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1.
在微波辐照下,以过硫酸钾(KPS)为引发剂,丙酮水溶液(质量比1∶ 1)为分散介质,进行了苯乙烯(ST)和其它共聚单体:甲基丙烯酸甲酯(MMA)、甲基丙烯酸丁酯(BMA)、丙烯酸乙酯(EA)及顺丁烯二酸酐(BDA)的无皂乳液聚合,得到了稳定的纳米胶乳粒子.讨论了共聚单体的种类和浓度对粒子水化半径的影响.增加配方中亲水性单体含量,使引发反应中引发剂的消耗量增加,粒子表面电荷密度增大,同时亲水性增加,油水界面张力减小,粒子变得稳定,有利于小粒子的生成.粒子的大小随亲水性单体的含量呈曲线关系,曲线上有最低点.  相似文献   

2.
Sn(0)‐mediated single electron transfer‐living radical polymerization (SET‐LRP) of acrylonitrile (AN) with carbon tetrachloride (CCl4) as initiator and hexamethylenetetramine (HMTA) as ligand in N, N‐dimethylformamide (DMF) was studied. The polymerization obeyed first order kinetic. The molecular weight of polyacrylonitrile (PAN) increased linearly with monomer conversion and PAN exhibited narrow molecular weight distributions. Increasing the content of Sn(0) resulted in an increase in the molecular weight and the molecular weight distribution. Effects of ligand and initiator were also investigated. The block copolymer PAN‐b‐polymethyl methacrylate with molecular weight at 126,130 and polydispersity at 1.36 was successfully obtained. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

3.
To obtain new polymer latices based on sugar derivative, batch emulsion copolymerizations of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (3‐MDG) and n‐butyl acrylate (BA) were carried out at 70 °C, with potassium persulfate as the initiator. 3‐MDG polymerizes faster than BA because of its higher reactivity ratio, r(3‐MDG) = 1.94 versus r(BA) = 0.54. The effect of the initial monomer composition on the polymerization rate and the thermal properties of the end copolymers was investigated. The overall rate of polymerization increases by enhancing the sugar content in the initial monomer composition. The glass‐transition temperature is linearly related to the sugar content in the copolymer. The influence of the type of surfactant showed that the particle size increases by changing from ionic to nonionic surfactant. Furthermore, the effect of the added acrylic acid (AA) on the rheological properties suggests that the sugar latices exhibit different non‐Newtonian flows depending on the pH of the latex and on the AA concentration on the particle surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 788–803, 2003  相似文献   

4.
Abstract

Atom transfer radical polymerization (ATRP) of styrene (St) proceeded using 5‐chloromethyl‐2‐hydroxy‐benzaldehyde as initiator, CuCl as catalyst, and N,N,N′,N′,N′‐pentamethyldiethyltriamine (PMDETA) as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (M n/M w ranges from 1.25 to 1.50). The end structure of PSt was analyzed by 1H‐NMR, and PSt initiated MMA to form block copolymer (PSt‐b‐PMMA), which also proved that the polymerization could be controlled. The effects of reaction temperature and monomer to initiator mole ratio on the polymerization displayed living character were discussed.  相似文献   

5.
Soap‐free poly(methyl methacrylate‐ethyl acrylate‐acrylic acid or methacrylic acid) [P(MMA‐EA‐AA or MAA)] particles with narrow size distribution were synthesized by seeded emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA) and acrylic acid (AA) or methacrylic acid (MAA), and the influences of the mass ratio of core/shell monomers used in the two stages of polymerization ([C/S]w) and initiator amount on polymerization, particle size and its distribution were investigated by using different monomer addition modes. Results showed that when the batch swelling method was used, the monomer conversion was more than 96.0% and particle size distribution was narrow, and the particle size increased first and then remained almost unchanged at around 600 nm with the [C/S]w decreased. When the drop‐wise addition method was used, the monomer conversion decreased slightly with [C/S]w decreased, and large particles more than 750 nm in diameter can be obtained; with the initiator amount increased, the particle size decreased and the monomer conversion had a trend to increase; the particle size distribution was broader and the number of new particles was more in the AA system than in the MAA system; but the AA system was more stable than the MAA system at both low and high initiator amount. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

