Thermosensitive Nanocables Prepared by Surface-Initiated Atom Transfer Radical Polymerization

Thermosensitive nanocables consisting of Au nanowire cores and poly(N-isopropylacrylamide) sheaths (denoted as Au/PNIPAAm) were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP). The formation of PNIPAAm sheath was verified by Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance (¹H NMR) spectroscopy. Transmission electron microscope (TEM) results confirmed the core/shell structure of nanohybrids. The thickness and density of PNIPAAm sheaths can be adjusted by controlling the amount of cross-linker during the polymerization. Signature temperature response was observed from Au/cross-linked-PNIPAAm nanocables. Such smart nanocables show immense potentials as building blocks for novel thermosensitive nanodevices in future.     

两个ATRP大分子引发剂的合成与表征

以十二醇为引发剂,通过开环聚合反应合成单端羟基的聚己内酯(PCL),将PCL进一步与α-溴丙酰溴反应,合成了原子转移自由基聚合(ATRP)的大分子引发剂-α-溴代丙酸聚己内酯。通过α-溴丙酰溴与聚乙二醇(PEG)的反应合成了另一种ATRP大分子引发剂-α-溴代丙酸聚乙二醇酯。用1H NMR和IR证实了这两种大分子引发剂的结构。     

电子活化再生原子转移自由基聚合的研究进展

原子转移自由基聚合是一种新兴的活性/可控聚合方法,AGET ATRP是在ATRP的基础上改进而发展起来的活性聚合方法。介绍了AGET ATRP的基本机理及研究进展,以及所用催化剂、引发剂、还原剂的研究情况,并展望了其发展前景。     

原子转移自由基聚合进展

综述了原子转移自由基聚合(ATRP)的发展：引发剂、过渡金属络合物的发展,低温下的反应可节省能源,水分散体系的ATRP也是发展的方向ATRP可合成结构清晰的嵌段、接枝、星型、超支化高聚物,大大拓宽了高聚物的应用范围。     

借助ATRP法合成星型多臂氯甲基苯乙烯甲基丙烯酸甲酯共聚物

以对氯甲基苯乙烯(CMS)作为活性单体,CuCl/2,2’-联吡啶(bpy)为催化体系,用原子转移自由基聚合(ATRP)法,在120℃下,通过改变n(CuCl):n(CMS)配比,合成具有不同支化度的超支化聚对氯甲基苯乙烯(h-PC MS),分别考察了催化剂与单体的配比、溶剂极性、用量等因素对所合成的h-PCMS的组成结构、相对分子质量分布指数和转化率的影响.再分别以具有不同支化度的h-PCMS作为大分子引发剂,引发第二单体甲基丙烯酸甲酯(MMA)聚合,制得以超支化大分子h-PCMS为核,以聚甲基丙烯酸甲酯(PMMA)为臂的星型多臂共聚物h-PCMS-b-PMMA.借助红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)、凝胶渗透色谱(GPC)等技术对所制得的聚合物进行表征.本研究的特点是运用先核后臂的方法来合成具有精确分子结构参数的星型多臂共聚物,为进一步深入研究其结构与性能的关系提供了物质依据,更重要的是提供了合成具有复杂但结构可控的多元共聚物的新思路.     

Preparation of a Thermoplastic Lignin-Based Biomaterial through Atom Transfer Radical Polymerization

Graft copolymerization of styrene onto kraft lignin (KL) was achieved by atom transfer radical polymerization (ATRP) using a fully substituted lignin-based macroinitiator (KLM). The number average of molecular mass (M_n) of polystyrene copolymer graft side-chains was achieved by varying the ratio of the DMF: water solvent system from 5:0 to 1:4. A M_n of up to ～206,000 was obtained using a DMF/water ratio of 3:2 (v/v). However, as the M_n increased, the overall ATRP became less controlled. In addition, the thermal properties of the lignin-g-polystyrene copolymers improved significantly with increasing M_n of polystyrene copolymer side-chains.     

