before the polymerization of the monomer has been completed. © 1992 John Wiley & Sons, Inc. 相似文献
4.
Lingmin Yi Xiaoli Zhan Fengqiu Chen Feng Du Linbing Huang 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4431-4438
A series of narrow molecular weight distribution (MWD) polystyrene‐b‐poly[methyl(3,3,3‐trifluoropropyl)siloxane] (PS‐b‐PMTFPS) diblock copolymers were synthesized by the sequential anionic polymerization of styrene and trans‐1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane in tetrahydrofuran (THF) with n‐butyllithium as the initiator. The diblock copolymers had narrow MWDs ranging from 1.06 to 1.20 and number‐average molecular weights ranging from 8.2 × 103 to 37.1 × 103. To investigate the properties of the copolymers, diblock copolymers with different weight fractions of poly[methyl(3,3,3‐trifluoropropyl)siloxane] (15.4–78.8 wt %) were prepared. The compositions of the diblock copolymers were calculated from the characteristic proton integrals of 1H NMR spectra. For the anionic ring‐opening polymerization (ROP) of 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane (F3) initiated by polystyryllithium, high monomer concentrations could give high polymer yields and good control of MWDs when THF was used as the polymerization solvent. It was speculated that good control of the block copolymerization under the condition of high monomer concentrations was due to the slowdown of the anionic ROP rate of F3 and the steric hindrance of the polystyrene precursors. There was enough time to terminate the ROP of F3 when the polymer yield was high, and good control of block copolymerization could be achieved thereafter. The thermal properties (differential scanning calorimetry and thermogravimetric analysis) were also investigated for the PS‐b‐PMTFPS diblock copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4431–4438, 2005 相似文献
5.
Satoshi Inoue Takeo Kumagai Hajime Tamezawa Hiroyuki Aota Akira Matsumoto Katsutoshi Yokoyama Yasuo Matoba Michirou Shibano 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):156-163
For a deeper understanding of allyl polymerization mechanism, the reinitiation efficiency of resonance‐stabilized monomeric allyl radical was pursued because in allyl polymerization it is commonly conceived that the monomeric allyl radical generated via the allylic hydrogen abstraction of growing polymer radical from monomer, i.e., “degradative monomer chain transfer,” has much less tendency to initiate a new polymer chain and, therefore, this monomer chain transfer is essentially a termination reaction. Based on the renewed allyl polymerization mechanism in our preceding article, the monomer chain transfer constant in the polymerization of allyl benzoate was estimated to be 2.7 × 10?2 at 80 °C under the polymerization condition, where the coupling termination reaction of growing polymer radical with allyl radical was negligible and, concurrently, the reinitiation reaction of allyl radical was enhanced significantly. The reinitiation efficiencies of monomeric allyl radical were pursued by the dead‐end polymerizations of allyl benzoate at 80, 105, and 130 °C using a small amount of initiators; they increased remarkably with raised temperature. Thus, the enhanced reinitiation reactivity of allyl radical at an elevated temperature could bias the well‐known degradative monomer chain transfer characteristic of allyl polymerization toward the chain transfer in common vinyl polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
6.
James T. Wiltshire Greg G. Qiao 《Journal of polymer science. Part A, Polymer chemistry》2009,47(6):1485-1498
Degradable polyester‐based star polymers with a high level of functionality in the arms were synthesized via the “arms first” approach using an acetylene‐functional block copolymer macroinitiator. This was achieved by using 2‐hydroxyethyl 2′‐methyl‐2′‐bromopropionate to initiate the ring‐opening polymerization (ROP) of caprolactone monomer followed by an atom transfer radical polymerization (ATRP) of a protected acetylene monomer, (trimethylsilyl)propargyl methacrylate. The hydroxyl end‐group of the resulting block copolymer macroinitiator was subsequently crosslinked under ROP conditions using a bislactone monomer, 4,4′‐bioxepanyl‐7,7′‐dione, to generate a degradable core crosslinked star (CCS) polymer with protected acetylene groups in the corona. The trimethylsilyl‐protecting groups were removed to generate a CCS polymer with an average of 1850 pendent acetylene groups located in the outer block segment of the arms. The increased functionality of this CCS polymer was demonstrated by attaching azide‐functionalized linear polystyrene via a copper (I)‐catalyzed cycloaddition reaction between the azide and acetylene groups. This resulted in a CCS polymer with “brush‐like” arm structures, the grafted segment of which could be liberated via hydrolysis of the polyester star structure to generate molecular brushes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1485–1498, 2009 相似文献
7.
