星形胶束自由能和聚集数的理论分析

ＡＢ型嵌段聚合物在选择性溶剂中将发生微相分离,形成一种球形胶束[1].所谓选择性溶剂是指此溶剂仅能溶解共聚物中某一链段,而对另一链段则为不良溶剂.对这一体系的实验研究是从80年代兴起的,主要采用现代测试技术来表征形成胶束的回转半径[2],动力学半径[3]、聚集数[4]和临界胶束浓度[5].从分子图景上看来,这种球形胶束包括两部分,内核(Ｃｏｒｅ)为密堆砌的链段Ａ;壳层(Ｃｏｒｏｎａ)为溶涨的链段.Ｈｅｌｆａｎｄ等[6]最早利用数值计算法来研究嵌段聚合物在本体中的微相分离的问题;Ｌｅｉｂｌｅｒ等[7]将此方法引入嵌段聚合物/均聚物体系.…     

用激基缔合物荧光研究聚苯乙烯-聚甲基丙烯酸甲酯嵌段共聚物在溶液中的分子构型

聚苯乙烯在溶液中的激基缔合物荧光被发现以来一直引起人们的兴趣^{[ 1, 2]}. 聚苯乙烯激基缔合作用主要与处于基态的苯环层叠对的形成有密切关系. 其形成方式主要有(1)符合n= 3规则的相邻苯环间的相互作用.(2)主链上非相邻苯环间由于链段的卷曲而相互作用.(3)分属于不同主链上的苯环相互贯穿时的相互作用. 由于激基缔合作用是近程作用, 因此利用它研究聚合物线团在稀溶液的变化及由稀溶液到浓溶液的变化是十分有效的^{[ 3]}. 嵌段聚合物在形成胶束时, 一种聚合物分子链段形成核, 在核内大分子链段相互缠结, 相互贯穿. 而另一种聚合物分子链段形成壳, 其链段较为舒展. 因此利用激基缔合物荧光技术研究分子链段在核内的变化也应是十分有效的. 本文研究聚苯乙烯-聚甲基丙烯酸甲酯嵌段共聚物体系。     

核-壳型聚丙烯酸酯复合乳液

简述了核-壳型聚丙烯酸酯复合乳液的合成方法、形态及其影响因素与判断方法、结构与性能等方面的研究进展;认为核-壳型复合乳液膜机械性能优良的原因是:核、壳两相间存在的过渡区适当地抑制了二者的相分离。     

苯乙烯-p-乙烯基苯甲酸两亲性嵌段共聚物在乙醇中自组装行为的电镜观察

两亲性嵌段共聚物在只对其中一链段为良溶剂的选择性溶剂中 ,能够自组装形成胶束 .胶束的形态和尺寸大小依赖于两链段的性质 ,共聚物的组成、浓度、溶剂的性质等[1] .这一性质使得嵌段共聚物在分子识别、药物和其他物质的输送、基因疗法、水系涂料、污染物的除去、纳米复合材料的制备、催化剂以及传感器等方面展示着潜在的应用前景 .因此 ,两亲性嵌段共聚物的合成及其在选择性溶剂中的自组装行为的研究近年来颇受关注[2 ] .依据两链段的比例不同 ,嵌段共聚物可形成星状胶束和“板寸头”(Ｃｒｅｗ ｃｕｔ)型胶束[3 ] .当可溶段远比不溶段长时…     

手性化合物环境下制备甲壳型液晶高分子

甲壳型液晶高分子的研究是我国独创[1 ,2 ] ,已产生了积极的科学影响 .虽然它们在化学结构上属于侧链型 ,但在分子形态上更接近于主链型液晶高分子[3] .由于庞大的液晶基元对空间的要求 ,液晶高分子主链被迫采取尽可能伸展的构象[4,5] .然而 ,至今尚不清楚主链与液晶基元之间是怎样协同作用以形成有序结构 .本文探索了在不同手性化合物环境下制备单手螺旋链甲壳型液晶高分子的可能性 .尽管最后并未获得螺旋链高分子 ,但仍取得了一些有价值的结果 .手性化合物环境分别是 ( )薄荷醇 ( 1 )作为反应溶剂、( )过氧化 二 (碳酸薄荷醇酯 ( 2 )作…     

