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1.
Thermo‐stable 2‐(arylimino)benzylidene‐9‐arylimino‐5,6,7,8‐tetrahydro cyclohepta[b]pyridyliron(II) precatalysts toward ethylene polymerization and highly linear polyethylenes 下载免费PDF全文
Fang Huang Tongling Liang Xinquan Hu Wen‐Hua Sun 《Journal of polymer science. Part A, Polymer chemistry》2017,55(5):830-842
A series of 2‐(arylimino)benzylidene‐9‐arylimino‐5,6,7,8‐tetrahydrocyclohepta[b] pyridyliron(II) chlorides was synthesized and characterized using FT‐IR and elemental analysis, and the molecular structures of complexes Fe3 and Fe4 have been confirmed by the single‐crystal X‐ray diffraction as a pseudo‐square‐pyramidal or distorted trigonal‐bipyramidal geometry around the iron core. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all iron precatalysts exhibited high activities toward ethylene polymerization with a marvelous thermo‐stability and long lifetime. The Fe4 /MAO system showed highest activity of 1.56 × 107 gPE·mol?1(Fe)·h?1 at 70 °C, which is one of the highest activities toward ethylene polymerization by iron precatalysts. Even up to 80 °C, Fe3 /MAO system still persist high activity as 6.87 × 106 g(PE)·mol?1(Fe)·h?1, demonstrating remarkable thermal stability for industrial polymerizations (80–100 °C). This was mainly attributing to the phenyl modification of the framework of the iron precatalysts. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 830–842 相似文献
2.
Synthesis,Structure, and Characterization of 3, 4′‐Bis‐1H‐1, 2,4‐triazolium Picrate Salt: A New High‐Energy Density Material 下载免费PDF全文
The environmentally friendly high‐energy density salt (TRTR)(PA) (TRTR = 3, 4′‐bis‐1, 2,4‐1H‐triazole, PA = 2, 4,6‐trinitrophenol, picric acid) was synthesized and characterized. The X‐ray single crystal diffraction results illustrate that the structure of title salt belongs to the monoclinic system, space group P21/c. Many parallel relationships exist in the molecule, as well as a strong intramolecular π–π stacking interaction. The DSC result shows only one exothermal decomposition step at 229.1 °C. The TG‐DTG curve demonstrates a 75.9 % mass loss from 180 °C to 300 °C at a rate of 3.01 % · K–1. Experimental data show that the combustion heat approximately equals to TNT (–15.22 MJ · kg–1) and the enthalpy of formation is +332.2 kJ · mol–1. Non–isothermal kinetic and thermodynamic parameters were obtained by two methods (Kissinger and Ozawa). Detonation pressure and velocity were calculated to be 23.4 GPa and 7.32 km · s–1, respectively. Additionally, the sensitivities towards impact and friction were assessed with relevant standard methods. 相似文献
3.
Prof. Dr. Thomas M. Klapötke Jörg Stierstorfer Prof. Dr. H. Donald Brooke Jenkins Rudi van Eldik Matthias Schmeisser 《无机化学与普通化学杂志》2011,637(10):1308-1313
This paper estimates some thermochemical (in kcal mol–1) and detonation parameters for the ionic liquid, [emim][ClO4] and its associated solid in view of its investigation as an energetic material. The thermochemical values estimated, employing CBS‐4M computational methodology and volume‐based thermodynamics (VBT) include: lattice energy, UPOT([emim][ClO4]) ≈? 123 ± 16 kcal · mol–1; enthalpy of formation of the gaseous cation, ΔfH°([emim]+, g) = 144.2 kcal · mol–1 and anion, ΔfH°([ClO4]–, g) = –66.1 kcal · mol–1; the enthalpy of formation of the solid salt, ΔfH°([emim][ClO4],s) ≈? –55 ± 16 kcal · mol–1 and for the associated ionic liquid, ΔfHo([emim][ClO4],l) = –52 ± 16 kcal · mol–1 as well as the corresponding Gibbs energy terms: ΔfG°([emim][ClO4],s) ≈? +29 ± 16 kcal · mol–1 and ΔfGo([emim][ClO4],l) = +24 ± 16 kcal · mol–1 and the associated standard absolute entropies, of the solid [emim][ClO4], S°298([emim][ClO4],s) = 83 ± 4 cal · K–1 · mol–1. The following combustion and detonation parameters are assigned to [emim][ClO4] in its (ionic) liquid form: specific impulse (Isp) = 228 s (monopropellant), detonation velocity (VoD) = 5466 m · s–1, detonation pressure (pC–J) = 99 kbar, explosion temperature (Tex) = 2842 K. 相似文献
4.
