树枝状大分子/聚(N-异丙基丙烯酰胺)纳米粒子的制备

使用溴乙酰溴对第四代聚丙烯亚胺树枝状大分子 (DAB-32)进行改性,成功合成了树枝状大分子引发剂DAB-32-Br。以DAB-32-Br/CuBr/Bpy为催化引发体系,分别在水和水/乙醇反应介质中,实现了N－异丙基丙烯酰胺（NIPAAm）的原子转移自由基聚合（ATRP）,得到粒径在60－150 nm范围内的树枝状大分子/聚（N－异丙基丙烯酰胺）纳米粒子。与水介质中ATRP相比,在水/乙醇介质中所得聚合物纳米粒子更加规则,而且粒子间聚集程度较低。     

PSt乳胶纳米粒子的制备

采用乳液原子转移自由基聚合法,成功制备出了聚合物乳胶纳米粒子。用光子相关光谱(PCS)和透射电子显微镜(TEM)对聚合物乳胶粒子的形貌、粒径和粒径分布进行了表征,结果表明:聚合物乳胶粒子的粒径小于100nm。研究了乳化剂的用量对乳胶粒子粒径大小的影响,研究发现:聚合物乳胶粒子的粒径随乳化剂用量的增大而减小。     

以可光交联胶束为模板的银纳米粒子的制备

采用原子转移自由基聚合及侧链化学修饰的方法,合成丙烯酸(AA)、丙烯酸-2-肉桂酰氧基乙酯(CEA)与丙烯酸正丁酯(nBA)的两亲性共聚物PAA-b-(PnBA-co-PCEA).PAA-b-(PnBA-co-PCEA)在选择性溶剂中自组装,形成以PCEA与PnBA链段为核、PAA链段为壳的球形胶束;胶束核内的肉桂酰基由紫外光引发光交联反应,得到结构稳定的胶束;以其为模板,硼氢化钠为还原剂,制备银(Ag)/胶束复合纳米粒子;使用X射线衍射、透射电子显微镜、傅立叶变换红外光谱、紫外吸收光谱等方法对制得的Ag纳米粒子进行了表征.结果表明,所得Ag纳米粒子为面心立方结构,其与胶束壳层中的羧基发生了结合;Ag/胶束复合纳米粒子的平均直径为12 nm,分散性较好,可作为导电填料用于制备聚合物基导电复合材料.     

表面引发活性聚合SiO2/PMMA核壳复合纳米粒子的制备及表征

在乙醇介质中,通过在窄粒径分布SiO2胶体粒子表面上接枝的α-溴代物引发甲基丙烯酸甲酯的原子转移自由基聚合,制备了具有核壳结构的SiO2/PMMA复合纳米粒子.采用FTIR、TGA和Acoustosizer等表征了该核壳结构粒子的结构与性能、粒径和粒径分布.结果表明:PMMA已经成功接枝到SiO2表面,并且其链长约为8...     

基于ATRP/CuAAC反应的降冰片烯类大分子单体的制备

利用原子转移自由基聚合合成了聚丙烯酸叔丁酯聚苯乙烯嵌段共聚物,通过取代反应在聚合物末端修饰叠氮基团,随后采用铜催化的叠氮-炔基环加成反应将含有炔基的顺-5-降冰片烯-外-2,3-二酸酐衍生物与嵌段共聚物偶联,得到大分子单体,最后通过大分子单体的开环易位聚合,制备了具有"Y"形的聚合物。通过核磁共振波谱仪、凝胶渗透色谱仪、原子力显微镜等研究了聚合物的结构与形貌。结果表明:通过活性可控聚合技术可以得到设计良好的具有复杂拓扑结构的聚合物。     

聚苯乙烯/纳米SiO_2复合材料的制备

经硅烷偶联剂KH-570改性后的纳米SiO2表面具有大量可反应性基团-CH=CH2。以苯乙烯和改性后的纳米SiO2为原料,利用自由基聚合反应,制备得到聚苯乙烯/纳米SiO2复合材料。FT IR和TG证明聚苯乙烯大分子链已成功接枝到纳米SiO2粒子表面。由于扩散作用的影响,相对于偶氮二异丁腈引发聚合反应,热聚合反应具有更高的接枝率。     