有机/无机纳米复合粒子平衡型态的热力学计算

有机/无机纳米复合粒子是一种应用广泛的复合材料, 采用细乳液聚合方法是制备此类复合粒子的有效途径, 其中分裂/融合过程是一种新型的制备工艺. 纳米复合粒子的型态控制是一个非常重要的方面, 从热力学角度出发, 把界面Gibbs自由能最低这一基本热力学原理应用于计算细乳液聚合、采用新型分裂/融合工艺制备的有机/无机纳米复合粒子平衡型态, 并推导了核壳型、半球型、夹心型和分离型复合粒子平衡型态的热力学方程. 通过比较特定制备条件下不同形态复合粒子的界面Gibbs自由能, 可以预测最稳定的有机/无机纳米复合粒子平衡型态.     

一种表面具有自由羧基的CdS纳米团簇

近年来 ,纳米晶和纳米团簇在免疫生物学和临床检验学等研究中的潜在应用价值已引起了科学工作者的极大关注 [1～ 3] .1 998年 ,Alivisatos等 [4 ]制备了 Cd Se-Zn S核壳结构的纳米晶 ,并用其作为荧光探针对老鼠的成纤维细胞进行了标识 .同年 Nie等 [5,6]发展了一种新的非同位素检测方法 ,将铁转移蛋白质或特异性抗体偶连到具有核 -壳型结构的纳米晶表面 ,利用纳米晶的荧光特性进行检测和标识 .上述工作的共同特点是在有机相中合成纳米晶 ,再用巯基乙酸将其萃取到水相中 ,使纳米晶的外表面被自由羧基包覆 ,这些羧基可与各种生物分子如特异…     

不同主链"甲壳型"高分子的合成及其液晶性研究

"甲壳型"液晶高分子(MJLCP)的概念是周其凤等[1]在1987年首次提出的,随后分别被文献[2～8]所证实.由于液晶基元对空间的要求,液晶高分子主链采取尽可能伸展的构象.虽然它们在化学结构上属于侧链型,但在分子形态上更接近于主链型液晶高分子,但至今尚不清楚其产生液晶性的原因.     

核壳型含氟丙烯酸酯共聚物的合成及性能

采用饥饿态半连续种子乳液聚合方法, 在十二烷基硫酸钠(SDS)/辛基苯基聚氧乙烯醚(TX-10)复合乳化剂的作用下, 分别选用甲基丙烯酸三氟乙酯(TFEM)、甲基丙烯酸六氟正丁酯(HFBM)和甲基丙烯酸十二氟庚酯(DFHM)为含氟单体, 合成以丙烯酸正丁酯(BA)、甲基丙烯酸甲酯(MMA)和含氟单体为原料的核壳型结构含氟丙烯酸酯共聚物乳液. FTIR, 1H NMR, TEM和DSC分析结果显示, 获得了BA/MMA/含氟单体的共聚物乳液, 且乳液具有明显的核壳结构. DSC, TGA和SEM-EDX的分析显示, 核壳型结构的共聚物具有优异的热力学稳定性能和成膜性能; 长侧链或短侧链含氟单体对共聚物的热稳定性影响不明显, 但侧链较长的含氟单体所获得的聚合物在成膜过程中更易向表面迁移, 更能体现含氟聚合物的优点.     

聚丙烯釜内合金的相态研究

聚丙烯釜内合金具有良好的刚韧平衡性能,历经30多年的发展,在包装、汽车和建筑等领域已得到广泛的应用。其优异的性能及复杂的多相、多组分结构更是引起了相关领域研究者的高度关注。聚丙烯釜内合金是一种在聚合釜内直接合成的多相、多组分聚合物体系,其初始产品常以粉末或球型颗粒的状态存在,具有非常复杂的相形态,并且在加工成型过程中,由于相形态的演变会形成更加丰富的微结构,从而对聚丙烯釜内合金最终的力学性能产生决定性的影响。目前对于聚丙烯釜内合金体系的分子链结构-聚集态结构-产品性能之间的构效关系仍然有很多问题亟待解决。近期研究表明在某些情况下,聚丙烯釜内合金体系中增韧相形成“核-壳”型结构(或多重“核-壳”型结构)时,可以实现最佳的刚性与韧性的平衡,但对于这些“核-壳”结构形成条件的控制及结构成分的精确测定仍有不足。本文主要总结了近年来聚丙烯釜内合金相态研究的进展,展望了该领域可能的发展方向。     

