表面活性剂PAA对羟基磷灰石微粒分散性的调控及机理研究

羟基磷灰石(hydroxyapatite,HAP)因其具有优良的生物相容性和生物活性而被广泛应用于临床。但由于制备过程中不可避免的团聚,严重影响其性能。本文首次借助阴离子表面活性剂聚丙烯酸(PAA),通过控制PAA的含量成功制备具有不同颗粒尺寸的HAP粉末样品,进而调控其分散性;同时借助多种表征技术包括扫描电子显微镜(SEM),X射线衍射(XRD)及粒径分析仪等等,获取HAP样品微观形貌及粒径尺寸,深入探究表面活性剂PAA对HAP微粒分散性的影响机制。     

改性羟基磷灰石/聚乳酸纳米复合材料的结晶行为

利用溶剂复合的方法制备了具有良好生物相容性的表面接枝聚(γ-苄基-L-谷氨酸)的改性羟基磷灰石/聚乳酸纳米复合材料, 并研究了其熔融与结晶行为. 结果表明, 聚乳酸的玻璃化转变温度为60.3 ℃, 而复合材料的玻璃化转变温度达到65.8 ℃, 不同样品在140 ℃等温结晶后, 改性羟基磷灰石/聚乳酸复合材料的球晶直径仅为聚乳酸(PLLA)球晶直径的16.7%~66.7%. 复合材料的熔点提高到184.4 ℃.     

原位聚合法制备聚合物/纳米SiO_2复合材料的研究进展

纳米SiO_2改性聚合物制备的关键在于提高纳米粒子与聚合物基体的相容性及分散性;对纳米SiO_2进行不同的表面改性及选择合适的复合材料制备方法可以改变纳米粒子与聚合物基体的界面结合方式以及相容性和分散性,进而在不同程度上影响材料的性能.本文介绍了改性前后纳米SiO_2与聚合物基体的多种界面结合方式,对近年来利用原位聚合法制备聚合物/纳米SiO_2复合材料的研究现状和进展进行了综述.     

基于胺基与环氧的开环反应构建医用阳离子聚合物

近些年,阳离子聚合物在生物医用材料方面的研究与应用得到了广泛的关注.通过胺基与环氧的开环反应,可以得到伯胺、仲胺、叔胺等含氮阳离子,同时也会产生丰富的羟基,这赋予了所得聚合物优异的生物相容性以及穿透细胞的能力.本文主要就近些年来通过胺基与环氧的开环反应,所得到的基于乙醇胺功能化的聚甲基丙烯酸缩水甘油酯(PGEA)的阳离子聚合物和支化阳离子聚合物的构建策略,以及其在核酸递送、抗菌等方面的应用进行总结阐述.     

表面富集季胺盐的交联聚苯乙烯微球合成与表征及其溶胀行为研究

在聚合物微球表面引入不同的基团 (如亲水性的羟基或羧基 ) ,可以改善聚合物微球的稳定性甚至生物相容性[1～ 4] ;利用表面基团可以把无机半导体微粒和功能有机分子以及生物分子引入聚合物微球[5～ 8] ,赋予聚合物微球特殊的性能 ,使其广泛应用于涂料、光电功能材料和生物医用材料等领域[9～ 15] .其中 ,表面带有阳离子的聚合物微球在絮凝剂、胶粘剂、水性涂料等方面已经得到广泛研究[16～ 2 0 ] .通常阳离子聚合物微球可以根据不同的需要利用常规乳液聚合、核壳乳液聚合等方法来合成 .亲水性和疏水性单体进行的无皂乳液聚合[2 1] ,因其能在…     

热塑性淀粉耐水性的化学与物理作用机制

石油资源的短缺以及减轻石油基聚合物所产生的环境负担的必要性,推动了生物可降解材料的开发和生产。近几十年来天然聚合物由于无毒性、可生物降解性和生物相容性正在某些领域取代目前的合成聚合物。淀粉由于其可再生性、可生物降解性、低成本和易获得性已经被广泛研究用于制造可生物降解的复合材料,应用于农业、食品、医药和包装行业。但淀粉的多羟基结构赋予其很强的亲水性,这种湿度敏感性限制了它们的机械性能并影响到其应用。本文主要从提高热塑性淀粉耐水性的物理与化学作用机理的角度出发,总结和归纳了近年来国内外以提高热塑性淀粉材料的耐水性能和降低其对环境湿度敏感性为目的的研究工作,介绍了影响耐水性能的相关因素以及改善方法,并指出今后研究工作的发展方向。     

