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1.
The anionic polymerization of allyl methacrylate was carried out in tetrahydrofuran, both in the presence and in the absence of LiCl, with a variety of initiators, at various temperatures. It was found that (1,1-diphenylhexyl)lithium and the living oligomers of methyl methacrylate and tert-butyl methacrylate are suitable initiators for the anionic polymerization of this monomer. The temperature should be below −30°C, even in the presence of LiCl, for the living polymerization to occur. When the polymerization proceeded at −60°C, in the presence of LiCl, with (1,1-diphenylhexyl)-lithium as initiator, the number-average molecular weight of the polymer was directly proportional to the monomer conversion and monodisperse poly(allyl methacrylate)s with high molecular weights were obtained. 1H-NMR and FT-IR indicated that the α CC double bond of the monomer was selectively polymerized and that the allyl group remained unreacted. The prepared poly(allyl methacrylate) is a functional polymer since it contains a reactive CC double bond on each repeating unit. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2901–2906, 1997  相似文献   

2.
The free radical polymerizations of higher n-alkyl methacrylates were not investigated in detail until now. In this work, the courses of the isothermal free radical bulk polymerization of dodecyl, quatrodecyl and hexadecyl methacrylates were investigated by differential scanning calorimetry. The effects of the polymerization temperature and the alkyl group length in the esters on the monomer conversions during polymerization were studied. It was found that the polymerization rate vs. time curves have two maxima. The free radical polymerizations of above-mentioned monomers proceed with slightly expressed gel effect at the temperatures below 90°C, at initiator concentration 1 mass% in monomer.  相似文献   

3.
Reversible addition‐fragmentation chain transfer (RAFT) miniemulsion polymerization of butyl methacrylate (BMA) and dodecafluoroheptyl methacrylate (DFMA) was carried out with 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) as chain transfer agent (CTA). Concentration effects of RAFT agent and initiator on kinetics and molecular weight were investigated. No obvious red oil layer (phase's separation) and coagulation was observed in the first stage of homopolymerization of BMA. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. At 75 °C, the monomer conversion could achieve above 96% in 3 h with [momomer]:[RAFT]:[KPS] = 620:4:1 (mole ratio). The results showed excellent controlled/living polymerization characteristics and a very fast polymerization rate. Furthermore, the synthesis of poly(BMA‐b‐DFMA) diblock copolymers with a regular structure (PDI < 1.30, PMMA calibration) was performed by adding the monomer of DFMA at the end of the RAFT miniemulsion polymerization of BMA. The success of diblock copolymerization was showed by the molecular weight curves shifting toward higher molar mass, recorded by gel permeation chromatography before and after block copolymerization. Compositions of block copolymers were further confirmed by 1H NMR, FTIR, and DSC analysis. The copolymers exhibited a phase‐separated morphology and possessed distinct glass transition temperatures associated with fluoropolymer PDFMA and PBMA domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1585–1594, 2007  相似文献   

4.
SG1-based amphiphilic macroinitiators were synthesized from oligoethylene glycol methyl ether methacrylate and 10 mol% acrylonitrile or styrene (as the controlling comonomer) to conduct the nitroxide mediated polymerization of bio-based methacrylic monomers (isobornyl methacrylate (IBOMA) and C13 alkyl methacrylate (C13MA)) in miniemulsion. The effect of the addition of surfactant (DOWFAX 8390), co-stabilizer (n-hexadecane) and different reaction temperatures (80, 90 and 100°C) on polymerization kinetics was studied. We found that the NMP of IBOMA/C13MA using amphiphilic macroalkoxyamines were most effective during miniemulsion polymerization (linear trend of Mn versus conversion and high latex stability) in presence of 2 wt% surfactant and 0.8 wt% co-stabilizer (relative to monomer) at 90°C. The effect of surfactant, co-stabilizer and temperature on particle size during the polymerization was studied and suggested a decrease in initial particle size with the addition of surfactant and co-stabilizer. Finally, the thermal properties of IBOMA/C13MA polymers, prepared by amphiphilic macroinitiators, were examined thoroughly, indicating a Tg in the range of −44°C < Tg < 109°C.  相似文献   

5.
To prepare high molecular weight (HMW) poly(methyl methacrylate) (PMMA)/silver microspheres, methyl methacrylate was suspension-polymerized in the presence of silver nanoparticles using a low-temperature initiator at different conditions. The rate of conversion was increased with increasing initiator concentration. In the case of adding silver nanoparticles, the rate of polymerization decreased slightly. High monomer conversion (about 95%) was obtained in spite of low polymerization temperature of 30 °C. Under controlled conditions, PMMA/silver microspheres with various viscosity-average degree of polymerization (6,000–37,000) were prepared.  相似文献   

