Solvent property induced morphological changes of ABA amphiphilic triblock copolymer micelles in dilute solution: A self-consistent field simulation study

The morphological changes of ABA amphiphilic triblock copolymer micelles in dilute solution were systematically studied by tuning the solvent property using self-consistent field simulation. The solvent property was tuned by changing the Flory-Huggins interaction parameters between each type of blocks and solvent, respectively. The simulation results show that by changing the solvent properties, a series of micelle morphologies such as vesicle, cage-like, ring-shaped, rod-like and spherical micelle morphologies can be obtained. Variations of the free energy of the solution system and the surface area of micelles with the Flory-Huggins interaction parameters were calculated to better understand the effect of solvent property on micelle morphologies. In addition, a phase diagram showing the morphological changes of micelles with the Flory-Huggins interaction parameters is provided.     

A facile approach to prepare hybrid nanoparticles with morphology controlled by the thickness of glyco-shell

Herein, we designed a novel amphiphilic triblock glycopolymer poly(oligo(ethyleneglycol) methacrylate)-block-poly(maltopyranoside methacrylate)-block-polystyrene(POMA-b-PMal-b-PS) via the combination of reversible addition-fragmentation chain transfer(RAFT) polymerization and postpolymerization modification. The micelles with core–shell–corona structures were prepared by direct self-assembly of this glycopolymer in water. We found that these micelles can be used in in situ formation and stabilization of Au NPs. By controlling the thickness of glyco-shell, we successfully obtained Janus particles and raspberry-like particles with Au NPs in the sugar shell.     

SYNTHESIS AND CHARACTERIZATION OF AMPHIPHILIC GRAFT COPOLYMER CONTAINING MICROPHASE SEPARATED AND LONG POLY(ETHYLENE OXIDE) SIDE CHAIN STRUCTURES**

Acryloyl terminated Poly (ethyleneoxide)macromonomers (PEO-A) with different PEO chain lengths have been prepared by deactivation of PEO alkoxide with acryloyl chloride. A new kind of amphiphilic polystyrene-g-poly (ethylene oxide)graft copolymer containing both microphase separated and PEO side chain structures has been synthesized from radical copolymerization of PEO-A macromonomer with styrene. After careful purification by a newly-developed method called "selective dissolution', the well-defined structure of the purified copolymers was confirmed by IR, ~1H-NMR and GPC. Various experimental parameters controlling the copolymerization were studied in detail. The results indicated that the feed ratio of styrene to macromonomer(S/M) was the most important determining factor for the composition of the copolymers. A detailed "comb- model" was proposed to describe the molecular structure of the graft copolymers. Finally, this amphiphilic graft copolymers may readily form microphase separated structures as clearly indicated by transmission electron microscopy.     

Elastic behavior of comb-like polymer chains

<正>Three-dimensional Monte Carlo simulations of comb-like polymer chains with various backbone lengths N_b,arm lengths N_a and arm densities m are carried out to study the elastic behavior of comb-like polymer chains.The radius of gyration,the shape factors and bond length in different cases during elastic process are calculated,and it is found that the comb-like polymer molecules with longer backbone or shorter arm are more close to linear chains.But the arm density m affects the chain conformation non-monotonously.Some thermodynamic properties are also studied.Average Helmholtz free energy and elastic force f all increase with elongation ratioλfor all chains.     

A Monte Carlo simulation study of the effect of chain length on the hydrolysis of poly(lactic acid)

Abstract The intrinsic relationship between molecular chain length and the probability of chain reaction during poly(lactic acid)(PLA)hydrolysis was investigated by Monte Carlo simulation.The chain reaction rate was calculated by introducing a power function of different molecular chain lengths.The hydrolysis of both amorphous and extended-chain crystal PLA was selected as the model system.It is found that,the chain reaction probability was proportional to the chain length with a power of 0.4 for amorphous PLA and 0.7 1 for extended-chain crystal PLA,respectively.These results indicate that PLA with longer chain length usually exhibits larger reaction rate than that with shorter length.Comparing the hydrolysis of the two kinds of PLA,the competition between longer and shorter chains in the different condensed structures is different.     