水分散体系中原子转移自由基聚合研究进展

水分散体系中原子转移自由基聚合(ATRP)具有自由基聚合、乳液聚合和活性/可控聚合的优点,因此近年来关于水分散体系中ATRP的研究日益增多。本文综述了近年来水分散体系(包括乳液体系、细乳液体系、微乳液体系)中原子转移自由基聚合的研究进展,对应用在水分散体系中的几种ATRP反应机理做了简要介绍,包括正向AT-RP、反向ATRP(RATRP)、正向/反向同时进行的(SR&NI)ATRP、电子转移活化剂(AGET)ATRP,并对RATRP、SR&NI、ATRPAGET ATRP的优缺点进行了总结。     

ATRP法合成两亲性聚乙二醇-聚丙烯酸叔丁酯嵌段共聚物

以mPEG-Br为大分子引发剂,CuBr/PMDETA为催化体系,采用原子转移自由基聚合法(ATRP)合成了两亲性嵌段共聚物聚乙二醇-聚丙烯酸叔丁酯(mPEG-b-PtBA),并采用FT-IR,1H-NMR和GPC等表征了聚合物的结构.考察了单体与引发剂的配比、反应时间、反应温度及催化剂与配体的比例等因素对产物的分子量...     

Synthesis and Properties of Electroactive Polyaniline-Graft Polymethyl Methacrylate Copolymer by Atom Transfer Radical Polymerization

In this research, N-substituted polyaniline was synthesized by chlorine-terminated chloroacetyl chloride incorporation and methylmethacrylate polymerization done onto the leucoemeraldine. The authors prepared polyaniline-graft-polymethylmethacrylate copolymer by methylmethacrylate ATRP using polyaniline macroinitiator. First, polyaniline was prepared by chemical oxidation. The macroinitiator was synthesized via reaction of leucoemeraldine's nitrogen with chloroacetyl chloride. Macroinitiator and graft copolymer were characterized by FT-IR and ¹H-NMR. SEM and AFM images showed the growing of poly methylmethacrylate chains on polyaniline backbone. Solubility test revealed that polyaniline-graft-poly(methylmethacrylate) was in some organic solvents. CV study confirmed this copolymer was electroactive. Elemental analysis determined the amount of grafting polymethylmethacrylate on leucoemeraldine.     

Progress in Carbon Fiber and Its Polypropylene- and Polyethylene-Based Composites

Due to their lightweight and excellent toughness, carbon fiber (CF) and its reinforced thermoplastic composites are suitable for high-performance applications such as aerospace, aviation, automotive and sport equipments. In this study, comprehensive detail is provided on the production of carbon fiber, its various forms and geometry and their corresponding effects on the mechanical properties of CF and its reinforced polypropylene (PP) and polyethylene (PE) composites. Here we discuss extensively various methods reported in literature on improving the interfacial fiber-matrix adhesion and dispersion in order to achieve better mechanical properties for such composites.     

原子转移自由基聚合在树形聚合物合成中的应用

原子转移自由基聚合(ATRP)技术是一种新型的可控/活性聚合技术,可有效地对聚合物的分子结构进行设计,制备出各种不同性能、不同组成、不同功能化的结构确定的聚合物。综述了利用ATRP技术合成树枝状-线性嵌段共聚物、类树枝状聚合物(dendrimer-like polymer)、具有刺激-响应性末端基团的树枝状聚合物、树枝状-星型嵌段共聚物和基于树枝状聚合物的聚合物刷的研究进展。     

原子转移自由基聚合在制备新型材料中的应用

原子转移自由基聚合（ATRP）技术是一种新型的可控活性聚合技术,可有效地对聚合物的分子结构进行设计,制备出各种不同性能、不同组成、不同功能化的结构确定的聚合物材料。综述了利用ATRP技术在制备有机一无机杂化材料、功能性膜材料、水凝胶材料、液晶材料方面的最新进展,最后对原子转移自由基聚合技术的发展做出了展望。     

Atom Transfer Radical Polymerization of Pyrrole-Bearing Methacrylate for Production of Carbonyl Iron Particles with Conducting Shell for Enhanced Electromagnetic Shielding