ZnO@PPEGMA纳米粒子的制备与性能的研究

本文首先通过溶胶凝胶原位水解法成功合成ZnO@PPEGMA壳核复合结构纳米晶。ATRP引发剂2-溴异丁酰溴通过酰溴与ZnO表面羟基的酯化反应固定在ZnO纳米粒子表面,再由ATRP引发聚合甲基丙烯酸甲基醚聚（乙二醇）酯（PEGMA）得到粒子表面接枝聚（甲基丙烯酸甲基醚聚（乙二醇）酯）（PPEGMA）的改性ZnO纳米粒子（PPEGMA@ZnO）,表面引入PPEGMA后,ZnO纳米粒子的在溶剂中分散性得到提高,它的近带边发射峰发生蓝移。     

聚苯乙烯纳米粒子的制备研究进展

尺寸在10～100 nm左右的聚合物纳米粒子是胶体和材料科学研究中的一个热点,它在光学、催化、微电子、涂料、粘合剂、生物材料和医药等领域都有广泛的应用。白色透明的聚苯乙烯纳米粒子,扩大了其在生物、光学方面的应用,前景广阔。综述了1979年以来国内外12种合成工艺方法,分析了其优缺点。     

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纳米粒子改性方面的研究进展

介绍了原子转移自由基聚合(ATRP)在纳米粒子改性方面的研究进展,综述了基于 ATRP 的多种不同催化体系的衍生技术在纳米粒子表面改性方面的应用,其中主要包括反向原子转移自由基聚合（RATRP）和电子转移活化再生催化剂原子转移自由基聚合(AGET ATRP),并对其特点进行了概述,对纳米粒子表面引发ATRP的发展进行了展望。     

Synthesis and self-assembly of poly(benzyl ether)-b-poly(methyl methacrylate) dendritic-linear polymers

Here, the dendritic chloric poly(benzyl ether) (G₁-Cl, G₂-Cl and G₃-Cl) as the macroinitiator for the controlled atom transfer radical polymerization (ATRP) of methyl methylacrylate was investigated. Polymers obtained were characterizated by GPC, ¹H NMR, FT-IR, TGA and DSC. These dendritic-linear block polymers that consist of linear and dendritic segments have very good solubility in common organic solvents at room temperature. In a selective solvent (THF/H₂O), polymers can self-assembled into the micelles that have a spherical morphology in shape due to the lowest of the surface energies.     

Initiator efficiency in ATRP: the tosyl chloride/CuBr/PMDETA system

The low efficiency of p-toluenesulfonyl chloride (TsCl) initiator for the polymerization of methyl methacrylate (MMA), when used in conjunction with N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) and CuBr under atom transfer radical polymerization (ATRP) conditions was investigated. A major by-product in the formation of poly(methyl methacrylate) was identified as N,N-dimethyl-p-toluenesulfonamide (5) and accounted for approximately half of the initiator. Compound 5 was shown to form by the direct reaction of PMDETA and TsCl. In a model experiment equimolar amounts of TsCl, PMDETA and CuBr reacted at 80°C in p-xylene resulted in the formation of 5 and two other unsaturated sulfones 2-methyl-3-[(4-methylphenyl)sulfonyl]-2-propenoic acid methyl ester (6) and 2-[[4-methylphenyl)sulfonyl]methyl]-2-propenoic acid methyl ester (7), formed by the dehydrohalogenation and subsequent isomerization of an intermediate chloro-adduct, 1-(4-methylbenzenesulfonyl)-2-chloro-2-(methyl)methyl propionate (2). Molecular modeling predicted the unsaturated sulfone 7 was thermodynamically more stable than the higher conjugated sulfone 6 and this was confirmed by the isomerization of 6 to 7 at room temperature under mild basic conditions. The absence of 6 and 7 in the polymerization of MMA under ATRP conditions showed that in the early stages of polymerization in the presence of excess MMA, the intermediate chloro-adduct 2 is not formed.     

