Comb-like Amphiphilic Copolymers Research Articles

Structural Characteristics and Fusion Pathways of Onion-Like Multilayered Polymersome Formed by Amphiphilic Comb-Like Graft Copolymers

The self-assembly behavior of amphiphilic comb-like graft copolymers bearing pH-responsive hydrophilic side-chains on hydrophobic backbone in a selective solvent is investigated by dissipative particle dynamics. The aggregate exhibits a rich variety of the morphological conformations dependent on pH, polymeric concentration, side-chain length, and grafting density. The morphological phase diagram shows that micellar aggregates take shape at low pH. As pH increases, unilamellar vesicle (ULV) can form at low polymer concentration and the vesicle size grows with increasing concentration. Further increment of pH to neutral leads to the formation of multilamellar vesicles (MLV) with the layer-by-layer structure similar to that of an onion. The total number of layers rises with increasing polymer concentration. Our simulation outcomes are consistent with the experimental observations. The simulation results also reveal that as the grafting density is decreased, the thickness of the hydrophobic layer grows and thus the total number of layers declines for MLVs. The water permeation process through ULV is monitored to explore the effects of grafting density and pH on the membrane permeability. As the grafting density is decreased or the neutral pH is approached, the permeability of the vesicle membrane descends. Controlled releases of two types of drugs with different hydrophobicity situated at different layers of MLV are also examined. The release rate of hydrophilic drug is faster than that of hydrophobic drug. Polymersomes tend to fuse but the fusion mechanism is different from that of liposomes. The fusion pathway of ULVs follows the anisotropic stalk-pore scenario and both stalk and pore formation prefer to occur on the edge of the contact zone due to significant deformations of comb-like polymers in this region. The fusion pathway of MLVs is layer-by-layer and the fusion time of the inner layer is faster than that of the outer layer. The fusion process is expedited at about neutral pH but is prolonged substantially as the side-chain length is increased. Finally, it is interesting to observe that the total number of layers of the fused MLV can be greater than that of MLVs before fusion.

Amphiphilic poly(vinyl chloride)‐g‐poly[poly(ethylene glycol) methylether methacrylate] copolymer for the surface hydrophilicity modification of poly(vinylidene fluoride) membrane

AbstractIn this study, a comblike amphiphilic graft copolymer containing poly(vinyl chloride) (PVC) backbones and poly(oxyethylene methacrylate) [poly(ethylene glycol) methylether methacrylate (PEGMA)] side chains was facilely synthesized via an atom transfer radical polymerization method. Secondary chlorines in PVC were used as initial sites to graft a poly[poly(ethylene glycol) methylether methacrylate] [P(PEGMA)] brush. The synthesized PVC‐g‐P(PEGMA) graft copolymer served as an efficient additive for the hydrophilicity modification of the poly(vinylidene fluoride) (PVDF) membrane via a nonsolvent‐induced phase‐inversion technique. A larger pore size, higher porosity, and better connectivity were obtained for the modified PVDF membrane; this facilitated the permeability compared to the corresponding virgin PVDF membrane. In addition, the modified PVDF membrane showed a distinctively enhanced hydrophilicity and antifouling resistance, as suggested by the contact angle measurement and flux of bovine serum albumin solution tests, respectively. Accordingly, the PVC‐g‐P(PEGMA) graft copolymer was demonstrated as a successful additive for the hydrophilicity modification, and this study will likely open up new possibilities for the development of efficient amphiphilic PVC‐based copolymers for the excellent hydrophilicity modification of PVDF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis of low-cost, rubbery amphiphilic comb-like copolymers and their use in the templated synthesis of mesoporous TiO2 films for solid-state dye-sensitized solar cells

Low-cost, rubbery amphiphilic comb-like copolymers consisting of hydrophobic poly(lauryl methacrylate) (PLMA) and hydrophilic poly(oxyethylene methacrylate) (POEM) were synthesized via one-step free radical polymerization. The synthesis of PLMA-POEM copolymers was confirmed using Fourier transform infra-red spectroscopy (FT-IR), (1)H-nuclear magnetic resonance ((1)H-NMR) and gel permeation spectroscopy (GPC). The PLMA-POEM copolymers were used as a structure-directing agent for the formation of anatase mesoporous TiO2 films. Careful adjustment of the precursor and polymer molecular weight (MW) was made to systematically vary the TiO2 structure and its effect on the performances of solid-state dye-sensitized solar cells (ssDSSCs). The use of a low MW polymer resulted in a worm-like structure with smaller pores, whereas an aggregated honeycomb-like structure with bimodal pores was obtained for the high MW system, as characterized by scanning electron microscopy (SEM), grazing incidence small-angle X-ray scattering (GI-SAXS) and N2 adsorption-desorption measurement. An efficiency of 4.2% was obtained at 100 mW cm(-2) when using 2 μm-thick TiO2 film prepared with a high MW copolymer. The higher efficiency was due to better pore filling of the solid electrolyte and improved light scattering properties. By using a layer-by-layer method, the efficiency was further improved to 5.0% at 7 μm thickness, which was greater than that of commercially available paste (3.9%).