6.
A novel phosphate monomer, Op‐(methacryloyloxymethyl)benzyl O,O‐diethyl phosphate (MDP) was synthesized by the reaction of diethyl phosphorochloridate with 1,4‐benzenedimethanol, followed by the reaction with methacryloyl chloride in the presence of triethylamine. The radical polymerization of MDP and copolymerization with methyl methacrylate were carried out in the presence of 2,2′‐azobisisobutyronitrile (3 mol %) in dimethylacetamide at 60 °C for 20 h to afford phosphate‐pendant polymers. The polymerization of glycidyl phenyl ether (GPE) was carried out with the phosphate‐pendant polymer as an initiator in the presence of ZnCl2. The polymerization did not proceed below 90 °C but rapidly proceeded above 90 °C to afford polyGPE. The phosphate‐pendant polymer served as a good thermally latent polymeric initiator. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3365–3370, 2001  相似文献   

7.
Differential scanning calorimetry (DSC) was used to measure the decomposition rates of four commercially used initiators, 2,2′-azobis(isobutyronitrile) 2,2′-azobis(2,4-dimethylvaleronitrile), dilauroyl peroxide and bis(4-t-butylcyclohexyl)peroxydicarbonate, in dynamic mode, while the courses of methyl methacrylate polymerization with the listed initiators at 65, 75 and 85°C were measured isothermally. From the DSC curves, the polymerization enthalpies, the overall reaction rate constants and the activation energies for the initial steady-state polymerization were calculated. It was found that the polymerization enthalpy and the kinetic parameters depended on the type of the initiator. An initiator with a shorter decomposition half-lifetime shifted the onset of the gel effect to a higher conversion, intensified it and decreased the average molar mass of the polymer.  相似文献   

8.
Iodine monobromide easily induces photopolymerization of methyl methacrylate (MMA) at 40°C under visible light. Initiator exponent and monomer exponent values were found to be 0.5 and 2, respectively, at low initiator concentrations, while the corresponding values at high initiator concentration conditions were zero and 3. The chain transfer constant of IBr at 40°C was found to be 13.0. Kinetic and other data indicate a radical polymerization mechanism involving complexation of monomer molecules with iodine monobromide prior to radical generation, and termination is believed to take place biomolecularly at low IBr concentrations and unimolecularly, involving reaction with the initiator, at high IBr concentrations (initiator termination).  相似文献   

9.
The paper describes the synthesis and characterization of comb polymers by a two-step chemo-enzymatic process. In the first step macromonomers bearing unsaturation at the chain end were prepared by lipase catalyzed ring-opening polymerization (ROP) of ε-caprolactone (CL) and 1,5-dioxepane-2-one (DXO). The ROP was carried out in bulk at 60 °C under anhydrous conditions using 2-hydroxyethyl methacrylate (HEMA) as the initiator. The DP of the macromonomers was controlled by regulating the monomer: HEMA molar feed concentration. The macromonomers were then homo- or co-polymerized in the second step with alkyl methacrylate monomers (methyl methacrylate or HEMA) using AIBN initiated free radical polymerization. Characterization of the polymers was done by 1H NMR, SEC and DSC techniques.  相似文献   

10.
In order to develop the seeded dispersion polymerization technique for the production of micron-sized monodispersed core/shell composite polymer particles the effect of polymerization temperature on the core/shell morphology was examined. Micron-sized monodispersed composite particles were produced by seeded dispersion polymerizations of styrene with about 1.4-μm-sized monodispersed poly(n-butyl methacrylate) (Pn-BMA) and poly(i-butyl methacrylate) (Pi-BMA) particles in a methanol/water (4/1, w/w) medium in the temperature range from 20 to 90 °C. The composite particles, PBMA/polystyrene (PS) (2/1, w/w), consisting of a PBMA core and a PS shell were produced with 2,2′-azobis(4-methoxy-2,4-dimethyl valeronitrile) initiator at 30 °C for Pn-BMA seed and with 2,2′-azobis(isobutyronitrile) initiator at 60 °C for Pi-BMA seed. The polymerization temperatures were a little above the glass-transition temperatures (T g) of both Pn-BMA (20 °C) and Pi-BMA (40 °C). On the other hand, when the seeded dispersion polymerizations were carried out at much higher temperatures than the T g of the seed polymers, composite particles having a polymeric oil-in-oil structure were produced. Received: 14 October 1998 Accepted in revised form: 2 June 1999  相似文献   