Itaru Mita Hiroshi Okuyama 《Journal of polymer science. Part A, Polymer chemistry》1971,9(12):3437-3452
Anionic living polymerization of α-methylstyrene containing a small amount of THF (less than 10%) was studied at temperatures between ?30°C and 50°C. At any temperature studied, a certain quantity of monomer remained without further polymerization. The effect of temperature and THF content on the final state was completely different in low and high temperature regions; at temperatures lower than ca. 20°C, the final monomer concentration decreased with increasing polymerization temperature and THF content. This is explained by the concept of “stopping of polymerization due to vitrification” of the polymerizing mixture. In fact, the final reaction mixture is really glassy in most cases and the red color of living polymer buried in the glass is discolored only very slowly when exposed to air. Detailed analysis of the results showed that the vitrification stopping holds only approximately. At temperatures higher than ca. 30°C, a normal equilibrium between propagation and depropagation holds, and the final monomer concentration increased with temperature. It is, however, far less than the equilibrium monomer concentration obtained in solution polymerization at the same temperature, and it increased appreciably with the increase in THF content. It is shown that the behavior of the equilibrium for the whole concentration range can be explained satisfactorily by a thermodynamic theory of ternary mixture. 相似文献
8.
Shengkang Ying 《Macromolecular Symposia》1994,85(1):251-266
The relationship between ideal copolymerization behavior and the nature of reactive species in butyllithium (n-BuLi) initiated anionic copolymerization of styrene (St)- butadiene (Bd) in nonpolar solvent has been discussed. The monomer reactivity ratios (m.r.r.) for various reactive species were evaluated by kinetic study and statistical approach (using 13C NMR data) in St-Bd anionic copolymerization system with THF as polar additive. The Markovian mechanisms for different propagating reactions in this complex copolymerizing system have been postulated. Furthermore, “pseudo” zero order Markovian mechnism could be sophisticatedly established in the n-BuLi/tertiary amyloxy potassium (t-AmOK)/THF initiated St-Bd copolymerization system, provided that the apparent rate constants of both monomers are equal. Thus, by adjusting the ratio of K/Li and THF/Li, copolymers with composition almost identical to the ratio of initial monomer feed composition at different stages of conversion could be obtained. 相似文献
9.
设计并合成了一种新型含甲酰基同时又含β-蒎烯单元的新单体2-β-蒎氧基-5-乙烯基苯甲醛(POVB),选择苯基双硫代乙酸1-苯基乙酯(PEPDA)为RAFT试剂、以AIBN为引发剂、在60℃下THF中实现了POVB的"活性"/可控RAFT自由基聚合.单体浓度半对数ln([M]0/[M])与聚合时间符合线性关系,聚合过程呈现一级动力学特征;聚合物分子量(Mn)随单体转化率几乎线性增加,而且整个反应过程中分子量分布(Mw/Mn1.2)保持在较窄的范围.1H-NMR的分析进一步证实了聚合物链的末端精细结构.此外,CD谱结果表明手性单元β-蒎烯基能赋予聚合物以光学活性. 相似文献
10.
