苯乙烯/丙烯酸丁酯反向原子转移自由基乳液聚合的合成与表征

采用Tween 80为乳化剂,FeCl3.6H2O/EDTA/AIBN为催化引发体系,在乳液体系中对苯乙烯、丙烯酸丁酯进行反向原子转移自由基(RATRP)共聚合。考察了原料加入方式、过渡金属催化剂浓度及反应温度对RATRP乳液聚合影响。结果表明,得到聚合物的分子量与单体转化率呈线性增长,分子量分布较窄(PDI为1.40)的无规共聚物。借助于凝胶渗透色谱(GPC)和红外光谱仪(IR)对RATRP共聚乳液进行表征,表明加入催化体系进行RA-TRP乳液聚合是"活性"可控聚合。     

Properties of poly(n‐butyl methacrylate) prepared by reverse atom transfer radical polymerization in an aqueous dispersed system

Reverse atom transfer radical polymerization (ATRP) of n‐butyl methacrylate (BMA) in waterborne media using Cu(II) complexes with azo initiators (i.e., reverse ATRP) was conducted. The influence of several factors, such as surfactant, catalyst, and reaction time, on the stability of the emulsion, the particle size, the morphology of the emulsion particles, and the control of the polymerization was investigated. The results showed great differences between ATRP and conventional emulsion polymerization, especially the nucleation mechanism and the kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1542–1547, 2003     

原子转移自由基乳液聚合研究进展

原子转移自由基聚合(ATRP)作为一种可控/活性聚合方法,可对聚合物结构进行精确控制;乳液聚合以水作为分散介质,具有经济、环保等特点。因此,乳液ATRP结合了两者的优点,具有工业化生产的潜力。首先分析了影响乳液ATRP的各种因素,然后综述了正向ATRP、RATRP(反向ATRP)、SR&NI ATRP(正向/反向同时进行的ATRP)和AGET ATRP(电子转移活化剂ATRP)等机制及研究进展,最后对乳液ATRP的发展方向进行了展望。     

Reverse atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system

Reverse atom transfer radical polymerization (ATRP) of n‐butyl methacrylate (BMA) was conducted in an aqueous dispersed system. The influence of the surfactant, catalyst, reaction time and temperature on the colloidal stability and the control of polymerization was investigated. As a result, using an azo initiator (AIBN), a non‐ionic surfactant (Brij 35) and a hydrophobic ligand (dNbpy) to complex a copper halide, polymers with predetermined molecular weight and low polydispersity were obtained as stable latexes. Copyright © 2004 Society of Chemical Industry     

N-(n-Alkyl)-2-pyridinemethanimine mediated atom transfer radical polymerization of lauryl methacrylate: Effect of length of alkyl group

The article describes the polymerization of lauryl methacrylate (LMA) using Cu(I)Br as catalyst for atom transfer radical polymerization in conjunction with N-(n-propyl) [PPMI]/(n-hexyl) [HPMI]/(n-octyl) [OPMI]-2-pyridinemethanimine as complex ligands. The polymerization of LMA was investigated in bulk and solution (toluene as solvent) using Cu(I)Br as catalyst, N-(n-alkyl)-2-pyridinemethanimine as ligands and ethyl-2-bromo isobutyrate (EBiB) as initiator. The ratio of LMA : CuBr : Ligand : EBiB was kept constant in all the polymerizations. In bulk polymerization, the solubility of the catalyst complex increased with increasing the length of alkyl chain on the ligand from propyl to octyl and also gave polymers with narrow molecular weight distribution. The PDI was further narrowed by using OPMI as ligand and toluene was used as solvent. The kinetics of polymerization was also analyzed and it clearly shows that % conversion increased with time. Increase in molecular weight with % conversion without affecting PDI clearly show that the system is living and living nature can be controlled by increasing the length of alkyl group. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rapid ambient temperature atom transfer radical polymerization of tert‐butyl acrylate

BACKGROUND: Atom transfer radical polymerization (ATRP) is considered to be one of the better and easier synthetic tools for the preparation of polymers with controlled molecular weights and polydispersities. Ambient temperature ATRP of tert‐butyl acrylate (tBA) was studied in a detailed manner with ethyl 2‐bromoisobutyrate (EBrB) and tert‐butyl 2‐bromoisobutyrate (tBuBrB) as the initiators for three different degrees of polymerization. RESULTS: Details pertaining to the kinetics of polymerization using different initiators are reported. It is observed that dimethylsulfoxide accelerates the polymerization at room temperature. The use of Cu(II) as the deactivator produces very narrow dispersity polymers. A diblock copolymer, poly(tert‐butyl acrylate)‐block‐poly(methyl methacrylate), was synthesized from the poly(tBA) macroinitiator demonstrating the controlled living nature of the polymerizations. CONCLUSIONS: The rate of polymerization is more rapid with a secondary initiator (ethyl 2‐bromopropionate) compared to the tertiary initiators EBrB and tBuBrB. From the detailed kinetic results it is observed that tris(2‐dimethylaminoethyl)amine was a better ligand compared to tris(2‐aminoethyl)amine in terms of achieving controlled polymerization. Copyright © 2007 Society of Chemical Industry     

