Synthesis and characterization of hyperbranched cationic polyelectrolytes via aqueous self‐condensing atom transfer radical polymerization

The hyperbranched cationic polyelectrolytes (PDMEAB) were directly prepared via the CuBr/ligand‐catalyzed (ligand = 2,2′‐bipyridine or pentamethyldiethylenetriamine) aqueous self‐condensing atom transfer radical polymerization (SCATRP) of a novel inimer, N,N‐dimethyl‐N‐(2‐methacryloyloxy)ethyl‐N‐(2‐bromoisobutyryloxy)ethyl ammonium bromide (DMEAB). Elemental analysis and nuclear magnetic resonance (NMR) spectroscopy confirmed the structure of DMEAB. The hyperbranched architecture and number‐average degree of polymerization (DP_n) of the PDMEAB was studied by ¹H‐ and ¹³C‐NMR. The kinetic results suggested that the DP_n of the hyperbranched PDMEAB grew gradually in the initial stage and exponentially in the later stage. The differential scanning calorimetry (DSC) showed that the glass transition temperature of the hyperbranched PDMEAB was much lower than that of the linear analogue. The solution rheometry showed that the aqueous PDMEAB solutions approximately underwent a Newtonian behavior and their shear viscosity maintained almost constant upon the addition of NaCl because of the spherical conformations of the hyperbranched cationic polyelectrolytes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of hyperbranched polyacrylate copolymers by self‐condensing vinyl copolymerization (SCVCP)

A series of hyperbranched polyacrylate copolymers have been synthesized by self‐condensing vinyl copolymerization (SCVCP) of 2‐(2‐bromopropionyloxy)‐ethyl acrylate (BPEA) and methyl acrylate (MA) in the presence of CuBr and bipyridine. The structures and properties of the polymers obtained are characterized by NMR and SEC/RALLS/DV/RI measurements. The effects of reaction conditions on molecular weight (MW), molecular weight distribution (MWD) and degree of branching (DB) are investigated. © 2002 Society of Chemical Industry     

Preparation of hyperbranched polymers through ATRP of in situ formed AB* monomer

The self‐condensing vinyl polymerization of an AB* monomer formed in situ by atom transfer radical addition from divinylbenzene (DVB) and (1‐bromoethyl)benzene (BEB) using atom transfer radical polymerization technique was studied. The catalyst concentration has a dramatic effect on polymerization. To study the polymerization mechanism and to achieve high molecular weight polymer, the polymerization was carried out in bulk with a catalyst to monomer ratio, 2,2′‐bipyridine to DVB, of 0.2 at 90°C. Proton nuclear magnetic resonance (¹H NMR) spectroscopy and size‐exclusion chromatography coupled with multiangle laser light scattering were used to analyze the polymerization aliquots and the obtained polymer. The intrinsic viscosities of the prepared polymers were also measured. Experimental results, from the comparison of the apparent molecular weights measured by size‐exclusion chromatography with the absolute values measured by multiangle laser light scattering as well as viscosity measurements, indicate the existence of hyperbranched structures in the prepared polymers. In sharp contrast to hyperbranched polymers from AB* monomer preprepared, hyperbranched ploy(divinylbenzene) prepared at equimolar amount of DVB and BEB has numerous residual pendant vinyl groups rather than only one double bond at its focal point. The hyperbranched polymers show relatively narrow molecular weight distribution (2.13–3.77) and exhibit excellent solubility in common organic solvents such as acetone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 850–856, 2006     

Synthesis of multi‐arm star polystyrene with hyperbranched polyester initiators by atom transfer radical polymerization

Multi‐arm star polystyrenes with hyperbranched polyester (HP3) core were prepared by atom transfer radical polymerization (ATRP). The structures of the polymers were investigated with FTIR and ¹H NMR. GPC results showed that the resultant polymers had relatively broad polydispersity indices that arouse from the macromolecular initiator (HP3‐Br). The thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis indicated that polystyrene star polymers had only the glass transition temperatures (T_g), which changes with the weight ratio of multi‐functional macroinitiator‐to‐monomer. In addition, these star polymers could form the spherical micelles in the selected solvent (THF/n‐hexane). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 728–733, 2006     

