用大分子引发剂法制备嵌段共聚物

主要介绍了用大分子引发剂法制备嵌段共聚物的方法。大分子引发剂是从已商品化的功能聚合物制得或用其它活性聚合方法合成。从单封端的端羟基聚合物、其它单官能团或双官能团聚合物以及双功能基团缩聚物制得大分子引发剂．然后用于原子转移自由基聚合(ATRP)、氮氧稳定自由基聚合以及可逆加成裂解链转移(RAFT)聚合等．可制得结构可控、分子量分布窄的嵌段共聚物。     

非线形嵌段共聚物的合成

主要介绍了非线形嵌段共聚物,如星型嵌段共聚物、杂臂星型共聚物、梳型聚合物等的合成方法,包括多官能团引发剂法、大分子引发剂法等。各种活性聚合方法,如阳离子开环聚合、原子转移自由基聚合(ATRP)和氮氧稳定自由基聚合等都可以用于合成非线形嵌段共聚物。     

羧甲基纤维素系列高分子表面活性剂的嵌段结构对其形态和性能的影响

采用超声波辐照聚合的羧甲基纤维素 (CMC)系列高分子表面活性剂是由CMC嵌段和含有等长双亲性支链的嵌段构成的共聚物 ,研究结果表明 ,CMC链段保证了共聚物的增粘性能 ,双亲性嵌段提供了共聚物优良的表面活性 ;CMC增粘嵌段与表面活性嵌段作为共聚物的两个嵌段 ,各发挥其作用 ,得到既有增粘性能又有高表面活性的双亲性共聚物 .     

末端四苯乙烯荧光团标记法研究双亲性嵌段聚合物的自组装行为

以四苯乙烯类分子2-溴-2-甲基-丙酸-3-(4-三苯乙烯基-苯氧基)-丙醇酯(E)作为引发剂,N-异丙基丙烯酰胺和苯乙烯为原料,通过活性自由基聚合,合成了末端具有聚集诱导发光(AIE)活性发光体的双亲性嵌段聚合物G。 详细研究了AIE活性引发剂E和嵌段聚合物G在不同状态下的光物理行为差异。结果表明,在相同浓度条件下,随着温度的升高,引发剂E分散液的荧光强度不断下降。 而嵌段聚合物的荧光强度先上升,当温度超过37 ℃后,嵌段聚合物的荧光强度不断下降。 同样地,通过改变引发剂E和嵌段聚合物G在四氢呋喃和水混合溶剂中的浓度发现,随着浓度的减小,引发剂E的荧光强度不断下降,而嵌段聚合物分散液在改变分散液浓度时荧光强度的变化规律和改变温度时荧光强度的变化趋势相似。 通过监控双亲性嵌段聚合物末端挂接的AIE活性发光分子发光性质的变化可以间接表征其聚集态结构的变化。     

RAFT聚合法制备聚合物胶束及其应用前景

聚合物胶束由于具有优良的组织渗透性、增容效果好、结构多样性和热稳定性等特点,成为国内外研究的热点之一。本文综述了近几年发展起来的一些具有特殊结构和特殊性能的双亲性嵌段聚合物胶束的研究进展,详细阐述了RAFT聚合法合成聚合物胶束的机理和优势,表明了RAFT聚合法可直接在水溶液中方便快捷地制备出温度和pH双响应性聚合物胶束。然而,当聚合物胶束的浓度低于其临界胶束浓度时,胶束的稀释效应大大影响了其实际应用,为提高聚合物胶束的稳定性,文章归纳总结了一系列有关壳交联聚合物胶束的制备方法及研究进展。最后,文章展望了聚合物胶束在药物可控释放、靶向、生物成像、催化剂负载及其他领域的应用前景。     

基于温敏性双亲嵌段共聚物的纳米胶束作为药物载体的研究

温度敏感性双亲嵌段共聚物由于其潜在的应用价值而引起广泛的关注。在药物控制释放领域,基于温敏性嵌段共聚物的纳米胶束作为药物载体显示了诸多特异的性能。在嵌段共聚物中引入具有温度敏感性的链段,使聚合物胶束具备天然被动靶向功能的同时,赋予了其主动靶向给药功能。本文从温度敏感性双亲嵌段共聚物的分子设计、合成、自组装性质和胶束的载药释药行为等方面进行了相关总结。重点介绍了含聚N-异丙基丙烯酰胺链段双亲嵌段共聚物的相关研究进展。     

活性正离子聚合转化法合成嵌段共聚物的研究进展

综述了国内外利用活性正离子聚合转化法合成嵌段聚合物的研究进展。     

基于树形链转移剂的可逆加成断裂链转移聚合

可逆加成断裂链转移(RAFT)聚合是最近十多年来发展起来的一种活性/可控技术,链转移剂(CTA)为该技术的核心.本文介绍了采用R路径合成法、Z路径合成法合成R核与Z核树形链转移剂以及它们调控不同单体的RAFT聚合,合成树形-线性二嵌段共聚物、树形-线性-树形三嵌段共聚物和树形-星形聚合物等树枝状聚合物的研究进展.     