原子转移自由基法合成乙丙橡胶接枝物中的热聚合研究

采用原子转移自由基聚合法(ATRP)合成了三元乙丙橡胶与苯乙烯的接枝共聚物(EPDM-g-St),动力学研究表明聚合过程为“活性”聚合。在接枝聚合过程中发现了明显的苯乙烯热聚合现象。对接枝聚合中得到的均聚苯乙烯进行表征的结果表明,苯乙烯在ATRP接枝体系中的热聚合过程在一定程度上受到ATRP机理的控制;升高温度和延长反应时间使得热聚合更为显著。     

反向原子转移自由基聚合研究进展

原子转移自由基聚合是一种新兴的活性/可控聚合方法,而反向ATRP又是在传统ATRP方法基础上衍生出的一种摒弃ATRP方法中一些缺点的新生活性聚合方法。文中介绍了反向ATRP的建立原理,从单体、引发剂、催化体系等方面综述了反向ATRP的研究进展。     

Radical polymerization of butyl acrylate and random copolymerization of styrene and butyl acrylate and styrene and methyl methacrylate mediated by monospiro- and dispiropiperidinyl-N-oxyl radicals

Radical polymerization of butyl acrylate (BA) and random copolymerizations of styrene (St) and BA and St and methyl methacrylate (MMA) in the presence of 7-aza-15-hydroxydispiro[5.1.5.3]hexadecane-7-yloxyl (1) and 1-aza-2,2-dimethyl-4-hydroxyspiro[5.6]dodecane-1-yloxyl (2) were carried out. Radical polymerization of BA at 120 °C in the presence of 1 gave poly(BA) with M_n=20200 and M_w/M_n=1.30 at 23% conversion. The termination of polymerization observed around ∼20% conversion was solved to a certain extent by an addition of small amounts of dicumyl peroxide, and poly(BA) with M_n=37400 and M_w/M_n=1.33 was obtained in 46% yield. Random copolymerizations of St and BA and St and MMA in the presence of 1 and 2 at 80 °C gave the corresponding random copolymers with narrow polydispersities of 1.12-1.38 at the molar fraction above 0.30 of St in feed. The kinetic study for the NO-C bond homolysis of the corresponding alkoxyamines prepared from 1 and 2 were carried out, and evaluation of the preexponential factors (A_act) and the activation parameters (E_act) showed that the steric factors of the nitroxides are reflected mainly on E_act.     

Preparation of nanoclay‐dispersed polystyrene nanofibers via atom transfer radical polymerization and electrospinning

In this study, clay‐dispersed polystyrene (PS) nanocomposites were prepared with the in situ atom transfer radical polymerization method and were subsequently electrospun to form nanofibers 450–650 nm in diameter. The polymer chains extracted from the clay‐dispersed nanofibers exhibited a narrow range of molecular weight distribution. Thermogravimetric analysis (TGA) confirmed a higher thermal stability of the resulting nanocomposites compared to PS. The effect of the weight ratio of montmorillonite on the thermal properties of the nanocomposites was also studied by TGA. Differential scanning calorimetry revealed that the addition of the nanoclay increased the glass‐transition temperature. Moreover, degradation of the bromide chain‐end functionality took place at low temperatures. Scanning electron microscopy showed that the average diameter of the fibers was around 500 nm. The dispersion of clay layers was also evaluated by Al atoms in the PS matrix with the energy‐dispersive X‐ray detection technique. Transmission electron microscopy confirmed the exfoliation of the nanoclay within the matrix. However, the clay layers were oriented along the nanofiber axis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

用电子转移活化再生原子转移自由基聚合制备含氟丙烯酸酯共聚物及其表征

在水分散介质中,以非离子乳化剂Tween-80和十二烷基磺酸钠作为复合乳化剂,通过电子转移活化再生原子转移自由基聚合,采用ab二次引发乳液聚合法制备了含氟丙烯酸酯三元共聚物,用傅里叶变换红外光谱、拉曼光谱、核磁共振波谱及凝胶渗透色谱等对其结构、组成和相对分子质量及其分布进行了表征。结果表明,含氟丙烯酸酯聚合物的分子结构及组成可控,转化率高达95%,相对分子质量分布较窄。优选憎水性配体和惰性乳化剂可提高反应的可控性。     