采用原子转移自由基聚合技术制备聚丙烯酸钠的研究

采用原子转移自由基聚合(ATRP)技术在水溶液和N,N-二甲基甲酰胺的混合溶液中一步合成了聚丙烯酸钠。考察了反应温度、溶液pH、维生素C(Vc)对聚合反应的影响。结果表明,采取ATRP技术可以制备得到数均分子量为6.8 kDa以及分散度2.4的聚丙烯酸钠。     

原子转移自由基聚合机理及其应用

原子转移自由基聚合(ATRP)是目前研究的热点之一。该文介绍了ATRP的反应机理及其应用。     

Synthesis of aromatic carboxyl functionalized polymers by atom transfer radical polymerization

The synthesis of aromatic carboxyl functionalized polymers by atom transfer radical polymerization is described. The α‐bromo‐p‐toluic acid ( 1 ) initiated polymerization of styrene in the presence of copper(I) bromide and 2,2′‐bipyridyl affords quantitative yields of the corresponding aromatic carboxyl functionalized polystyrene ( 2 ). Polymerization proceeded via a controlled free radical process to afford quantitative yields of the corresponding aromatic carboxyl functionalized polymers with predictable molecular weights (M_n = 1600–25 900 g mol⁻¹), narrow molecular weight distribution (M_w /M_n = 1.1–1.40) and an initiator efficiency above 0.87. The polymerization process was monitored by gas chromatographic analysis. The functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, spectroscopy, potentiometry and elemental analysis. © 2000 Society of Chemical Industry     

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     

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     

Well-defined dibenzocyclooctyne end functionalized polymers from atom transfer radical polymerization

The dibenzocyclooctyne end functionalized agent 1 was designed as atom transfer radical polymerization (ATRP) initiator. The ATRP was then explored on three types of monomers widely used in free radical polymerization: methyl methacrylate, styrene, and acrylates (n-butyl acrylate and tert-butyl acrylate). The living polymerization behaviors were obtained for the methyl methacrylate and styrene monomers. The SPAAC click reactivity of dibenzocyclooctyne end group were demonstrated by successfully reacting with azide functionalized small chemical agents and polymers. Various topological polymers such as block and brush polymers were produced from strain-promoted azide-alkyne cycloaddition reaction (SPAAC) using the resultant dibenzocyclooctyne end functionalized poly(methyl methacrylate)/polystyrene as building blocks. For the acrylates, however, the polymerization did not hold the living characteristics with the dibenzocyclooctyne end functionalized ATRP initiator 1.     

Primary amine functionalized polystyrenes by atom transfer radical polymerization

Primary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (M_n = 2 × 10³ to 10 × 10³ g mol^?1), relatively narrow molecular weight distributions (M_w/M_n = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion. © 2003 Society of Chemical Industry     

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。     

Synthesis and characterization of hyperbranched azobenzene-containing polymers via self-condensing atom transfer radical polymerization and copolymerization

We report on the synthesis of an azobenzene-containing inimer 6-{4-[4-(2-(2-bromoisobutyryloxy)hexyloxy)phenylazo]phenoxy}hexyl methacrylate (I) and used it to prepare hyperbranched homopolymer and copolymers by self-condensing vinyl polymerization (SCVP) and copolymerization (SCVCP) with its precursor 6-{4-[4-(6-hydroxyhexyloxy)phenylazo]phenoxy}hexyl methacrylate (M) using atom transfer radical polymerization (ATRP). Depending on the comonomer ratio, γ=[M]₀/[I]₀, branched polymethacrylates with number-average weights between 8000 and 20,000 and degree of branching (DB) between 0.08 and 0.49 were obtained by SCVCP, as evidenced by GPC and ¹H NMR analysis. In addition, the photochemical properties of the polymers were also studied by UV-vis spectra and found the structure of polymers affect obviously the trans-cis isomerization properties of the branched polymers.     