Atom transfer radical polymerization of methyl methacrylate with low concentration of initiating system under microwave irradiation

Homogeneous atom transfer radical polymerization of methyl methacrylate (MMA) under microwave irradiation (MI) with low concentration of initiating system [ethyl 2-bromobutyrate (EBB)/CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)] was successfully carried out in N,N-dimethylformamide (DMF) at 69 °C. Plots of ln ([M]₀/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence. A 27.3% conversion for a polymer with number-average molecular weight (M_n) of 57,280 and a polydispersity index (PDI) of 1.19, was obtained under MI (360 W) with the ratio of [MMA]₀/[EBB]₀/[CuCl]₀/[PMDETA]₀=2400/1/2/2 in only 150 min; but 963 min was needed under conventional heating (CH) process to reach a 26.0 % conversion (M_n=63,990 and PDI=1.14) under identical polymerization conditions, indicating a significant enhancement of the polymerization rate under MI.     

Comparison of thermomechanical properties of statistical, gradient and block copolymers of isobornyl acrylate and n-butyl acrylate with various acrylate homopolymers

Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structure-property correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (T_g) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single T_g, block copolymers showed two T_gs and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition.     

Synthesis of thermoresponsive poly(N-isopropylmethacrylamide) and poly(acrylic acid) block copolymers via post-functionalization of poly(N-methacryloxysuccinimide)

Polymers exhibiting a thermoresponsive, lower critical solution temperature (LCST) phase transition have proven to be useful for many applications as “smart” or “intelligent” materials. A series of poly(N-isopropylmethacrylamide) (PNIPMAM) polymer, poly(N-isopropylmethacrylamide)-b-poly(acrylic acid) (PNIPMAM-b-PAA) diblock, and poly(acrylic acid)-b-poly(N-isopropylmethacrylamide)-b-poly(acrylic acid) (PAA-b-PNIPMAM-b-AA) triblock copolymer samples were synthesized via ATRP. A facile post-functionalization route was developed that uses an activated ester functionality to convert poly(N-methacryloxysuccinimide) (PMASI) blocks to LCST capable polyacrylamide, while poly(t-butyl acrylate) (PtBA) blocks were converted to water-soluble poly(acrylic acid) (PAA). The post-functionalization was monitored via ¹H NMR and ATR-FTIR. The aqueous solution properties were explored and the PNIPMAM polymers were shown to have a LCST phase transition varying from 35 to 60 °C. The ability to synthesize block copolymers that are thermoresponsive and water-soluble will be of great benefit for broader applications in drug delivery, bioengineering, and nanotechnology.     

Preparation of onion-like multilayered particles comprising mainly poly(iso-butyl methacrylate)-block-polystyrene by two-step AGET ATRP

Synthesis of multilayered composite polymer particles comprising mainly poly(iso-butyl methacrylate)-block-polystyrene (PiBMA-b-PS) has been carried out by the use of two-step activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in aqueous microsuspension. PiBMA-Br macroinitiator seed particles were prepared in the first step, followed by swelling with styrene and second step (seeded) polymerization. The blocking efficiency in the second step was found to be crucial with regards to the resulting particle morphology. A disordered sea-island morphology was obtained when the blocking efficiency was 47% (73% conversion), whereas a blocking efficiency of 61% (71% conversion) resulted in the formation of multilayered particles. High blocking efficiency can be achieved by careful adjustment of the activation rate by proper choice of polymerization temperature and amount of reducing agent (ascorbic acid).     