11.
The homopolymerization of N‐vinylcarbazole was performed with atom transfer radical polymerization (ATRP) with Cu(I)/Cu(II)/2,2′‐bipyridine (bpy) as the catalyst system at 90 °C in toluene. N‐2‐Bromoethyl carbazole was used as the initiator, and the optimized ratio of Cu(I) to Cu(II) was found to be 1/0.3. The resulting homopolymer, poly(N‐vinylcarbazole) (PVK), was formed after a monomer conversion of 76% in 20 h. The molecular weight as well as the polydispersity index (PDI) showed a linear relation with the conversion, which showed control over the polymerization. A semilogarithmic plot of the monomer conversion with time was linear, indicating the presence of constant active species throughout the polymerization. The initiator efficiency and the effect of the variation of the initiator concentration on the polymerization were studied. The effects of the addition of CuBr2, the variation of the catalyst concentration with respect to the initiator, and CuX (X = Br or Cl) on the kinetics of homopolymerization were determined. With Cu(0)/CuBr2/bpy as the catalyst, faster polymerization was observed. For a chain‐extension experiments, PVK (number‐average molecular weight = 1900; PDI = 1.24) was used as a macroinitiator for the ATRP of methyl methacrylate, and this resulted in the formation of a block copolymer that gave a monomodal curve in gel permeation chromatography. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1745–1757, 2006  相似文献   

12.
A study of the polymerization of methyl methacrylate initiated by the binary systems of some activated metals and organic halides has been made. It was found that the initiator activities of these systems were greatly dependent on the kind and the preparation or activation method of the metals (i.e., oxidation potential, surface area, and purity), and also on the kind of organic halides (i.e., bond-dissociation energy of their carbon–halogen bonds). From the kinetic studies of the polymerization at 60°C with the system reduced nickel–carbon tetrachloride, the rate of polymerization was found to be proportional to the monomer concentration and to the square root of concentration of both nickel and carbon tetrachloride at the lower concentration range of carbon tetrachloride, indicating that the system induced the radical polymerization. A similar conclusion was also obtained from the copolymerization with styrene with this system at 60°C, i.e., the resulting copolymer composition curve was in agreement with that obtained with azobisisobutyronitrile (AIBN). The apparent overall activation energy for the methyl methacrylate polymerization with this system was estimated to be 7.5 kcal/mole, which was considerably lower than that with AIBN. On the basis of the results obtained, an initiation mechanism for the polymerization with these initiator systems is presented and discussed.  相似文献   

13.
The emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4‐butylene glycol di(2‐bromoisobutyrate). The system was mediated by copper bromide/4,4′‐dinonyl‐2,2′‐bipyridyl and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low‐temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate–2‐ethylhexyl methacrylate–methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a nonlinear least‐square method were ~0.903 and ~0.930, respectively, at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1914–1925, 2006  相似文献   

14.
《European Polymer Journal》1986,22(10):783-786
Kinetic features of radical polymerizations of 1-vinylimidazole initiated by azoisobutyronitrile and by benzoyl peroxide have been investigated in several solvents and at several temperatures. Polymerizations initiated both by the azo compound and by the peroxide have abnormally low monomer exponents and abnormally high initiator exponents, features first noted by Bamford and Schofield and attributed by them to degradative addition of monomer. Polymerizations initiated by benzoyl peroxide appear to be further complicated by induced decomposition of the initiator; conversion vs time curves, especially for polymerizations in dimethylformamide and particularly at 80°C, show pronounced curvature. These curves can be approximately interpreted in terms of the Tobolsky theory of “dead-end” radical polymerization.  相似文献   

15.
Chain transfer constants (Ctr) for thiuram disulfide (TD) groups, included in the backbone of polydimethylsiloxane (PDMS) of different chain lengths, in methyl methacrylate (MMA) and styrene (St) were determined from measurements of the degree of polymerization. Two methods were used. The first consisted of using the initiation and transfer properties of the thiuram disulfides groups, and the second, of using a more efficient free radical initiator than TD groups, in which case the former behaves only as a transfer agent. In both the methods, the Ctr of TD was evaluated in bulk polymerization of MMA at 60, 70, 80, and 90°C. Using the first method, the Ctr of TD was measured also in solution polymerization of MMA in toluene at 100°C and, with the second one, in bulk polymerization of styrene at 60, 80, and 90°C. PDMS-based macrothiuram disulfide (macroiniferter) behaves as an “azeotropic” transfer agent for MMA and styrene at 125°C and 110°C, respectively. © 1994 John Wiley & Sons, Inc.  相似文献   