Acid and reduction dually cleavable amphiphilic comb-like copolymer micelles for controlled drug delivery

Disulfide- and acetal-functionalized comb-like copolymers (SACP) with poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) side chains and a polymethacrylate backbone were synthesized and self-assembled for in vitro encapsulation and release of an anticancer drug, doxorubicin (DOX). Three step reactions including RAFT copolymerization of 2-hydroxyethyl methacrylate and poly(ethylene glycol) methyl ether methacrylate mediated by a disulfide-functionalized RAFT agent, hydroxyl-vinyloxy addition reaction to introduce acid cleavable PEG segments, and CL polymerization to grow PCL chains were used to generate the target dual-sensitive comb-like copolymers. Meanwhile, well-defined normal comb-like polymers (CP), acid-cleavable comb-like polymers (ACP) and disulfide-linked comb-like polymers (SCP) with PEG and PCL pendent chains were also prepared and acted as analogues of SACP. All the resultant comb-like copolymers had the desired chemical structures, well-controlled molecular weight and relatively low polydispersity (PDI = 1.09–1.16), evident from 1H NMR and GPC-MALLS analyses. DLS and TEM measurements revealed that these copolymers were liable to self-assemble into micelles or large compound micelles in aqueous solution, and SACP aggregates could be dissociated and reaggregated in the presence of acidic PBS solution (pH 5.0) or 10 mM DL-dithiothreitol (DTT). Compared with CP aggregates with a lack of cleavable linkage, ACP, SCP and SACP aggregates upon acid and reduction stimuli could quickly release the encapsulated DOX, and the cumulative release from SACP aggregates could be roughly adjusted by addition of a single stimulus or dual stimuli. These results confirmed their great potential as novel nanocarriers and delivery systems.

Dynamic Origin and Thermally Induced Evolution of New Self‐Assembled Aggregates from an Amphiphilic Comb‐Like Graft Copolymer: A Multiscale and Multimorphological Procedure

