以纳米球形聚电解质刷为载体原位还原制备贵金属纳米粒子的研究

以具有核壳结构的纳米球形聚电解质刷为载体,通过吸附不同种类的贵金属离子并将其原位还原,得到分布和粒径不同的贵金属纳米粒子。采用动态光散射(DLS)研究了金属离子浓度和pH对壳层聚电解质链长的影响,使用透射电镜(TEM)观察了贵金属粒子在纳米球形聚电解质刷中的分布,并测量了金属粒子的尺寸。结果表明:金属离子浓度增大,聚电解质链长减小;pH>5时,负载金属粒子之后的聚电解质链长度均大于负载前的长度。不同金属粒子的负载情况相差较大:相同温度下,纳米金属粒子的尺寸符合Ni>Ag>Co的顺序;较高温下制得的金属粒子尺寸要高于低温下制得的金属粒子尺寸;三种纳米金属粒子中,Co纳米粒子具有最好的分布和最小的尺寸。     

基于科教融合的实验教学探索与实践——以纳米球形聚电解质刷胶体粒子的制备与表征实验为例

为促进轻化工程专业本科生对胶体化学及纳米材料基础知识的理解和运用,将纳米球形聚电解质刷胶体粒子的制备与表征实验引入教学,利用光乳液聚合的方法,合成粒径均匀的聚苯乙烯纳米粒子,并通过光引发聚合的方式在聚苯乙烯纳米粒子表面接枝聚电解质链,制备具有良好稳定性和分散性的纳米球形聚电解质刷胶体粒子。该实验利用动态光散射表征所制备纳米球形聚电解质刷胶体粒子的粒径、分散性及表面带电性等性质及其对盐浓度、pH的依赖性。该实验旨在通过科教融合的形式,强化学生对专业知识的理解和运用,使学生形成严谨规范的科学思维,进而培养具有创新能力的工程科技人才。     

双亲性无规共聚物自组装胶束化研究

以偶氮二异丁腈(AIBN)为引发剂，由大分子单体己内酯改性丙烯酸酯(FA)、甲基丙烯酸甲酯(MMA)和亲水性单体丙烯酸(AA)在N，N-二甲基甲酰胺(DMF)中通过自由基共聚反应得到双亲性类接枝共聚物(MAF)。将MAF与可生物降解均聚物聚己内酯(PCL)在水溶液中进行自组装，形成以。MAF中PFA链段与PCL为核、MAF中PAA链段为壳的核壳结构复合纳米胶束，进一步对PAA壳进行化学交联，最终得到具有核壳结构的复合纳米微球。动态激光光散射(DLS)和透射电子显微镜(TEM)结果显示胶束为球形，粒径在100nm左右且呈窄分布，有一定的核壳结构。     

包覆多层聚电解质/树状大分子的聚合物微球表面CdS纳米粒的形成

将聚酰胺-胺(PAMAM)树形大分子、聚对苯乙烯磺酸钠(PSS)和聚二烯丙基二甲基氯化铵(PDADMAC)在三聚氰胺甲醛(MF)微球上进行静电自组装,制得聚电解质壳层的核壳式微球. 通过反应沉积吸附方法生成具有稳定荧光性能的CdS/聚电解质核壳式复合微球. 用透射电镜表征复合微球形貌,用反射紫外和荧光表征了CdS/聚电解质核壳式复合微球的光学特性.     

原子转移自由基聚合法制备磁性球形聚电解质刷及其应用研究

以正硅酸四乙酯为原料,采用溶胶凝胶法制备包覆有Fe_3O_4的复合磁性纳米SiO_2微球(MS),经氨基化改性后接枝引发剂,通过热诱导原子转移自由基聚合法(ATRP)制备磁性球形纳米聚电解质刷(MSPB),并对其结构和性能进行表征,考察聚合条件对制备MSPB分子量的影响。将MSPB应用在牛血清蛋白(BSA)和血管紧张素转化酶(ACE)抑制肽FFVAP二元模拟体系中的吸附FFVAP。结果表明,MSPB能优先吸附小分子多肽FFVAP,可作为分离ACE抑制肽的载体。     

水介质中表面引发ATRP法合成PMAA聚电解质刷

水介质中以表面引发ATRP法在单分散的二氧化硅微球表面接枝了一层PMMA聚合物刷,然后通过水解得到PMAA聚电解质刷。通过控制ATRP的反应时间得到了不同分子量且分子量分布较窄的聚电解质刷。结果表明,接枝硅烷偶联剂APTES的最佳反应方式为静置反应,对于1 g微球最佳接枝量为4 mL,聚电解质刷的分子量随ATRP反应时间增长而增大。     