酶促聚合和原子转移自由基聚合“一锅法”合成嵌段聚合物及其性能表征

用酶促聚合和原子转移自由基聚合相结合的"一锅法"合成了聚甲基丙烯酸正丁酯嵌段聚10-羟基癸酸[PBMA-b-P(10-HD)],通过核磁共振(1H NMR)、傅里叶红外光谱(FTIR)和凝胶渗透色谱(GPC)对其结构以及分子量与其分子量分布进行了表征,并通过动态光散射仪(DLS)和原子力显微镜(AFM)对聚合物在水溶液中的性质进行了研究.所得嵌段聚合物纳米粒子呈球形结构,平均直径为135 nm左右.     

双亲嵌段共聚物PSt-b-PAA在甲苯中的自聚集行为

以α-溴乙苯为引发剂,溴化亚铜为催化剂,2,2'-联吡啶为配体,用原子转移自由基聚合(ATRP)法合成了结构一定的嵌段共聚物聚苯乙烯-b-聚丙烯酸丁酯(PSt-b-PBA).经水解制备了双亲性嵌段共聚物聚苯乙烯-b-聚丙烯酸(PSt-b-PAA);采用单溶剂溶解法配制了PSt-b-PAA在甲苯中的反胶束溶液;以极性荧光化合物N-1-萘乙二胺盐酸盐(NEAH)为极性微区探针,用荧光光谱法并配合透射电镜观察探索了双亲嵌段共聚物PSt-b-PAA在甲苯溶液中的自聚集行为,考察了双亲性嵌段共聚物浓度、链结构及温度等因素对反胶束化行为的影响规律.结果表明,亲水链PAA短而亲油链PSt长的双亲嵌段共聚物PSt-b-PAA,用单溶剂溶解法可使其在甲苯中发生自聚集,形成以亲水段为核,疏水段为壳的星状反胶束结构;反胶束为10-20nm的球形聚集态结构;PSt-b-PAA的自聚集行为及临界胶束浓度与分子链的微结构和温度等因素相关,且随着共聚物浓度的增大,小胶束会逐渐结合形成大的纺垂状聚集体.     

Amphiphilic Triblock Copolymers Containing Polypropylene as the Middle Block

The synthesis of stereoregular telechelic polypropylene (PP) and their use to access triblock amphiphilic copolymers with the PP block located in the center is described. The strategy consists of selectively copolymerizing propylene and a di-functional co-monomer (1,3-diisopropenylbenzene) to yield a α,ω-substituted polypropylene. Initiation of the copolymerization favors insertion of DIB over propylene; propagation steps favor insertion of propylene. Termination via a chain-transfer reaction yields the terminal unsaturation of the polymer. The telechelic polypropylene is then converted into α,ω-hydroxyl-terminated polypropylene and used as a macroinitiator for the synthesis of triblock copolymers. Water-soluble amphiphilic triblock polymers are also synthesized. The use of catalytic reactions simultaneously provides the stereocontrol of the polypropylene and high productivity (multiple chains of block copolymer per metal center).     

丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的粘度性能

通过改变丙烯酰胺 (AM)与苯乙烯 (St)两单体的投料比 ,在微乳液介质中制备了分子组成系列变化的丙烯酰胺 苯乙烯双亲嵌段共聚物 (PAM b PSt) ,使用旋转粘度计测定了共聚物水溶液的表观粘度 ,详细考察了共聚物浓度、共聚物链结构、剪切速率、盐度及温度等因素对共聚物水溶液表观粘度的影响规律 .研究结果表明 ,由于PAM b PSt分子链中的PSt疏水嵌段链段之间具有强的疏水缔合作用 ,导致其具有独特的流变性能 .当共聚物水溶液的浓度高于某一临界值后 ,疏水缔合作用以分子间的缔合为主 ,大分子链之间会形成动态物理交联网络 ,增大了流体力学体积 ,使PAM b PSt水溶液可产生良好的增稠性能 ;疏水缔合作用是一吸热过程 ,升高温度有利于分子间的缔合 ,因此PAM b PSt水溶液具有良好的耐温性 ;聚合物水溶液中盐类物质的存在 ,会增强溶剂的极性 ,有利于分子间的缔合 ,使PAM b PSt水溶液具有良好的耐盐性 .     