Mingqiang Xue Hongmei Sun Hui Zhou Yingming Yao Qi Shen Yong Zhang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1147-1152
Ring‐opening polymerization of ε‐caprolactone (ε‐CL) was carried out using β‐diketiminato‐supported monoaryloxo ytterbium chlorides L1Yb(OAr)Cl(THF) (1) [L1 = N,N′‐bis(2,6‐dimethylphenyl)‐2,4‐pentanediiminato, OAr = 2,6‐di‐tert‐butylphenoxo‐], and L2Yb(OAr′)Cl(THF) (2) [L2 = N,N′‐bis(2,6‐diisopropylphenyl)‐2,4‐pentanediiminato, OAr′ = 2,6‐di‐tert‐butyl‐4‐methylphenoxo‐], respectively, as single‐component initiator. The influence of reaction conditions, such as polymerization temperature, polymerization time, initiator, and initiator concentration, on the monomer conversion, molecular weight, and molecular weight distribution of the resulting polymers was investigated. Complex 1 was well characterized and its crystal structure was determined. Some features and kinetic behaviors of the CL polymerization initiated by these two complexes were studied. The polymerization rate is first order with respect to monomer. The Mn of the polymer increases linearly with the increase of the polymer yield, while polydispersity remained narrow and unchanged throughout the polymerization in a broad range of temperatures from 0 to 50 °C. The results indicated that the present system has a “living character”. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1147–1152, 2006 相似文献
11.
Kazuhiko Hashimoto Hiroshi Sumitomo Shinji Ohsawa 《Journal of polymer science. Part A, Polymer chemistry》1975,13(12):2775-2783
Anionic polymerization of β-methoxypropionaldehyde (MPA) was carried out in tetrahydrofuran (THF) by using benzophenone–monolithium complex as an initiator. An equilibrium between polymerization and depolymerization was observed at a temperature range of ?90 to ?70°C. From the temperature dependence of the equilibrium monomer concentration, thermodynamic parameters for the polymerization of MPA in THF were evaluated as follows: ΔHss = ?4.8 ± 0.2 kcal/mole, ΔHSS = ?22.4 ± 1.3 cal/mole-deg, and (Tc)ss = ?59°C. The thermodynamic change upon the conversion of liquid monomer to condensed polymer was computed from both the partial mixing energy of MPA with THF and the linear relationship between the equilibrium volume fraction of MPA monomer and that of the resulting polymer: ΔH1c = ?4.7 ± 0.2 kcal/mole, ΔS1c = ?19.5 ± 1.3 cal/mole-deg, and (Tc)1c = ?35°C. 相似文献
12.
Hardy Müller Christine Schmidt Simone Kehr M. Hagedorn 《Macromolecular rapid communications》2000,21(8):449-452
The anionic homopolymerization of 2,5‐dimethylhexa‐1.5‐dien‐3‐yne (DMDEY) was investigated by utilizing butyllithium, sec‐butyllithium, diphenylmethylsodium, and naphthalene/sodium as initiators. Soluble polymers with molecular weights up to 50 000 g/mol corresponding to Mw/Mn of 1.05 were obtained through homopolymerization with diphenylmethylsodium as initiator in THF at low temperatures. The homopolymers consist of 1,2‐linked monomer units with pendant 3‐methylbut‐3‐en‐1‐yne groups. 相似文献
13.
14.
Kozo Matsumoto Hironobu Shimazu Hitoshi Yamaoka 《Journal of polymer science. Part A, Polymer chemistry》1998,36(2):225-231
A new class of polar polysilabutanes with mono- or tri-(oxyethylene)phenyl groups on the silicon atom have been synthesized by anionic polymerization of silacyclobutanes having ω-(t-butyldimethylsilyl-protected) mono- or tri-(oxyethylene)phenyl groups and subsequent deprotection of the silyl groups. The monomers were synthesized by treatment of 1,1-dichlorosilacyclobutane with ω-(t-butyldimethylsilyl-protected) mono- or tri-(oxyethylene)phenyl Grignard reagents. Anionic polymerization of silacyclobutane was performed with butyllithium initiator in THF. t-Butyldimethylsilyl-protecting groups at polymer pendant groups were hydrolyzed with tetrabutyl ammonium fluoride in water-containing THF. The obtained polysilabutanes were soluble in a polar organic solvent such as methanol, and their mass distributions were analysed by matrix-assisted laser-desorption-ionization mass spectrometry (MALDI TOF MS). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 225–231, 1998 相似文献
15.
