Atom Transfer Radical Polymerization of N‐Isopropylacrylamide

Summary: Controlled polymerization of N‐isopropylacrylamide (NIPAAM) was achieved by atom transfer radical polymerization (ATRP) using ethyl 2‐chloropropionate (ECP) as initiator and CuCl/tris(2‐dimethylaminoethyl)amine (Me₆TREN) as a catalytic system. The polymerization was carried out in DMF:water 50:50 (v/v) mixed solvent at 20 °C. The first order kinetic plot was linear up to 92% conversion. Controlled molecular weights up to 2.2 × 10⁴ and low polydispersities (1.19) were obtained. The living character of the polymerization was also demonstrated by self‐blocking experiments. Block copolymers with N,N‐dimethylacrylamide (DMAAM) and 3‐sulfopropyl methacrylate (SPMA) were successfully prepared.

Molecular weights and polydispersities of polyNIPAAM versus NIPAAM conversion for two different degrees of polymerization.     

Atom Transfer Radical Polymerization of N,N‐Dimethylacrylamide

Summary: The living polymerization of N,N‐dimethylacrylamide was achieved by atom transfer radical polymerization catalyzed by copper chloride complexed with a new ligand, N,N′‐bis(pyridin‐2‐ylmethyl 3‐hexoxo‐3‐oxopropyl)ethane‐1,2‐diamine (BPED). With methyl 2‐chloropropionate as the initiator, the polymerization reached high conversions (> 90%) at 80 °C and 100 °C, producing polymers with very close to theoretical values and low polydispersity. The ligand, temperature, and copper halide strongly affected the activity and control of the polymerization.

PDMA molecular weight and polydispersity dependence on the DMA conversion in the DMA bulk polymerizations at different temperatures: DMA/CuCl/MCP/BPED = 100/1/1/1, 100 °C (♦, ⋄); 80 °C (▴, ▵); 60 °C (▪, □); and DMA/CuCl/MCP/BPED = 100/1/1/2, 80 °C (•, ○).     

利用反向原子转移自由基聚合反应合成聚甲基丙烯酸缩水甘油酯

以偶氮二异丁腈为引发剂,CuBr2/bpy为催化体系,甲基丙烯酸缩水甘油酯(GMA)通过反向原子转移自由基聚合反应合成了聚甲基丙烯酸缩水甘油酯(PGMA),其结构经1H NMR,IR和GPC确证。聚合反应符合活性自由基聚合特征,在聚合过程中GMA转化率和PGMA分子量随反应时间的延长而增大,分子量分布较窄。     

Morphology and Electrical Conductivity of Poly(N‐vinylcarbazole)/Carbon Nanotubes Nanocomposite Synthesized by Solid State Polymerization

This communication describes the morphology and DC conductivity of poly(N‐vinylcarbazole) (PNVC)/multi‐walled carbon nanotubes (MWCNTs) nanocomposite. The nanocomposite has been synthesized by solid state in situ polymerization of N‐vinylcarbazole (NVC) monomer in the presence of MWCNTs at an elevated temperature. Fourier transform infrared (FT‐IR) spectroscopy studies reveal the ability of MWCNTs to promote the in situ polymerization of the NVC monomer. Field‐emission scanning electron microscopy (FE‐SEM) observations show the homogeneous wrapping of MWCNTs' outer surface by PNVC polymer. Transmission electron microscopy (TEM) images and Raman spectroscopy results support the SEM observations. Thermogravimetric analyses reveal a significant improvement of thermal stability of the nanocomposite sample in the higher temperature region. The resulting nanocomposite material exhibits a dramatic improvement of the DC conductivity inherent to the PNVC. For example, the DC conductivity increases from ≈5.9 × 10⁻¹³ S · cm⁻¹ for PNVC to ≈12 S · cm⁻¹ for the nanocomposite, an increase of about 10¹³ in the electrical conductivity.

