两亲性无规共聚物MAA-SMA-PEGMA的表面活性研究

利用功能性单体甲基丙烯酸(MAA)、甲基丙烯酸十八烷基酯(SMA)和聚乙二醇甲基丙烯酸酯(PEGMA)通过常规自由基无规共聚反应,合成了两亲性共聚物Poly(MAA-SMA-PEGMA)。对其结构、临界胶束质量浓度(CMC),表面张力等进行了研究,并对由共聚物与低分子表面活性剂组成的复配体系进行了探讨。实验结果表明:高低分子表面活性剂复配体系在质量比为5∶5后,体系的表面张力和临界胶束浓度都有所降低,接近于低分子表面活性剂。     

两亲性无规共聚物的自组装及模拟释药性能

通过自由基聚合得到两亲性甲基丙烯酸-co-甲基丙烯酸甲酯无规聚合物P(MAA-co-MMA)。用红外光谱、核磁共振和黏度法对聚合物进行表征。用此共聚物进行自组装成胶束,并用罗丹明B进行模拟载药、释药。用激光粒度散射仪和紫外分光光度计对胶束载药、释药性能进行表征。结果表明,此聚合物能够自组装形成315～384 nm胶束。胶束的药物包封率达1%,在模拟生理pH值条件下载药胶束能起到明显的长循环药物缓释作用。     

无规共聚物P(AA-co-BA)的制备及表面活性研究

研究无规共聚物P(AA-co-BA)作为高分子表面活性剂的可行性。以丙烯酸(AA)和丙烯酸丁酯(BA)为单体,采用自由基溶液聚合法成功制备了5种投料比的无规共聚物P(AA-co-BA),其热稳定性良好。研究比较了表面张力法和电导法对该聚合物临界胶束浓度(cmc)的测试,结果表明,两种方法在测试聚合物cmc时结果一致,电导法虽简便,但表面张力法更适合进行物质的表面活性研究。当单体投料比m(BA)∶m(AA)=1∶10～1∶5时,聚合物的cmc为0.6～0.9?g/L,对应的表面张力为44.8～49.5?mN/m,这表明适当投料比的无规共聚物P(AA-co-BA)可以作为高分子表面活性剂。     

溶液聚合法合成苯乙烯—马来酸酐无规共聚物

采用溶液聚合法合成了苯乙烯－马来酸酐无规共聚物,用ＩＲ、ＮＭＲ、ＤＳＣ及乌氏粘度计对共聚物进行了表征。     

两亲性无规聚合物P（MMA-co-MAA）的合成及其自组装研究

由疏水性单体甲基丙烯酸甲酯（MMA）和亲水性单体甲基丙烯酸（MAA）进行自由基溶液共聚,合成了一系列配比不同的两亲性无规聚合物P（MMA-co-MAA）,用红外光谱、核磁共振和凝胶渗透色谱对聚合物结构进行了表征。采用一种操作过程简单、快捷、环保的新方法制备了聚合物胶束,即将一定质量的聚合物溶于碱性水溶液中,通过中和原理进行自组装,并得到球形胶束。通过透射电子显微镜（TEM）和激光光散射（DLS）法,研究了聚合物中基团摩尔比例不同时对胶束形貌和流体动力学半径（Rh）的影响。     

两亲性无规聚合物P(MMA-co-MAA)的合成及其自组装研究

由疏水性单体甲基丙烯酸甲酯(MMA)和亲水性单体甲基丙烯酸(MAA)进行自由基溶液共聚,合成了一系列配比不同的两亲性无规聚合物P(MMA-co-MAA),用红外光谱、核磁共振和凝胶渗透色谱对聚合物结构进行了表征。采用一种操作过程简单、快捷、环保的新方法制备了聚合物胶束,即将一定质量的聚合物溶于碱性水溶液中,通过中和原理进行自组装,并得到球形胶束。通过透射电子显微镜(TEM)和激光光散射(DLS)法,研究了聚合物中基团摩尔比例不同时对胶束形貌和流体动力学半径(Rh)的影响。     