The conducting polymer poly(2-(1H-pyrrole-1-yl)ethyl methacrylate (PPEMA) was synthesized by conventional atom transfer radical polymerization for the first time from free as well as surface-bonded alkyl bromide initiator. When grafted from the surface of carbonyl iron (CI) a substantial conducting shell on the magnetic core was obtained. Synthesis of the monomer as well as its polymer was confirmed using proton spectrum nuclear magnetic resonance (¹H NMR). Polymers with various molar masses and low dispersity showed the variability of this approach, providing a system with a tailorable structure and brush-like morphology. Successful grafting from the CI surface was elucidate by transmission electron microscopy and Fourier-transform infrared spectroscopy. Very importantly, thanks to the targeted nanometer-scale shell thickness of the PPEMA coating, the magnetization properties of the particles were negligibly affected, as confirmed using vibration sample magnetometry. Smart elastomers (SE) consisting of bare CI or CI grafted with PPEMA chains (CI-PPEMA) and silicone elastomer were prepared and dynamic mechanical properties as well as interference shielding ones were investigated. It was found that short polymer chains grafted to the CI particles exhibited the plasticizing effect, which might be interesting from the magnetorheological point of view, and more interestingly, in comparison to the neat CI-based sample, it provided enhanced electromagnetic shielding of nearly 30 dB in thickness of 500 μm. Thus, SE containing the newly synthesized CI-PPEMA hybrid particles also exhibited considerably enhanced damping factor and proper mechanical performance, which make the material highly promising from various practical application points of view.     

Synthesis and Characterization of Polystyrene-b-Poly(4-vinyl pyridine) Block Copolymers by Atom Transfer Radical Polymerization

We aimed at the synthesis of well-define PS-b-P4VP by using atom transfer radical polymerization in two-step process. First, polystyrenes with benzyl bromide end group (PS-Br; by ATRP) were prepared as macroinitiator for the next ATRP of 4-vinyl pyridine and characterized these polymers from ¹H-NMR and MALDI-TOF. Comparing with MALDI-TOF-MS, ¹H-NMR and GPC analyses, this indicates that the formation of the block copolymer can be observed. During the polymerizations, molecular weight distribution and kinetics have been evaluated from GPC traces and ¹H-NMR analyses. We further characterized the thermal properties of these block polymers by DSC and TGA. DSC measurement on the PS-b-P4VP block copolymers exhibited two glass transitions, indicating that the resulting block copolymers are phase separated. Two maxima differential peaks were observed on the TGA trace for the PS-b-P4VP block copolymers might be assigned to the decomposition of the P4VP blocks at 380 ^○C and the PS blocks at higher temperature.     

Polystyrene Nanospheres Modified with a Hydrophilic Polymer Brush through Subsurface‐Initiated Atom Transfer Radical Polymerization as Biolubricating Additive

Hydration lubrication plays an important role including the cartilage of an organism. Here, polystyrene nanospheres modified with a hydrophilic polymer through subsurface‐initiated grafting as a biolubricating additive is proposed. The material provides good tribological performance when subjected to high load. Compared with surfaced‐initiated grafting polymer brushes, subsurface initiation can form much thicker hydration layers to obtain a lower friction coefficient and better mechanical properties for withstanding prolonged shearing forces with less measurable damage. The polymer brushes penetrate through the covalent network of the polystyrene nanospheres providing a match in mechanical properties between them, so that the additives obtain more excellent lubricity in an aqueous environment under shear pressure, which is expected to become a promising artificial joint biolubricating additive.     

Facile Preparation of Crosslinked Polymeric Nanocapsules via Combination of Surface-Initiated Atom Transfer Radical Polymerization and Ultraviolet Irradiated Crosslinking Techniques

A facile approach for the preparation of crosslinked polymeric nanocapsules was developed by the combination of the surface-initiated atom transfer radical polymerization and ultraviolet irradiation crosslinking techniques. The well-defined polystyrene grafted silica nanoparticles were prepared via the SI-ATRP of styrene from functionalized silica nanoparticles. Then the grafted polystyrene chains were crosslinked with ultraviolet irradiation. The cross-linked polystyrene nanocapsules with diameter of 20–50 nm were achieved after the etching of the silica nanoparticle templates with hydrofluoric acid. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy.     