The formation mechanism of poly(vinyl acetate)/poly(butyl acrylate) core/shell latex in two-stage seeded semi-continuous starved emulsion polymerization process

In this paper, the morphological evolution of latex particles on poly(vinyl acetate) (PVAc)/poly(butyl acrylate) (PBA) in two-stage seeded semi-continuous starved emulsion polymerization is studied, and the thermodynamic analysis and a mathematic model are derived to describe the interfacial free energy changes corresponding to various possible thermodynamically unstable morphologies during the polymerization process. The comparisons between the morphological evolution and the related thermodynamic analysis show that the morphological evolution of latex particles is oriented to the thermodynamic preferred morphology which is an inverted core/shell structure with PBA as core and PVAc as shell. Based on the comparisons, the possible morphological developmental pathway of PVAc/PBA core/shell latex is described. The possible morphological developmental pathway suggests that the observed multi-particle morphology in the polymerization process is due to restricted chain mobility related to high internal viscosity. The formation mechanism of PVAc/PBA core/shell latex, based on the experiments as well as the thermodynamic and dynamic analyses, is proposed, which signifies that PBA is first formed outside the PVAc seed and then migrate to the inside of the PVAc seed.     

核壳型PVAc/PBA乳胶粒热力学平衡状态

乙酸乙烯酯;形态;核壳型PVAc/PBA乳胶粒热力学平衡状态;核壳结构;丙烯酸丁酯;乳液聚合;     

EFFECT OF THE PHASE STRUCTURE EVOLUTION ON THE PROPERTIES OF FILMS FORMED FROM PBA/P(St-co-MMA) COMPOSITE LATEX

A group of heterogeneous latexes poly(butyl acrylate)/poly(styrene-co-methyl methacrylate)(PBA/P(St-co-MMA)) were prepared by a semi-continuous seeded emulsion polymerization process under monomer starved conditions.The glass transition temperature(T_g)and the mechanical properties of the film formed from the composite latex changed with the evolution of the particle morphology.A photon transmission method was used to monitor the phase structure evolution of films which were prepared from core-shell PBA/...     

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-free hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate(MMA),butyl acrylate(BA), methacrylic acid(MAA),styrene(St)and ethylene glycol dimethacrylate(EGDMA)as monomers,and the influences of MMA content used in the core preparation on polymerization,particle size and morphology were investigated by transmission electron microscopy,dynamic light scattering and conductometric titration.The results showed that the seeded emulsion polymerization could be carried out smoothly using "starved monomer feeding process" when MAA content in the core preparation was equal to or less than 24 wt%,and the encapsulating efficiency of the hydrophilic P(MMA-BA-MAAEGDMA) core with the hydrophobic PSt shell decreased with the increase in MAA content.When an interlayer of P(MMAMAA -St)with moderate polarity was inserted between the P(MMA-BA-MAA-EGDMA)core and the PSt shell,well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt%MAA content in the core preparation were obtained.     

单分散聚丙烯酸丁酯-二氧化硅核壳粒子的制备

近年来,有机-无机核壳材料因其具有可调的光、电、磁等特性而备受关注．无机物外壳可以增强粒子的热力学稳定性、机械强度和抗拉性能．高分子乳胶粒内核具有弹性,且易成膜,外部包覆无机物的乳胶粒可结合两者特性并产生协同效应．     

Effect of Monomer Feeding Mode on thePreparation of Hollow Latexes with High MAA Content in the Core Latex Preparation简