6.
The copolymerization of a highly fluorinated cyclic monomer, octafluorocyclopentene (OFCPE, M1), with ethyl vinyl ether (EVE, M2) was investigated with a radical initiator in bulk. Despite the poor homopolymerizability of each monomer, the copolymerization proceeded successfully, and the molecular weights of the copolymers reached up to more than 10,000. Incorporation of the OFCPE units into the copolymer led to an increase in the glass‐transition point. The copolymer composition was determined from 1H NMR spectra and elemental analysis data. The molar fraction of the OFCPE unit in the copolymer increased and approached but did not exceed 0.5. The monomer reactivity ratios were estimated by the Yamada–Itahashi–Otsu nonlinear least‐squares procedure as r1,OFCPE = ?0.008 ± 0.010 and r2,EVE = 0.192 ± 0.015. The reactivity ratios clearly suggest that the copolymerization proceeds alternatively in the case of an excessive feed of OFCPE. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1151–1156, 2002  相似文献   

7.

A new methacrylic monomer, 4‐nitro‐3‐methylphenyl methacrylate (NMPM) was prepared by reacting 4‐nitro‐3‐methyl phenol dissolved in methyl ethyl ketone (MEK) in the presence of triethylamine as a catalyst. Copolymerization of NMPM with methyl methacrylate (MMA) has been carried out in methyl ethyl ketone (MEK) by free radical solution polymerization at 70±1°C utilizing benzoyl peroxide (BPO) as initiator. Poly (NMPM‐co‐MMA) copolymers were characterized by FT‐IR, 1H‐NMR and 13C‐NMR spectroscopy. The molecular weights (Mw and Mn) and polydispersity indices (Mw/Mn) of the polymers were determined using a gel permeation chromatograph. The glass transition temperatures (Tg) of the copolymers were determined by a differential scanning calorimeter, showing that Tg increases with MMA content in the copolymer. Thermogravimetric analysis of the polymers, performed under nitrogen, shows that the stability of the copolymer increases with an increase in NMPM content. The solubility of the polymers was tested in various polar and non‐polar solvents. Copolymer compositions were determined by 1H‐NMR spectroscopy by comparing the integral peak heights of well separated aromatic and aliphatic proton peaks. The monomer reactivity ratios were determined by the Fineman‐Ross (r1 =7.090:r2=0.854), Kelen‐Tudos (r1=7.693: r2=0.852) and extended Kelen‐Tudos methods (r1=7.550: r2= 0.856).  相似文献   

8.
A functionalized cyclic carbonate monomer containing a cinnamate moiety, 5‐methyl‐5‐cinnamoyloxymethyl‐1,3‐dioxan‐2‐one (MC), was prepared for the first time with 1,1,1‐tri(hydroxymethyl) ethane as a starting material. Subsequent polymerization of the new cyclic carbonate and its copolymerization with L ‐lactide (LA) were successfully performed with diethyl zinc (ZnEt2) as initiator/catalyst. NMR was used for microstructure identification of the obtained monomer and copolymers. Differential scanning calorimetry (DSC) was used to characterize the functionalized poly(ester‐carbonate). The results indicated that the copolymers displayed a single glass transition temperature (Tg) and the Tg decreased with increasing carbonate content and followed the Fox equation, indicative of a random microstructure of the copolymer. The photo‐crosslinking of the cinnamate‐carrying copolymer was also demonstrated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 161–169, 2009  相似文献   

9.
Novel poly(ester carbonate)s were synthesized by the ring‐opening polymerization of L ‐lactide and functionalized carbonate monomer 9‐phenyl‐2,4,8,10‐tetraoxaspiro[5,5]undecan‐3‐one derived from pentaerythritol with diethyl zinc as an initiator. 1H NMR analysis revealed that the carbonate content in the copolymer was almost equal to that in the feed. DSC results indicated that Tg of the copolymer increased with increasing carbonate content in the copolymer. Moreover, the protecting benzylidene groups in the copolymer poly(L ‐lactide‐co‐9‐phenyl‐2,4,8,10‐tetraoxaspiro[5,5]undecan‐3‐one) were removed by hydrogenation with palladium hydroxide on activated charcoal as a catalyst to give a functional copolymer, poly(L ‐lactide‐co‐2,2‐dihydroxylmethyl‐propylene carbonate), containing pendant primary hydroxyl groups. Complete deprotection was confirmed by 1H NMR and FTIR spectroscopy. The in vitro degradation rate of the deprotected copolymers was faster than that of the protected copolymers in the presence of proteinase K. The cell morphology and viability on a copolymer film evaluated with ECV‐304 cells showed that poly(ester carbonate)s derived from pentaerythritol are good biocompatible materials suitable for biomedical applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45:1737 –1745, 2007  相似文献   