Daisuke Nagai Atsushi Sudo Fumio Sanda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2001,39(13):2078-2084
A living anionic alternating copolymerization of ethylphenylketene (EPK) with 4‐methoxybenzaldehyde (MBA) was achieved. When n‐butyllithium was added to a mixture of EPK and MBA in tetrahydrofuran at ?40 °C in the presence of an excess amount of lithium chloride, the copolymerization of these monomers proceeded via complete 1:1 alternating manner to afford the polymer with a narrow molecular weight distribution. A linear relationship was observed between the molecular weight and the monomer/initiator ratio, keeping a narrow molecular weight distribution. The structure of the obtained polymer was determined to be a polyester by IR spectroscopy together with the reductive degradation of the polymer by lithium aluminum hydride, which quantitatively afforded the corresponding diol to the repeating unit of the expected polyester structure. Both conversions of EPK and MBA agreed to a first‐order kinetic equation with linear evolution between the molecular weight and conversion. These observations along with the successful results in two‐stage polymerization indicate that the present copolymerization proceeded through a living mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2078–2084, 2001 相似文献
16.
Stable dispersions of polyacrylonitrile (PAN) nanoparticles in the size range between 100 nm < d < 180 nm were made by polymerization in miniemulsion and characterized by dynamic light scattering, transmission electron microscopy (TEM), and wide angle X‐ray scattering (WAXS). Due to the insolubility of the polymer in its monomer, such particles are not accessible by classical emulsion polymerization. The pure PAN particles are composed of ca. 10 nm large polymer nanocrystals, i. e., the formed polymer precipitates and crystallizes direct after formation. As a consequence, the final latexes do not adopt spherical shape, but show a well defined, narrowly distributed boulder‐like phenotype which is called “crumpled latexes”. Copolymerization with styrene results in a continuous transition between the crumpled and a smooth spherical morphology, which is again related to a decreased degree of crystallinity. 相似文献
17.
Kozo Matsumoto Hironobu Shimazu Masaki Deguchi Hitoshi Yamaoka 《Journal of polymer science. Part A, Polymer chemistry》1997,35(15):3207-3216
Anionic polymerizations of 1,1-dimethylsilacyclobutane, 1,1-diethylsilacyclobutane and 1-methyl-1-phenylsilacyclobutane were investigated. Addition of 5 mol % of butyllithium to a solution of 1,1-dimethylsilacyclobutane in THF-hexane (1 : 1) at −48°C provided poly(1,1-dimethylsilabutane) in 99% yield. Mn and Mw/Mn of the obtained polymer were 2400 and 1.10. This polymerization proceeded with a living nature. Mn increased in proportion as the yield of polymer increased. Addition of the second fresh feed of the monomer to the reaction mixture restarted polymerization of the second monomer at the same rate as in the initial stage. Addition of styrene to the living poly(1,1-dimethylsilabutane) provided a poly(1,1-dimethylsilabutane-b-styrene) block copolymer. It was also found that a polymerization of 1,1-diethylsilacyclobutane in THF-hexane at −48°C showed a living nature. In contrast, a polymerization of 1-methyl-1-phenylsilacyclobutane in THF at −78°C did not show a living nature. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3207–3216, 1997 相似文献
18.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):379-395
ABSTRACT Radiation induced solid-state polymerization of acetylenedicarboxylic acid was carried out at room temperature in open atmosphere and under vacuum conditions. The gray colored powder polymer obtained was insoluble in most common solvents but only partially soluble in DMSO and THF. The limiting conversion to polymer was about 5%. The polymer was characterized by IR, UV, DP-MS, DSC, TGA, and XRD. The mechanism of polymerization was elucidated from the available data. Polymerization followed a free radical mechanism. However, before the addition of monomer molecules to the growing chain, at least one of the carboxylic groups of the monomer breaks away as CO or CO2. The formation of side group cyclization takes place. At least one of the bonds in the side cyclic group is an etheric bond. The DSC, TGA, and XRD results showed that the polymer was partially crystalline and showed no melting up to 1200°C. The mechanism of polymerization and assigned chain structure was studied by the direct pyrolysis mass spectrometric method. The crystal structure of monomer and polymer was investigated by the XRD method. Both monomer and crystalline polymer were monoclinic with similar cell parameters. Thus, the polymerization follows a topotactic mechanism. The unpolymerized monomer retains its crystal structure and, therefore, CO or CO2 in the monomer molecule has to be eliminated before polymerization could take place. 相似文献
19.
