烷基链封端的两亲性超支化聚缩水甘油的合成及自组装

通过阳离子开环聚合和端基改性的方法合成了以亲水性超支化聚缩水甘油为核和疏水性十六烷基链为臂的两亲性超支化多臂共聚物(HPG-g-C16),研究了十六烷基疏水臂的接枝率对该两亲性聚合物在溶剂中自组装行为的影响.结果表明:接枝率45%以上的HPG-g-C16在四氢呋喃(THF)中以单分子胶束的形式存在,在THF与水的混合溶剂中会自组装形成尺寸为1～10 μm的巨型囊泡,而接枝率为15% 的HPG-g-C16能直接在水中自组装形成球形胶束.     

部分水解的疏水改性聚丙烯酰胺分子构型与体相行为的关系

采用介观模拟耗散颗粒动力学(DPD)方法研究分子构型变化对聚电解质疏水改性聚丙烯酰胺(HMHPAM)在水溶液中的行为和性质的影响. 模拟中采用均方根末端距量化表征聚合物的伸展程度, 并通过计算溶液中水分子的扩散系数考察大分子形态和构型变化对体系粘度的影响, 探讨了聚合物的浓度、聚合方式、疏水改性比例及水解程度对聚合物溶液的影响机制, 预测了重复单元的种类和排列方式对聚合物构型和溶液性质的影响规律, 为HMHPAM聚合物的分子设计、合成及应用提供指导.     

疏水改性聚丙烯酰胺溶液的分子模拟

设计了几种不同的非离子型改性聚丙烯酰胺(HM-PAM)和阴离子型改性聚丙烯酰胺(HM-HPAM). 通过分子动力学模拟(MD)方法研究了在聚合物链上加入不同疏水改性单体对提高聚丙烯酰胺耐盐性的影响, 考察了盐浓度对疏水改性聚丙烯酰胺的回旋半径(R_g)、 特性黏数([η])、 径向分布函数(RDF)和均方位移(MSD)的影响以及聚合物的微观结构与特性黏数之间的关系. 研究结果表明, 引入疏水改性单体后, 改性聚丙烯酰胺具有较好的耐盐性. 通过研究非键作用与氢键相互作用可知, 体系中溶质和溶剂间的相互作用及氢键作用越弱, 溶液的特性黏数越大. O-H原子对的RDF结果表明, 聚合物链的伸展与聚合物链及官能团间的相互作用有关. 当RDF峰较弱时, 聚合物链与水的作用越弱, 越有利于聚合物链保持舒展状态, 溶液的特性黏数也就越大. 另外, 从聚合物链的MSD曲线发现, 聚合链的移动性与特性黏数呈负相关.     

电荷密度和疏水性对疏水改性聚丙烯酰胺与牛血清蛋白相互作用的影响

对比研究了牛血清蛋白(BSA)与部分水解的未改性聚丙烯酰胺(PAM-AA)、疏水改性聚丙烯酰胺(PAM-C12)和含有丙烯酸基团的疏水改性聚丙烯酰胺(PAM-C12-AA)之间的相互作用.等温滴定量热实验结果表明,除PAM-C12外,其他聚合物与BSA的结合焓均为放热,随AA含量的增加,放热焓值增大.与PAM和PAM-C12相比,PAM-C12-AA能够诱导BSA二级结构和微环境的明显变化,表明疏水性和电荷密度均对聚合物与BSA相互作用有重要影响.另外,不同浓度的PAM-C12-AA与BSA的作用方式不同,当聚合物的浓度略高于临界胶束浓度(CMC)时,由于聚合物的量较少,BSA分子改变其构型从而最大程度地与聚合物结合;当聚合物的浓度远高于CMC时,更多的聚合物链结合到BSA分子的正电荷"patch"上,PAM-C12-AA与BSA的紧密聚集体利于BSA二级结构的稳定.     

