树形大分子/聚苯乙烯纳米粒子的制备

将树形大分子DAB-32通过酰氯化改性,制成树形大分子引发剂(DAB-32-Cl),成功地进行了苯乙烯原子转移自由基聚合。利用透射电子显微镜(TEM)和原子力显微镜(AFM)观察所制备树形大分子/聚苯乙烯复合聚合物的形态结构。研究发现所制备树形大分子/聚苯乙烯复合聚合物呈球形结构,粒径小于100nm、大小分布较为均一。     

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。     

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。     

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.     

乳液法制备聚合物纳米粒子的研究进展

综述了乳液法制备聚合物纳米粒子的研究进展,详细介绍了采用新型乳化剂,即高分子表面活性剂与反应性表面活性剂,和以超声波辐照技术为主的新技术制备聚合物纳米粒子方面的研究成果。     

中空聚合物乳胶粒子的制备

研究了在制备中空乳胶粒子的过程中,复合乳液（苯乙烯（Ｓｔ）－丙烯酸丁酯（ＢＡ）－甲基丙烯醛（ＭＡ））进行种子聚合时,Ｓｔ／ＢＡ的质量比和ＭＡ的用量对胶乳粒子的空径、粒径和表面羧基质量摩尔浓度的影响。实验结果表明,当Ｓｔ／ＢＡ的质量比为１９,ＭＡ质量分数为单体的５．６％时,形成的乳胶粒子的空径最大。     

活性自由基乳液聚合的研究进展

活性自由基乳液聚合是一个非常新的研究领域。介绍了目前活性自由基乳液聚合领域的3种常用的方法及应用这些方法进行乳液聚合的研究进展,包括:原子转移自由基聚合(ATRP),氮氧调节自由基聚合(NMP)和可逆加成-断裂链转移自由基聚合(RAFT)。     

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。     

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...     

聚合物纳米粒子的制备及其对橡胶的增强

采用乳液聚合法分别制备了粒径为40 nm、单分散的交联聚苯乙烯(PS)和α-甲基苯乙烯-丙烯腈共聚物(α-MS/AN)乳胶粒子, 将其作为填料,通过乳液共混共沉法分别添加到丁苯橡胶(SBR)和丁腈橡胶(NBR)中.结果表明,当填料用量相同时,PS增强SBR的力学性能优于α-MS/AN增强SBR;而α-MS-AN增强NBR的力学性能优于PS增强NBR.聚合物纳米粒子对橡胶具有良好的增强效果,且增强橡胶的密度低.     

Preparation of Ni-g-polymer core–shell nanoparticles by surface-initiated atom transfer radical polymerization

Surface-initiated atom transfer radical polymerization (si-ATRP) technique was successfully employed to modify Ni nanoparticles with polymer shells. ATRP initiators were covalently bonded onto Ni nanoparticle surfaces by a combination of ligand exchange and condensation reactions. Various kinds of polymers including poly(methyl methacrylate) (PMMA) and poly(n-isopropylacrylamide) (PNIPAM) were grafted from the immobilized initiators. The grated polymer shells gave Ni nanoparticles exceptionally good dispersion and stability in solvents. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and transmission electron spectroscopy (TEM) were employed to confirm the grafting and to characterize the nanoparticle core–shell structure. Gel permeation chromatography (GPC) studies of cleaved polymer chains revealed that the grafting polymerization was well controlled. The magnetic properties of Ni-g-polymer nanoparticles were also studied.     

Characterization of aqueous micellar solutions of amphiphilic block copolymers of poly(acrylic acid) and polystyrene prepared via ATRP. Toward the control of the number of particles in emulsion polymerization

A series of diblock, triblock and star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by ATRP. The structure of the copolymers, the size of the blocks and the composition were varied, keeping however a short polystyrene block and a poly(acrylic acid) content larger than 60 mol% to allow solubility in alkaline water. Their micellization was studied by static and dynamic light scattering and the influence of their structural characteristics on the aggregation number, N_agg, was examined at low salt concentration and alkaline pH. It was shown that micelles were in thermodynamic equilibrium and that N_agg followed the power law N_agg∼N_A^−0.9N_S² (with N_A, the total number of acrylic acid units in the copolymer and N_S, the total number of styrene units), that is characteristic of amphiphile micelles formed from strongly segregated block copolymers. Moreover, N_agg was independent of salt concentration in the investigated range. The same copolymers were previously used as stabilizers in emulsion polymerization [Macromolecules 34 (2001) 4439]. The final latex particle concentration, N_p, was compared with N_m, the initial micelle concentration. This enabled us to conclude that among the block copolymers studied, those with high acid content behaved like low molar mass surfactants. In contrast, those with low acid content formed stable micelles that could be directly nucleated to create latex particles, allowing a good control over N_p.     

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.     

Surface-initiated atom transfer radical polymerization of methyl methacrylate on magnetite nanoparticles

The synthesis of magnetite nanoparticles coated with a well-defined graft polymer is reported. The magnetite nanoparticles with an initiator group for copper-mediated atom transfer radical polymerization (ATRP), 2-(4-chlorosulfonylphenyl) ethyltrichlorosilane (CTCS) chemically bound on their surfaces were prepared by the self-assembled monolayer-deposition method. The surface-initiated ATRP of methyl methacrylate (MMA) was carried out with the CTCS-coated magnetite nanoparticles in the presence of free (sacrificing) initiator, p-toluenesulfonyl chloride. Polymerization proceeded in a living fashion, exhibiting first-order kinetics of monomer consumption and a proportional relationship between molecular weight of the graft polymer and monomer conversion, thus providing well-defined, low-polydispersity graft polymers with an approximate graft density of 0.7 chains/nm². The molecular weight and polydispersity of the graft polymer were nearly equal to those of the free polymer produced in the solution, meaning that the free polymer is a good measure of the characteristics of the graft polymer. The graft polymer possessed exceptionally high stability and remarkably improved dispersibility of the magnetite nanoparticles in organic solvent.     