10.
高浓度窄分布无皂高分子纳米粒子胶乳的制备   总被引:17,自引:0,他引:17  
在微波辐照和丙酮存在下,进行了苯乙烯(ST)和甲基丙烯酸甲酯(MMA)的无皂乳液聚合.当丙酮的含量在50%以下时,可以得到稳定的窄分布的纳米粒子胶乳.丙酮的含量由0增加到50%,粒子的平均水化半径由278nm降低到35.4nm.在一定的浓度范围内,固定引发剂过硫酸钾(KPS)的用量,则粒子的平均水化半径与单体的浓度成正比;当单体浓度一定时,随着引发剂浓度的增加,粒子平均水化半径从25nm减少到22nm然后又增大.考虑到引发剂既是粒子表面电荷的来源,又增加了体系的离子强度,在粒子形成过程中,起着稳定和絮凝的双重作用,我们得到了一个简单的公式用以描述粒子的平均水化半径<R  相似文献   

11.
Microwave assisted free radical copolymerization of diisopropyl fumarate (DIPF) and benzyl acrylate (BzA) with different copolymer compositions was performed using benzoyl peroxide as initiator. The effect of the reaction conditions on the macromolecular characteristics, monomer reactivity ratio and copolymer properties were studied. The monomer conversion and average molecular weights increase with the content of BzA units in the copolymer. The copolymers were characterized by IR, 1H and 13C-NMR spectroscopies and the molecular weights were analyzed with size exclusion chromatography (SEC). The reactivity ratios obtained from an extended Kelen-Tüdös method under microwave irradiations are a factor which is double than those obtained by thermal copolymerization. The product r1r2 = 0.152 suggests a preference of both propagating macroradicals toward consecutive homopolymerization. The hydrodynamic and polydispersity size were measured in ethylacetate, tetrahydrofuran and methylethylketone with a quasi-elastic light scattering (QELS) technique showing that the quality of the solvents increases in the order: EA < THF < MEK.  相似文献   

12.

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d6 (DMSO‐d6) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line 1H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the 1H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of kp /kt 0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.  相似文献   

13.
The grafting of the methyl methacrylate (MMA) monomer onto natural rubber (NR) was carried out by supercritical carbon dioxide (scCO2) swelling polymerization with benzoyl peroxide (BPO) as an initiator. Fourier transform–infrared spectroscopy (FT–IR) was used to confirm the formation of graft copolymers with the characteristic bands of symmetric C?O and C? O? C stretching vibrations at 1728 cm?1 and 1147 cm?1, respectively. The effects of the rubber‐to‐monomer ratio, amount of initiator, reaction time, and pressure on the monomer grafting level (GL) and grafting efficiency (GE) were investigated, and the optimum conditions for the preparation of NR‐g‐MMA were found to be 70:30 of the rubber‐to‐monomer ratio, 1.2% of the initiator content, and the reaction pressure of 23 MPa for 6 h. The thermal behavior of the NR and the different NR/MMA molar ratio grafted copolymer samples was studied by differential scanning calorimetry (DSC). The observed glass transition temperature (Tg) was consistent with the GL. The tensile strength, modulus of elasticity, elongation at break, hardness, and oil resistance of graft copolymers were determined and compared with the values of NR and that of polymerization products prepared in traditional toluene solution. The results showed that the tensile strength, modulus of elasticity, hardness and oil resistance were greatly improved after modification in scCO2. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.