含胆汁酸和胆固醇的双亲性聚合物的研究进展

胆固醇和胆汁酸是广泛存在于自然界中的天然物质 ,生物相容性好 ,被广泛地用于高分子的疏水性改性 ,得到的双亲性聚合物 ,在水相中可以自组装或自聚集成纳米粒子。本文综述了含胆固醇或胆汁酸的双亲性聚合物的最新研究进展以及它们在药物载体系统中的应用。     

纤维素基吸附分离材料研究进展

以纤维素为原料制备吸附分离材料可以减少对石油资源的依赖,并具有成本低、环境友好和生物相容性好等优点。利用纤维素中的羟基基团,通过交联、接枝、引入无机粒子或与聚合物复合,可以制备出微球和薄膜等不同形态的吸附分离材料,广泛应用于生物医学,废水处理、气体分离等领域。本文结合近五年来国内外纤维素及其复合材料在吸附分离领域的研究近况,从水、油、重金属、气体和有机物的应用进行了综述,总结了纤维素基吸附分离材料的研究尚存在的问题,探讨了今后的研究方向。     

Tb掺杂的纳米羟基磷灰石生物荧光探针的合成与表征

本文在室温下用Tb(Ⅲ)对纳米羟基磷灰石(HAP)进行表面修饰制成了新型无机生物荧光探针。在十六烷基三甲基溴化铵(CTAB)参与调控下,控制适当的反应条件,可生成20 nm左右的HAP颗粒。经表面修饰后所得的Tb-HAP颗粒的尺寸范围仍在20±5 nm之间,但具有发光特性,其最大发射峰值在544 nm,且能在可见光波段(488 nm)下进行激发。生物TEM结果表明,这种20 nm左右大小的Tb-HAP可以很容易地进入兔脊髓间充质干细胞。因此,这一具有荧光特性的Tb-HAP有望成为具有良好生物兼容性的并可在细胞内稳定存在的生物无机纳米探针。     

光引发甲基丙烯酸聚合改性羟基磷灰石表面的研究

羟基磷灰石(HPA)具有良好的生物相容性和生物活性,被认为是最有前途的陶瓷人工齿和人工骨置换材料。然而,纯HAP的力学性能比较差,断裂韧性(KIC)不超过1.0MPa.m1/2(自然骨为2-12MPa.m1/2)[1],作为人工种植体其使用可靠性较差。这大大限制了它在承载部位骨替换中的应用。为了改善     

Comparative study of particle size analysis of hydroxyapatite-based nanomaterials

The purpose of this work was to compare hydroxyapatite (HAP) and composites of HAP, HAP with chitosan (CS), and HAP with poly(vinyl pyrrolidone) (PVP), in terms of their particle size and morphology, using different methods, such as Coulter counter analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Although many researchers have studied HAP and CS/HAP and PVP/HAP composites extensively, there is no evidence of a comparative study of their particle sizes. For this reason, different complementary methods have been used so as to provide a more complete image of final product properties — particle size — from the perspective of possible applications. The syntheses of HAP and HAP with polymer nanoparticles were carried out employing a precipitation method. Variation in particle size with synthesis time and influence of the reactants’ concentration on the materials’ preparation were systematically explored. Crystallite size calculated from XRD data revealed nanosized particles of HAP, CS/HAP, and PVP/HAP materials in the range of 2.5–9.2 nm. Coulter counter analysis revealed mean particle sizes of one thousand orders of magnitude larger, confirming that this technique measures agglomerates, not individual particles. In addition, the particles’ morphology and an assessment of their binding mode were completed by TEM measurements.     