纳米SiO_2表面接枝甲基丙烯酸甲酯的研究

为了提高纳米二氧化硅(SiO2)粒子在阻燃型聚合物基纳米复合材料中的有效利用,需要对粒子的表面进行改性。此实验采用溶液聚合法,使甲基丙烯酸甲酯单体(MMA)在烷基化预处理的纳米SiO2粒子的表面进行接枝聚合,得到以纳米SiO2粒子为核、接枝聚甲基丙烯酸甲酯为壳的复合颗粒(SiO2-g-PMMA)。结果表明,PMMA以化学键成功地接到纳米SiO2的表面,并可通过改变接枝聚合的条件来调节粒子上所接聚甲基丙烯酸甲酯的结构,改性后的纳米SiO2粒子具有良好的热稳定性及分散性。     

表面紫外光接枝聚丙烯酸的聚电解质刷型纳米纤维素晶须

为了研究快速地制备改性纳米纤维素的方法,将低相对分子质量(简称分子量,下同)聚丙烯酸(PAA)以紫外光引发聚合的方法接枝到纳米纤维素晶须上,制备出聚电解质刷型纳米纤维素晶须。采用红外光谱、固体核磁、透射电镜、X射线衍射、热重分析等对刷型纳米纤维素晶须进行了表征测试。考察了单体浓度、光引发剂用量、紫外光照射时间等对接枝聚合反应的影响。结果表明,PAA与纳米纤维素晶须的质量比大于1∶1,光引发剂用量为纳米纤维素晶须质量的0.8%~1.0%,反应时间为90 s时,所得接枝产物中羧基含量最高,达到0.012 75 mol/g。紫外光接枝减少了制备改性纳米纤维素的步骤和时间,将扩展纳米纤维素的表面改性方法和用途。     

一种抗滴落、热塑化的橡胶接枝共聚物及其制备方法

正由广东盛化塑胶科技有限公司申请的专利(公开号CN 104945578A,公开日期2015-09-30)"一种抗滴落、热塑化的橡胶接枝共聚物及其制备方法",涉及的橡胶接枝共聚物具有由核层和壳层组成的核壳结构,核层为聚(四氟乙烯接枝丁二烯),且呈纳米级的两相互穿网络结构,壳层为由甲基丙烯酸烷基酯、苯乙烯和丙烯腈中的至     

RAFT与点击化学结合合成SiO2/PNIPAm杂化微球

利用可逆加成-断裂链转移(RAFT)聚合与点击化学相结合的方法,将大分子链末端含巯基的聚(N-异丙基丙烯酰胺)(PNIPAm-SH)接枝到SiO2纳米粒子上制备了温度响应的SiO2为核、PNIPAm为壳的核-壳结构的SiO2/PNIPAm纳米杂化微球。采用FTIR、热重分析(TGA)、透射电镜(TEM)和动态光散射(DLS)对SiO2/PNIPAm杂化微球进行了表征。结果表明,SiO2/PNIPAm杂化微球粒径约为286 nm,尺寸均一。热重分析表明,PNIPAm接枝率为87%(质量分数),PNIPAm分子链在SiO2粒子上的接枝密度为0.4分子链/nm2。杂化微球表现出明显的温度响应性,温度从25℃升至35℃时,杂化微球粒径从286 nm减小至268 nm,PNIPAm壳层的厚度从16 nm减小至7 nm。     

Surface modification and characterization of carbon spheres by grafting polyelectrolyte brushes

Modified carbon spheres (CSPBs) were obtained by grafting poly(diallyl dimethyl ammonium chloride) (p-DMDAAC) on the surface of carbon spheres (CSs). It can be viewed as a kind of cation spherical polyelectrolyte brushes (CSPBs), which consist of carbon spheres as core and polyelectrolytes as shell. The method of synthesizing carbon spheres was hydrothermal reaction. Before the polyelectrolyte brushes were grafted, azo initiator [4,4′-Azobis(4-cyanovaleric acyl chloride)] was attached to the carbon spheres'' surface through hydroxyl groups. CSPBs were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), conductivity meter, and system zeta potential. The results showed that compared with carbon spheres, the conductivity and zeta potential on CSPBs increased from 9.98 to 49.24 μS/cm and 11.6 to 42.5 mV, respectively, after the polyelectrolyte brushes were grafted. The colloidal stability in water was enhanced, and at the same time, the average diameter of the CSPBs was found to be 173 nm, and the average molecular weight and grafted density of the grafted polyelectrolyte brushes were 780,138 g/mol and 4.026 × 10⁹/nm^2, respectively.     

