Synthesis and morphology transformation of amphiphilic diblock polyurethane copolymers in aqueous solution

Amphiphilic block copolymers possess both hydrophobic and hydrophilic properties and can form versatile micellar structures in aqueous solution. The aim of the research presented was to prepare a series of non‐ionic amphiphilic diblock polyurethane copolymers (PUn) based on isophorone diisocyanate, monoallyl‐end‐capped poly(ethylene oxide) and poly(propylene oxide) (PPO), followed by an investigation of their micellization properties and morphology transformation in aqueous solution. The PUn samples were synthesized by condensation polymerization. These polyurethanes exhibit surface tension as low as 33.7–37.0 mN m^?1. There is an obvious decrease in critical micelle concentration as the hydrophobic PPO molecular weight increases. According to transmission electron microscopy, the morphology of aggregates of the copolymers can be tuned by varying the concentration in aqueous solution rather than organic solvent. For example, for PU7, large compound micelles are produced instead of vesicles. For PU17, the concentration can be used to control the size and thickness of vesicles. Vesicle size increases from 60 to 500 nm and vesicle thickness from 40 to 60 nm with concentration ranging from 0.003 to 0.03 wt%. The study shows that the copolymers in aqueous solution have excellent surface activities. In addition, they can self‐assemble into large compound micelles or vesicles at certain concentrations. Moreover, the synthesis method described allows one to obtain a desired morphology of aggregates by adjusting the composition of hydrophilic and hydrophobic segments, which provides a novel and simple way to obtain particles on the nanometer scale. Copyright © 2010 Society of Chemical Industry     

Synthesis of magnetite/polyamino-ester dendrimer based on PCL/PEG amphiphilic copolymers via convergent approach for targeted diagnosis and therapy

The aim in this study is to synthesize amphiphilic linear-dendritic-linear block copolymers consisting of a poly ?-caprolactone linear block, poly(amino-ester) dendritic block and m-PEG linear block. G1, G2 and G3 dendrons were produced by sequential acrylation and Micheal addition reactions, using required amounts of acryloyl chloride and diethanolamine respectively to achieve quantitative growth. Amphiphilic dendrons were synthesized from the reaction of hydroxyl group of G1, G2 and G3 with mPEG-adipoyl chloride and their structures were characterized by FT-IR and ¹H NMR spectroscopy. The amphiphilic dendrons can self-assemble and form micelles in water. Their critical micelle concentration (CMC), particle size and zeta potential were determined by fluorescence spectroscopy and dynamic light scattering, respectively. Convergent dendrimers were prepared by self-assembly of the dendrons around oleic acid-stabilized Fe₃O₄ nanoparticles via the ligand exchange method and their morphologies were characterized by transmission electron microscopy (TEM). The in-vitro release behavior of quercetin from dendrimers and hydrolytic degradation of them were investigated at two pHs (7.4 and 5.8).     

Synthesis,Surface Activity and Aggregation Properties of Glucosamide‐Based Polysiloxanes

Three glucosamide‐based polysiloxanes (GAPS) surfactants were prepared by amidation of gluconolactone with amino functional polysiloxanes synthesized by polymerization. GAPS were characterized by FT‐IR, ¹H NMR and ¹³C NMR. Surface activity and aggregation behavior in aqueous solution were studied by surface tension measurements, dynamic light scattering and transmission electron microscopy. GAPS can reduce the surface tension of water to 24 mN m^?1 at concentration levels of 10^?4 g mL^?1 and self‐assemble in water at room temperature to form spherical micelles with average diameters ranging from 30 to 1000 nm. The micelle diameter increases with increasing degree of polymerization.     

Amphiphilic linear–hyperbranched polymer poly(ethylene glycol)–branched polyethylenimine–poly(ϵ‐caprolactone): synthesis,self‐assembly and application as stabilizer of platinum nanoparticles