Preparation and characterization of proton conducting polysulfone grafted poly(styrene sulfonic acid) polyelectrolyte membranes

The syntheses of series of proton conducting comb copolymer membrane involving polysulfone back bone as main chain and poly(styrene sulfonic acid) (PSSA) being side chain, i.e. polysulfone grafted poly(styrene sulfonic acid) (PSU-g-PSSA) are presented. Chloromethylation of the polysulfone backbone was done by Fridel Craft alkylation reaction. Atom transfer radical polymerization was used for control grafting from the chloromethylated positions. The successful substitution of the chloromethyl group and its grafting with PSSA was characterized by elemental analysis and proton nuclear magnetic resonance. Water uptake, electrochemical properties like ion exchange capacity (IEC) and proton conductivities increase with increase in PSSA contents. Thermal gravimetric analysis (TGA) showed the thermal stability of membranes up to 250 °C. Proton conductivity for maximum amount of grafting is 0.02 S/cm.     

Memory effect in polymer brushes containing pendant carbazole groups

Poly(9-(2-(4-vinyl(benzyloxy)ethyl)-9H-carbazole)) (PVBEC) brushes, have been successfully prepared on the silicon surfaces via surface-initiated atom transfer radical polymerization (ATRP). Conductance switching at a voltage of about −2.1 V is observed in the memory device based on the PVBEC brushes. The fabricated device shows the good memory characteristics as the ON/OFF current ratio up to 10⁵, and enduring 10⁶ read cycles under −1 V pulse voltages. Compared with those of the conventional Si/PVBEC/Al device fabricated by spin-coating, the switch voltage is lower and the ON/OFF current ratio is higher in the volatile Si-g-PVBEC/Al memory device.     

Fabrication of patterned high-density polymer graft surfaces. II. Amplification of EB-patterned initiator monolayer by surface-initiated atom transfer radical polymerization

Patterned films of a low-polydispersity polymer densely end-grafted on a silicon substrate were fabricated for the first time by the combined use of electron beam (EB) lithography and living radical polymerization; a focused EB was scanned on an initiator-immobilized substrate to selectively bombard and decompose the initiator, and then the EB-induced pattern was amplified by the atom transfer radical polymerization (ATRP) technique using Cu/ligand complexes. Ellipsometric and atomic force microscopic studies indicated that doses sufficiently larger than 2000 μC/cm² would completely decompose the monolayer of the initiator, 2-(4-chlorosulfonylphenyl)ethyltrichlorosilane, and that the surface-initiated ATRP could amplify the EB-produced fine pattern of the initiator monolayer.     

Preparation of hyperbranched copolymers of maleimide inimer and styrene by ATRP

Novel hyperbranched copolymers were prepared by the atom transfer radical copolymerization of N-(4-α-bromobutyryloxy phenyl) maleimide (BBPMI) with styrene in 1-methyl-2-pyrrolidone (NMP) using the complex of CuBr/2,2′-bipyridine as catalyst. The copolymerization behavior was investigated by comparison of the conversion of double bond of BBPMI determined by ¹H NMR with that of styrene. The hyperbranched structure of resulting copolymers was verified by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS). The influences of dosage of catalyst and monomer ratio on the polymerization rate and structure of the resulting polymers were also investigated. The glass transition temperature of the resulting hyperbranched copolymer increases with increasing mole fraction of BBPMI, f_BBPMI. The resulting copolymers exhibit improved solubility in organic solvents; however, they show lower thermal stabilities than their linear analogues.     

Preparation of block copolymer particles by two-step atom transfer radical polymerization in aqueous media and its unique morphology

Submicron-sized poly(i-butyl methacrylate)-block-polystyrene particles were successfully prepared by two-step atom transfer radical polymerization (ATRP) in aqueous media: ATRP in miniemulsion (miniemulsion-ATRP) followed by ATRP in seeded emulsion polymerization (seeded-ATRP). When PiBMA particles, which were prepared by the miniemulsion-ATRP process with polyoxyethylene sorbitan monooleate (Tween 80, nonionic emulsifier) of 6-10 wt % based on iBMA, were used as seed in the seeded-ATRP of styrene, the block copolymer particles having narrow molecular weight distribution and pre-determined molecular weight were prepared at high conversion. Some block copolymer particles had an ‘onion-like’ multilayered structure. In this way, controlled/living free radical polymerization can be employed to obtain unique particle morphologies that may not be easily accessible using conventional free radical polymerization.     

One pot,two step sequence converting atom transfer radical polymerization directly to radical trap-assisted atom transfer radical coupling

Monobrominated polystyrene (PStBr) chains were prepared using standard atom transfer radical polymerization (ATRP) procedures at 80 °C in THF, with monomer conversions allowed to proceed to approximately 40%. At this time, additional copper catalyst, reducing agent, and ligand were added to the unpurified reaction mixture, and the reaction was allowed to proceed at 50 °C in an atom transfer radical coupling (ATRC) phase. During this phase, polymerization continued to occur as well as coupling; expected due to the substantial amount of residual monomer remaining. This was confirmed using gel permeation chromatography (GPC), which showed increases in molecular weight not matching a simple doubling of the PStBr formed during ATRP, and an increase in monomer conversion after the second phase. When the radical trap 2-methyl-2-nitrosopropane (MNP) was added to the ATRC phase, no further monomer conversion occurred and the resulting product showed a doubling of peak molecular weight (M_p), consistent with a radical trap-assisted ATRC (RTA-ATRC) reaction.