天然气水合物抑制剂用高分子研究进展

海底天然气开采过程中,甲烷和水可以形成天然气水合物,阻塞油气管道。本文先简要介绍高分子化合物用于水合物抑制剂的发展过程,从抗冻抑制剂的结构与性能关系,探讨了高分子型的低剂量天然气水合物抑制剂的特性、作用机理和主要影响因素。近年来的研究发现在寒冷地区海洋鱼类和昆虫体内存在一些抗冻蛋白,不仅能够降低水的冰点,而且能抑制天然气水合物的形成,是绿色环保的天然抑制剂,模拟这些具有抗冻性能的蛋白质结构的高分子化合物为今后水合物抑制剂研究提供一个新的发展方向。本文还提出了今后值得开展研究和应用的若干问题。     

仿细胞膜结构共聚物的合成及涂层性能

采用饥饿法将2-甲基丙烯酰氧乙基磷酰胆碱(MPC)分别与甲基丙烯酸十八烷基酯(SMA)、 甲基丙烯酸十二烷基酯(LMA)及甲基丙烯酸正丁酯(BMA)聚合, 通过改变投料比例和沉淀剂种类, 合成了一系列含磷酰胆碱基团的仿细胞膜结构的两亲性二元随机共聚物. ¹H NMR和元素分析结果表明, 合成的两亲性二元随机共聚物的组成与投料比相近. DSC结果表明, 聚合物具有较低的玻璃化转变温度. 表面张力及水的动态接触角(DCA)研究发现, 聚合物涂层表面具有明显的两亲性及表面结构易变性, 在空气中憎水基团在表面取向, 在水环境中亲水的磷酰胆碱基团则迁移取向到涂层表面形成仿细胞外层膜结构界面, 最终形成不溶于水的仿细胞膜结构涂层.     

聚(L-丙氨酸-co-羟丙-L-谷氨酰胺)无规共聚物的两亲性及其胶束行为研究

采用丙氨酸作为疏水聚合单体,谷氨酸作为亲水聚合单体,一步开环聚合反应,合成了具有两亲性的聚氨基酸无规共聚物.利用IR,1H-NMR等方法对所合成的聚合物进行了详细的表征,结果表明两种单体都能够按照投料比参加聚合反应生成无规共聚物.对比聚丙氨酸-聚羟丙谷氨酰胺嵌段共聚物,探讨了无规共聚物与嵌段共聚物在两亲性及结构性质上的差异和特点.研究表明,聚(L-丙氨酸-co-羟丙-L-谷氨酰胺)无规共聚物与嵌段共聚物一样,具有两亲性,在水溶液中也能够形成胶束,但胶束尺寸较嵌段共聚物要小,胶束形态也不像嵌段共聚物是规整的球形.实验发现,亲疏水单体的比例对胶束的形成有很大影响,P(A10-co-HPG40)所制得的胶束分散最为均匀.所形成的胶束以疏水的聚丙氨酸为内核,亲水的聚羟丙谷氨酰胺为外壳.     

热分析技术研究疏水缔合微区对含氟丙烯酸酯共聚物凝胶中水状态的影响

丙烯酸 (AA)与不同含量的 2 (N 乙基全氟辛烷基磺酰胺 )乙基甲基丙烯酸酯 (FMA)在叔丁醇中进行自由基共聚 ,合成了一系列疏水改性共聚物凝胶 .用示差扫描量热法 (DSC) ,热失重分析 (TGA)研究了含氟疏水改性凝胶中水的状态 ,证明FMA改性凝胶中存在 3种状态的水 ,即不可冻结水 ,可冻结结合水和自由水 .对于未改性凝胶和FMA含量为 1mol%的疏水改性凝胶 ,在凝胶中水含量分别低于 0 60 9mol%和 0 698mol%时 ,DSC升温曲线上观察不到熔融峰 ,说明凝胶中存在不可冻结水 .提出计算凝胶中 3种状态的水含量和熔融焓的理论假设 .计算出FMA含量为 1mol%的疏水改性凝胶中自由水和可冻结结合水的摩尔熔融焓分别为75 89 0 3和 6864 0 6J mol.计算结果表明疏水改性后 ,单位聚合物单元上结合的可冻结水数目 (n1 )和非冻结水的数目 (n0 )都增加     