Amphiphilic linear–hyperbranched polymer poly(ethylene glycol)–branched polyethylenimine–poly(?‐caprolactone) (PEG‐PEI‐PCL) was synthesized by progressively conjugating PEG (one chain) and PCL (multi‐chains) to PEI (hyperbranched architecture) with a yield of 87%. PEG‐PEI‐PCL forms nano‐sized uniform spherical micelles by self‐assembly in water. The micelles had an average diameter of 56 nm determined using dynamic light scattering and 35 nm observed from transmission electron microscopy images. PEG‐PEI‐PCL was used as a stabilizer of platinum nanoparticles (PtNPs) for the first time. The particle diameter of PEG‐PEI‐PCL‐stabilized PtNPs was 7.8 ± 1.4 nm. Amphiphilic (hydrophilic–hydrophilic–hydrophobic) and hyperbranched (linear–hyperbranched–grafted) structures enabled PtNPs to effectively stabilize and disperse in liquid‐phase synthesis. The highly disperse PtNPs in PEG‐PEI‐PCL micelles improved the catalytic activity for the reduction of 4‐nitrophenol with a catalytic yield of near 100%. © 2016 Society of Chemical Industry     

Structure Characterization of Surfactant Assisted Polymer Thickeners by Silica Nanocasting

The aggregation behavior of the hydrophobically modified polyelectrolytes which act in the interplay with special surfactant mixtures as a thickener is examined by replication of the different soft matter nanostructures into silica gels. The inorganic solidified replicas can be easily microtomed and analyzed by gas sorption measurements, quantitative small angle X‐ray scattering and transmission electron microscopy. The bare hydrophobically modified polyelectrolytes show a very homogeneous structure, free of larger aggregated moieties. In addition, a transition between a weakly‐ or unaggregated structure and an aggregated structure of the bare copolymer with hydrophobic moieties of ca. 3 nm diameter was found which depends on the degree of hydrophobic substitution, the concentration, and the salt content. The simultaneous presence of surfactant in the polymer solution leads to nanocasting of both spherical (ionic surfactant) and worm‐like (zwitterionic surfactant) micelles, which are essentially unperturbed by the incorporate the hydrophobic moieties of the polymer. Optimal thickening efficiency is obtained when each of those micelles is coupled to at least two of the polymers. The resulting sterical demands are best met by the presence of worm‐like surfactant micelles.     

Synthesis and Solution Properties of Carbohydrate‐Modified Polysiloxane Bola Surfactants

Three carbohydrate‐modified polysiloxane bola surfactants (ATPS‐GA) were synthesized using a two‐step method. Their chemical structures were characterized by infrared spectroscopy (FT‐IR) and proton nuclear magnetic resonance spectroscopy (¹H NMR). Their surface properties and aggregation properties in aqueous solution were determined using surface tension measurements and transmission electron microscopy (TEM). Surface tension measurement results indicated that the three bola surfactants are under 25 mN m^?1, and much lower than those of conventional hydrocarbon bola surfactants due to the siloxane moiety at the end of the hydrophobic chains. TEM analysis results indicated that the ATPS‐GA can self‐assemble into spherical micelles with a wide range of average diameters from 100 nm to above 600 nm.     

Acetylation of dendrimer‐entrapped gold nanoparticles: Synthesis,stability, and X‐ray attenuation properties

Functionalized dendrimer‐entrapped gold nanoparticles (Au DENPs) are of scientific and technological interest in biomedical applications. In this study, Au DENPs prepared with amine‐terminated generation 5 (G5) poly(amido amine) dendrimers as templates were subjected to acetylation to neutralize the positive surface charge of the particles. By varying the molar ratio of Au salt to G5 dendrimer, we prepared acetylated Au DENPs with a size range of 2–4 nm. Meanwhile, we attempted to add glucose to the dialysis liquid of the acetylated Au DENPs to prevent possible particle aggregation after lyophilization. The acetylated Au DENPs with different compositions (Au salt/dendrimer molar ratios) were characterized with ¹H‐NMR, transmission electron microscopy, ultraviolet–visible (UV–vis) spectrometry, and ζ‐potential measurements. We show that when the molar ratio of Au salt to dendrimer was equal to or larger than 75:1, the acetylated Au DENPs showed a significant aggregation after lyophilization, and the addition of glucose was able to preserve the colloidal stability of the particles. X‐ray absorption measurements showed that the attenuation of the acetylated Au DENPs was much higher than that of the iodine‐based contrast agent at the same molar concentration of the active element (Au vs iodine). In addition, the acetylated Au DENPs enabled X‐ray computed tomography (CT) imaging of mice after intravenous injection of the particles. These findings suggest a great potential for acetylated Au DENPs as a promising contrast agent for CT imaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