Interfacial assembly and host-guest interaction of anthracene-conjugated L-glutamate dendron with cyclodextrin at the air/water interface

The interfacial assembly of photo-induced dimerization of atypical anthracene-containing amphiphilic dendron and host-guest interaction with γ-cyclodextrin has been investigated.It has been proved that even without long alkyl chain the amphiphilic dendron could still form stable Langmuir monolayer at the air/water interface.Through the host-guest interaction,γ-cyclodextrin can be used to encapsulate two headgroups of amphiphilic dendron in the antiparallel direction.However,the formed host-guest complex was sensitive to the surface pressure.Slight compression of surface pressure led amphiphilic dendron to reassemble into nanofibers through the strong π-π stacking between headgroups.On the other hand,under in sitv irradiation,the amphiphilic dendron was stabilized in the cavity of γ-cyclodextrin through headgroup dimerization and the host-guest complex further irregularly aggregated to nanoparticles.Meanwhile,γ-cyclodextrin,as a silencer,blocked the supramolecular chirality transfer.Our conclusion was demonstrated through UV/vis,FT-IR,CD spectrum and AFM images,respectively.     

Hierarchical self-assembly of 3D amphiphilic discrete organoplatinum(Ⅱ)metallacage in water

Here we described the design and synthesis of a discrete 3D amphiphilic metallacage 4,in which the tetragonal prismatic frameworks act as the hydrophobic cores and the poly(ethylene glycol)(PEG)chains as the hydrophilic tails.The structure of 4 was characterized by 1H NMR,31P NMR and electrospray ionization time-of-flight mass spectrometry(ESI-TOF-MS).Notably,4 with its Iong PEG tails was subsequently ordered into micelles at a low concentration(1.20×10^-6 mol/L)in water.As the concentration and cultivation time increased,the micelles can further self-assembly into nanofibers and nanoribbons.Considering the dynamic property of the coordination bond,these structures show reversible transformation under external stimuli.     

Mesoscopic Simulation of Aggregates in Surfactant／Oil／Water Systems

The aggregates in sodium dedecylsulphate(SDS)/dimethylbenzene/water systems have been investigated using dissipative particles dynamic(DPD) simulation method.Through analyzing three-dimensional structures of aggregates,three simulated results are found.One is the phase separation,which is clearly observed by water density and the aggregates in the simulated cell;another is the water morphology in reverse micelle,which can be found through the isodensity slice of water including bound water,trapped water and bulky water;the third is about the water/oil interface,i.e.,ionic surfactant molecules,SDS,prefer to exist in the interface between water and oil phase at the low concentraion.     

In situ Observation of the Photochromism in the Langmuir Monolayer of a Non—typical Amphiphilic Spiropyran Derivative at the Air／Water Interface

In situ photochromic process in the monolayer of aphotochromic spiropyran derivative without long alkyl chain,was investigated.The photochromism at the air/water interface under differnet surface pressures was studied by surface pressure-area isotherms,surface pressure-time curves,area-time curves and Brewster angle microscopy.Both forms of the compound were found to form monolayers at the air/water interface althouhg it does not have long alkyl chain.A large area expansion in the monolayer corresponding to a zreo^th order reaction was found at the initial stage of the UV light irradiation.A series of dynamic investigations revealed that at high pressure after phase transition in the monolayer,the surface pressure changes greatly umder alternative irradiation of UV and visible light.An obvious morphological change accompanying with the photochromism was observed in situ.     

Control on the Morphology of ABA Amphiphilic Triblock Copolymer Micelles in Dioxane/Water Mixture Solvent