In the past several decades, the self-assembly of block copolymers in selective solvents has attracted extensive interest due to the formation of various aggregates including spherical and cylindrical micelles, vesicles, tubes, helices, toroids, and other complex forms. Research has been focused on aggregates with spherical, flowerlike, tubular or sheet-like superstructures, obtained through the hierarchical self-assembly of Janus micelles or Janus nanoparticles, owning to their formation mechanisms and potential applications in biomedical materials and new nanodevices. The self-assembled aggregates can also be constructed from amphiphilic comb-like graft copolymers in water or organic solvents. Despite that many interesting aggregates including petal-like micelles, spindle-like micelles, wormlike micelles, chiral helices, and so on, are obtained by the change of structural and environmental parameters, in most cases conventional spherical micelles and vesicles are observed. In comparison with block copolymers, self-assembled aggregates of amphiphilic comb-like graft copolymers reveal the morphological characteristics of obviously low diversity and complexity. Considering the shape plays a crucial role in determining physical and chemical properties of aggregates, the controlled fabrication and switch of morphologies have been paid a great attention, which has been implemented by regulating the conditions, such as solvent, pH, redox, and so on. Typically, crystallization is an important factor utilized to control the self-assembly of semicrystalline block copolymers consisting of the crystallizable block and amorphous block, which has been actively researched recently. Inspired by this specific class of copolymer, we have designed an amphiphilic comb-like graft copolymer consisting of poly(p-dioxanone) (PPDO) as a crystallizable hydrophobic side chain and poly(vinyl alcohol) (PVA) as a hydrophilic main chain, and found that this copolymer presented an unique self-assembled behavior. In fact, recently we reported a “star anise”-like nanoaggregate from a PPDO-based branched alternating multi-block copolymer. Herein, by directly dispersing this PPDO-based amphiphilic comb-like graft copolymer into water, more complex and regular aggregates with a well-defined snowflake-like superstructure was obtained, and their origin involving a dynamically disorder–order change from nanoto submicroscale was visualized. Moreover, the aggregates showed thermally induced multimorphological evolution from a snowflake-like to cluster-like structure. As an original and significant work, this superstructure enriches the self-assembled morphology of amphiphiles, especially comb-like macromolecules. Furthermore, the direct water phase self-assembled strategy of PPDO-based amphiphilic copolymers and temperature-adjusted morphological change could provide a new idea to construct complex multimorphological and multiscale objects. The precursors of the copolymers were synthesized through ring-opening polymerization and the acylation, respectively. The copolymers were prepared in DMSO by a coupling reaction between carboxyl groups presenting on PPDO chain-end and hydroxyl groups of PVA (Scheme 1). The information of the molecular structure of copolymers is listed in the Supporting Information, Table S1. The self-assembly was achieved by adding PVA500-g5.6%PPDO15 to water at room temperature, heating the system to homogenous phase (to erase the thermal history), and aging it at 25 8C. Tests of dynamic light scattering (DLS) indicated the presence of monodispersed and stable particles with 791 nm of intensity-averaged hydrodynamic diameter ( ) and a polydispersity index (PDI) of 0.053 (Figure 1a, their and PDI after 7 days was shown in the Supporting Information, Figure S1). Transmission electron microscopy (TEM) images revealed well-defined snowflakelike aggregates having about 260 nm of average thickness, 530 nm of average width, and 620 nm of average length, respectively (marked by short arrows in Figure 1band 1c). For monodisperse spherical aggregates, they have same diffusion coefficient in every direction, and their size from CONTIN analysis is independent of scattering angles. Conversely, for the anisotropic or polydisperse aggregates, the results of DLS are dependent of scattering angles. By multi-angle DLS experiment, we found that the diameter and apparent [a] G. Wu, Dr. S.-C. Chen, Dr. X.-L. Wang, Dr. K.-K. Yang, Prof. Y.-Z. Wang National Engineering Laboratory of Eco-Friendly Polymeric Materials (Sichuan) State Key Laboratory of Polymer Materials Engineering College of Chemistry, Sichuan University 29 Wangjiang Road, Chengdu 610064 (P.R. China) Fax: (+86)28-85410259 E-mail : chensichong@scu.edu.cn yzwang@scu.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201103961.

Synthesis and properties of monocleavable amphiphilic comblike copolymers with alternating PEG and PCL grafts

AbstractSymmetric reduction‐responsive amphiphilic comblike copolymers mid‐disulfide‐functionalized comblike copolymers with alternating copolymer comprised of styrenic unit and N‐(2‐hydroxyethyl) maleimide (HEMI) unit (poly(St‐alt‐HEMI)) backbones and alternating PEG and PCL side chains (S‐CP(PEG‐alt‐PCL)) with poly(St‐alt‐HEMI) backbones and alternating poly(ε‐caprolactone) (PCL) and poly(ethylene glycol) (PEG) side chains were synthesized and used as nanocarriers for in vitro release of doxorubicin. The target copolymers with predetermined molecular weight and narrow molecular weight distribution (Mw/Mn = 1.15–1.20) were synthesized by reversible addition‐fragmentation chain transfer (RAFT) copolymerization of vinylbenzyl‐terminated PEG and N‐(2‐hydroxyethyl) maleimide mediated by a disulfide‐functionalized RAFT agent S‐CPDB, and followed by ring‐opening polymerization of ε‐caprolactone. When compared with linear block copolymer comprised of poly(ethylene glycol) (PEG) and poly(ϵ‐caprolactone) (PCL) segments (PEG‐b‐PCL) copolymers, comblike copolymers with similar PCL contents usually exhibited decreased crystallization temperature, melting temperature, and degree of crystallinity, indicating the significant influence of copolymer architecture on physicochemical properties. Dynamic light scattering measurements revealed that comblike copolymers were liable to self‐assemble into aggregates involving vesicles and micelles with average diameter in the range of 56–226 nm and particle size distribution ranging between 0.07 and 0.20. In contrast to linear copolymer aggregates, comblike copolymer aggregates with similar compositions were of improved storage stability and enhanced drug‐loading efficiency. In vitro drug release confirmed the disulfide‐linked comblike copolymer aggregates could rapidly release the encapsulated drug when triggered by 10 mM DL‐dithiothreitol. These reduction‐sensitive, biocompatible, and biodegradable aggregates have a potential as controlled delivery vehicles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Surface modification of seawater reverse osmosis (SWRO) membrane using methyl methacrylate-hydroxy poly(oxyethylene) methacrylate (MMA-HPOEM) comb-polymer and its performance