用分子动力学模拟天然气水合物的抑制效应

用分子动力学模拟方法确定了结构H型(SH)天然气水合物的稳定晶体生长面为(001), 系统研究了277 K时三种动力学抑制剂对此晶面的影响. 模拟显示抑制剂中的氧与表面水分子形成氢键, 从而破坏原有的稳定结构, 造成水合物笼型结构坍塌, 达到抑制水合物形成的效果. 比较三种不同动力学抑制剂对SH的抑制效果得出: PVCap＞PEO＞PVP. 在此基础上研究了PVCap对天然气水合物结构I型(SI), 结构II型(SII)和SH三种不同晶型的抑制效应. 模拟发现抑制效果的次序为: SH＞SI＞SII.     

聚皂凝胶在溶液中的溶胀-消溶胀研究

聚皂是一类疏水改性的聚合物电解质,在其大分子结构中既带有亲水基团又带有疏水基团．通过一定程度的交联,可获得聚皂水凝胶．与近年来颇受关注的智能聚合物水凝胶一样,聚皂凝胶也表现出了相当的环境敏感特性．一般来说,聚合物水凝胶的ｐＨ敏感特性取决于分子链上所含...     

聚乙烯基吡咯烷酮修饰多壁碳纳米管的研究

采用超声波辅助技术,研究了两亲性聚合物聚乙烯基吡咯烷酮(PVP)修饰多壁碳纳米管(MWNTs)的效果、作用机理及影响因素.研究结果表明在适合的条件下两亲性聚合物PVP可以被引入到多壁碳纳米管表面,修饰后的MWNTs在DMF、乙醇和水等溶剂中具有良好的分散性.通过红外光谱(FTIR)和拉曼光谱(Raman)分析表明,两亲性聚合物与MWNTs之间产生了化学接枝作用,高分辨透射电镜分析表明两亲性聚合物不均匀地存在于MWNTs的表面和端部.两亲性聚合物的浓度对接枝量的影响不大,但超声波作用时间对MWNTs表面两亲性聚合物PVP的接枝量有较大的影响,在超声时间为4h时接枝量最大.两亲性聚合物修饰效果不同于表面活性剂,采用表面活性剂十二烷基苯磺酸钠(SDBS)修饰的MWNTs经过洗涤过滤后,不能重新溶于水中,而两亲性聚合物PVP修饰的MWNTs可以重新溶解.     

Studies of relationship between polymer structure and hydration environment in amphiphilic polytartaramides

The relationships between the chemical structures and hydration environment of the polymers can provide significant insight into the water‐amphiphilic polymer interactions. Here, the hydrophobicity of amphiphilic block copolymers poly(ethylene tartaramide‐b‐alkyl isocyanate) is gradually tuned by using of a series of pendant alkyl (isopropyl, n‐butyl, cyclopentyl, and cyclohexyl) groups. Dynamics of hydration probed by low‐field NMR relaxometry exhibits a heterogeneous environment of water molecules, corresponding to tightly bound water with slow re‐orientational mobility and loosely bound water with fast re‐orientational mobility. Progressively larger amounts of bound water are present in the copolymers, ongoing from pendant isopropyl, n‐butyl, cyclopentyl, and finally to cyclohexyl group. Water in the copolymer bearing the cyclohexyl group has a significantly high partial specific heat capacity. Therefore, hydrophobic interaction between the polymer and water is enhanced when the hydrophobicity of the polymer is increased, resulting in considerable hydrophobic hydration with decreased mobility of the bound water. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 138–145     

Silica nanoparticles at interfaces modulated by amphiphilic polymer and surfactant