Kangzhen Xu Xiaolei Ren Jirong Song Fengqi Zhao Li Ding Jianhua Yi Yaoyu Wang 《中国化学》2009,27(10):1907-1913
A new compound, 2‐(dinitromethylene)‐1,3‐diazacyclopentane (DNDZ), was prepared by the reaction of 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) with 1,2‐diaminoethane in N‐methylpyrrolidone (NMP). Thermal decomposition of DNDZ was studied under non‐isothermal conditions by DSC, TG/DTG methods, and the enthalpy, apparent activation energy and pre‐exponential factor of the exothermic decomposition reaction were obtained as 317.13 kJ·mol?1, 269.7 kJ·mol?1 and 1024.51 s?1, respectively. The critical temperature of thermal explosion was 261.04°C. Specific heat capacity of DNDZ was determined with a micro‐DSC method and a theoretical calculation method, and the molar heat capacity was 205.41 J·mol?1·K?1 at 298.15 K. Adiabatic time‐to‐explosion was calculated to be a certain value between 263–289 s. DNDZ has higher thermal stability than FOX‐7. 相似文献
5.
《国际化学动力学杂志》2018,50(7):495-506
The kinetic and mechanistic study of Ag(I)‐catalyzed chlorination of linezolid (LNZ) by free available chlorine (FAC) was investigated at environmentally relevant pH 4.0–9.0. Apparent second‐order rate constants decreased with an increase in pH of the reaction mixture. The apparent second‐order rate constant for uncatalyzed reaction, e.g., k″app = 8.15 dm3 mol−1 s−1 at pH 4.0 and k″app. = 0.076 dm3 mol−1 s−1 at pH 9.0 and 25 ± 0.2°C and for Ag(I) catalyzed reaction total apparent second‐order rate constant, e.g., k″app = 51.50 dm3 mol−1 s−1 at pH 4.0 and k″app. = 1.03 dm3 mol−1 s−1 at pH 9.0 and 25 ± 0.2°C. The Ag(I) catalyst accelerates the reaction of LNZ with FAC by 10‐fold. A mechanism involving electrophilic halogenation has been proposed based on the kinetic data and LC/ESI/MS spectra. The influence of temperature on the rate of reaction was studied; the rate constants were found to increase with an increase in temperature. The thermodynamic activation parameters Ea, ΔH#, ΔS#, and ΔG# were evaluated for the reaction and discussed. The influence of catalyst, initially added product, dielectric constant, and ionic strength on the rate of reaction was also investigated. The monochlorinated substituted product along with degraded one was formed by the reaction of LNZ with FAC. 相似文献
6.
Benjamin Renault Thierry Tassaing Eric Cloutet Henri Cramail 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5649-5661
Well‐defined polyurethane–polydimethylsiloxane particles of tunable diameter in the range of 0.5–20 μm were synthesized in “one‐shot” by step‐growth polymerization using supercritical carbon dioxide (scCO2) as a dispersant medium. Polymerizations were carried out at 60 °C and above 25 MPa, after the solubility of each reactant in scCO2 has been determined in its typical reaction concentration. The synthesis of such copolymers was achieved by polyaddition between short aliphatic diols, that is, ethylene glycol, 1,4‐butanediol (BD) or polyethylene oxide (Mn = 200 g mol?1), and tolylene‐1,4‐di‐isocyanate (TDI) in the presence of mono or di‐isocyanate‐terminated polydimethylsiloxane (PDMS) as reactive stabilizers and dibutyltin dilaurate as a catalyst. The nature of the diol used as well as the functionality of the reactive stabilizer incorporated was found to have a dramatic effect on the molar mass and the morphology of the resulting product. Thus, copolymers obtained from the polyaddition of BD and TDI in the presence of di‐isocyanate‐terminated PDMS exhibit molar mass up to 90,000 g mol?1. Thermal behaviors of copolymers were also examined by differential scanning calorimetry. All samples exhibited only one glass transition temperature (Tg) and were found to be totally amorphous. A logical decrease of the Tg was observed as the length of the diol incorporated increased, that is, as the density of urethane linkages within the polymer decreased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5649–5661, 2007 相似文献
7.