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。     

原子转移自由基聚合合成支化聚丙烯腈

以二乙烯苯为支化单体,α-溴代异丁酸叔丁酯为引发剂,CuBr和2,2'-联吡啶为催化体系,利用本体和溶液原子转移自由基聚合合成了支化聚丙烯腈.采用核磁共振谱仪、凝胶渗透色谱仪和多角度激光光散射仪等测试了聚合物结构、相对分子质量及其分布.用无水乙酸钠对支化聚丙烯腈进行末端改性,得到了在硫氰酸钠水溶液中性能稳定、可长期保存的支化聚丙烯腈,而改性对聚合物的耐热性能没有影响.     

High‐molecular‐weight polyacrylonitrile by atom transfer radical polymerization

A single‐pot atom transfer radical polymerization was used for the first time to successfully synthesize polyacrylonitrile with a molecular weight higher than 80,000 and a narrow polydispersity as low as 1.18. This was achieved with CuBr/isophthalic acid as the catalyst, 2‐bromopropionitrile as the initiator, and N,N‐dimethylformamide as the solvent. The effects of the solvent on the polymerization of acrylonitrile were also investigated. The induction period was shorter in N,N‐dimethylformamide than in propylene carbonate and toluene, and the rate of the polymerization in N,N‐dimethylformamide was fastest. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in N,N‐dimethylformamide. When chlorine was used in either the initiator or the catalyst, the rate of polymerization showed a trend of decreasing, and the molecular weight deviated from the theoretical predication significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3372–3376, 2006     

原子转移自由基聚合法合成PS-g-PMMA

以氯乙酰化聚苯乙烯微球（PS-acyl-Cl）为大分子引发剂,甲基丙烯酸甲酯（MMA）为单体,CuCl/CuCl₂及N,N,N′,N′-四甲基乙二胺（TMEDA）为催化体系的原子转移自由基聚合反应,成功在PS-acyl-Cl表面接枝上PMMA分子链而获得聚苯乙烯 接枝 聚甲基丙烯酸甲酯（PS-g-PMMA）。考察了催化剂、反应温度、溶剂用量等条件对接枝反应的影响,优化的反应条件下,使用氯乙酰基担载量3.44 mmol.g^-1的PS-acyl-Cl,15 h可获得增重率687% 的PS-g-PMMA,且反应表现出一级动力学特征（k=513×10^-5 s^-1）。通过改变反应条件,可得到不同PMMA接枝链长的PS-g-PMMA。反应得到的PS-g-PMMA经水解后有望作为高担载量弱酸型离子交换树脂或进一步功能化后作为酶的柔性固定化载体。     

原子转移自由基聚合最新研究进展

概述了原子转移自由基聚合（ATRP）在引发体系、反应温度、反应介质、实施方法等方面的进展；介绍了3种不同催化剂脱除技术；结合最新的研究成果，着重论述了ATRP在进行聚合物分子设计，制备窄分子量分布聚合物、无规、梯度和交替共聚物，嵌段共聚物，末端官能团聚合物，接枝和梳状聚合物，星型及高支化聚合物等方面的应用。     

Optically active photochromic methacrylic polymers with controlled average molecular weight and defined end-groups by atom transfer radical polymerization

We report a new approach based on atom transfer radical polymerization (ATRP) to produce optically active polymers containing azoaromatic moieties in the side chain with controlled average molecular weights, that can be used to investigate the conformational origin of chirality in this class of synthetic materials. The ATRP technique has been successfully applied to the synthesis of a series of optically active photochromic homopolymers poly[(S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine] {poly[(S)-MAP]}, containing a chiral group of one prevailing configuration interposed between the methacrylic moiety and the photochromic azoaromatic chromophore. By just changing the duration of the polymerization process, macromolecules having distinct average chain lengths with low polydispersity values and well defined end-groups have been obtained.Optical activity and thermal properties of the resulting polymeric derivatives result to depend on their average molecular weight. In particular, a dependence of optical rotation and circular dichroism on chain-length has been evidenced.