苯乙烯—马来酸酐无规共聚物合成研究

以过氧化二异丙苯为引发剂,采用本体聚合法合成了苯乙烯－马来酸酐无规共聚物,用ＩＲ、ＮＭＲ、ＤＳＣ及乌氏粘度计对共聚物进行了表征,同时对反应条件作了初步探讨。     

水溶性紫杉醇两亲性共聚物纳米胶束研究

聚乙二醇聚己内酯聚乙二醇采用三嵌段共聚物为载体包载紫杉醇形成纳米胶束,胶束具有明显的核壳结构,有效地改善了紫杉醇的水溶性。研究表明,采用蒸发溶剂法、透析法和熔融法制备的胶束对紫杉醇都呈现良好的包封效果,其中,以熔融法制得的胶束粒径最小,分布最窄。文中还考察了蒸发溶剂法实验条件对胶束的影响,发现低沸点有机溶剂有利于获得小粒径胶束,胶束平均粒径随着载药量的提高相应增大。体外释药的结果表明,载药量高的胶束释药率却相对较小。     

丙烯酸-丙烯酸甲酯无规共聚物的聚合及表征

以丙烯酸(AA)、丙烯酸甲酯(M A)为共聚单体,以过硫酸铵和亚硫酸氢钠为氧化还原引发体系,以异丙醇为链转移剂,以水为溶剂,采用溶液聚合法合成了P(AA-M A)无规共聚物。采用红外光谱仪、表面张力仪、透射电子显微镜、热分析仪对共聚物的组成、结构、表面张力、透射形貌和热性质进行了表征。结果表明聚合条件为单体AA/M A(摩尔比)=6/1,异丙醇、过硫酸铵、亚硫酸氢钠添加量都为2%(均以单体计),加料时间30m in,聚合温度60℃,反应时间1.5h。产物为浅黄色黏稠液体,有两头尖的椭球形和球形的两种形态、较好的表面活性和热稳定性。     

丙烯酸/丙烯酸甲酯无规共聚物的性质研究及其表征

本研究以丙烯酸(AA)、丙烯酸甲酯(MA)为共聚单体,以过硫酸铵和亚硫酸氢钠为氧化还原体系引发剂,异丙醇为链转移剂,以水为溶剂,采用溶液聚合方法合成了P(AA-MA)无规共聚物。采用表面张力仪、热分析仪对共聚物的表面张力和热力学性质进行分析,利用红外光谱、透射电子显微镜对共聚物的结构和形貌进行了表征。     

Preparation of pH-responsive membranes with amphiphilic copolymers by surface segregation method☆

Novel pH-responsive membranes were prepared by blending pH-responsive amphiphilic copolymers with pol-yethersulfone (PES) via a nonsolvent-induced phase separation (NIPS) technique. The amphiphilic copolymers bearing Pluronic F127 and poly(methacrylic acid) (PMAA) segments, abbreviated as PMAAn–F127–PMAAn, were synthesized by free radical polymerization. The physical and chemical properties of the blend membranes were evaluated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrum, water con-tact angle, Zeta potential and X-ray photoelectron spectroscopy (XPS). The enrichment of hydrophilic PMAA seg-ments on the membrane surfaces was attributed to surface segregation during the membrane preparation process. The blend membranes had significant pH-responsive properties due to the conformational changes of surface-segregated PMAA segments under different pH values of feed solutions. Fluxes of the blend membranes were larger at low pH values of feed solutions than that at high pH values. The pH-responsive ability of the mem-branes was enhanced with the increase of the degree of PMAA near-surface coverage.     