This work offers a typical understanding of the factors that govern the nanostructures of poly(4-vinyl pyridine)-b-polystyrene-bpoly(4-vinyl pyridine)(P4 VP-b-PS-b-P4 VP) block copolymers(BCs) in dioxane/water, in which water is a selective solvent for the P4 VP block. It is achieved through an investigation of the amphiphilic triblock copolymer micelles by variation of three different factors, including water content(above CWC but under the immobile concentration), temperature(ranging from 20 °C to 80 °C), and copolymer composition(low and high PS block length). Transition of bead-like micelles to vesicles is observed with the increase of water content due to the increase of interfacial energy between the copolymer and the solvent. Effect of temperature superposed on that of water content results in various morphologies, such as beads, fibers, rods, capsules, toroids, lamellae, and vesicles. The interfacial tension between the BC and the solvent increases with the increase of water content but decreases with the increase of temperature, indicating that the micellar morphologies are resulted from the competitive interplay between the temperature and the water content and always change in a direction that decreases the interfacial energy. Based on the micellar structures obtained in this work and the effects of temperature superposed on water concentration, a diagram of phase evolution of different micellar morphologies is illustrated here, covering the temperature range from 20 °C to 80 °C and the water content changing from 20 vol% to 35 vol%. For the investigation of BC composition, morphological transition of vesicle-to-fiber, for high PS length, is observed as compared with bead-to-capsule for low PS length, as the temperature changes from 20 °C to 80 °C. Our research complements the protocols to control over the morphologies and the phase diagram describing P4 VP-b-PS-b-P4 VP micellar nanostructures in aqueous solution.     

Influence of comb-like copolymer dispersants with different molecular structures on the performance of CaCO3 suspension in organic system

A series of comb-like copolymer poly(styrene-co-maleic anhydride)-graft-poly(ε-caprolactone) (SMA-g-PCL, SP) with variation in PCL side chain length and side chain density were synthesized and employed as an efficient dispersant for CaCO₃ suspension in organic solvent. The effects of molecular structures of comb-like copolymer on adsorption, rheological behavior, and suspension stability were investigated systemically to elucidate the governing dispersing mechanism. The molecular structures of comb-like copolymer not only significantly influenced the adsorption behavior but also the rheological behavior and suspension stability. Calculations based on the scaling law and Flory theory made a profound understanding of the impact of the molecular structure of comb-like copolymer on dispersion property. The results revealed that the steric repulsive force was enhanced by increasing of side chain length or density. However, the surface area for one molecule on CaCO₃ surface was also increased for its larger radius of the hemispheres of comb-like copolymer. This led to the worse activity of adsorption. The dispersion of CaCO₃ was due to the synergistic effects of adsorption and steric hindrance effect, which resulted that the comb-like copolymer with moderate length and density of side chain presented the best dispersability.     

两亲性共聚物的分子设计与合成及其共混膜性能

从分子结构设计出发,采用自由基聚合、醚化、酯化、原子转移自由基聚合(ATRP)、可逆加成断裂链转移自由基聚合(RAFT)等方法合成了一系列具有不同分子结构(包括接枝、嵌段、交替、超支化等)和链形态(包括直链、梳状、哑铃状、链球状等)的两亲性共聚物,并对这些聚合物进行了谱学表征和性能测试.将这些两亲性共聚物与聚合物膜材料(包括聚偏氟乙烯、聚氯乙烯、聚砜、聚醚砜、聚醚砜酮等)进行溶液共混,通过相转化法制备共混膜,在成膜热力学和动力学分析的基础上,对共混膜的结构和性能进行调控.研究发现,两亲性共聚物在成膜过程中自发地向膜表面迁移富集,并进行自组装,在膜表面形成两亲性共聚物包膜,显著改善了聚合物多孔膜的亲水性和抗污染性能.此外,两亲性共聚物中的功能基团还可赋予共混膜某些功能特性,如生物相容性、环境响应性(pH、温度敏感性)、酶活性等.     

Synthesis of New Amphiphilic Comb-Like Copolymers Based on Maleic Anhydride and α-Olefins

Summary: Novel amphiphilic comb-like poly(α-olefin-co-maleic anhydride) with a controlled ratio of hydrophilic (polyoxyethylene) and hydrophobic (polymethylene) side chains have been synthesized and characterized. The comb-like copolymers are soluble in organic and aqueous media and form micelles whose behaviour could be correlated to the chemical structure of polymers. We foresee that amphiphilic properties of the novel comb-like polymers are obviously the basis of new architectures in solution which could be used in a broad range of applications. Using micelles from these copolymers, silver nanoparticles with a narrow particle size distribution have been obtained as stable dispersion in both polar and non-polar media.     