表面改性氢氧化镁阻燃聚丙烯的研究进展

聚丙烯是综合性能良好的五大通用塑料之一,但是其易燃的特点限制了其在很多领域的应用。氢氧化镁(MH)作为一种环境友好型的无机阻燃剂,常被用于阻燃聚丙烯,但是未经改性的MH极性强,易团聚,与基体的相容性差,难以在聚合物基体中均匀分散,在导致阻燃效率低的同时,对复合材料的力学性能也有很大的负面影响,为提高MH在聚合物基体中的界面相容性,往往需要对MH进行表面改性。本文总结了近几年来以表面化学改性、表面接枝改性、微胶囊化改性三种方法改性的MH阻燃聚丙烯的研究进展,并对其下一步的研究方向进行了展望。     

Thermodynamic state parameters of a system as a prognostic factor of strength properties of composites with different natures of a surface

It is shown that, upon the modification of filler particles by a polymer film of the same nature as the polymer matrix, intermolecular bonds become stronger in a boundary layer between a polymer and a filler and the level of mechanical characteristics of polymer composite increases correspondingly. In order to ensure the working capacity of the metal-epoxy primer-polyethylene system, along with cohesive and adhesive properties of epoxide polymers, it is also necessary to take into account acid-base properties of solid metal and polymer surfaces.     

Functional inorganic nanofillers for transparent polymers

The integration of inorganic nanoparticles into polymers has been used for the functionalization of polymer materials with great success. Whereas in traditional polymer composites, micron sized particles or agglomerates typically cause significant light scattering hampering optical applications, in nanocomposites the particle dimensions are small enough for the production of highly transparent composites. A challenge for the generation of such materials is to develop an integrated synthesis strategy adapting particle generation, surface modification and integration inside the polymer. Surface grafting using polymerizable surfactants or capping agents allows for linking the particles to the polymer. Novel techniques such as in situ polymerization and in situ particle processing are beneficial to avoid aggregation of inorganic particles inside the polymer matrix. The functions associated with inorganic fillers are widespread. Layered silicates and related materials are nowadays commercially available for improving mechanical and barrier properties in packaging. With the availability of highly transparent materials, the focus has shifted towards optical functions such as luminescence and UV-protection in transparent polymers. IR-active fillers are used in laser-holography for transparent poly(methyl methacrylate) (PMMA) nanocomposites. Refractive index modulation and ultrahigh refractive index films were developed based on inorganic materials such as PbS. The integration of magnetic nanoparticles has a great potential for applications such as electromagnetic interference shielding and magneto-optical storage.This tutorial review will summarize functions associated with the integration of inorganic nanofillers in polymers with a focus on optical properties.     

Epoxy nanocomposites with high thermal conductivity and low loss factor: Realize 3D thermal conductivity network at low content through core-shell structure and micro-nano technology

Dielectric polymers with high thermal conductivity are very promising in the fields of aerospace and electronic device packaging. However, composites with excellent dielectric properties usually have low thermal conductivity. It is usually to fill the polymer with thermal conductivity particles to improve the thermal conductivity, but the high content of filler often reduces the mechanical properties of the polymer. In this paper, the traditional insulating polymer epoxy resin was used as the matrix, by covering the surface of silicon carbide with graphene to form a core-shell structure and co-filled with nano diamonds to achieve the preparation of high-performance epoxy resin at low content. The results showed that at the filling content of 30 wt%, the thermal conductivity of epoxy nanocomposites showed a dramatic thermal conductivity enhancement of 1263%, the energy storage modulus increased by 1.1 GPa, and the dielectric loss remained unchanged at 50 Hz. The advantages of the composite are the structural design and surface modification of the filler, which not only take advantage of its inherent advantages, but also improve the interface area with the epoxy matrix. The composite materials with excellent properties are expected to provide theoretical guidance for the application of high thermal conductivity dielectric materials.     

Impact modification of thermoplastics by methyl methacrylate and styrene-grafted natural rubber latexes

The preparation and characterization of polymer blends with structured natural rubber (NR)-based latex particles are presented. By a semicontinuous emulsion polymerization process, a natural rubber latex (prevulcanized or not) was coated with a shell of crosslinked polymethylmethacrylate (PMMA) or polystyrene (PS). Furthermore, core–shell latexes based on a natural rubber/crosslinked PS latex semi-interpenetrating network were synthesized in a batch process. These structured particles were incorporated as impact modifiers into a brittle polymer matrix using a Werner & Pfleiderer twin screw extruder. The mechanical properties of PS and PMMA blends with a series of the prepared latexes were investigated. In the case of PMMA blends, relatively simple core (NR)–shell (crosslinked PMMA) particles improved the mechanical properties of PMMA most effectively. An intermediate PS layer between the core and the shell or a natural rubber core with PS subinclusions allowed the E-modulus to be adjusted. The situation was different with the PS blends. Only core–shell particles based on NR-crosslinked PS latex semi-interpenetrating networks could effectively toughen PS. It appears that microdomains in the rubber phase allowed a modification of the crazing behavior. These inclusions were observed inside the NR particles by transmission electron microscopy. Transmission electron photomicrographs of PS and PMMA blends also revealed intact and well-dispersed particles. Scanning electron microscopy of fracture surfaces allowed us to distinguish PS blends reinforced with latex semi-interpenetrating network-based particles from blends with all other types of particles.     