16.
The initial stages of the free radical polymerization of diethylene glycol bis(allyl carbonate) at temperatures of 35–65°C have been studied. The polymer is unsaturated and cyclization to give a 16-membered ring occurs only to a small extent. The kinetic order with respect to the initiator, di-sec-butyl peroxydicarbonate, has an average value of 0.79; the order increases slightly with peroxydicarbonate concentration over the range 0.018–0.22M. The molecular weight of the polymer isolated after 3% polymerization is close to 19,000. It shows no significant dependence on initiator concentration or on temperature. The dominant feature of the bulk polymerization, as in free radical polymerization of the other allyl and diallyl monomers, is degradative chain transfer in which the growing polymer radical abstracts a hydrogen atom from a monomer unit to give a relatively unreactive allylic radical. The dependence of rate on initiator concentration is rationalized if some of these allylic radicals are able to reinitiate polymerization. The transfer constant to monomer is 0.014 at 50°C, assuming that the main termination step involves mutual termination of allylic radicals. Carbon tetrachloride is an active transfer agent with a transfer constant of 0.20 ± 0.04 at 50°C. Toluene, which is less active, has a transfer constant of 0.0064 at 50°C and also retards the polymerization. Some kinetic studies have been made with other initiators, including di-2-methyl-pentanoyl peroxide which initiates polymerization at temperatures as low as 13°C.  相似文献   

17.
This study aimed at polymerization of methyl methacrylate with novel catalysts in the atom transfer radical polymerization (ATRP) condition at 90 °C. This was accomplished using CuBr/N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (CuBr–AEAPTMS) as a homogeneous catalyst and one time with CuBr@AEAPTMS/SBA-15 as a heterogeneous catalyst. Catalysts were characterized using TGA, FT-IR, and UV–Vis spectroscopy. The structural analysis of the polymer was carried out by 13C NMR spectroscopy and GPC. Three characteristic parts of polymer produced by ATRP method including the initiator, monomer units, and end group was shown in 13C NMR spectra. In addition, the presence of C–Br unit showed that the polymerization process is alive. The 1H NMR analysis was used for kinetic investigation of methyl methacrylate polymerization with homogeneous and heterogeneous catalysts that showed high monomer conversion (98 and 90% after 35 min, respectively) and good control of molecular weight with a dispersity (Р= 1.5–1.7). In addition, the plot of ln ([monomer]0/[monomer] t ) versus time gave linear relationships indicating a constant concentration of the propagating species throughout the polymerization. Finally, the results of the polymerization using heterogeneous catalyst compared with homogeneous catalyst revealed that it was according to ATRP method.  相似文献   

18.
The redox system composed of potassium bromate and thiomalic acid was used to initiate the aqueous polymerization of methyl methacrylate under nitrogen atmosphere at 35 ± 0.2°C. The initial rates of polymerization have been found to be approximately proportional to the first power of the initiator concentration in the range of 2.5 to 6.0 ± 10?3 M and to the first power (1.15) of monomer concentration in the range of 3.72 to 11.16 ± 10?2 M The overall rate was independent of activator concentration, approaching a maximum at 10 × 10?3 M. The overall energy of activation was found to be 8.80 kcal/mol. The initial rate and the maximum conversion attained a maximum value at 35°C in the temperature range of 20 to 45°C.  相似文献   

19.
The degradation of poly(hydroxyethyl methacrylate), PHEMA obtained by γ -radiation induced polymerization of HEMA in aqueous solution, was studied. The polymer was a gel type and insoluble in common organic solvents. The DSC thermogram of the polymer gave a Tg value at 88.2°C and an endothermic peak showed further polymerization or crosslinking at 110–160°C. The degradation observed in TGA was a depolymerization type. However, the FT-IR of TGA fragments showed no monomer, which was degraded further. The degradation of monomer was studied by the GC-MS method. Similar results were also observed.  相似文献   

20.
Anionic polymerization of lauryl methacrylate (LMA) with 1,1‐diphenylhexyl lithium in tetrahydrofuran (THF) at ?40 °C resulted in a multimodal and broad molecular weight distribution (MWD) with poor initiator efficiency. In the presence of additives such as dilithium salt of triethylene glycol (G3Li2), LiCl, and LiClO4, the polymerization resulted in polymers with a narrow MWD (≤ 1.10). Diblock copolymers of methyl methacrylate (MMA) and LMA were synthesized by anionic polymerization using DPHLi as initiator in THF at ?40 °C with the sequential addition of monomers. The molecular weight distribution of the polymers was narrow and without homopolymer contamination when LMA was added to living PMMA chain ends. Diblock copolymers with broad/bimodal MWD were obtained with a reverse‐sequence monomer addition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 875–882, 2004  相似文献   

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