Phase behavior of amphiphilic polymers: A dissipative particles dynamics study

Dissipative particle dynamics is a mesoscopic simulation method which allows one to predict the self-assembly of amphiphilic polymers and surfactants. It was possible to reproduce the formation of microemulsions of the oil/water (o/w), water/oil (w/o), and L₃-type of C10E4 in water and n-decane with excellent accuracy. We are able to predict the experimentally not investigated emulsion formation of a poly(ethylene butylene)–poly(ethylene oxide) in water and methylcyclohexane.     

Modification of porous poly(vinylidene fluoride) membrane using amphiphilic polymers with different structures in phase inversion process

Three kinds of amphiphilic polymers, including the tri-block copolymer of (polyethylene oxide)–(polypropylene oxide)–(polyethylene oxide) (I, EPTBP), the comb-like copolymer of polysiloxane with polyethylene oxide and polypropylene oxide side chains (II, ACPS) and the hyperbranched star copolymer of polyester-g-methoxyl polyethylene glycol (III, HPE-g-MPEG), were blended with PVDF to fabricate porous membranes via a phase inversion process, respectively, and the effects of the different structures of the amphiphilic polymers on the properties of the blend membranes were compared. The membranes were characterized by scanning electron microscopy (SEM), elemental analysis, X-ray photoelectron spectroscopy (XPS) analysis, mercury porosimetry, water contact angle measurements, etc. The anti-fouling properties of the prepared membranes were evaluated by static and dynamic bovine serum albumin (BSA) adsorptions. Specially, the stabilities of these amphiphilic polymers in the final membranes were estimated by continuous leaching tests. At the same time, the properties of the membranes using the amphiphilic polymers as modifiers were compared with those of the membrane using poly(ethylene glycol) (PEG) as modifier.     

A Phytic Acid Induced Super‐Amphiphilic Multifunctional 3D Graphene‐Based Foam

Surfaces with super‐amphiphilicity have attracted tremendous interest for fundamental and applied research owing to their special affinity to both oil and water. It is generally believed that 3D graphenes are monoliths with strongly hydrophobic surfaces. Herein, we demonstrate the preparation of a 3D super‐amphiphilic (that is, highly hydrophilic and oleophilic) graphene‐based assembly in a single‐step using phytic acid acting as both a gelator and as a dopant. The product shows both hydrophilic and oleophilic intelligence, and this overcomes the drawbacks of presently known hydrophobic 3D graphene assemblies. It can absorb water and oils alike. The utility of the new material was demonstrated by designing a heterogeneous catalytic system through incorporation of a zeolite into its amphiphilic 3D scaffold. The resulting bulk network was shown to enable efficient epoxidation of alkenes without prior addition of a co‐solvent or stirring. This catalyst also can be recovered and re‐used, thereby providing a clean catalytic process with simplified work‐up.     

Study of Winsor I to Winsor II transitions in a lattice model

Experiments show that with increasing temperature, microemulsion systems undergo Winsor transitions. The transitions occur from Winsor I (oil droplets in water media) to Winsor II (water droplets in oil media) via Winsor III (bicontinuous phase) with an increase in the temperature. In this paper, it has been shown, for the first time, how one can study the qualitative effects of temperature, head, tail, and oil chain lengths, on these transitions. Simple cubic lattice with excluded volume and periodic boundary conditions is used to mimic the box of the simulation as a bulk of solution. The simulations have been done using the standard traditional Metropolis algorithm in the canonical ensemble (N, V, T). Configurational bias Monte Carlo and reptation moves are used with an equal probability to relax the systems. A very simple interaction model, i.e., the repulsions of water (or heads of surfactants) with oil (or tails of surfactants), is used due to the main characteristic of oil-water mixtures or amphiphilic molecule that is the hydrophobicity. The interfacial tension between oil and water (gammaow) is related to the averaged total energy of the lattice. The model shows that the Winsor III has a minimum interfacial tension (gammaow) similar to experimental results. Changing the phase structure from Winsor III to Winsor I (or Winsor II), increases the interfacial tension which is in agreement with experiments. To relate interfacial tension with the interaction parameter, the simple theory of Bragg-Williams has been used. All of the results such as the effects of oil chain length, head and tail beads number are all similar to the experimental results. Using the Davies method for calculating hydrophilic-lypophilic Balance (HLB), similar to the experimental results, Winsor III phase is formed at HLB value nearly to 10.     