Covalently functionalized hexagonal boron nitride nanosheets by nitrene addition

The covalent functionalization of exfoliated hexagonal boron nitride (h-BN) nanosheets by nitrene addition is described. Integration of functionalized h-BN nanosheets within a polycarbonate matrix is demonstrated and was found to afford significant increases in mechanical properties. This integration methodology was further extended by the covalent modification of the h-BN nanosheets with polymer chains of a polycarbonate analogue, and the integration of the polymer modified h-BN within the polymer matrix.     

Porous composite scaffolds of hydroxyapatite/silk fibroin via two‐step method

A two‐step method was used to fabricate the hydroxyapatite (HAP)/silk fibroin (SF) scaffolds, i.e. the nano‐sized HAP/SF composite powders were prepared by co‐precipitation, which were then blended with SF solution to fabricate the HAP/SF composite scaffolds. The obtained scaffolds showed a 3D porous structure. The porosity was higher than 90% with the average macropore size of 214.2 µm. Moreover, the nano‐sized HAP/SF composite powders were uniformly dispersed in the silk fibroin matrix, which provided the scaffolds enhanced compressive properties. The cell culture assay showed that the scaffolds fabricated by the two‐step method could improve the cell proliferation and osteogenic differentiation when compared with those prepared by the conventional one‐step blending method. The results suggested that the two‐step method could promote the uniform dispersion of HAP in the SF matrix and efficient combination between the HAP and the matrix, which may provide a potential application in the composite scaffold preparation for tissue engineering. Copyright © 2009 John Wiley & Sons, Ltd.     

Surface modification of liquid metal as an effective approach for deformable electronics and energy devices

The fields of flexible or stretchable electronics and energy devices, reconfigurable and compliant soft robotics, wearable e-textiles or health-care devices have paid significant attention to the need of deformable conductive electrodes due to its critical role in device performances. Gallium-based liquid metals, such as the eutectic gallium–indium (EGaIn) being an electrically conductive liquid phase at room temperature, have attracted immense interests as a promising candidate for deformable conductor. However, in the case of bulk liquid metal, there are several limitations such as the need of encapsulation, dispersion in a polymer matrix, or accurate patterning. For these reasons, the preparation of liquid metal particles in harnessing the properties in a non-bulk form and surface modification is crucial for the success of incorporating liquid metal into functional devices. Herein, we discuss the current progress in chemical surface modification and interfacial manipulations of liquid metal particles. The physical and chemical properties of the surface modification-assisted liquid metal polymer composite are also reviewed. Lastly, the applications of the surface-modified liquid metal particles such as flexible electrode, soft robotics, energy storage or harvester, thermal conductor, dielectric sensor, and bioelectronics are discussed, and the corresponding perspectives of deformable electronics and energy devices are provided. In particular, we focus on the functionalization method or requirement of liquid metal particles in each application. The challenging issues and outlook on the applications of surface-modified liquid metal particles are also discussed.

In this review, we summarize the recent progress in chemical surface modification and interfacial manipulations of liquid metal particles and discuss the modification method or requirement of liquid metal particles in emerging applications.     

Polymer Nanocomposites from Organoclays: Structure and Properties

Summary: Polymer nanocomposites formed from organically modified montmorillonite offer the promise of greatly improved properties over those of the matrix polymer, provided the organoclay can be dispersed, or exfoliated, into the polymer matrix to generate high aspect ratio particles. The exfoliation of organoclays in two series of ethylene-based polymers, ethylene-vinyl acetate copolymers and sodium ionomers of ethylene-methyacrylic acid copolymers, is described along with the properties of these nanocomposites.