Janus gold nanoparticle with bicompartment polymer brushes templated by polymer single crystals

Janus particles have attracted increasing attention from the communities of materials science, chemistry, physics and biology. While large size Janus particles are readily achieved, synthesizing Janus nanoparticles (JNP) with diameters smaller than ∼20 nm remains a challenging task. In this article, we report a systematic study on growing polymer brushes on polymer-single-crystal-immobilized 6 and 15 nm diameter gold nanoparticles (AuNPs) using atom transfer radical polymerization. JNPs with bicompartment polymer brushes, such as poly(ethylene oxide) (PEO)/poly(methyl methacrylate), PEO/poly(tert-butyl acrylate), and PEO/poly(acrylic acid), were synthesized. The grafting densities can be carefully controlled. The Janus feature of these particles was confirmed using both platinum nanoparticle decoration and UV/Vis spectroscopy analysis. The surface plasmon resonance absorbance of Janus particles exhibited a blue shift compared with that of symmetric AuNPs with either homopolymer or mixed polymer brushes. This work demonstrated that using polymer single crystal as the templates, small size (<20 nm diameter) JNPs having bicompartment polymer brushes can be readily obtained. The ability to tune grafting density and molecular weight of polymer brushes can lead to controlled particle amphiphilicity.     

Functionalization of fluoropolymer surfaces with nanopatterned polyelectrolyte brushes

We present a strategy to combine the excellent bulk properties of fluoropolymer substrates with the wide range of functionalities of surface-grafted polyelectrolyte brushes. Patterns of radicals serving as initiators were created by irradiation with extreme ultraviolet light (EUV) in an interference setup at the Swiss Light Source. From these initiators, brushes of poly(methacrylic acid) or poly(4-vinylpyridine) were grafted in one step by free-radical polymerization. Brushes carrying primary or secondary amines, i.e. poly(vinylamine), poly(allylamine) and poly(N-methyl-vinylamine), were obtained by grafting vinylformamide and acrylonitrile followed by hydrolysis or reduction. Periodic patterns with a resolution of 200 nm were achieved, while the thickness of the brushes in unpatterned areas could be controlled over a range of several hundred nanometers by variation of EUV dose and grafting parameters. The maximum dry brush thickness was used to estimate the average molecular weight of the polymer chains.     

Surface-initiated controlled polymerization as a convenient method for designing functional polymer brushes: From self-assembled monolayers to patterned surfaces

Surface-functionalization mediated through “grafting from” methods is of considerable interest as means to tailor the chemical and physical properties of functional substrates in a reliable way. The resulting polymer brushes, obtained by a “grafting from” strategy, are composed of grafted polymer chains tethered from one of their extremities to a surface by a covalent bond. Tuning the molecular parameters of these polymeric brushes such as the nature of monomer, the grafting density, and the chain length as well as the design of micropatterned structures enables delicate modification of the properties of these substrates, paving the way to the development of functional surfaces. In this review, we highlight recent and most important approaches to form monolayers and to subsequently elaborate homogeneous and heterogeneous coatings of polymer brushes by surface-initiated polymerization. The control of initiator molecule assembly is particularly important for the final configuration of polymer brushes. We report the creation of homopolymers and block copolymers using major controlled polymerization techniques as well as lithographic techniques aiming at the design of polymeric (micro- or nano-) patterns.     

Programming nanostructures of polymer brushes by dip-pen nanodisplacement lithography (DNL)

We report a facile and versatile scanning probe based approach-dip-pen nanodisplacement lithography (DNL)--for manipulating nanostructures of polymer brushes. Nanostructured polymer brushes with sizes as small as 25 nm are made by DNL patterning of the initiator molecules and subsequent surface-initiated polymerization. Nanoconfinement effects including chain collapsing and spreading are observed in the nanopatterned polymer brushes. In addition to chemical structure, size, topography and shape, our approach can also readily program the grafting density, chain configuration, hierarchical structure and multiplexing of the polymer brushes, which allows for the realization of complex chemical surfaces.     

A numerical study of spherical polyelectrolyte brushes by the self-consistent field theory

The self-consistent field theory (SCFT) is employed to numerically study the scaling laws of brush height and the amount of counter-ions trapped inside a spherical polyelectrolyte (PE) brush immersed in a good solvent with no added salt ions. In particular, the curvature effect of the grafting substrate on the brush height and the amount of counter-ions trapped inside the PE brush is carefully examined. It is found that the brush height shows a non-trivial dependence on the radius of the grafting substrate. The numerical result reveals that the brush height scales linearly with respect to the grafting density and the average degree of ionization of PE chains in the planar surface limit, but not in the opposite limit. The numerical results show that, in a salt-free solution, about 96% of the counter-ions are trapped within the range of extension of grafted PE chains in the planar surface limit, irrespective of other system parameters. On the contrary, for the grafting substrate with high curvature, i.e., the radius of the grafting substrate is much smaller than the brush height, the amount of counter-ions trapped inside the PE brush approaches zero in the large system size limit. The underlining mechanisms governing the curvature effect of the grafting substrate on the brush height and the amount of counter-ions trapped inside PE brushes are elucidated.     