Impact of molecular size of SMA-g-MPEG comb-like polymer on the dispersion of CaCO3 suspensions

Poly(styrene-co-maleic anhydride)-g-methoxypolyethylene glycols comb-like polymer was employed as the dispersant of CaCO₃ suspensions in this paper. The comb-like polymer had much better dispersability than traditional linear polyelectrolyte. By changing the length of side chains to alter the molecular size, the dispersion of CaCO₃ suspensions was greatly influenced. The absolute value of zeta potential and the adsorption density decreased with increasing the length of side chains, while the rheological and dispersion properties had a best value when using polymers with moderate length of side chain. Calculations were performed based on the scaling law and Flory theory. It was known from the calculations that by increasing the length of side chains, the molecular size and the steric repulsion were both increased. But due to the worse activity of adsorption, the comb-like polymers with longer side chains had lower adsorption amount. The dispersability was due to the cooperation of steric repulsion and adsorption, which resulted that comb-like polymers with moderate length of side chain presented the best dispersability in actual application.     

Removal of oil spills by novel amphiphilic Chitosan-g-Octanal Schiff base polymer developed by click grafting technique

Novel Chitosan-g-Octanal Schiff base amphiphilic polymer has been developed by click grafting technique and evaluated successfully in removing different types of oils spills. The chemical structure and the morphological changes of the developed Chitosan-g-Octanal Schiff base amphiphilic polymer have been followed using FT-IR spectroscopy and SEM. The amphiphilic character of the developed Chitosan-g-Octanal Schiff base polymer has been controlled through variations of the Octanal grafting percentages from 38% to 82%. Dramatic changes of the Chitosan-g-Octanal Schiff base polymer solubility have been founded. The ion exchange capacity and water uptake have been affected in the same manner. The oils adsorption capacity was founded in direct relation to the Octanal grafting percentages and followed the order: mineral < kerosene < diesel < light crude oil (LCO) < heavy crude oil (HCO). Operational conditions such as oil amount, adsorption time, adsorbent dose, and agitation speed have been studied. The oil adsorption capacity of the Chitosan-g-Octanal Schiff base polymer for light and heavy crude oil has been increased by 167% and 110% over Chitosan ones. Finally, the removal process is optimized using response surface methodology (RSM).     

New amphiphilic polyacrylamides: Synthesis and characterisation of pseudo-micellar organisation in aqueous media

In order to offer new tools for developing structure-property relationships for intramolecular associative polymers (polysoaps), the synthesis of three families of comb-like amphiphilic cationic polymers with great structure variability is described. These polymers with amphiphilic repeating units are polyacryl or methacrylamides laterally substituted by a group containing a quaternary ammonium site and a hydrophobic alkyl side chain with 10-16 carbon atoms. Two complementary synthesis methods were developed successfully. In the first method, the tertiary amine groups of neutral polymer precursors were quaternised with various n-alkyl bromides. Five polymers were obtained in this way. On the contrary, the second method consisted of synthesizing first amphiphilic cationic acryl or methacrylamide monomers. The 11 monomers thus obtained were then polymerised by conventional free radical polymerisation in solution. The polymers obtained by both methods only differed in their molecular weights, the second method leading to much higher molecular weights (up to 2 × 10⁶ g/mol). A preliminary investigation of the properties of a few of these polymers in solution showed interesting amphiphilic behaviour. The variation of the reduced viscosity of hydro-methanolic polymer solutions with polymer concentration revealed a strong intramolecular macromolecular folding. The microdomains corresponding to the intramolecular association of the hydrophobic alkyl side chains were eventually characterised by pyrene fluorescence spectroscopy. The local polarity of the pyrene probe was considerably lowered with respect to that of the surrounding aqueous phase and was dependent upon the macromolecular structure of the amphiphilic cationic polymers.