Radical copolymerization reaction of vinyl acetate (VA) and methyl acrylate (MA) was performed in a solution of benzene‐d6 using benzoyl peroxide (BPO) as the initiator at 60°C. Kinetic studies of this copolymerization reaction were investigated by on‐line 1H‐NMR spectroscopy. Individual monomer conversions vs. reaction time, which was followed by this technique, were used to calculate the overall monomer conversion, as well as the monomer mixture and the copolymer compositions as a function of time. Monomer reactivity ratios were calculated by various linear and nonlinear terminal models and also by simplified penultimate model with r 2(VA)=0 at low and medium/high conversions. Overall rate coefficient of copolymerization was calculated from the overall monomer conversion vs. time data and k p  . k t ?0.5 was then estimated. It was observed that k p  . k t ?0.5 increases with increasing the mole fraction of MA in the initial feed, indicating the increase in the polymerization rate with increasing MA concentration in the initial monomer mixture. The effect of mole fraction of MA in the initial monomer mixture on the drifts in the monomer mixture and copolymer compositions with reaction progress was also evaluated experimentally and theoretically.  相似文献   

15.
The new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxy‐ carbonyl)aminobenzenesulfonamide (MPBAS) (M1) is synthesized using sulfadiazine as parent compound. It could be homopolymerized and copolymerized with N‐phenyl maleimide (NPMI) (M2) by radical mechanism using AIBN as initiator at 60 °C in dimethylformamide. The new monomer MPBAS and polymers were identified by IR, element analysis and 1H NMR in detail. The monomer reactivity ratios in copolymerization were determined by YBR method, and r1 (MPBAS) = 2.39 ± 0.05, r2 (NPMI) = 0.33 ± 0.02. In the presence of ammonium formate, benzyloxycarbonyl groups could be broken fluently from MPBAS segments of copolymer by catalytic transfer hydrogenation, and the copolymer with sulfadiazine side groups are recovered. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2548–2554, 2000  相似文献   

16.
The newly synthesized 1‐TiCl (C3 symmetric) and 2‐TiCl (Cs symmetric) precatalysts in combination with MAO polymerized ethylene, cyclic olefins, and copolymerized ethylene/norbornene in good yields. The catalyst with C3 symmetry exhibits moderate catalytic activity and efficient norbornene incorporation for E/NBE copolymerization in the presence of MAO [activity = 360 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL, 10 min], affording poly(ethylene‐co‐NBE)s with high norbornene contents (42.0%) and the Cs symmetric catalyst showed an activity of 420 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL affording poly(ethylene‐co‐NBE)s with 33.0% norbornene content. The effect of monomer concentration at ambient temperature and constant Al/Ti ratio for the homo and copolymerization was studied in a detailed manner. We found that apart from the electronic environment around the metal center the steric environment provided by the symmetry of the catalyst systems has a considerable influence on the percentage of norbornene content of the copolymer obtained. We also found that with a given catalyst a variable clearly influencing the copolymer microstructure, hence also the copolymer properties, is the monomer concentration at a given feed ratio. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 444–452, 2008  相似文献   

17.
The synthesis, micelle formation, and bulk properties of semifluorinated amphiphilic poly(ethylene glycol)‐b‐poly(pentafluorostyrene)‐g‐cubic polyhedral oligomeric silsesquioxane (PEG‐b‐PPFS‐g‐POSS) hybrid copolymers is reported. The synthesis of amphiphilic PEG‐b‐PPFS block copolymers are achieved using atom transfer radical polymerization (ATRP) at 100 °C in trifluorotoluene using modified poly(ethylene glycol) as a macroinitiator. Subsequently, a proportion of the reactive para‐F functionality on the pentafluorostyrene units was replaced with aminopropylisobutyl POSS through aromatic nucleophilic substitution reactions. The products were fully characterized by 1H‐NMR and GPC. The products, PEG‐b‐PPFS and PEG‐b‐PPFS‐g‐POSS, were subsequently self‐assembled in aqueous solutions to form micellar structures. The critical micelle concentrations (cmc) were estimated using two different techniques: fluorescence spectroscopy and dynamic light scattering (DLS). The cmc was found to decrease concomitantly with the number of POSS particles grafted per copolymer chain. The hydrodynamic particle sizes (Rh) of the micelles, calculated from DLS data, increase as the number of POSS molecules grafted per copolymer chain increases. For example, Rh increased from ~60 nm for PEG‐b‐PPFS to ~80 nm for PEG‐b‐PPFS‐g‐POSS25 (25 is the average number of POSS particles grafted copolymer chain). Static light scattering (SLS) data confirm that the formation of larger micelles by higher POSS containing copolymers results from higher aggregation numbers (Nagg), caused by increased hydrophobicity. The Rg/Rh values, where Rg is the radius of gyration calculated from SLS data, are consistent with a spherical particle model having a core‐shell structure. Thermal characterization by differential scanning calorimetry (DSC) reveals that the grafted POSS acts as a plasticizer; the glass transition temperature (Tg) of the PPFS block in the copolymer decreases significantly with increasing POSS content. Finally, the rhombohedral crystal structure of POSS in PEG‐b‐PPFS‐g‐POSS was verified by wide angle X‐ray diffraction measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 152–163, 2010  相似文献   