Surface‐Initiated Atom Transfer Radical Polymerization from Electrospun Mats: An Alternative to Nafion

Proton exchange membranes for fuel cell applications are synthesized by surface‐initiated (SI) atom transfer radical polymerization (ATRP). Poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) is electrospun into 50 µm thick mat, which is then employed as multifunctional initiator for copper‐mediated SI ATRP of 4‐styrene sulfonic acid sodium salt. Fine‐tuning of the ATRP conditions allows adjustment of the membrane's ion exchange capacity by varying the loading of the grafted ionomer. Structure and composition of the membranes are investigated by spectroscopic means and thermogravimetric analysis, respectively. The membrane morphology is probed by scanning electron microscopy. A membrane with proton conductivity as high as 100 mS cm⁻¹ is obtained. Long‐term durability study in direct methanol fuel cells is conducted for over 1500 h demonstrating the viability of this novel facile approach.

     

表面引发原子转移自由基聚合合成聚苯乙烯接枝纳米SiO2复合乳液

采用偶联剂对纳米SiO2粒子表面进行处理,将原子转移自由基聚合(ATRP)引发剂引入到SiO2粒子表面合成大分子引发剂,通过细乳液聚合工艺制备了相对分子质量分布窄的聚合物基纳米SiO2复合乳液,利用红外光谱(FT-IR)、X射线光电子能谱(XPS)和凝胶色谱(GPC)等对复合乳液粒子及表面接枝聚苯乙烯进行了表征分析。结果表明:聚合物的相对分子质量在反应过程中随单体转化率的增大呈线性增长趋势,相对分子质量分布较窄(Mw/Mn=1.34),接枝在纳米SiO2粒子表面聚苯乙烯的分子大小比较均匀;TEM和SEM观察表明:通过合成复合乳液使纳米SiO2粒子在涂膜中达到均匀的单分散状态;所合成的纳米复合粒子在功能涂层材料方面具有良好的应用潜能。     

Core Cross-Linked Amphiphilic Star-Block Copolymers with (Meth)acrylic Acid Shells Prepared by Atom Transfer Radical Polymerization

Core cross-linked amphiphilic star-block copolymers were prepared by hydrolysis of the outer shell of star-block copolymers prepared using copper mediated atom transfer radical polymerization (ATRP). In an arm-first approach, linear poly(tert-butyl methacrylate) macroinitiators (PtBMA-Cl) were extended with styrene to yield PtBMA-b-PS-Cl and then cross-linked with divinylbenzene (DVB) in order to yield (PtBMA-b-PS)_arms-PDVB_core star-block copolymers. Then, PMAA-b-PS block and (PMAA-PS)_arms-PDVB_core star-block copolymers were obtained by hydrolysis of the PtBMA blocks in both linear and cross-linked copolymers, as confirmed by ¹H NMR analyses. The amphiphilic character of these copolymers was confirmed by solubilisation in water. Several factors affecting the polymer aggregation and solubility such as the length, the composition of the arms and the catalyst used were studied. An acrylate analogue, that is, (PAA-b-PS)_arms-PDVB_core, was also prepared for comparison purposes. Atomic force microscopy (AFM) and differential scanning calorimetry (DSC) were used to elucidate the morphology and the thermal behaviour of the star-block copolymers.     

吡啶基三唑配合物催化下甲基丙烯酸甲酯的原子转移自由基聚合研究

以配体3,5-二-(4-吡啶基)-1,2,4-三唑与CuX形成催化剂,分别以α-溴代异丁酸乙酯和氯化苄为引发剂,环己酮为溶剂,进行了甲基丙烯酸甲酯(MMA)的原子转移自由基聚合(ATRP),同时考察了配比、溶剂量以及温度对聚合速率、聚合物分子量及分子量分布的影响.80℃下的聚合反应速度高于70℃;以环己酮为溶剂,单体与溶剂之比为1∶1.5时可得到较低分子量分布的聚合物.实验结果表明以吡啶基三唑为配合物催化甲基丙烯酸甲酯的聚合过程中,转化率和分子量随时间的增加而增大,聚合反应符合一级动力学规律,所得聚合物分子量分布较窄(1.21～1.46),结合端基分析和扩链反应结果,证明该聚合反应符合"活性"/可控自由基聚合.