Ultra-thin films of cationic amphiphilic poly(2-(dimethylamino)ethyl methacrylate) based block copolymers as surface wettability modifiers

Ultra-thin films of cationic amphiphilic block and statistical copolymers were applied on silica surfaces from aqueous solutions through electrostatic interactions, and the resulting modification in the wettability of the surfaces was studied. A copolymer series from 2-(dimethylamino)ethyl methacrylate with methyl methacrylate and butyl methacrylate was polymerized by ATRP. Subsequently, the conformation of the polymers in aqueous solutions was studied by surface tension measurements, dynamic light scattering, ¹H NMR and cryogenic transmission electron microscopy. Unimeric conformation, equilibrium micelles or frozen micellar structures were observed, depending on polymer composition and the ionic strength of the solution. The polymers were applied on silica from aqueous solutions by either spin coating or adsorption. The formed ultra-thin film surfaces were studied by AFM and water contact angle measurements. The spin-coated surfaces were highly hydrophilic with rapidly dropping contact angles, whereas the surfaces prepared by adsorption had stable water contact angles between 30-60°, depending on polymer. The difference between the spin-coated and adsorbed surfaces is explained by the formation of a monolayer in the adsorbed surfaces.     

Facile preparation of amphiphilic oxyethylene-oxypropylene block copolymers by selective triazine coupling

A novel synthetic route for preparing high molecular weight poly(oxyalkylene) block copolymers has been developed by using 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride, cc) as the coupling core. The coupling reaction involves the selective substitutions of oligo(oxyalkylene)-amines onto three chlorides of the triazine ring in a stepwise manner at 0, 25 and 130 °C. By judiciously selecting the starting amines and reaction conditions, one can tailor the copolymer structures with different block configurations (tri-block, multi-block, random and alternating block). The prepared copolymers can have a high molecular weight, up to 25,600 g/mol (GPC polydispersity=1.48), and also high thermal stability due to the presence of triazine functionalities. The copolymers with hydrophilic and hydrophobic oligo(oxyalkylene) blocks are of versatile properties in solubility (water soluble or water insoluble) and morphology (crystalline or amorphous). With a specific structure of alternating oligo(oxyethylene)/oligo(oxypropylene) blocks (2000 g/mol each block), the copolymer exhibits the property of self-association. It reduces the interfacial tension of toluene/water as low as 0.5 dyne/cm at the critical micelle concentration of 0.01 wt%.     

两亲嵌段共聚物的合成及其自组装研究进展

作者介绍了两亲嵌段共聚物的活性阴离子聚合、基团转移聚合、开环歧化聚合、活性阳离子聚合、活性／可控自由基聚合、缩聚法、嵌段共聚物化学改性法等合成方法,并对其自组装形成聚合物纳米胶束的制备方法、形成机理以及在药物控制释放领域的应用进行了综述,并对其未来发展趋势进行了展望。     

Synthesis and micelle behavior of (PNIPAm-PtBA-PNIPAm)m amphiphilic multiblock copolymer

A linear amphiphilic multiblock copolymer (PNIPAm-PtBA-PNIPAm)_m was successfully synthesized by a two-step reversible addition-fragmentation transfer (RAFT) polymerization in the presence of a cyclic trithiocarbonate as RAFT agent. The micelle behavior of (PNIPAm-PtBA-PNIPAm)_m multiblock copolymer in aqueous solution was then investigated by means of normal TEM, cryo-TEM, static and dynamic light scattering. The morphology, size, and size distribution of (PNIPAm-PtBA-PNIPAm)_m micelles were found to be dependent on the initial concentration of multiblock copolymer in THF. Spherical micelles, associated aggregates of spherical micelles, cage-like micelles, layered structures, and vesicular micelles were experimentally observed, which were in good agreement with the prediction of theory and simulations on linear amphiphilic multiblock copolymer in selective solvent. The (PNIPAm-PtBA-PNIPAm)_m micelles also exhibit thermo-sensitive behavior in aqueous solution because of the PNIPAm blocks.     

Synthesis and characterization of biodegradable and biocompatible amphiphilic block copolymers bearing pendant amino acid residues

Polylactide (PLA)-based biodegradable and biocompatible amphiphilic block copolymers bearing pendant amino acid residues were synthesized through a relatively easy and efficient way. The composition and structure of these copolymers were characterized by gel permeation chromatography (GPC) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. The self-assembly behavior of the copolymers was investigated by fluorescence (FL), dynamic light scattering (DLS), and transmission electron microscope (TEM). It was shown that aggregates less than 100 nm in average size were formed by these copolymers, which changed from micelles to vesicles with the variation of the block length. In addition, the in vitro cytotoxicity of these copolymers was determined and compared with that of PEO-b-PLA in the presence of Bel-7402 cells. The result suggested that the block copolymers PAGE/cys-b-PLA exhibited better biocompatibility. Therefore, these PLA-based copolymers are expected to find promising applications in drug delivery or tissue engineering.     