Synthesis strategies and properties of smart amphiphilic networks

This paper briefly surveys recent developments in the field of amphiphilic networks (APN) which are a new class of crosslinked polymer systems consisting of covalently bonded hydrophobic and hydrophilic chain segments. The covalent bonds between immiscible hydrophobic and hydrophilic polymer chains prevent demixing and yield polymer networks with unique structure and properties. Telechelic macromonomers provide the basis for the first generation of APNs obtained by copolymerization of the macromonomer with selected low molecular weight monomers. Synthesis of a variety of APNs using methacrylate-telechelic polyisobutylene (PIB) macromonomers prepared by living carbocationic polymerization (LCCP) and quantitative chain end derivatization is reviewed. The second generation of PIB-based amphiphilic networks is prepared by crosslinking of well-defined hydroxy-telechelic PIB and partially deprotected silylated poly(2-hydroxyethyl methacrylate) (PHEMA) precursor chains. Other opportunities providing better structural control of APNs by crosslinking of functional amphiphilic block copolymers (or precursors) obtained by combining living carbocationic and anionic polymerizations are outlined as well. Properties of APNs, such as control of swellability by composition, pH-response of swelling, fast surface structure reorganization by contacting with solvent, morphology, sustained release of drugs and bio- and blood compatibility, are also summarized.     

Block copolymerization of methyl methacrylate with poly(ethylene oxide) radicals formed by high-speed stirring

A block copolymer of methyl methacrylate with poly(ethylene oxide) was synthesized by initiation with poly(ethylene oxide) radicals formed by high-speed stirring. The effects of the concentration of the monomer, the concentration of the polymer, the degree of polymerization, the rotation speed, and the solvent on the rate of copolymerization were studied. It was found that the rate of copolymerization was proportional to the concentration of the monomer and to the square root of the rate of scission of the polymer chain. The block copolymerization of methyl methacrylate monomer and styrene monomer (1 : 1 mole ratio) with poly(ethylene oxide) radicals was also carried out by the same method and it was found that the block copolymerization was a radical one.     

Introduction of Quantum Dots into PNIPAM microspheres by precipitation polymerization above LCST

Amphiphilic polymers having different polymerizable functional groups were synthesised and investigated as coatings for semiconductor nanoparticles (Quantum Dots, QDs). QDs coated with hydrophobic ligands were successfully transferred into water using these polymers and the assemblies were co-polymerized with N-isopropylacrylamide (NIPAM) by a precipitation polymerization method. In the resulting hybrid microspheres, QDs were uniformly distributed within the PNIPAM matrix. The influence of different polymerizable groups and counter ions of the amphiphilic polymer on the copolymerization process were investigated.     

Development of PEG-PLA/PLGA microparticles for pulmonary drug delivery prepared by a novel emulsification technique assisted with amphiphilic block copolymers

We developed a novel "spray dry-based" method for preparing surface-modified particle via "block copolymer-assisted" emulsification/evaporation for pulmonary drug delivery. The method included three steps: (1) o/w emulsion containing both hydrophobic polymers and amphiphilic block copolymers was obtained by emulsification of water and a polymer-containing organic solvent, (2) the o/w emulsion was misted with a nebulizer, and (3) the emulsion mists were dried by a heater. In this way, the hydrophobic polymers and the hydrophobic part of the amphiphilic block copolymers gradually tangled during the evaporation of organic solvents from the o/w emulsion. Consequently, the hydrophilic polymer chain was introduced on the particle surface. The particle surface can be easily modified although there are no reactive groups in the hydrophobic polymer molecules. We successfully obtained dry PEG-PLA/PLGA microparticles by controlling the weight ratio of the block copolymer and the hydrophobic polymer. The introduction of PEG to the particle surface involves an increase in the Zeta potential of the particles. Interestingly, the "dimpled" microparticles having a diameter of approximately 2 μm were obtained. The "dimpled" microparticles can serve as drug carriers for pulmonary drug delivery, because the particles have a large surface area. We expect that this novel surface-modification technique will enable efficient fabrication of particles in drug delivery systems.     