Leonie Barner Christopher Barner‐Kowollik Thomas P. Davis 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1064-1074
The free‐radical copolymerization of m‐isopropenyl‐α,α′‐dimethylbenzyl isocyanate (TMI) and styrene was studied with 1H NMR kinetic experiments at 70 °C. Monomer conversion vs time data were used to determine the ratio kp × kt?0.5 for various comonomer mixture compositions (where kp is the propagation rate coefficient and kt is the termination rate coefficient). The ratio kp × kt?0.5 varied from 25.9 × 10?3 L0.5 mol?0.5 s?0.5 for pure styrene to 2.03 × 10?3 L0.5 mol?0.5 s?0.5 for 73 mol % TMI, indicating a significant decrease in the rate of polymerization with increasing TMI content in the reaction mixture. Traces of the individual monomer conversion versus time were used to map out the comonomer mixture composition drift up to overall monomer conversions of 35%. Within this conversion range, a slight but significant depletion of styrene in the monomer feed was observed. This depletion became more pronounced at higher levels of TMI in the initial comonomer mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1064–1074, 2002 相似文献
8.
The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N‐N‐bis[N‐(2,2,2‐tri‐nitroethyl)‐N‐nitro]ethylenediamine in a temperature‐programmed mode have been investigated by means of differential scanning calorimetry (DSC). The results show that kinetic model function in differential form, apparent activation energy Ea and pre‐exponential factor A of this reaction are 3(1 ‐α)2/3, 203.67 kJ·mol?1 and 1020.61s?1, respectively. The critical temperature of thermal explosion of the compound is 182.2 °C. The values of ΔS≠ ΔH≠ and ΔG≠ of this reaction are 143.3 J·mol?1·K?1, 199.5 kJ·mol?1 and 135.5 kJ·mol?1, respectively. 相似文献
9.
Hongxia Feng Mohamad Al‐Sheikhly Joseph Silverman Douglas E. Weiss Pedatsur Neta 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):196-203
The bulk polymerization of 2‐ethylhexyl acrylate (2‐EHA), induced by a pulsed electron beam, was investigated with pulse radiolysis, gravimetry, and Fourier transform infrared spectroscopy. The roles of the dose rate, pulse frequency, and added acrylic acid (AA) in the polymerization of 2‐EHA were examined at ambient temperature. In the range of 12.6–71.2 Gy/pulse, the polymerization of 2‐EHA was dose‐rate‐dependent: at the same total dose, a lower dose rate yielded a higher conversion. Also, a lower pulse rate gave a higher conversion at the same total dose. The addition of up to 10 wt % AA showed no increase in the conversion of 2‐EHA at a low conversion (8 kGy), but at a higher conversion (16 kGy), a 20 wt % increase in the conversion of 2‐EHA was observed. The estimated values (1.6 ± 0.3) × 10?3 (dm3 s)3/2 mol?1 s?1/2 for kp(G/2kt)1/2 and 2.6 ± 0.8 dm3 s J?1 for 2ktG (where kp is the rate constant of propagation, kt is the rate constant of bimolecular termination, and G is the yield of free radicals) were obtained at relatively low conversions. The reaction rate constant of the addition of 2‐EHA· free radicals to the monomer was measured by pulse radiolysis and found to be 2.8 × 102 mol?1 dm3 s?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 196–203, 2003 相似文献
10.
Valrie Sciannamea Maxime Bernard Jean‐Marie Catala Robert Jrme Christophe Detrembleur 《Journal of polymer science. Part A, Polymer chemistry》2006,44(21):6299-6311
The C‐phenyl‐N‐tert‐butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n‐butyl acrylate as long as a two‐step process is implemented, that is, the prereaction of the nitrone and the initiator in toluene at 85 °C for 4 h followed by the addition and polymerization of n‐butyl acrylate at 110 °C. The structure of the in situ formed nitroxide has been established from kinetic and electron spin resonance data. The key parameters (the dissociation rate constant, combination rate constant, and equilibrium constant) that govern the process have been evaluated. The equilibrium constant between the dormant and active species is close to 1.6 × 10?12 mol L?1 at 110 °C. The dissociation rate constant and the activation energy for the C? ON bond homolysis are 1.9 × 10?3 s?1 and 122 ± 15 kJ mol?1, respectively. The rate constant of recombination between the propagating radical and the nitroxide is as high as 1.2 × 109 L mol?1 s?1. Finally, well‐defined poly(n‐butyl acrylate)‐b‐polystyrene block copolymers have been successfully prepared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6299–6311, 2006 相似文献
11.