Preparation and evaluation of novel amphiphilic glycopeptide block copolymers as carriers for controlled drug release

In the present study we describe a synthesis and self-assembly and an in vitro evaluation of a kind of novel amphiphilic glycopeptide block copolymers as carriers for controlled drug release. Initially, an amphiphilic ABA triblock copolymer comprising polytetrahydrofuran (PTHF) as a central hydrophobic block flanked by poly(l-lysine)s (PLLs) as outer hydrophilic blocks was synthesized through the ring-opening polymerization of ?-benzyloxycarbonyl-l-lysine N-carboxyanhydride with a distal amine-terminated PTHF as a macroinitiator, followed by removal of the protecting group. Afterwards the resulting triblock copolymer was allowed to react with d-gluconolactone and lactobionolactone in the varying feeding ratios in the presence of diisopropylethylamine leading to the target glycopeptide block copolymers with high yields. They were found to easily self-assemble into nano-sized aggregates in water. The critical aggregation concentrations (CACs) were assessed by fluorescence measurement with N-phenyl-1-naphthylamine employed as a molecular probe. The particle sizes of the aggregates before and after doxorubicin loading were determined by dynamic light scattering (DLS) and the aggregate morphologies were evidenced by transmission electron microscopy (TEM) measurements. Finally, the in vitro doxorubicin loading capacity and release behavior were investigated with these glycopeptide copolymers as carriers for controlled release.     

Influence of chemical structure on enzymatic degradation of single crystals of PCL-b-PEO amphiphilic block copolymer

Solution-grown lamellar single crystals of PCL homopolymer and amphiphilic block copolymers of PCL-b-PEO-b-PCL and PCL-b-PEO-FG (functional groups FG = NH₂, OCH₃) were prepared by self-seeding procedures. The crystal structure and morphology of these single crystals were mainly studied by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results indicated that the shorter PEO blocks as well as the functional groups bonded to the end of PEO block are in an amorphous state and located in the surface of single crystals. The enzymatic degradation of single crystals prepared from these homopolymer and amphiphilic block copolymers has been well-studied to demonstrate the effects of chemical structure on degradation behavior. The single crystals showed similar morphologies before enzymatic degradation but very different surface character after enzymatic degradation. Such differences resulted from the PEO block and functional end groups. The results of this work indicated the important role of chemical structure in determining biodegradation behavior.     

Adsorption of anionic amphiphilic polyelectrolytes onto amino-terminated solid surfaces

The adsorption behavior of several amphiphilic polyelectrolytes of poly(maleic anhydride-alt-styrene) functionalized with naphthyl and phenyl groups, onto amino-terminated silicon wafer has been studied by means of null- ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The maximum of adsorption, Γ_plateau, varies with the ionic strength, the polyelectrolyte structure and the chain length. Values of Γ_plateau obtained at low and high ionic strengths indicate that the adsorption follows the “screening-reduced adsorption” regime. Large aggregates were detected in solution by means of dynamic light scattering and fluorescence measurements. However, AFM indicated the formation of smooth layers and the absence of aggregates. A model based on a two-step adsorption behavior was proposed. In the first one, isolated chains in equilibrium with the aggregates in solution adsorbed onto amino-terminated surface. The adsorption is driven by electrostatic interaction between protonated surface and carboxylate groups. This first layer exposes naphtyl or phenyl groups to the solution. The second layer adsorption is now driven by hydrophobic interaction between surface and chains and exposes carboxylate groups to the medium, which repel the forthcoming chain by electrostatic repulsion. Upon drying some hydrophobic naphtyl or phenyl groups might be oriented to the air, as revealed by contact angle measurements. Such amphiphilic polyelectrolyte layers worked well for the building-up of multilayers with chitosan.