     

表面引发的原子转移自由基聚合法在聚偏二氟乙烯表面制备可控的聚甲基丙烯酸甲酯刷

采用表面引发的原子转移自由基聚合法(ATRP)在聚偏二氟乙烯(PVDF)表面制备结构可控的聚甲基丙烯酸甲酯刷。通过碱处理和紫外光照溴代的方法,将ATRP引入到PVDF表面; 然后采用ATRP法将甲基丙烯酸甲酯接枝到溴代的PVDF表面。采用傅里叶变换红外光谱和X-射线光电子能谱对改性前后PVDF表面的结构进行了表征。结果表明甲基丙烯酸甲酯成功地接枝到了PVDF表面。     

原子转移自由基悬浮聚合制备PVC-g-PMMA共聚物

原子转移自由基悬浮聚合制备PVC-g-PMMA共聚物;聚氯乙稀;甲基丙烯酸甲酯;原子转移自由基悬浮聚合     

Highly Conductive Core–Shell Nanocomposite of Poly(N‐vinylcarbazole)–Polypyrrole with Multiwalled Carbon Nanotubes

In this communication, the synthesis, characterization, and properties of highly conductive core–shell nanocomposites of poly(N‐vinylcarbazole) (PNVC)–polypyrrole (PPY) copolymers with multi‐walled carbon nanotubes (MWCNTs) are described. A unique free‐radical coupling reaction between PNVC and PPY cation radicals in chloroform solvent, using feric chloride as an oxidant, in the presence of suspended MWCNTs in the reaction medium, was used for the synthesis of nanocomposite. Field‐emission scanning and transmission electron microscopy studies showed the formation of the core–shell nanocomposite. Raman spectrocopy results as well as thermogravimetric analysis supported the electron microscopic observations. The resulting PNVC–PPY copolymer‐coated MWCNTs showed an unprecedentedly increased value of direct electrical conductivity (bulk) compared to the conductivity of all samples even with pure MWCNTs.

     

原子转移自由基聚合的最新研究进展*

原子转移自由基聚合(ATRP)是目前为止最具工业化应用前景的“活性”/可控自由基聚合之一。近年来对其广泛的研究使这一技术逐渐向着“提高可操作性”与“尽可能地减少金属催化剂用量”方面发展;与此同时,诞生了不同催化体系的ATRP衍生技术,如反向原子转移自由基聚合(RATRP)、正向反向同时引发的原子转移自由基聚合(SR&NI ATRP)、引发剂连续再生催化剂原子转移自由基聚合(ICAR ATRP)、电子转移生成催化剂的原子转移自由基聚合(AGET ATRP)和电子转移再生催化剂原子转移自由基聚合(ARGET ATRP)等多种基于ATRP的新方法。本文概述了这几种ATRP体系的发展历程与基本原理,并对其国内外的最新研究进展进行了综述。     

Functional Polyolefins: Poly(ethylene)‐graft‐Poly(tert‐butyl acrylate) via Atom Transfer Radical Polymerization From a Polybrominated Alkane

Poly(cis‐cyclooctene) is synthesized via ring‐opening metathesis polymerization in the presence of a chain‐transfer agent and quantitatively hydrobrominated. Subsequent graft polymerization of tert‐butyl acrylate (tBA) via Cu‐catalyzed atom transfer radical polymerization (ATRP) from the non‐activated secondary alkyl bromide moieties finally results in PE‐g‐PtBA copolymer brushes. By varying the reaction conditions, a series of well‐defined graft copolymers with different graft densities and graft lengths are prepared. The maximum extent of grafting in terms of bromoalkyl groups involved is approximately 80 mol%. DSC measurements on the obtained graft copolymers reveal a decrease in T_m with increasing grafting density.     