Stimuli‐responsive 4‐acryloylmorpholine/4‐acryloylpiperidine copolymers via nitroxide mediated polymerization 下载免费PDF全文
Xeniya Savelyeva Adrien Métafiot Lucia Li Ian Bennett Milan Marić 《Journal of polymer science. Part A, Polymer chemistry》2017,55(13):2160-2170
4‐acryloylmorpholine/4‐acryloylpiperidine statistical copolymers were synthesized by nitroxide mediated polymerization (NMP) with BlocBuilder unimolecular initiator in dimethylformamide solution at 120 °C. The copolymers had narrow molecular weight distributions (dispersity ? = 1.25–1.35, number average molecular weights M n = 8.5–13.7 kg mol?1). The copolymer microstructure was essentially statistical (reactivity ratios r 4AP = 0.81 ± 0.73, r 4AM = 0.73 ± 0.68 based on non‐linear fitting of the Mayo‐Lewis equation). Cloud point temperatures (CPT) in aqueous media were tuned from 11 °C to 92 °C, merely by adjusting the initial monomer composition. Using NMP permitted sharper control of the CPT transitions, compared to the similar copolymer made using conventional radical polymerization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2160–2170 相似文献
12.
Valérie Sciannamea Jean‐Marie Catala Robert Jérôme Christophe Detrembleur 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1219-1235
Kinetics of the free radical polymerization of styrene at 110 °C has been investigated in the presence of C‐phenyl‐N‐tert‐butylnitrone (PBN) and 2,2′‐azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 °C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 °C), and ultimately on the control of the styrene polymerization at 110 °C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide‐mediated polymerization. Only one type of nitroxide (low‐molecular‐mass nitroxide) is formed whatever the prereaction conditions at 85 °C, and the equilibrium constant (K) between active and dormant species is 8.7 × 10?10 mol L?1 at 110 °C. At this temperature, the dissociation rate constant (kd) is 3.7 × 10?3 s?1, the recombination rate constant (kc) is 4.3 × 106 L mol?1 s?1, whereas the activation energy (Ea,diss.), for the dissociation of the alkoxyamine at the chain‐end is ~125 kJ mol?1. Importantly, the propagation rate at 110 °C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 °C, is higher than that for the thermal polymerization at 110 °C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1219–1235, 2007 相似文献
13.
Angiebelk Monsalve Felix Rosas María Tosta Armando Herize Rosa M. Domínguez Doris Brusco Gabriel Chuchani 《国际化学动力学杂志》2006,38(2):106-114
The gas‐phase elimination kinetics of the above‐mentioned compounds were determined in a static reaction system over the temperature range of 369–450.3°C and pressure range of 29–103.5 Torr. The reactions are homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius expressions: ethyl 3‐(piperidin‐1‐yl) propionate, log k1(s?1) = (12.79 ± 0.16) ? (199.7 ± 2.0) kJ mol?1 (2.303 RT)?1; ethyl 1‐methylpiperidine‐3‐carboxylate, log k1(s?1) = (13.07 ± 0.12)–(212.8 ± 1.6) kJ mol?1 (2.303 RT)?1; ethyl piperidine‐3‐carboxylate, log k1(s?1) = (13.12 ± 0.13) ? (210.4 ± 1.7) kJ mol?1 (2.303 RT)?1; and 3‐piperidine carboxylic acid, log k1(s?1) = (14.24 ± 0.17) ? (234.4 ± 2.2) kJ mol?1 (2.303 RT)?1. The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene through a concerted six‐membered cyclic transition state type of mechanism. The intermediate β‐amino acids decarboxylate as the α‐amino acids but in terms of a semipolar six‐membered cyclic transition state mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 106–114, 2006 相似文献
14.
Der‐Jang Liaw Been‐Yang Liaw 《Journal of polymer science. Part A, Polymer chemistry》2000,38(3):469-473
New functional monomer methacryloyl isocyanate containing 4‐chloro‐1‐phenol (CPHMAI) was prepared on reaction of methacryloyl isocyanate (MAI) with 4‐chloro‐1‐phenol (CPH) at low temperature and was characterized with IR, 1H, and 13C‐NMR spectra. Radical polymerization of CPHMAI was studied in terms of the rate of polymerization, solvent effect, copolymerization, and thermal properties. The rate of polymerization of CPHMAI has been found to be smaller than that of styrene under the same conditions. Polar solvents such as dimethylsulfoxide (DMSO) and N,N‐dimethyl formamide (DMF) were found to slow the polymerization. Copolymerization of CPHMAI (M1) with styrene (M2) in tetrahydrofuran (THF) was studied at 60°C. The monomer reactivity ratio was calculated to be r1 = 0.49 and r2 = 0.66 according to the method of Fineman—Ross. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 469–473, 2000 相似文献
15.