Comb-like amphiphilic copolymer, methyl methacrylate-hydroxy poly(oxyethylene) methacrylate (MMA-HPOEM), was synthesized by free radical polymerization and then applied to a seawater reverse osmosis (SWRO) membrane to introduce hydrophilicity and fouling resistance. The amphiphilic copolymer preparation was verified using nuclear magnetic resonance, and the deposition of the copolymer on the membrane using dip-coating method was confirmed using X-ray photoelectron spectroscopy. The surface charge that resulted from the amphiphilic copolymer application was analyzed using zeta-potential analysis. Cross-flow fouling test studies showed that the MMA-HPOEM coating on the membrane improved the fouling resistance to bovine serum albumin, Escherichia coli, and seawater. Although the initial flux of the modified membrane was lower than that of the virgin membrane due to the additional hydraulic resistance, the rate of flux decline slowed after the modification and compensated for the initial flux decline within several days.

Aggregation behavior of amphiphic comb-like copolymer containing poly(ethylene oxide) methyl ether grafts

The amphiphilic comb-like copolymer, poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether) (SMA-M), was prepared by one-pot method. Its aggregation behavior was investigated by equilibrium surface tension method, rheological technology and transmission electron microscopy (TEM). The equilibrium surface tension of SMA-M solution with various pH at different temperatures was plotted against molar concentration of St-co-MA unit. The adsorption data, such as the saturation surface excess concentration ( Γ max), the minimum area ( A min) and the adsorption standard free energy Δ G ads ° , were evaluated using the average monomeric molecular weight ( M nA). The results showed that Γ max decreased with the increase in pH and the corresponding A min enlarged with the increase in pH. But Γ max increased with the increase in temperature, as the corresponding A min shrank with the increase in temperature. The variations of Δ G ads ° with pH and temperature indicated that the increase in expansion degree of backbone with the increase in pH was the dominative factor influenced the adsorption data. The results of micellization standard free energy Δ G mic ° suggested that the increase in expansion degree of backbone made it difficult to form micelle-like aggregates, even though the increase in temperature leaded to the stronger hydrophobic property. Associated the results from rheological measurement and TEM method, the conclusion was reached that the aggregate structure of as-prepared SMA-M transformed from micelle-like aggregates connected by “necklace” to isolated swollen micelle-like aggregates, then to rod-like aggregates with the increase in pH.

Self-assembly of pH-responsive and fluorescent comb-like amphiphilic copolymers in aqueous media

“Comb-like” graft copolymers, consisting of a poly((N-vinylcarbazole)-co-(4-vinylbenzyl chloride)) (P(NVK-co-VBC)) copolymer backbone from free radical polymerization and poly(((2-dimethylamino)ethyl methacrylate)-co-(tert-butyl acrylate)) (P(DMAEMA-co-tBA)) side chains from atom transfer radical polymerization (ATRP), were hydrolyzed to produce the acrylic acid (AAc)-containing “comb-like” graft copolymers of P(NVK-co-VBC)-comb-P(DMAEMA-co-AAc). The amphiphilic copolymers possess a fluorescent hydrophobic P(NVK-co-VBC) backbone and pH-sensitive hydrophilic P(DMAEMA-co-AAc) side chains. Arising from acid–base interaction of the hydrophilic side chains, the copolymers can self-assemble into pH-responsive fluorescent and multi-walled hollow vesicles of well-defined morphology in aqueous media. The size and layered wall thickness of the vesicles are also dependent on the length of the copolymer side chains, while the number of wall layers is dependent on the concentration of the vesicles in the aqueous media. In comparison, a N-isopropylacrylamide (NIPAAm)-containing comb-like amphiphilic copolymer (P(NVK-co-VBC)-comb-P(NIPAAm-co-DMAEMA)) of similar structure, albeit with non-interacting hydropholic side chains, self-assembles only into temperature and pH-responsive single-shelled hollow nanoparticles in aqueous media.