The interfacial behavior of silica nanoparticles in the presence of an amphiphilic polymer poly( N-isopropylacrylamide) (PNIPAM) and an anionic surfactant sodium dodecyl sulfate (SDS) is studied using neutron reflectivity. While the nanoparticles do not show any attraction to hydrophilic and hydrophobic surfaces in pure water, presence of the amphiphilic polymer induces significant adsorption of the nanoparticles at the hydrophobic surface. This interfacial behavior is activated due to interaction of the nanoparticles with PNIPAM, the amphiphilic nature of which leads to strong adsorption at a hydrophobic surface but only weak interaction with a hydrophilic surface. The presence of SDS competes with nanoparticle-PNIPAM interaction and in turn modulates the interfacial properties of the nanoparticles. These adsorption results are discussed in relation to nanoparticle organization templated by dewetting of charged polymer solutions on a solid substrate. Our previous studies showed that nanoparticle assembly can be induced to form complex morphologies produced by dewetting of the polymer solutions, such as a polygonal network and long-chain structures. This approach, however, works on a hydrophilic substrate but not on a hydrophobic substrate. These observations can be explained in part by particle-substrate interactions revealed in the present study.     

Reduced hydrophobic interaction of polystyrene surfaces by spontaneous segregation of block copolymers with oligo (ethylene glycol) methyl ether methacrylate blocks: force measurements in water using atomic force microscope with hydrophobic probes

Reduction of hydrophobic interaction in water is important in biological interfaces. In our previous work, we have found that poly(styrene- b-triethylene glycol methyl ether methacrylate) (PS-PME3MA) segregates the PME3MA block to the surface in hydrophobic environment, such as in air or in a vacuum, and shows remarkable resistance against adsorption or adhesion of proteins, platelets, and cells in water. In this paper, we report that atomic force microscopy (AFM) with hydrophobic probes can directly monitor the reduced hydrophobic interaction of the PS surfaces modified by poly(styrene- b-origoethylene glycol methyl ether methacrylate) (PS-PME NMA), where N is the number of ethylene glycol units. The pull-off forces between the hydrophobic probes that are coated with octyltrichlorosilane (OLTS) and the PS-PME NMA modified polystyrene (PS) surfaces in water were measured. The absolute spring constants and tip-curvatures of the AFM cantilevers were measured to compute the work of adhesion by the Johnson, Kendall, and Roberts (JKR) theory, which relates the pull-off force at which the separation occurs between a hemisphere and a plane to the work of adhesion. The hydrophobic interactions between the hydrophobic tip and polymer surfaces in water were greatly reduced with the segregated PME NMA blocks. The hydrophobic interactions decrease with increasing N of the series of PS-PME NMA and show a correlation with the amount of protein adsorbed.     

Micellization of non-surface-active diblock copolymers in water. Special characteristics of poly(styrene)-block-poly(styrenesulfonate)

Strongly ionized amphiphilic diblock copolymers of poly(styrene)-b-poly(styrenesulfonate) with various hydrophilic and hydrophobic chain lengths were synthesized by living radical polymerization, and their properties and self-assembling behavior were systematically investigated by surface tension measurement, foam formation, hydrophobic dye solubilization, X-ray reflectivity, dynamic light scattering, small-angle neutron scattering, small-angle X-ray scattering, and atomic force microscope techniques. These copolymer solutions in pure water did not show a decrease of surface tension with increasing polymer concentration. The solutions also did not show foam formation, and no adsorption at the air/water interface was confirmed by reflectivity experiments. However, in 0.5 M NaCl aq solutions polymer adsorption and foam formation were observed. The critical micelle concentration (cmc) was observed by the dye solubilization experiment in both the solutions with and without added salt, and by dynamic light scattering we confirmed the existence of polymer micelles in solution, even though there was no adsorption of polymer molecules at the water surface in the solution without salt. By the small-angle scattering technique, we confirmed that the micelles have a well-defined core-shell structure and their sizes were 100-150 A depending on the hydrophobic and hydrophilic chain length ratio. The micelle size and shape were unaffected by addition of up to 0.5 M salt. The absence of polymer adsorption at the water surface with micelle formation in a bulk solution, which is now known as a universal characteristic for strongly ionized amphiphilic block copolymers, was attributed to the image charge effect at the air/water interface due to the many charges on the hydrophilic segment.     