Surface-initiated ring opening polymerization of N-carboxy anhydride of benzyl-l-glutamate monomers on soft flexible substrates

The potential of pulsed plasma deposited polyallylamine (PAA) adlayer has been successfully demonstrated for fabrication of polypeptide brushes functionalized soft flexible polymeric surfaces. Polymeric substrates functionalized with the plasma deposition PAA adlayer resulted in polymeric surfaces functionalized with amino groups, which are the suitable initiating moieties for ring-opening polymerization (ROP) of N-carboxy anhydride of benzyl-l-glutamate (NCA-BLG) monomer. Poly(γ-benzyl-l-glutamate) (PBLG) brushes were grown on PAA functionalized polypropylene (PP), and polytetrafluoroethylene (PTFE) polymeric substrates. These substrates were intentionally chosen for their inert chemical nature towards most wet chemical surface modification reactions. Surface grafted thin films of poly(γ-benzyl-l-glutamate) PBLG on both the PP and PTFE polymeric substrates yielded high density PBLG brushes. PBLG chain orientation, secondary structure and grafting density were characterized by infra-red spectroscopy. The synthesis of PBLG brushes on a flexible polymeric substrate is unprecedented and technologically important, since PBLG possess good electro-optical activity. Analysis of brush layers by Attenuated Total Reflectance Infra-Red (ATR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) as well as atomic force microscopy (AFM) fully corroborated the success of the plasma activated soft surface grafting approach.     

Spherical polymer brushes with vinylimidazolium-type poly(ionic liquid) chains as support for metallic nanoparticles

We present here the synthesis of spherical polyelectrolyte brushes by photo-emulsion polymerization with a solid polystyrene core (diameter ～ 100 nm) onto which chains of vinylimidazolium-type poly(ionic liquid)s have been densely grafted. The as-synthesized brush particles were employed as nanoreactors for the generation and immobilization of metal nanoparticles. Transmission electron microscopy characterization shows that Au and Pd nanoparticles with diameter of 2.1 ± 0.2 nm and 2.5 ± 0.3 nm are homogeneously embedded inside the PIL brushes, respectively. The study of swelling behavior of the brush particles before and after metal deposition indicates obviously ion-specific effect. The composite particles exhibit a long-term colloidal stability in aqueous solutions as well as in ionic liquids. Catalytic activity of the as-synthesized metal nanocomposite particles is investigated by using the reduction of 4-nitrophenol with NaBH₄ as a model reaction, which can be compared directly with reported systems. In addition, it is found that the rate constant k_app of PIL-metal nanocatalyst could be modulated by salt concentration.     

Synthesis and characterization of TiO2 nanoparticles chemically coated with zwitterionic polymer brushes

This study introduces a synthetic method to graft zwitterionic poly (2-methacryroyloxyethyl phosphoryl choline) brushes onto TiO₂ nanoparticles with thickness of a few nanometers. The grafting of zwitterionic polymer brushes was characterized by electron microscope measurements, zeta-potential analysis, and thermo-gravimetric analysis. The technique we employed to synthesize those hybrid nanoparticles was a modified seeded emulsion polymerization in which the polymerization loci were changed in the stage of radical initiation and chain propagation. We have found that the polymerization loci should be on the surface for achieving the effective grafting of polymer brushes. From the suspension rheology studies, we have observed that the suspension of our hybrid nanoparticles was dominated by the attractive force as well as by packing volume effect. This unique rheological behavior is expected to be useful for understanding the inter-particle interactions in complex formulations.     

Ultrasonic sealing versus heat conductive sealing of polyethylene/polybutene‐1 peel films

Functional brushes have recently emerged as an extremely versatile way to modify surface properties in a robust and controlled way. In this study, well‐defined, high density oligo‐N‐isopropylacrylamide (oligoNIPAM) brushes with ? OH and ? COOH end‐groups were fabricated through a reliable strategy by the combination of the self‐assembly of bimolecular macroazoinitiator on silicon surface and surface‐initiated nitroxide mediated polymerization of N‐isopropylacrylamide in the presence of chain transfer agent (i.e., 2‐mercaptoethanol or 3‐mercaptopropionic acid). The living polymerization produced silicon substrate‐coated with functional oligoNIPAM with a target molecular weight and a grafting density as high as 8.14 chains nm^?2. The functional oligoNIPAM brushes can be employed for the adsorption of biomacromolecules such as DNA and proteins. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013