枝化-环化结构共聚物用于酸响应载药体系

将溴代聚乙二醇(PEG2000Br)和缩醛化物二(2-丙烯酰氧基乙氧基)-(4-甲氧基苯基)甲烷(ACD)分别作为引发剂和单体,采用逆向增强原子转移自由基聚合(DE-ATRP)法得到嵌段共聚物聚乙二醇-b-聚[二(2-丙烯酰氧基乙氧基)-(4-甲氧基苯基)甲烷](PEG-b-PACDs)。通过核磁共振氢谱和凝胶渗透色谱表征了该聚合物的结构;用动态光散射和透射电镜表征了胶束的尺寸和形貌。结果表明,聚合物呈现枝化-环化结构,空白胶束的尺寸在70 nm左右,载药胶束尺寸在90 nm左右,胶束的药物包封率为48.7%。在pH为7.4时透析48 h后,药物释放率只有32.5%,在pH为5.4时透析48 h后,药物释放率为68.3%,表明共聚物在酸性条件下具有良好的药物缓释性。     

Cationic amphiphilic copolymers: synthesis,characterization, self‐assembly and drug‐loading capacity

Amphiphilic copolymers with cationic hydrophilic moieties and different ratios of hydrophobic portion to hydrophilic portion were designed and synthesized via the combination of hydrosilylation reactions and quaternization reactions. The structures were characterized through Fourier transform infrared spectroscopy, ¹H NMR , ¹³C NMR and gel permeation chromatography. The measurements of critical micelle concentrations, electrical conductivities and zeta potentials indicated that the copolymers could self‐assemble into nanoparticles with charges around the surface in aqueous solution. The sizes of the micelles were between 67 nm and 104 nm detected by dynamic light scattering. The self‐assembled micelles were used as drug carriers to encapsulate a model drug (tocopherol), and their drug‐loading content (DLC ) and efficiency (DLE ) were determined by UV ?visible spectra, resulting in considerable drug‐loading capacity to a tocopherol maximum up to 17.2% (DLC ) and 80.3% (DLE ) with a size of 90 nm. The blank micelles and drug‐loaded micelles displayed a spherical shape detected by transmission electron microscopy, which demonstrated not only the self‐assembly behaviors but also the drug‐loading performances of the cationic amphiphilic copolymers. All the results demonstrated that the cationic amphiphilic copolymers could be used as potential electric‐responsive drug carriers. © 2017 Society of Chemical Industry     

一种基于胆固醇衍生物的两亲分子的合成及其聚集行为

合成了以胆固醇为疏水基、双甘肽为亲水基的两亲分子N-胆固醇甲酰基双甘肽钾盐(Chol-GG-K)。利用透射电镜(TEM)、激光共聚焦显微镜(CLSM)等手段研究了该分子在水中的聚集行为,发现其在水中形成了多分散的囊泡结构。胆固醇的范德华力形成强疏水作用和聚集能力,亲水基的氢键作用也是产生聚集作用的驱动力。     

Synthesis of amphiphilic graft copolymer with hydrophilic poly(acrylic acid) backbone and hydrophobic polystyrene side chains

A series of well-defined amphiphilic graft copolymers consisting hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chains were synthesized by successive atom transfer radical polymerization (ATRP) followed by hydrolysis of poly(methoxymethyl acrylate) (PMOMA) backbone. Grafting-from strategy was employed for the synthesis of graft copolymers with narrow molecular weight distribution. Hydrophobic side chains were connected to the backbone through stable C-C bonds. The backbone can be easily hydrolyzed with HCl without affecting hydrophobic side chains. This family of amphiphilic graft copolymers can form stable micelles in water. The critical micelle concentration was determined by fluorescence spectroscopy. The micellar morphologies and sizes were studied using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The sizes of micelles were dependent on ionic strength, pH value and preparation conditions.     

Complexes comprised of a dendrimer and a vesicle: role of vesicle size and the surface tension of the vesicle membrane

Mesoscale simulations are performed to study the complexes between a dendrimer and a vesicle of amphiphilic molecules. In particular, the assembled structures and dynamics of these complexes are investigated by tuning vesicle size and the surface tension of vesicle membrane. Our simulations demonstrate that a dendrimer-based bulge containing amphiphilic molecules forms in the vesicle membrane when a dendrimer adheres to a vesicle. We find that vesicle size and the surface tension of the vesicle membrane permit effective accesses to control the shape change of the bulge structure with respect to various hydrophobic interactions in the complexes. The analysis for the energy of the vesicle reveals that the change of elastic energy induced by various densities of amphiphilic molecules in the membrane plays an important role in this bulge-shape control. Because both charged dendrimers and vesicles are effective nanodevices for targeted drug delivery, our findings shed light on the effective means of developing multitasking nanocarriers as targeted drug delivery platforms.     