Jerzy Szafko Wadysaw Feist Barbara Pabin‐Szafko 《Journal of polymer science. Part A, Polymer chemistry》2000,38(12):2156-2166
The thermal decomposition rate constant (kd ) of 2,2′‐azoisobutyronitrile in acrylonitrile (AN; monomer A)–methyl methacrylate (MM; monomer B) comonomer mixtures in N,N‐dimethylformamide (DMF) as a function of the comonomer mixture composition and its concentration in the solvent at 60 °C was studied. The dependences kd = f(xA ,C) [xA (mole fraction of A in the comonomer mixture) = A/(A + B) = A/C, where C is the comonomer mixture concentration] have a different course as a function of C: from a curve kd = f(xA ) approaching the straight line (C = 2 mol · dm−3) to a convex curve possessing a maximum at a point xA = 0.7 (C = 4 mol · dm−3) to a curve with a flattened wide maximum within the range of xA = 0.2–0.8 (C = 7 mol · dm−3) to a curve with the shape of a lying s (C = 9 mol · dm−3). All the courses of the experimental dependences kd = f(xA ,C) can be explained with a hypothesis of initiator solvation by the comonomers AN and MM and the solvent DMF. The existing solvated forms, their relative stability constants, the thermal decomposition rate constants, and the relative contents in the system were determined. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2156–2166, 2000 相似文献
16.
Substituent effect of N‐aryl‐N′‐pyridyl ureas as thermal latent initiators on ring‐opening polymerization of epoxide 下载免费PDF全文
Naoyuki Makiuchi Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2015,53(22):2569-2574
A series of N‐aryl‐N′‐pyridyl ureas were synthesized by the reactions of 4‐aminopyridine (4AP) with the corresponding isocyanates such as phenyl isocyanate, 4‐methylphenyl isocyanate, 4‐methoxyphenyl isocyanate, 4‐chlorophenyl isocyanate, 4‐(trifluoromethyl)phenyl isocyanate, and 4‐nitrophenyl isocyanate. Bulk polymerization of diglycidyl ether of bisphenol A (DGEBA) in the presence of the ureas as initiators was evaluated by differential scanning calorimetry (DSC) at a heating rate of 10 °C/min. The resulting DSC profiles indicated exothermic peaks above 140 °C, while the DSC profile measured for a formulation composed of DGEBA and pristine 4AP indicated an exothermic peak at around 120 °C, implying that the derivation of 4AP into the corresponding ureas is a useful strategy to achieve thermal latency. The peak top temperatures were correlated with the electron density of the aromatic ring of the ureas, that is, as the electron‐withdrawing nature of the substituent on the aromatic ring became larger, the peak increases. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2569–2574 相似文献
17.
Christopher Barner‐Kowollik Philipp Vana Thomas P. Davis 《Journal of polymer science. Part A, Polymer chemistry》2002,40(5):675-681
Pulsed laser polymerization (PLP) experiments were performed on the bulk polymerization of methyl methacrylate (MMA) at ?34 °C. The aim of this study was to investigate the polymer end groups formed during the photoinitiation process of MMA monomer using 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) and benzoin as initiators via matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. Analysis of the MALDI‐TOF spectra indicated that the two radical fragments generated upon pulsed laser irradiation show markedly different reactivity toward MMA: whereas the benzoyl fragment—common to both DMPA and benzoin—clearly participates in the initiation process, the acetal and benzyl alcohol fragments cannot be identified as end groups in the polymer. The complexity of the MALDI‐TOF spectrum strongly increased with increasing laser intensity, this effect being more pronounced in the case of benzoin. This indicates that a cleaner initiation process is at work when DMPA is used as the photoinitiator. In addition, the MALDI‐TOF spectra were analyzed to extract the propagation‐rate coefficient, kp, of MMA at ?34 °C. The obtained value of kp = 43.8 L mol?1 s?1 agrees well with corresponding numbers obtained via size exclusion chromatography (kp = 40.5 L mol?1 s?1). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 675–681, 2002; DOI 10.1002/pola.10150 相似文献
18.