Synthesis of novel amphiphilic graft copolymers composed of poly(ethylene oxide) as backbone and polylactide as side chains

A well-defined amphiphilic comb-like copolymer of poly(ethylene oxide)(PEO) as main chain and polylactide (PLA) as side chain was successfully prepared via a combination of anionic polymerization and coordination-insertion ring-opening polymerization. The anionic copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out using potassium 2-(2-methoxyethoxy)ethoxide as initiator, and then ethoxyethyl groups of EEGE units of the copolymers obtained were removed by hydrolysis. Two copolymers of methoxypoly(ethylene oxide-co-glycidol) [mpoly(EO-co-Gly)] were formed with multiple hydroxyl sites (the molar ratio values of Gly to EO in copolymers: 1/10.6 and 1/5.2; Mn: 10,100 and 5,020 respectively), and them were used further to initiate the ring-opening polymerization of lactide in the presence of stannous octoate, and a well-defined comb-like copolymer of PEO as main chain and PLA as side chain was obtained. The intermediate and final products of PEO-g-PLA were characterized by GPC and NMR in detail.

Kinetics of styrene miniemulsion polymerization using poly[(stearyl methacrylate- co-( N, N-dimethylamino)ethyl methacrylate] as surfactant

Two comb-like amphiphilic copolymers have been prepared via conventional free-radical random copolymerization of stearyl methacrylate (SMA) and 2-( N, N-dimethylamino)ethyl methacrylate (DMAEMA) with different feed ratios. The resultant copolymers, poly(SMA- co-DMAEMA), were then characterized by 1H NMR and gel permeation chromatography (GPC) measurements. The surface activity of these copolymers in aqueous solution with different pH values was studied by surface tension measurements. Finally, these amphiphilic cationic copolymers were used as polymeric surfactants in the miniemulsion polymerization of styrene. The hydrophobic stearyl side chains of SMA could be strongly adsorbed onto the monomer droplets or propagating particles during the miniemulsion polymerization, while the hydrophilic and protonated PDMAEMA units at low pH media could stabilize the latexes. Moreover, the influences of the composition and amounts of the polymeric surfactants on the kinetics of the miniemulsion polymerization and colloidal stability have been investigated. The reaction rate of miniemulsion polymerization was found to increase with increasing amounts of polymeric surfactants and decrease with the increase of pH values of aqueous solution.

Nanocomposite proton conducting membranes based on amphiphilic PVDF graft copolymer

A novel comb-like amphiphilic graft copolymer of poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(4-styrene sulfonic acid-co-trimethoxysilyl propyl methacrylate), i.e. P(VDF-co-CTFE)-g-P(SSA-co-TMSPMA) was synthesized using an atom transfer radical polymerization (ATRP) technique. Successful synthesis and a microphase-separated structure of the copolymer were confirmed by proton nuclear magnetic resonance (1H NMR), FTIR spectroscopy and transmission electron microscopy (TEM). This graft copolymer was combined with tetraethoxysilane (TEOS) under acidic conditions to produce organic-inorganic nanocomposite membranes through an in-situ sol-gel reaction between TEOS and PTMSPMA, as characterized by X-ray diffraction (XRD) and TEM. Upon the introduction of silica, the proton conductivity and water uptake of the membranes decreased slightly but the thermal and mechanical properties of the membranes were enhanced significantly. Various morphologies of the nanocomposite membranes were obtained after controlling the TEOS concentration, which were correlated with the thermal, mechanical and transport properties.

Sol-gel transition behavior of amphiphilic comb-like poly[(PEG-b-PLGA)acrylate] block copolymers

