光散射技术在研究高分子溶液和凝胶方面的应用

从溶液中的高分子、凝胶粒子及微乳胶粒子形态结构的表征和凝胶化过程、微乳液聚合及大分子缔合等动态过程的跟踪等方面的研究综述了近十几年来光散射技术在高分子溶液和凝胶领域的应用,并简单介绍了光散射技术的基本原理、发展简史和仪器及使用方法。     

溶液小角散射技术在软物质研究中的应用与展望※

溶液小角散射实验方法是表征溶液体系多尺度时空结构的研究利器, 在软物质研究领域已得到广泛应用. 溶液小角散射包括X射线散射和中子散射, 可以在纳米到微米空间尺度以及毫秒时间尺度对溶液软物质微观结构进行表征. 微纳尺度结构与研究对象的宏观性能密切相关, 利用同步辐射X射线小角散射高通量、快速时间分辨以及中子小角散射无损、深穿透性的特点, 可以在不同环境变量下系统研究软物质体系的纳米结构及演变过程. 系统介绍了溶液小角散射实验方法的发展现状以及溶液小角散射的基本原理. 结合典型的应用案例, 展望了溶液小角散射技术的发展趋势及其在软物质领域研究中的应用前景.     

含功能性羟基的温敏性聚(N-异丙基丙烯酰胺)微凝胶的制备及性能研究

采用两步合成路线合成了二缩三乙二醇单甲基丙烯酸酯 (TREGMA) ,并对其结构进行了表征 ;利用无皂乳液聚合法使N 异丙基丙烯酰胺 (NIPAM)、TREGMA和N ,N 亚甲基双丙烯酰胺 (BA)交联共聚 ,制备了含有功能性羟基的温敏性微凝胶 .微凝胶的去溶胀性能研究表明 ,TREGMA的引入使得微凝胶的体积相转变温度得到提高 ,同时所制得微凝胶具有较好的温敏性 .该类微凝胶有望成为良好的生物医用材料 .     

体积相转变温度可调的温敏性N-异丙基丙烯酰胺共聚物微凝胶的制备与性能研究

选用甲基丙烯酸异丙酯(iPMA)与N-异丙基丙烯酰胺(NIPAM)共聚,制备了一系列疏水改性、相转变温度可调的温敏性P(NIPAM-co-iPMA)微凝胶.利用透射电子显微技术(TEM)、浊度法、动态光散射(DLS)技术及示差扫描量热(DSC)技术对所得微凝胶的形态及去溶胀行为进行了表征.TEM与DLS结果表明,所制备的微凝胶具有规则的球型形态.浊度、DLS及DSC结果表明,疏水性单体iPMA的引入能有效调节共聚物微凝胶的相转变温度;在所考察的范围内,微凝胶的相转变温度随iPMA投料比的增加几乎呈线性降低.     

无皂种子分散聚合法制备单分散双重响应性微凝胶

以N-异丙基丙烯酰胺及2-乙烯基吡啶为主要单体, 采用无皂种子分散聚合法制备了单分散的、具有温度及pH双重响应性能的核-壳结构微凝胶, 并以扫描电镜及动态激光光散射等手段对微凝胶粒子的结构和性能进行了研究. 溶胀行为研究表明, 微凝胶粒子具有独立的互不干扰的温度及pH敏感性能, 其体积相变温度与纯聚N-异丙基丙烯酰胺(PNIPAM)凝胶基本一致, 说明局部分布的弱电离单体不会对PNIPAM凝胶的体积相变温度造成影响.     

药物缓释载体用温敏性水凝胶

近年来温敏性水凝胶作为药物缓释载体的研究十分广泛。本文在简要介绍了温敏性水凝胶的结构与性质、蛋白质的包埋技术和释药机理后,较为详细地综述了温敏性水凝胶在药物控制释放领域中的应用情况。     

变温反相悬浮聚合制备温度敏感性聚合物微凝胶

报道了一种利用变温的途径制备具有温度敏感性聚合物凝胶微粒的悬浮聚合方法.以正庚烷为连续相,过硫酸铵和四甲基乙二胺为引发剂,采用将具有反向温敏性的可降解大分子单体水溶液在低温下分散好以后再升高到聚合温度的变温反相悬浮聚合的方法制备了反向温敏性的可降解微凝胶.该方法避免了由于分散相在聚合温度下发生物理凝胶化所导致的分散困难等问题.考察了微凝胶的温敏性、粒径分布和降解行为等,并研究了油水比对微凝胶形貌的影响.     