Man Zhao Hongtao Zhang Fengning Ma Ying Zhang Xianzhi Guo Huiqi Zhang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(9):1983-1998
The facile and efficient one‐pot synthesis of monodisperse, highly crosslinked, and “living” functional copolymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization (ILRPP) is described for the first time. The simple introduction of iniferter‐induced “living” radical polymerization (ILRP) mechanism into precipitation polymerization system, together with the use of ethanol solvent, allows the direct generation of such uniform functional copolymer microspheres. The polymerization parameters (including monomer loading, iniferter concentration, molar ratio of crosslinker to monovinyl comonomer, and polymerization time and scale) showed much influence on the morphologies of the resulting copolymer microspheres, thus permitting the convenient tailoring of the particle sizes by easily tuning the reaction conditions. In particular, monodisperse poly(4‐vinylpyridine‐co‐ethylene glycol dimethacrylate) microspheres were prepared by the ambient temperature ILRPP even at a high monomer loading of 18 vol %. The general applicability of the ambient temperature ILRPP was confirmed by the preparation of uniform copolymer microspheres with incorporated glycidyl methacrylate. Moreover, the “livingness” of the resulting polymer microspheres was verified by their direct grafting of hydrophilic polymer brushes via surface‐initiated ILRP. Furthermore, a “grafting from” particle growth mechanism was proposed for ILRPP, which is considerably different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
20.
Lifen Wu Valerie V. Sheares 《Journal of polymer science. Part A, Polymer chemistry》2001,39(19):3227-3238
2‐[(N‐Benzyl‐N‐methylamino)methyl]‐1,3‐butadiene (BMAMBD), the first asymmetric tertiary amino‐containing diene‐based monomer, was synthesized by sulfone chemistry and a nickel‐catalyzed Grignard coupling reaction in high purity and good yield. The bulk and solution free‐radical polymerizations of this monomer were studied. Traditional bulk free‐radical polymerization kinetics were observed, giving polymers with 〈Mn〉 values of 21 × 103 to 48 × 103 g/mol (where Mn is the number‐average molecular weight) and polydispersity indices near 1.5. In solution polymerization, polymers with higher molecular weights were obtained in cyclohexane than in tetrahydrofuran (THF) because of the higher chain transfer to the solvent. The chain‐transfer constants calculated for cyclohexane and THF were 1.97 × 10?3 and 5.77 × 10?3, respectively. To further tailor polymer properties, we also completed copolymerization studies with styrene. Kinetic studies showed that BMAMBD incorporated into the polymer chain at a faster rate than styrene. With the Mayo–Lewis equation, the monomer reactivity ratios of BMAMBD and styrene at 75 °C were determined to be 2.6 ± 0.3 and 0.28 ± 0.02, respectively. Altering the composition of BMAMBD in the copolymer from 17 to 93% caused the glass‐transition temperature of the resulting copolymer to decrease from 64 to ?7 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3227–3238, 2001 相似文献