The effects of comb-like amphiphilic block copolymer architectures on the physical properties such as sol-gel transition and micellization behaviors with the change of temperature and pH were examined. Comb-like poly((poly(ethylene glycol)-b-(poly(lactic acid-co-glycolic acid))acrylate-co-acrylic acid) (poly((PEG-b-PLGA)A-co-AA)) copolymers were synthesized by coupling of poly(acrylic acid) (PAA) with two different kinds of PEG-b-PLGA diblock copolymers to investigate the effects of the number of branches and hydrophilicity/hydrophobicity on the sol-gel transition and micellization. The molecular weights and chemical structures were confirmed by GPC and 1H NMR. The number of PEG-b-PLGA branches was gradually deviated from the feed molar ratio with increasing the molecular weight and the number of branches and due to the bulkiness of PEG-b-PLGA. Poly[(PEG-b-PLGA)A-co-AA] aqueous solutions showed thermosensitive sol-gel transition behavior, and the gelation took place at lower concentration with increasing the number of branches and PLGA chain length due to the increase of hydrophobicity. The temperature, at which abrupt increase of viscosity by dynamic rheometer appeared, was also in good agreement with sol-gel transition by tube-titling method. The CMC, calculated from UV-Visible spectroscopy using DPH as hydrophobic dye, also decreased with increasing the number of PEG-b-PLGA branches and PLGA chain length with same reason. The micelle size was increased with increasing temperature at the initial stage, however, decreased with further increase of temperature, since the micelles were, first, aggregated by hydrophobic intermolecular interaction, and then fragmented by dehydration of PEG segments with increasing temperature. PH-sensitive PAA backbone played a key role in physical properties. With decreasing pH, sol-to-gel transition temperature, CMC values, and micelle size were decreased because of the increase of hydrophobicity resulting form non-ionized acrylic acid. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1287–1297, 2010

Associative Properties of Amphiphilic Statistical Polymers in Aqueous Media

A novel series of comb-like amphiphilic statistical copolymers were synthesized by polymerization of an amphiphilic macromonomer, 2-(acrylamido)-dodecanesulfonic acid (AMC12S), with 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS). The association behaviors of the polymers in NaCl aqueous solution were investigated by steady-state fluorescence measurements with pyrene as a polarity probe, quasielastic light scattering techniques (QELS), and a transmission electron micrograph (TEM). It was found that the series of polymers shows a strong tendency for interpolymer association, leading to the formation of multimolecular aggregates. The critical aggregation concentration (CAC) and the micropolarity of the polymer aggregates strongly depend on AMC12S mole fraction (X). An interesting feature of the polymers is that hydrodynamic sizes of the aggregates (Rh) continuously decrease with increasing X, and the increase extent of Rh with increasing polymer concentration (C) inclines to be smaller for higher X, suggesting that the polymer aggregates become a closed type progressively with increasing X.

Role of grafted chains for the in situ formation of Ag nanoparticles within poly(epichlorohydrin)- g-polymethacrylate films

Two kinds of amphiphilic comb-like copolymer, i.e., poly(epichlorohydrine)- g-poly(methyl methacrylate) (PECH- g-PMMA) and poly(epichlorohydrine)- g-poly(butyl methacrylate) (PECH- g-PBMA) were synthesized via atom transfer radical polymerization (ATRP) using directly initiating the chlorine atoms of PECH macroinitiator. The amphiphilic comb-like copolymers were used as a template film for the in situ growth of silver nanoparticles from AgCF 3SO 3 precursor using NaBH 4. UV–visible spectroscopy and transmission electron microscopy (TEM) images indicated that (1) Ag nanoparticles were selectively confined in the comb-like polymer films persisting microphase-separated morphology and (2) Ag nanoparticles (4–7 nm) formed in PECH- g-PBMA were smaller than those in PECH- g-PMMA (6–11 nm). This represents that the longer hydrophobic side chains in a comb-like copolymer is more effective in controlling the formation of metal nanoparticles.

Synthesis of silver halide nanocomposites templated by amphiphilic graft copolymer and their use as olefin carrier for facilitated transport membranes

A novel amphiphilic comb-like copolymer consisting of poly(vinyl chloride) (PVC) main chains and poly(4-vinyl pyridine) (P4VP) side chains, i.e. PVC- g-P4VP with 65:35 wt% is synthesized via atom transfer radical polymerization (ATRP). This self-assembled copolymer is used to template the growth of silver bromide (AgBr) nanoparticles with diameters of 10–50 nm, as characterized by UV–vis spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Upon introduction of ionic liquid, i.e. 1-methyl-3-octylimidazolium nitrate (MOIM +NO 3 −), the surface of AgBr nanoparticles is more partially positively charged due to the interactions between NO 3 − ions and the surfaces of nanoparticles, as revealed by FT-Raman and X-ray photon spectroscopy (XPS). We also demonstrate the ability of AgBr as a new type of olefin carrier by tuning the interactions of positively charged AgBr with the C C bond of olefin molecules. As a result, the membranes containing AgBr nanocomposites exhibit highly stable separation performances for propylene/propane mixture, i.e. a mixed gas selectivity of 6 and a permeance of 5.7 GPU.