含自由氨基酸侧链的温敏性微凝胶的制备及性能

采用无皂乳液聚合法使N-异丙基丙烯酰胺(NIPAM)、ε-丙烯酰基-L-赖氨酸(εACRLLY)和N,N-亚甲基双丙烯酰胺(BA)交联共聚,制备了含有自由氨基酸侧链的温敏性微凝胶.利用透射电子显微技术(TEM)、动态光散射技术(DLS)及浊度法对所制备的微凝胶的形态及相转变进行了表征.TEM结果表明,所得的微凝胶具有规则的球型形态,微凝胶的粒径随εACRLLY含量的增加而减小.DLS及浊度结果表明,微凝胶粒径呈单分散的窄分布,随着温度的升高,微凝胶粒径减小,有着明显的体积相转变温度(VPTT);亲水单体εACRLLY的引入能够有效地调节共聚物微凝胶的VPTT,并且VPTT随εACRLLY含量的增加几乎呈线性上升.微凝胶在对盐酸阿霉素的药物释放研究表明,所制备的微凝胶在20℃,12 h内释放了56%,37℃下释放了73%;37℃,pH=7.4下13 h内释放73%,pH=4.5下基本释放完毕,该微凝胶表现出良好的药物缓释性能.     

聚丙烯酰胺凝胶结构非均匀性的动态光散射研究

利用动态光散射技术研究了聚丙烯酰胺 (PAAm)凝胶结构的非均匀性 ,分析了PAAm凝胶结构非均匀性的形成原因及凝胶动态光散射的数据处理方法和分析结果的物理意义 .研究结果表明 ,PAAm凝胶中含有动态相关长度 (LC)不同的两相 ,其中 ,LC 为 10～ 2 0nm的区域是聚合物稀疏相 ,LC 为 85nm左右的区域是聚合物密集相 ,两相的不均匀分布形成了PAAm凝胶结构的非均匀性 .分析表明 ,PAAm凝胶存在两相主要是由于单体和交联剂的溶解度存在差异所致 .随交联度增大 ,PAAm凝胶结构的非均匀性显著增强     

新型温敏羟丙基纤维素微凝胶的合成

天然高分子具有良好的生物相容性和生物可降解性,因此用天然高分子制备的微凝胶更适合于生物医学领域的应用。羟丙基纤维素(HPC)是一种具有温度敏感性的纤维素衍生物,可通过不同的方法制备为微凝胶,然而现有方法制备的HPC微凝胶都不能完全降解。我们采用一种新方法制备HPC微凝胶。首先通过NaIO4处理将醛基引入HPC。红外光谱检测证明了醛基的生成。氧化后的HPC仍具温敏性,其最低临界溶解温度(LCST)保持不变;当加热到LCST以上时,HPC分子通过疏水相互作用聚集成纳米小球;再加入交联剂己二酸二酰肼,通过醛基与胺基之间的反应,使纳米小球共价交联得到HPC微凝胶。电镜研究表明HPC微凝胶呈球形,粒径在100～300nm之间。浊度和光散射研究表明HPC微凝胶仍具温敏性。细胞毒性实验表明我们制备的微凝胶几乎没有细胞毒性。由于HPC及交联剂己二酸二酰肼均可生物降解,预期我们制备的微凝胶也能很好地降解,并有望应用于生物医学领域。     

Temperature-sensitive aqueous microgels

An account of the preparation and characterization of temperature-sensitive aqueous microgels based on poly(N-isopropylacrylamide) was first published in 1986. Since then there has been a steady increase in the number of publications describing preparation, characterization and applications of temperature-sensitive microgels. This paper reviews the important developments in the area of temperature-sensitive aqueous microgels over the last decade. Although most of the work involves gels based on poly(N-isopropylacrylamide), other polymers are also considered. Core-shell latex particles exhibiting temperature-sensitive properties are also described.     

Temperature-sensitive hybrid microgels with magnetic properties

In the present paper, we report the preparation of hybrid temperature-sensitive microgels which include magnetite nanoparticles in their structure. Polymeric microgels have been prepared by surfactant-free emulsion copolymerization of acetoacetoxyethyl methacrylate (AAEM) and N-vinylcaprolactam (VCL) in water with a water-soluble azo-initiator. The obtained microgels possess a low critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures. Magnetite was deposited directly into microgels, leading to the formation of composite particles which combine both temperature-sensitive and magnetic properties. The influence of magnetite load on microgel size, morphology, swelling-deswelling behavior, and stability is discussed.     

Aqueous microgels for the growth of hydroxyapatite nanocrystals

In present article, we demonstrate that aqueous microgels can be used as containers for the in-situ synthesis of hydroxyapatite. The hydroxyapatite nanocrystals (HAp NCs) become integrated into microgels forming hybrid colloids. The HAp NCs loaded in the microgel can be varied over a broad range. The HAp NCs are localized within the microgel corona. The deposition of the inorganic nanocrystals decreases the colloidal stability of the microgels and leads to particle aggregation at high HAp NCs loading. Because of the strong interactions between HAp NCs and polymer chains, the swelling degree of microgels decreases, and temperature-sensitive properties disappear at high loading of the inorganic component. We demonstrate that hybrid colloids can be used as building blocks for the preparation of nanostructured films on solid substrates.     