Synthesis,characterization and micellization of heterograft copolymers based on phosphoester functionalized macromonomers via “grafting through” method

Novel amphiphilic heterograft copolymers consisting of phosphoester functionalized PEG (phosPEG) and PCL (phosPCL) were synthesized by the ring‐opening polymerization via “grafting through” method. The heterograft structure and thermal properties of these copolymers with various compositions were characterized by ¹H‐NMR, ³¹P NMR, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) in detail. These amphiphilic copolymers could self‐assemble into micellar structures in aqueous solution, and their critical micellization concentrations (CMC) were determined to be 0.69–1.25 mg/L by fluorescence technique. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements show that these heterograft copolymer micelles are spherical in shape with the particle size ranging from 20 to 60 nm, which has potential in biomedical application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel amphiphilic diblock copolymers bearing acid-labile oxazolidine moieties: Synthesis, self-assembly and responsive behavior in aqueous solution

A novel oxazolidine based acid-labile monomer N-acryloyl-2,2-dimethyl-1,3-oxazolidine (ADMO) was synthesized and polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization using poly(ethylene glycol) based chain transfer agent (PEG-CTA). The diblock copolymers PEG-b-PADMO were composed of hydrophilic PEG with fixed length and hydrophobic PADMO with different lengths, which formed core-shell micelles in water. Morphologies and sizes of micelles were obtained by transmission electron microscopy (TEM) and dynamic light scattering (DLS), which showed that the shapes of polymeric aggregates developed from small spherical micelles, worm-like micelles to larger size of vesicles, as the length of PADMO increased. The hydrolysis kinetics of the micelles was studied using ¹H NMR, DLS and release of loaded Nile Red dye, whose rate strongly depended on pH and micellar structure. It led to the disruption of polymeric micelles and concomitant release of the guest molecules, due to the transformation of hydrophobic PADMO into hydrophilic poly(2-hydroxyethyl acrylamide) (PHEAM).     

Synthesis and characterization of amphiphilic graft copolymers with hydrophilic poly(acrylic acid) backbone and hydrophobic poly(methyl methacrylate) side chains

A series of well-defined amphiphilic graft copolymers containing hydrophilic poly(acrylic acid) backbones and hydrophobic poly(methyl methacrylate) side chains were synthesized by successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl acrylate) backbone. Grafting-from strategy was employed for the synthesis of graft copolymers with narrow molecular weight distributions. Hydrophobic side chains were connected with the backbone through stable C-C bonds instead of ester connections. The backbone can be easily hydrolyzed to poly(acrylic acid) with HCl without affecting the hydrophobic side chains. The amphiphilic graft copolymers can form stable micelles in water. The critical micelle concentration was determined by fluorescence spectroscopy. The micellar morphologies were found to be vesicles by transmission electron microscopy and changed to spheres with the addition of NaCl.     

Synthesis and Solution Properties of Novel Sugar-Based Polysiloxane Surfactants

Two sugar‐based polysiloxane surfactants with well‐defined structures, 3‐(2‐aminoethylamino)propyl functional polysiloxane glucosamide grafted (AEAPFPS‐GA) and 3‐(2‐aminoethylamino)propyl functional polysiloxane lactobionamide grafted (AEAPFPS‐LA), were successfully synthesized and characterized by FT‐IR and ¹H NMR. Their surface activities and aggregation behavior in aqueous solution were investigated by surface tension measurements, dynamic light scattering (DLS) and negative‐stain transmission electron microscopy (TEM). The surface tension measurements provided the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC), which revealed that these two surfactants have a much higher surface activity than those of conventional hydrocarbon surfactants. DLS and TEM analysis of the two polysiloxane surfactants aqueous solutions revealed that the AEAPFPS‐GA can self‐assemble into collapsed spherical micelles, and the AEAPFPS‐LA can self‐assemble into spherical micelles.     