Synthesis and self-assembly of comb-like amphiphilic Doxifluridine–poly(ɛ-caprolactone)-graft-poly(γ-glutamic acid) copolymer

Advances in amphiphilic copolymers can potentially be exploited in drug or gene delivery. This study develops novel comb-like amphiphilic copolymers that comprise poly(γ-glutamic acid) (γ-PGA) as a hydrophilic backbone and Doxifluridine–poly-(ɛ-caprolactone) (5′-deoxy-5-fluorouridine–poly(ɛ-caprolactone), 5′DFUR–PCL) as a hydrophobic side chain. A novel 5′DFUR–PCL polymer was synthesized with antitumor agent Doxifluridine (5′DFUR) as the initiator via the ring-opening polymerization of ɛ-caprolactone (ɛ-CL) using tin(II) 2-ethylhexanoate (Sn(Oct)2) as the catalyst. The 5′DFUR–PCL polymer was then grafted on γ-PGA to yield a 5′DFUR–PCL–γ-PGA comb-like copolymer with the help of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide (EDC). The characteristics of these copolymers were examined by 1H NMR, FT-IR, GPC, contact angle measurement and thermal properties. Grafting 5′DFUR–PCL would significantly increase the contact angle and decrease the melting temperature (Tm) of the copolymers. The micelles self-assembled from these amphiphilic copolymers were formed in an aqueous phase and were examined via fluorescence approaches, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The average sizes of the micelles were in the range from 130 to 230nm and their zeta potentials were negative and less than −16.7mV. The critical micelle concentration (CMC) was from 1.49mg/L to 4.63mg/L at 25°C. TEM images demonstrated that the micelles were spherical and clearly had a core–shell structure.

Templated synthesis of Ag–Au bimetallic nanoparticles by amphiphilic PVC- g-PSSA graft copolymer film

Amphiphilic comb-like copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly(styrene sulfonic acid) (PSSA) side chains, i.e. PVC- g-PSSA at 68:32 wt.% was synthesized via atom transfer radical polymerization (ATRP). This self-assembled graft copolymer film was used to template the growth of Ag–Au bimetallic nanoparticles in the solid state by introducing NaBH 4 as a reducing agent. The in situ formation of Ag–Au bimetallic nanoparticles in the graft copolymer film was confirmed by UV–visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). High resolution TEM picture showed the formation of spherical Ag-Au core-shell nanoparticles. To the best of our knowledge, this is the first report on the solid-state synthesis of Ag–Au bimetallic core-shell nanoparticles using amphiphilic comb-like copolymer film.

Synthesis and self-assembly of comb-like amphiphilic copolymer poly(maleic anhydride-alt-stearyl methacrylate)-b-poly(stearyl methacrylate)

Comb-like amphiphilic block copolymers of maleic anhydride (MA) and stearyl methacrylate (SMA) were prepared through the reversible-addition-fragmentation-transfer polymerization. The resultant copolymers were characterized by gel permeation chromatograph and 1H NMR. The aggregation behaviors of P(MA-alt-SMA)-b-PSMA were investigated in tetrahydrofuran/water. It is of great interest that the aggregates with different morphologies and dimensions could be obtained by adjusting the polymer concentration, water content, and pH. The dimension and structure of these aggregates were investigated by transmission electron microscopy and dynamic light scattering. The effect of the copolymer–solvent interaction on these aggregations was discussed.

Effect of the surface-modifying macromolecules on the duration of the surface functionalization

Functionalization of polystyrene films by the preferential surface enrichment of surface-modifying macromolecules (SMM) to achieve a hydrophilic surface with long effective duration is described. The comb-like amphiphilic copolymers (PKG-g-PS) based on styrene-maleic anhydride copolynier (SMA) backbone was synthesized by esterification of SMA with poly(ethylene glycol) (PEG). When PEG-g-PS was melt blended with polystyrene, the preferential surface enrichment of PEG-g-PS was much evident resulting in the large increase of the surface polarity. The effective duration of the surface functionalizatoin was also hugely extended as SMMs were added into the blends. Furthermore, more polyether chain segments on PEG-g-PS could selectively migrate to the surface by the inducement of polar solvent. Compared with the PEG-g-PS/PS and PEG/PEG-g-PS/PS blends, the surface polarity and the effective duration of surface modification both increased greatly when PEG-g-PS was used as the compatibilizer of PEG/PS blends. It was an effective solution to balance the conflict between the duration and efficiency of the surface-modifying additives.