Surface active properties of polyoxyethylene macromonomers and their role in radical polymerization in disperse systems

Conventional dispersion polymerization and copolymerization of low-molecular weight (conventional) unsaturated monomers allows preparation of monodisperse and micronsize polymer particles. A similar behavior can be found in the surfactant-free dispersion polymerization of non-traditional vinyl monomers, unsaturated macromonomers. The latter systems allow preparation of random, comb-like, star-like and graft copolymers as well. An interesting alternative arises with the use of amphiphilic reactive macromonomers that contain a polymerizable group and aggregate into an organized structure -- a micelle. Under such conditions the high rate of polymerization and ultrafine (microparticles) polymer dispersions are generated. Thus, the surface-active macromonomers promote the formation of micelles and polymer growth within the main reaction loci -- polymer particles. Furthermore, the surface-active compounds can be formed during the copolymerization of hydrophilic macromonomer and hydrophobic low-molecular weight comonomer. The reactive surface-active oligomeric radicals are incorporated into the polymer matrix or the particle surface layer, which prevents them from subsequent migration. Besides, the covalently bound surface-active groups at the particle surface strongly increase the colloidal stability of final polymer dispersion. This article presents a review of the current literature in the field of the surfactant-free dispersion polymerization of the polyoxyethylene unsaturated macromonomers. Besides a short introduction into some kinetic aspects of radical polymerization of traditional monomers in homogeneous and disperse systems, we mainly focus on the organized aggregation of amphiphilic polyoxyethylene macromonomers, the characterization of amphiphilic graft copolymers and their aggregation properties, and radical copolymerization of polyoxyethylene macromonomers. We discuss the birth and growth of chains, the transfer of reaction loci from the continuous phase to polymer particles, the diffusion-controlled termination, association of amphiphilic reaction by-products, the particle growth by agglomeration, the particle nucleation, the deactivation of polymer chain growth and the colloidal stability. Effects of initiator type and concentration, the surface activity of macromonomer, the macromonomer type and concentration, temperature, additives and the type of continuous phase on the kinetics of polymerization, and colloidal parameters of the reaction system are also evaluated. Variation of the polymer coil density, the polymer-polymer interaction, and polymer-solvent interaction with the molecular weight, diluent and method (light scattering, the size exclusion, etc.) are discussed. Polymerization of macromonomers provides regularly branched polymers with varied branching density. Since both the degree of polymerization and the length of branches may be varied, polymeric materials with specific properties can be prepared.     

Solid‐supported synthesis of well‐defined amphiphilic block copolymer from methacrylates

A new facile method for preparation of an amphiphilic block copolymer via a one‐pot sequential atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) on solid support was developed. As a model homopolymerization for the solid‐supported block copolymerization, ATRPs of MMA and HEMA in toluene and in 2‐butanone/1‐propanol solvent system were carried out, respectively. Crosslinked polystyrene beads bearing 2‐bromoisobutyrate moieties successfully initiated the polymerizations of MMA and HEMA in controlled manner. On the basis of the successful results, the one‐pot synthesis of amphiphilic block copolymer by changing the reaction medium was performed. After the ATRP of MMA in toluene at 90 °C for 1 h, the poly(MMA) formed on the beads were washed by continuous flow of 2‐butanone/1‐propanol under nitrogen with the aid of a glass filter in a U‐shaped glass vessel. Then, 2‐butanone/1‐propanol, copper chloride (I), 2,2′‐bipyridyl, and HEMA were added and heated at 50 °C for 48 h with shaking the vessel, followed by treatment with trifluoroacetic acid to isolate the well‐defined amphiphilic block copolymer, poly(MMA‐b‐HEMA). These demonstrated the feasibility of the present strategy for well‐defined synthesis of amphiphilic block copolymers via a one‐pot procedure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1990–1997, 2008     

Synthesis of new amphiphilic and lypophilic polymer networks containing 2‐methyl‐ and 2‐nonyl‐2‐oxazoline by the macroinitiator method

New amphiphilic and lypophilic polymer networks were obtained by the copolymerization of 2‐methyl‐2‐oxazoline (MeOXA), and/or 2‐nonyl‐2‐oxazoline (NoOXA) and 2,2′‐tetramethylenebis(2‐oxazoline) (BisOXA), respectively, initiating the copolymerization by random copolymers of chloromethylstyrene and methyl methacrylate or of chloromethylstyrene and styrene (macroinitiator method). Potassium iodide was used as an activator agent and the reaction was carried out in benzonitrile at 110 °C. In general, the polymer gels were obtained with a yield of 62 to 88%. The networks were characterized by high‐resolution magic angle spinning (HRMAS) NMR spectroscopy and by its absorption of polar and nonpolar solvents. In the case of amphiphilic polymer networks, the absorption of solvents depends on the molar ratio of 2‐methyl‐ to 2‐nonyl‐2‐oxazoline inside the polymer network favoring the absorption of polar solvents with a higher content of 2‐methyl‐2‐oxazoline. These gels showed a maximal swelling degree of 13 mL of water, 20 mL of methanol, and 13 mL of chloroform, respectively, per g of polymer. The lypophilic polymer networks containing only 2‐nonyl‐2‐oxazoline showed a maximal swelling degree of 8 mL of toluene, 14 mL of chloroform, and 2 mL of methanol, respectively, per g of the lypophilic network. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 122–128, 2005