Synthesis of heteroarm star-shaped (polystyrene)n–[poly(ethyl acrylate)]m via atom transfer radical polymerization

Heteroarm star-shaped polymer, (polystyrene)_n–[poly(ethyl acrylate)]_m [(PS)_n–(PEA)_m], was synthesized in three steps. In the first step, star-shaped polystyrene, (PS)_n, was synthesized by the arm-first method via atom transfer radical polymerization (ATRP) using a preformed PS macroinitiator, which was obtained by ATRP of styrene with ethyl 2-bromoisobutyrate as the initiator, in the presence of divinyl benzene (DVB). In the microgel core of (PS)_n, there were not only a number of active initiating sites for ATRP, but also some unreacted vinyl groups. Then, in the second step, the residual vinyl groups were converted to 1-bromoethylbenzene groups by hydrobromination. In the last step, heteroarm star-shaped polymer, (PS)_n–(PEA)_m, where the arm number of PEA was greater than that of PS, was prepared by ATRP of ethyl acrylate using the hydrobrominated (PS)_n as the macroinitiator from 1-bromoethylbenzene initiating sites, obtained by both the addition of linear PS macroinitiators to vinyl groups of DVB and the hydrobromination of residual vinyl groups.     

Synthesis of block copolymers for surface functionalization with stimuli-responsive macromolecules

Using block copolymers with poly(n-butyl acrylate) (PBA) as anchor block being capable to tether the temperature-responsive block poly(N-isopropylacrylamide) (PNIPAAm) to the surface, polysulfone (PSf) films were functionalized applying an adsorption/surface entrapment process. Homo and block copolymer synthesis was investigated applying atom transfer radical polymerization (ATRP) using tris(2-(dimethylamino)ethyl)amine (Me₆TREN), CuCl and N,N-dimethylformamide (DMF). On basis of the determined critical micelle concentration of the block copolymers, surface functionalization of PSf was performed from an aqueous solution containing 25 vol% dimethylacetamide. These functionalized surfaces exhibit reversible temperature dependent properties due to the lower critical solution temperature (LCST) of PNIPAAm as can be proven by contact angle measurement. Furthermore, the beneficial effect of the PBA block with adjusted molecular weight on the stability of these coatings was proven. This surface functionalization method has various potential applications and the resulting surfaces are anticipated to exhibit actively triggerable ‘chaotic’ properties as basis of an efficient anti-biofouling strategy.     

Synthesis and photoluminescent property of star polymers with carbzole pendent and a zinc porphyrin core by ATRP

Styrene-type monomer 9-(4-vinylbenzyl)-9H-carbazole (VBCz) and methacrylate-type monomer 2-(9H-carbazole-9-yl)-ethyl methacrylate (CzEMA) were polymerized to star polymers respectively via atom transfer radical polymerization (ATRP) using zinc 5,10,15,20-tetrakis(4-(2-methyl-2-bromopropoxy) phenyl) porphyrin as an initiator. The emission spectra of two star polymers (star poly(VBCz) and star poly(CzEMA)) in the solid state displayed red light emission, while those of two monomers showed blue light emission. The result demonstrates that effective energy transfer occurs from the carbazole to the Zn porphyrin core. However, two star polymers in DMF solution emit week red light and strong UV light at 350-400 nm, it points that energy transfer cannot occur from the carbazole to the Zn porphyrin core effectively. They exhibit good thermal stability with T_{d poly(VBCz)} = 374 °C and T_{d poly(CzEMA)} = 297 °C at 5% weight loss. The DSC curves show that the glass transition temperature of styrene-type (T_{g poly(VBCz)} = 177 °C) was better than that of methacrylate-type (T_{g poly(CzEMA)} = 148 °C).     

Emulsion atom transfer radical polymerization of 2-ethylhexyl methacrylate

The emulsion atom transfer radical polymerization (ATRP) of 2-ethylhexyl methacrylate (EHMA) was carried out with ethyl 2-bromoisobutyrate (EBiB) as an initiator and copper bromide (CuBr)/4,4′-dinonyl-2,2′-bipyridyl (dNbpy) as a catalyst system. The effects of surfactant type and concentration, temperature, monomer/initiator ratio, and CuBr₂ addition on the system livingness, polymer molecular weight control, and latex stability were examined in detail. It was found that the polymerization systems with Tween 80 and Brij 98 as surfactants at 30 °C gave the best latex stability. The polymer samples prepared under these conditions had narrow molecular weight distributions (M_w/M_n=1.1-1.2) and linear relationships of number-average molecular weight versus monomer conversion.