原子转移自由基聚合法制备侧链型磺化聚醚醚酮阳离子交换膜

以二氟二苯甲酮、双酚A和邻甲基氢醌为单体先经缩聚反应生成聚醚醚酮(PEEK),PEEK经修饰合成含有溴异丙基侧基的聚醚醚酮,以此为原子转移自由基聚合(ATRP)大分子引发剂,通过ATRP法聚合,在PEEK主链上接枝引入聚苯乙烯磺酸钠侧链,得到侧链型PEEK接枝聚合物(PEEK-g-StSO3Na)。 用傅里叶变换红外(FTIR) 光谱、核磁共振氢谱(1H NMR)、热重分析(TG)和扫描电子显微镜(SEM)等技术手段对PEEK-g-StSO3Na的结构进行表征。 结果表明,苯乙烯磺酸钠成功的被接枝到聚醚醚酮主链上,PEEK-g-StSO3Na膜具有明显的亲水疏水微相分离结构,磺酸基团相互聚集形成离子通道,离子交换容量为2.034 mmol/g的PEEK-g-StSO3Na膜的电导率为8.34×10-2 S/cm,膜的尺寸稳定性优于Nafion 117。     

Synthesis of Comblike Poly（methyl methacrylate） by Atom Transfer Radical Polymerization with Poly（ethyl 2-bromoacrylate） as Macroinitiator

Comblike poly(methyl methacrylate) was synthesized by atom transfer radical polymerization of methyl methacrylate with poly(ethyl 2-bromoacrylate) as a macroinitiator, which was prepared by conventional free radical polymerization of ethyl 2-bromoacrylate. The obtained comblike polymers were characterized by GPC and ^1H NMR.     

Synthesis of Fullerene-end Functionalized Poly（methyl methacrylate） via Reverse Atom Transfer Radical Polymerization

The use of the reverse atom transfer radical polymerization （RATRP） to end-functionalize poly（methyl methacrylate） （PMMA） with fullerenes, e.g. C60 and C70 was described in this paper. The Cl-terrninated PMMA was prepared via RATRP with designed molecular weight and narrow molecular weight distributions, and then directly used to react with fullerenes to produce C60（C70） terminated PMMA polymers in the presence of CuBr/Cu/bipy or FeCl2/bipy catalysts. The resultant polymers exhibit good solubility in some common organic solvents, e.g. THF, CHCl3 and toluene, and were well structurally characterized by a variety of physical techniques.     

Polymer‐Grafted Carbon Spheres by Surface‐Initiated Atom Transfer Radical Polymerization

Summary: In situ atom transfer radical polymerization techniques have been used to produce polymer‐grafted carbon spheres (CSs). The surfaces of as‐prepared CSs were functionalized in the presence of CS‐supported macroinitiators. The resulting materials were characterized by FTIR and NMR spectroscopy, TGA, SEM, TEM, and HRTEM. The amount of polymer grafted onto the surfaces of the spheres can be controlled by varying the monomer/initiator feed ratio. The wetting ability and dispersibility of the polymer‐grafted CSs were improved significantly, compared with crude CSs, enabling stable dispersions in organic solvents to be produced. SEM and TEM studies indicate that a uniform distribution of the carbon spheres in the continuous polymer phase can be produced.

SEM image (left) of poly(glycerol monomethacrylate) grafted carbon spheres, inset shows the structure. HRTEM image (right) of a polystyrene grafted carbon sphere, inset is the SAED pattern.     

Photoinduced Energy Transfer from Poly(N‐vinylcarbazole) to Tricarbonylchloro‐(2,2′‐bipyridyl)rhenium(I)

This work investigates the photoinduced energy transfer from poly(N‐vinylcarbazole) (PVK), as a donor material, to fac‐(2,2′‐bipyridyl)Re(CO)₃Cl, as a catalyst acceptor, for its potential application towards CO₂ reduction. Photoluminescence quenching experiments reveal dynamic quenching through resonance energy transfer in solid donor/acceptor mixtures and in solid/liquid systems. The bimolecular reaction rate constant at solution–film interfaces for the elementary reaction of the excited state with the quencher material could be determined as 8.8(±1.4)×10¹¹ L mol^?1 s^?1 by using Stern–Volmer analysis. This work shows that PVK is an effective and cheap absorber material that can act efficiently as a redox photosensitizer in combination with fac‐(2,2′‐bipyridyl)Re(CO)₃Cl as a catalyst acceptor, which might lead to possible applications in photocatalytic CO₂ reduction.     

Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) is a robust method for the preparation of well‐defined (co)polymers. This process has also enabled the preparation of a wide range of polymer brushes where (co)polymers are covalently attached to either curved or flat surfaces. In this review, the general methodology for the synthesis of polymer brushes from flat surfaces, polymers and colloids is summarized focusing on reports using ATRP. Additionally, the morphology of ultrathin films from polymer brushes is discussed using atomic force microscopy (AFM) and other techniques to confirm the formation of nanoscale structure and organization.

Formation of polymer brushes by ATRP.     

Facile Soap‐Free Miniemulsion Polymerization of Methyl Methacrylate via Reverse Atom Transfer Radical Polymerization

A facile soap‐free miniemulsion polymerization of methyl methacrylate (MMA) was successfully carried out via a reverse ATRP technique, using a water‐soluble potassium persulfate (KPS) or 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (V‐50) both as the initiator and the stabilizer, and using an oil‐soluble N,N‐n‐butyldithiocarbamate copper (Cu(S₂CN(C₄H₉)₂)₂) as the catalyst without adding any additional ligand. Polymerization results demonstrated the “living”/controlled characteristics of ATRP and the resultant latexes showed good colloidal stability with average particle size around 300–700 nm in diameter. The monomer droplet nucleation mechanism was proposed. NMR spectroscopy and chain‐extension experiments under UV light irradiation confirmed the attachment and livingness of UV light sensitive  S C(S) N(C₄H₉)₂ group in the chain end.     

Facile Synthesis of Brush Poly(phosphoamidate)s via One‐Pot Tandem Ring‐Opening Metathesis Polymerization and Atom Transfer Radical Polymerization

Poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA)‐based brush poly(phosphoamidate)s are successfully synthesized by a combination of ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) following either a commutative two‐step procedure or a straightforward one‐pot process using Grubbs ruthenium‐based catalysts for tandem catalysis. Compared with the traditional polymerization method, combining ROMP and ATRP in a one‐pot process allows the preparation of brush copolymers characterized by a relatively moderate molecular weight distribution and quantitative conversion of monomer. Moreover, the surface morphologies and aggregation behaviors of these polymers are studied by AFM and TEM measurements.

     

Synthesis of Novel μ‐Star Copolymers with Poly(N‐Octyl Benzamide) and Poly(ε‐Caprolactone) Miktoarms through Chain‐Growth Condensation Polymerization,Styrenics‐Assisted Atom Transfer Radical Coupling,and Ring‐Opening Polymerization

Star copolymers are known to phase separate on the nanoscale, providing useful self‐assembled morphologies. In this study, the authors investigate synthesis and assembly behavior of miktoarm star (μ‐star) copolymers. The authors employ a new strategy for the synthesis of unprecedented μ‐star copolymers presenting poly(N‐octyl benzamide) (PBA) and poly(ε‐caprolactone) (PCL) arms: a combination of chain‐growth condensation polymerization, styrenics‐assisted atom transfer radical coupling, and ring‐opening polymerization. Gel permeation chromatography, mass‐analyzed laser desorption/ionization mass spectrometry, and ¹H NMR spectroscopy reveal the successful synthesis of a well‐defined (PBA₁₁)₂‐(PCL₁₅)₄ μ‐star copolymer (M _n,NMR ≈ 12 620; Đ = 1.22). Preliminary examination of the PBA₂PCL₄ μ‐star copolymer reveals assembled nanofibers having a uniform diameter of ≈20 nm.