18.

Free radical copolymerization of N‐vinyl‐2‐pyrrolidone with 2‐ethoxyethyl methacrylates was carried out with 2,2′‐azobisisobutyronotrile as an initiator in 1,4‐dioxane. The resulting copolymer was characterized by FTIR, H1‐NMR and C13‐NMR spectroscopic techniques thermal properties of copolymer were determined by DSC and TGA. The reactivity ratios of the monomers were computed by the Fineman‐Rose (F‐R), Kelen‐Tudos (K‐T) and extended Kelen‐Tudos (EK‐T) method at lower conversion, using the data obtained from both FTIR and elemental analysis studies; the results are in good agreement with each other. The average reactivity ratio, Alfrey‐Price Q and e values were found to be r 1=0.769, r 2=0.266 and Q 1=0.0859, e 1=0.4508, respectively for NVP/EOEMA copolymer. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on obtained reactivity ratio. The number average molecular weight and polydispersity were determined by GPC.  相似文献   

19.
Abstract

The free radical copolymerization of N‐(4‐carboxyphenyl)maleimide (CPMI) (M1) with hydropropyl methacrylate (HPMA) (M2) was carried out with 2,2′‐azobis(isobutyronitrile) (AIBN) as an initiator in ethyl acetate at 75°C. The composition of copolymer prepared at low conversion was determined by elemental analysis. The monomer reactivity ratios were found to be r 1?=?0.31 and r 2?=?1.11 as determined by the YBR equation. The number‐average molecular weight and polydispersity were determined by gel permeation chromatography (GPC). Furthermore, the solvent effect on this copolymerization system was also investigated. The resulting copolymer was characterized by FTIR and 1H‐NMR spectroscopy. The thermal stability of copolymers was determined by thermogravimetric analysis (TGA). It was found that the copolymer shows step‐by‐step degradation, the initial decomposition temperature (T i), and final decomposition temperature (T f) increased with increasing the component of CPMI in copolymer.  相似文献   

20.
Poly(butadiene‐co‐acrylonitrile) (NBR) nanoparticles were synthesized in a semibatch emulsion polymerization system using Gemini surfactant trimethylene‐1,3‐bis (dodecyldimethylammonium bromide), referred to as Gemini‐type surfactant (GS) 12‐3‐12, as the emulsifier. In this polymerization system, an enhanced decomposition rate of initiator ammonium persulfate was achieved even under the low temperature of 50 °C which is attributed to the acidic initiation environment provided using GS 12‐3‐12. The microstructure and copolymer composition of the polymer nanoparticles were characterized by Fourier‐transformed infrared and 1H nuclear magnetic resonance spectroscopy. The effects of the surfactant concentration on the particle size, zeta potential, polymerization conversion, copolymer composition, molecular weight, and glass transition temperature (Tg) were investigated. It was found that the particle diameter can be controlled by the surfactant concentration and monomer/water ratio and particle sizes below 20 nm can be reached. The obtained latex particles exhibit a spherical morphology. A kinetic study of the copolymerization reaction was carried out, which indicated that an azeotropic composition was produced. The synthesized fine NBR nanoparticles can be employed as the nano substrate for a subsequent hydrogenation process so as to overcome the challenge involved in the field of latex hydrogenation of polymers, which can be found in a related report: Organic Solvent‐Free Catalytic Hydrogenation of Diene‐based Polymer Nanoparticles in Latex Form: Part II. Kinetic Analysis and Mechanistic Study. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

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