In order to prepare hollow latex particles with optimum morphology based on osmotic swelling principle, three- layer core/shell latex particles with 40 wt% MAA in the core were first prepared via multistep seeded emulsion copolymerization, in which monomers were added by a semi-continuous process with monomer addition under two different forms： pure monomers＇ mixture （monomer addition）, and pre-emulsified monomers （pre-emulsion addition）. Then, the hollow latex particles with different morphologies were obtained after alkali post-treatment. Influences of the monomer feeding mode on the emulsion polymerization and the particle morphology were investigated. Results showed that the pre- emulsion addition could significantly improve the polymerization stability in each step, and greatly enhance the uniformity of shell encapsulation. The sizes of the core and core/shell latex particles obtained by the pre-emulsion addition were smaller and more uniform than those synthesized by the monomer addition, and the hollow latex particles with intact morphology were generated by alkali post-treating of the core/shell latexes prepared from the pre-emulsion addition. As the core size increased, the morphology of the post-treated particles underwent evolution from hollow to collapse. Moreover, the mechanism of the particle morphological evolution was proposed.     

SiO_2/PVAc无机-有机复合微球的合成及其膜性能研究

以纳米二氧化硅粒子(SiO2)为稳定剂,在少量反应型阴离子乳化剂——烯丙氧基羟丙磺酸钠(HAPS)作助稳定剂的情况下,制备了具有草莓型结构的二氧化硅/聚醋酸乙烯酯(SiO2/PVAc)无机-有机纳米复合微球.研究表明,纳米SiO2与PVAc的氢键作用是形成这种单分散草莓型SiO2/PVAc无机-有机纳米复合微球的关键.透射电镜(TEM)观察显示,纳米SiO2吸附在PVAc表面,形成草莓型结构.讨论了纳米二氧化硅溶胶的种类和用量、乳化剂种类对复合微球形态及其膜性能的影响,并讨论了复合微球的形成机理.     

丙烯酸甲酯与醋酸乙烯酯的种子乳液聚合

以过硫酸铵（ＡＰＳ） 为引发剂,合成了粒径分布较均匀的聚醋酸乙烯酯种子乳液（ＰＶＡｃ） ,然后以丙烯酸甲酯（ ＭＡ） 为第二单体和以油溶性偶氮二异丁腈（ＡＩＢＡ） 为引发剂,分别进行不溶胀与溶胀条件下的无皂种子乳液聚合,并用透射电子显微镜（ＴＥＭ） 表征了胶粒形态．表明在不溶胀条件下,胶粒形态随ＰＶＡｃ／ ＭＡ 重量比的不同而变化,当ＰＶＡｃ／ ＭＡ 为１／２ 时,形成以ＰＭＡ 为核,ＰＶＡｃ 为壳的胶粒．在溶胀条件下则得到类似互穿网络型乳胶粒．     

Preparation of Bowl-Like Polymer Particles via Multi-Step Emulsion Polymerization and Alkali Post-Treatment

Summary : Monodisperse P(BA-MMA-MAA-EGDMA)/P(St-MAA-DVB) core/shell latex particles were first synthesized by a four-step emulsion polymerization, and a new kind of latex particles with “bowl-like” morphology were obtained by post-treating the resultant core/shell particles under alkali condition. Results indicated that the feeding rates of the monomer mixture and initiator aqueous solution were the key parameters to obtain monodisperse core/shell latex particles in the emulsion polymerization process, and the latex particles with “bowl-like” morphology could be generated only when the treatment temperature was equal or higher than 70 °C.     

Effect of the Shell Crosslinking Level andCore/Shell Ratio on the Morphology of LatexParticles in the Preparation of Hollow Latexes简

Three-layer core/shell latex particles with various shell crosslinking level and shell thickness were prepared by multistep emulsion polymerization, and the hollow latex particles with different morphologies were then obtained after alkali post-treatment. Influences of divinyl benzene(DVB) content and the core/shell mass ratio on emulsion polymerization and particle morphology were investigated. Results showed that with the increase of DVB content, the percentage of total amount of ―COOH on the particle surface and free in aqueous phase(PSFa) decreased, and the morphology of the post-treated particles underwent evolution from cracked, intact hollow to deficient swelling structure. Decreasing the core/shell mass ratio could not only make more carboxyl groups encapsulated by the shell, but also increase the shell resistance to the swelling of the core. The uniform hollow latex particles with intact morphology were obtained when the DVB content was 3.54 wt% and the core/shell mass ratio was 1/6.