Jun‐Hwan Ahn Choon‐Hwa Lee Yeong‐Deuk Shin Jae‐Suk Lee 《Journal of polymer science. Part A, Polymer chemistry》2004,42(4):933-940
To study living anionic polymerization, 3‐(triethylsilyl)propyl isocyanate (TEtSPI) monomer was synthesized by hydrosilylation of allylamine with triethylsilane and treatment of the resulting amine with triphosgene. The polymerization of TEtSPI was performed with sodium naphthalenide (Na‐Naph) as an initiator and in the absence and presence of sodium tetraphenylborate (NaBPh4) as an additive in tetrahydrofuran (THF) at ?78 and at ?98 °C. A highly stabilized amidate anion for living polymerization of isocyanates was generated for the first time with the combined effect of the bulky substituent and the shielding action of the additive NaBPh4, extending the living character at least up to 120 min at ?98 °C. Even the anion could exist at ?78 °C for 10 min. A block copolymer, poly(n‐hexyl isocyanate)‐b‐poly[(3‐triethylsilyl)propyl isocyanate]‐b‐poly(n‐hexyl isocyanate), was synthesized with quantitative yields and controlled molecular weights via living anionic polymerization in THF at ?78 °C for TEtSPI and ?98 °C for n‐hexyl isocyanate, respectively, with Na‐Naph with three times of NaBPh4 as a common ion salt. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 933–940, 2004 相似文献
19.
Pierre‐Eric Millard Leonie Barner Martina H. Stenzel Thomas P. Davis Christopher Barner‐Kowollik Axel H. E. Müller 《Macromolecular rapid communications》2006,27(11):821-828
Summary: The ambient temperature (20 °C) reversible addition fragmentation chain transfer (RAFT) polymerization of N‐isopropylacrylamide (NIPAAm) and acrylic acid (AA) conducted directly in aqueous media under γ‐initiation (at dose rates of 30 Gy · h−1) proceeds in a controlled fashion (typically, < 1.2) to near quantitative conversions and up to number‐average molecular weights of 2.5 × 105 g · mol−1 for PNIPAAm and 1.1 × 105 g · mol−1 for PAA via two water‐soluble trithiocarbonate chain transfer agents, i.e., S,S‐bis(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate (TRITT) and 3‐benzylsulfanylthiocarbonylsulfanyl propionic acid (BPATT). The generated polymers are successfully chain extended, which suggests that the RAFT agents are stable throughout the polymerization process so that complex and well‐defined architectures can be obtained.
20.
Paul Dervan Fawaz Aldabbagh Per B. Zetterlund Bunichiro Yamada 《Journal of polymer science. Part A, Polymer chemistry》2003,41(2):327-334
Styrene radical polymerizations mediated by the imidazolidinone nitroxides 2,5‐bis(spirocyclohexyl)‐3‐methylimidazolidin‐4‐one‐1‐oxyl (NO88Me) and 2,5‐bis(spirocyclohexyl)‐3‐benzylimidazolidin‐4‐one‐1‐oxyl (NO88Bn) were investigated. Polymeric alkoxyamine (PS‐NO88Bn)‐initiated systems exhibited controlled/living characteristics at 100–120 °C but not at 80 °C. All systems exhibited rates of polymerization similar to those of thermal polymerization, with the exception of the PS‐NO88Bn system at 80 °C, which polymerized twice as quickly. The dissociation rate constants (kd) for the PS‐NO88Me and PS‐NO88Bn coupling products were determined by electron spin resonance at 50–100 °C. The equilibrium constants were estimated to be 9.01 × 10?11 and 6.47 × 10?11 mol L?1 at 120 °C for NO88Me and NO88Bn, respectively, resulting in the combination rate constants (kc) 2.77 × 106 (NO88Me) and 2.07 × 106 L mol?1 s?1 (NO88Bn). The similar polymerization results and kinetic parameters for NO88Me and NO88Bn indicated the absence of any 3‐N‐transannular effect by the benzyl substituent relative to the methyl substituent. The values of kd and kc were 4–8 and 25–33 times lower, respectively, than the reported values for PS‐TEMPO at 120 °C, indicating that the 2,5‐spirodicyclohexyl rings have a more profound effect on the combination reaction rather than the dissociation reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 327–334, 2003 相似文献