两亲性超支化聚(酯-胺)在染料相转移中的应用

具有树枝状结构的大分子由于其独特的结构、大量的分子内空穴、可修饰的表面端基及良好的溶解性，已被用作主体分子与客体分子进行复合，并在药物释放、纤维染色、印刷、传感器等方面显示良好的应用前景。通过长烷基链或氟碳链改性的两亲性树枝状分子可以将水溶性酸性染料     

Hydration characterization of hydrophobically modified polymers by dielectric measurements in the millimeter range

Bound water molecules, the fraction of water molecules that are present in the hydration shells of polymers, lose their rotational mobility in the time scale of 10-50 ps, leading to additional ordering compared with unperturbed water. The amount of bound water per number of carbons in the nonpolar groups as measured by the method of waveguide dielectric resonance increased in the following order: hydrophobically modified chitosan < globular protein < hydrophobically modified polyacrylamide. The hydrophobic modification of acrylamide and chitosan polymers gave smaller variation in hydration than did both the coil-to-globule transition of poly(N-isopropylacrylamide) and the masking of nonpolar groups within the protein globule.     

A series of poly[N-(2-hydroxypropyl)methacrylamide] copolymers with anthracene-derived fluorophores showing aggregation-induced emission properties for bioimaging

A series of new poly[N-(2-hydroxypropyl)methacrylamide]-based amphiphilic copolymers were synthesized through a radical copolymerization of a monomeric/hydrophobic fluorophore possessing aggregation-induced emission (AIE) property with N-(2-hydroxypropyl)methacrylamide. Photophysical properties were investigated using UV-Vis absorbance and fluorescence spectrophotometry. Influences of the polymer structures with different molar ratios of the AIE fluorophores on their photophysical properties were studied. Results show that the AIE fluorophores aggregate in the cores of the micelles formed from the amphiphilic random copolymers and polymers with more hydrophobic AIE fluorophores facilitate stronger aggregations of the AIE segments to obtain higher quantum efficiencies. The polymers reported herein have good water solubility, enabling the application of hydrophobic AIE materials in biological conditions. The polymers were endocytosed by two experimental cell lines, human brain glioblastoma U87MG cells and human esophagus premalignant CP-A, with a distribution into the cytoplasm. The polymers are non-cytotoxic to the two cell lines at a polymer concentration of 1 mg/mL.     

Hofmeister effects of anions on self-assembled thermogels

Thermogels are temperature-responsive soft biomaterials with numerous biomedical applications. They possess high water content and can spontaneously gelate by forming non-covalent physical crosslinks between their constituent amphiphilic polymers when warmed. However, despite the ubiquity of salts in biological fluids and buffer media, the influence of salts on thermogelling polymers and the overall physical properties of the resulting hydrogels are poorly understood. Herein, we elucidate the effects of common inorganic salts on the gelation and micellization properties of a thermogelling polymer containing poly(ethylene glycol), poly(propylene glycol), and poly(caprolactone) components. The identity of the salts' anions and their concentrations was found to exhibit significant effects on the thermogel properties, in some cases being able to decrease the sol-to-gel phase transition by up to 10 °C. We demonstrate that these notable influences are likely brought about by the changes in solvation of both the polymer's hydrophobic and hydrophilic segments, as well as by direct interactions of poorly hydrated anions with the hydrophobic polymer segments. Our findings show that the effects of salts on amphiphilic thermogelling polymers are non-negligible and hence need to be taken into account for engineering and optimization of thermogel properties for different biomedical applications.