Preparation and characterization of silver nanoparticles with dendrimers as templates

In this study, crystal silver nanoparticle clusters, prepared by the reduction of AgNO₃ in the presence of third-to-sixth-generation dendrimers with a trimesyl core, were characterized with ultraviolet–visible spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The results showed that the particle size of the silver nanoparticles was considerably affected by the generation of the dendrimers as well as the dendrimer concentration. When the concentration ratios of Ag⁺ to the third-to-sixth-generation dendrimers were all 4 : 1, the average diameters of the obtained particles were 6.7, 6.0, 5.2, and 4.3 nm, respectively. The data from high-resolution transmission electron microscopy and electron diffraction indicated that the particles belonged to a simple cubic crystal structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

纤维素基高分子表面活性剂的合成及性能表征

以聚合度为280的纤维素为原料,通过两步反应,制备了纤维素基高分子表面活性剂纤维素棕榈酰酯硫酸钠,利用红外光谱、动态接触角测定仪、透射电镜和动态光散射等对产物的结构和性能进行了表征.结果表明,该纤维素两亲高分子的临界聚集含量为0.60%(质量分数),对应的表面张力为57 mN/m;当水溶液浓度在临界聚集含量附近时,即水溶液的质量分数由0.5%增大到1.0%,胶束的平均粒径由388.0 nm增大到549.7 nm,此时表面活性剂分子已不断聚集成胶束或胶团;此外该类表面活性剂还具有高分子特有的流变性.     

Synthesis,characterization and surface properties of star‐shaped polymeric surfactants with polyhedral oligomeric silsesquioxane core

Star‐shaped amphiphilic polymeric surfactants comprising a hydrophobic polyhedral oligomeric silsesquioxane (POSS) core and hydrophilic poly(ethylene glycol) (PEG) arms with various chain lengths are successfully synthesized using copper(I)‐catalysed azide–alkyne cycloaddition (CuAAC) click reaction. Their chemical structures and molecular characteristics are clearly confirmed using Fourier transform infrared and ¹H NMR spectroscopies and gel permeation chromatography, and no homopolymer is found after CuAAC click reaction. Aqueous solutions of these star‐shaped polymers have been investigated using atomic force and transmission electron microscopies and dynamic light scattering studies and it is found that they can self‐assemble into micelles. The sizes of the micelles can be adjusted by the length of the PEG arms, where longer chains not only lead to increased micelle sizes, but also reduce the contact angle values. Moreover, the melting points and root mean square roughness of the obtained star‐shaped polymers are slightly increased on increasing the chain length of the PEG arms. © 2017 Society of Chemical Industry     

Preparation of stealth micellar nanoparticles of novel biodegradable and biocompatible brush copolymers with cholesteryl-modified PLA and PEG side chains

Novel amphiphilic brush copolymers, P(CPLAMA)-co-P(PEGMA), of cholesteryl poly(l-lactic acid) (CPLA) and poly(ethylene glycol) monomethyl ether (PEG) with determined hydrophobic/hydrophilic ratios were synthesized by the methacrylate (MA) macromonomer copolymerization method. Brush copolymers were prepared via both free radical polymerization (FRP) and atom transfer radical polymerization (ATRP). The copolymer compositions were determined by ¹H NMR spectroscopy. The synthesized copolymers were used to prepare the micellar nanoparticles with hydrophobic CPLA and hydrophilic PEG forming the core and shell, respectively. The critical micelle concentration (CMC) values of the samples produced by FRP (brush copolymer 1) and ATRP (brush copolymer 2) were estimated to be approximately 0.9 and 0.7 mg/L in aqueous solution by a fluorescence probe technique, respectively. The transmission electron microscopy (TEM) images of micelles of the brush copolymers 1 and 2 showed that micelles were spherical in shape with a mean diameter of 111 and 32 nm, respectively. The results showed that the size of micelles became larger with the increase of the molecular weight of polymer and the relative content of the hydrophilic PEG as well. The drug loading efficiency and drug-releasing properties of the micelles were investigated by using naproxen as a hydrophobic model drug. The in vitro release of naproxen-loaded micelles with about 85–89 % loading efficiency and 17–18 % loading capacity was studied by a using dialysis method in phosphate-buffered solution at 37 °C. The drug-releasing characteristics exhibited a phase of slow release. On the basis of the results obtained, the proposed brush copolymers may be useful in various targeted drug delivery applications, especially those involving hydrophobic drugs.