Unperturbed volume transition of thermosensitive poly-(N-isopropylacrylamide) microgel particles embedded in a hydrogel matrix

The thermoresponsive behavior of poly-(N-isopropylacrylamide) (PNiPAM) microgels embedded in a covalently cross-linked polyacrylamide hydrogel matrix was investigated using ultraviolet-visible (UV-vis) spectroscopy, small-angle neutron scattering (SANS), and confocal laser scanning microscopy. The hydrogel synthesis was performed at two different temperatures, below and above the volume phase transition temperature of PNiPAM, resulting in highly swollen or fully collapsed PNiPAM microgel particles during the incorporation step. UV-vis spectroscopy experiments verify that the incorporation of thermosensitive microgels leads to temperature-sensitive optical properties of the composite materials. SANS measurements at different temperatures show that the thermosensitive swelling behavior of the PNiPAM microgels is fully retained in the composite material. Volume and structure criteria of the embedded microgel particles are compared to those of the free microgels in acrylamide solution. To visualize the temperature responsive behavior of larger PNiPAM particles, confocal fluorescence microscopy images of PNiPAM beads, of 40-microm size, were taken at two different temperatures. The micrographs also demonstrate the retained temperature sensitivity of the embedded microgels.     

侧链含不同功能性羟基的温敏性N-异丙基丙烯酰胺共聚物微凝胶的制备及性能比较

选择含有活性羟基的亲水单体多缩乙二醇单甲基丙烯酸酯(PEGMA)、甲基丙烯酸羟乙酯(HEMA),分别和N-异丙基丙烯酰胺(NIPAM)交联共聚,制备了侧链含有功能性羟基、链长不同的温敏性微凝胶.研究发现,亲水单体HEMA和PEGMA的引入对微凝胶的去溶胀性能有不同的影响,PEGMA的引入使得微凝胶的体积相转变温度升高,微凝胶的去溶胀比随着PEGMA投料比的增加而降低.而HEMA的引入使得微凝胶的体积相转变温度降低;微凝胶的去溶胀比随着HEMA投料比的增加先是增加然后降低,当HEMA的投料比为8mol%时,去溶胀比达到最大.     

New “smart” poly(NIPAM) microgels and nanoparticle microgel hybrids: Properties and advances in characterisation

This review is devoted to poly(NIPAM) based microgels and nanoparticle/polymer hybrid microgels. It tries to give a brief overview of recent developments with respect to new systems and experimental methods. The properties of these fascinating materials are reported together with advances in their characterisation by imaging and scattering techniques. Aspects of their application in the area of mesotechnology will also be discussed.     

Control of colloidal interactions between microgels with stimulus-responsive properties

Microgels can switch their chemical/physical properties with external stimulus, and the colloidal behavior of microgels is strongly affected by interparticle interactions. In this article, we introduce smart microgels, focusing on Janus microgels and oscillating microgels developed by our group. Janus microgels show anisotropic shape and chemical/physical properties, and thus the structures of their flocs are also anisotropic. Oscillating microgels show autonomous swelling/deswelling and dispersing/flocculating oscillations through synchronization with chemical reactions. The interparticle interactions of these microgels are discussed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3021–3026     

Temperature-sensitive membranes prepared from blends of poly(vinylidene fluoride) and poly(N-isopropylacrylamides) microgels

In this study, temperature-sensitive membranes were prepared by phase transition of the mixture of the temperature-sensitive poly(N-isopropylacrylamides) (PNIPAAM) microgels and poly(vinylidene fluoride). The results of Fourier transformed infrared spectrometer, X-ray photoelectron spectroscopy, elemental analysis, and scanning electron microscope photographs indicate that the PNIPAAM microgels are distributed more in the inner membrane than on the surface. The scanning electron microscope photographs reveal the blend membranes having porous surfaces with nanometer sizes and porous cross-sections with micrometer sizes. The addition of the PNIPAAM microgels is found to improve the porosity, the pore size, water flux, as well as to enhance the hydrophilicity and anti-fouling property of the blend membranes. The blend membrane shows temperature-sensitive permeability and protein rejection with the most dramatic change at around 32 °C which is the lower critical solution temperature of PNIPAAM, when water or bovine serum albumin solution flow through. Specifically, below 32 °C, the blend membrane shows a high protein rejection ratio which decreases with increasing temperature and a low water flux which increases with increasing temperature; above 32 °C, the blend membrane shows a low protein rejection ratio which decreases with increasing temperature and a high water flux which increases with increasing temperature.     

粘土对N-异丙基丙烯酰胺和丙烯酸叔丁酯共聚形成微凝胶的影响

以无机粘土(锂蒙脱石)作为物理交联剂,在不加任何乳化剂的条件下,通过无皂乳液聚合制备了一系列粒径在250nm左右且具有温敏性的N-异丙基丙烯酰胺(NIPAM)和丙烯酸叔丁酯(tBA)共聚微凝胶,并通过傅立叶变换红外光谱、扫描电镜、准静态光散射、X射线衍射仪和差示扫描量热法对所合成微凝胶的化学结构、表面形态和温度敏感性进行了表征.研究表明,粘土起到交联剂的作用;tBA的引入可以调节微凝胶的体积相转变温度;所制得的粘土交联微凝胶具有较好的粒径分布且粒径在140nm至350nm之间.