Uniform star‐polystyrene nanoparticles prepared by emulsion atom transfer radical polymerization

Pentaerythritol (PT) was converted into four‐arm initiator pentaerythritol tetrakis(2‐chloropropionyl) (PT‐Cl) via reaction with 2‐chloropropionyl chloride. Uniform (monodisperse) star‐polystyrene nanoparticles were prepared by emulsion atom transfer radical polymerization of styrene, using PT‐Cl/CuCl/bpy (bpy is 2,2′‐dipyridyl) as the initiating system. The structures of PT‐Cl and polymer were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The morphology, size and size distribution of the star‐polystyrene nanoparticles were characterized by transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy. It was found that the average diameters of star‐polystyrene nanoparticles were smaller than 100 nm (30–90 nm) and monodisperse; moreover, the particle size could be controlled by the monomer/initiator ratio and the surfactant concentration. The average hydrodynamic diameter (D_h) of the nanoparticles increased gradually on increasing the ratio of styrene to PT‐Cl and decreased on enhancing the surfactant concentration or increasing the catalyst concentration. Copyright © 2011 Society of Chemical Industry     

New fluorous bipyridine ligands for copper‐catalyzed atom transfer radical polymerization of methyl methacrylate in the thermomorphic mode

The atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) is often carried out under homogeneous conditions, so the residual metal catalyst in the polymer often influences the quality of the polymer and causes environmental pollution in the long run. Novel CuBr/4,4′‐bis(R_fCH₂OCH₂)‐2,2′‐bpy complexes (R_f = n‐C₉F₁₉, n‐C₁₀F₂₁, or n‐C₁₁F₂₃; 2,2′‐bpy = 2,2′‐bipyridine) are insoluble in toluene at room temperature yet readily dissolve in toluene at elevated temperatures to form homogeneous phases for use as catalysts in the ATRP reaction, and the Cu complexes precipitate again upon cooling. The CuBr/4,4′‐bis(n‐C₉F₁₉CH₂OCH₂)‐2,2′‐bpy system produced the best results (e.g., polydispersity index by gel permeation chromatography = 1.26–1.41), in that the residual Cu content in the polymer was as low as 19.3 ppm when the ATRP of MMA was carried out in the thermomorphic mode. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Reverse atom transfer radical polymerization of acrylonitrile

FeCl₃ coordinated by succinic acid was used as the catalyst for the first time in azobisisobutyronitrile‐initiated reverse atom transfer radical polymerization of acrylonitrile (AN). N,N‐dimethylformamide (DMF) was used as a solvent to improve the solubility of the ligand. A FeCl₃ to succinic acid ratio of 0.5 not only gives the best control of molecular weight and its distribution but also provides rather rapid reaction rate. Effects of different solvents on polymerization of AN were also investigated. The rate of the polymerization in DMF is faster than that in propylene carbonate and toluene. The molecular weight of polyacrylonitrile agrees reasonably well with the theoretical molecular weight in DMF. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 64.8 kJ mol^?1. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 32–36, 2006     

Reverse atom transfer radical polymerization of styrene in the presence of tetraethylthiuram disulfide

Reverse atom transfer radical polymerization (ATRP) of styrene initiated with tetraethylthiuram disulfide (TD)/cuprous bromide (CuBr)/2,2′-bipyridine (bpy) has been successfully carried out at 120 °C. The kinetic plot was first order in monomer. The measured number-average molecular weight was in good accordance with the theoretical one. Radical scavenger 1,1-diphenyl-2-picrylhydrazyl (DPPH) immediately terminated the reaction, which supported the radical essence of this polymerization. ¹H NMR and UV spectra analyses revealed α-S₂CNEt₂ and ω-Br end groups on the polystyrene chain. Conventional ATRP of methyl methacrylate could progress with the obtained polymer acting as the macroinitiator and CuBr/bpy or CuCl/bpy as the catalyst.     

Atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system

Atom transfer radical polymerization of n‐butyl methacrylate (BMA) was conducted in an aqueous dispersed system with different kinds of copper complexes. The partitioning behavior of the copper complexes, including CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipydine (dNbpy), CuCl₂/dNbpy, CuCl/2,2′‐bipydine (bpy), CuCl₂/bpy, CuCl/bis(N,N′‐dimethylaminoethyl)ether (bde), and CuCl₂/bde between the monomer (BMA), and water was studied in detail with ultraviolet‐visible spectroscopy. The results show that with a less hydrophobic ligand, such as bpy or bde, most of the Cu(I) or the Cu(II) complexes migrated from the BMA phase to the aqueous phase, the atom transfer equilibrium was destroyed, and the polymerization was nearly not controlled; it converted to classical emulsion polymerization. As to the very hydrophobic ligand dNbpy, although the partitioning study of the copper complexes indicated that not all the copper species were restricted to the organic phase, the linear correlation between the molecular weight and the monomer conversion and the narrow polydispersities confirmed that the polymerization was still quite well controlled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3175–3179, 2003     

Synthesis and characterization of poly(n‐butyl methacrylate)‐b‐polystyrene diblock copolymers by atom transfer radical emulsion polymerization

Poly(n‐butyl methacrylate) (PBMA)‐b‐polystyrene (PSt) diblock copolymers were synthesized by emulsion atom transfer radical polymerization (ATRP). PBMA macroinitiators that contained alkyl bromide end groups were obtained by the emulsion ATRP of n‐butyl methacrylate with BrCH₃CHCOOC₂H₅ as the initiator; these were used to initiate the ATRP of styrene (St). The latter procedure was carried out at 85°C with CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as the catalyst and polyoxyethylene(23) lauryl ether as the surfactant. With this technique, PBMA‐b‐PSt diblock copolymers were synthesized. The polymerization was nearly controlled; the ATRP of St from the macroinitiators showed linear increases in number‐average molecular weight with conversion. The block copolymers were characterized with IR spectroscopy, ¹H‐NMR, and differential scanning calorimetry. The effects of the molecular weight of the macroinitiators, macroinitiator concentration, catalyst concentration, surfactant concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are also reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2123–2129, 2005     

退化转移自由基聚合制备氯丁二烯-丙烯酸丁酯嵌段共聚物

采用退化转移自由基聚合,用溶液聚合和乳液聚合2种方法制备了氯丁二烯-丙烯酸丁酯嵌段聚合物,通过凝胶渗透色谱、核磁共振氢谱及动态光散射仪对聚合物进行了分析。结果表明,用以碘仿作链转移剂的氯丁二烯低温乳液聚合得到的聚氯丁二烯为大分子链转移剂,以偶氮二异丁腈为引发剂,进行丙烯酸丁酯的溶液聚合,制得了氯丁二烯-丙烯酸丁酯嵌段共聚物。用以碘仿作为链转移剂进行氯丁二烯的低温乳液聚合得到的聚氯丁二烯为种子乳液,然后加入第2单体丙烯酸丁酯进行乳液聚合,制得了氯丁二烯-丙烯酸丁酯嵌段聚合物。     

Synthesis of diblock and triblock copolymers from butyl acrylate and styrene by reverse iodine transfer polymerization

Well‐defined AB and BA diblock copolymers were obtained by a one‐pot two‐step sequential block copolymerization by reverse iodine transfer polymerization (RITP), A being a poly(styrene) block and B a poly(butyl acrylate) block. High monomer conversions during the formation of the first block avoided the purification steps before growing the second block. In a third sequential step, the diblock copolymers were further extended to synthesize ABA and BAB triblock copolymers. Furthermore, the synthesis of ABA and BAB copolymers in only two steps by RITP was investigated starting with the formation of the central block using 2,5‐di(2‐ethylhexanoylperoxy)‐2,5‐dimethylhexane as a difunctional initiator and then resuming the polymerization to grow the external blocks in a second step. The obtained copolymers were analyzed by size exclusion chromatography, transmission electron microscopy, and differential scanning calorimetry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of hyperbranched polymers by atom transfer radical polymerization

A cheap acrylic AB* monomer, 2‐(2‐chloroacetyloxy)‐isopropyl acrylate (CAIPA), was prepared from 2‐hydroxyisopropyl acrylate with chloroacetyl chloride in the presence of triethylamine. The self‐condensing vinyl polymerization by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization, has yielded hyperbranched polymers. All the polymerization products were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR). CAIPA exhibited distinctive polymerization behavior that is similar to a classical step‐growth polymerization in the relationship of molecular weight to polymerization time, especially during the initial stage of the polymerization. However, a significant amount of monomer remained present throughout the polymerization, which is consistent with typical chain polymerization. Also, if a much longer polymerization time was used, the polymer became gel. As a result of the unequal reactivity of group A* and B*, the polymerization is different from an ideal self‐condensing vinyl polymerization: the branch structures of polymers prepared depend dramatically on the ratio of 2,2'‐bipyridyl to CAIPA. Hyperbranched polymers exhibit improved solubility in organic solvent, however, they have lower thermal stability than their linear analogs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2114–2123, 2002