Membranes from poly(aryl ether)‐based ionomers containing multiblock segments of randomly distributed nanoclusters of 18 sulfonic acid groups

Multiblock copolymers 1a (M_n = 31,500–47,400) of sulfonated poly(aryl ether)s were synthesized by polycondensation of 4,4′‐difluorobenzophenone (DFBP), bis(4‐hydroxyphenyl)sulfone (BHPS), and an hydroxy‐terminated sulfonated oligomer, which was synthesized from DFBP and 2,2′,3,3′,5,5′‐hexaphenyl‐4,4′‐dihydroxybiphenyl a . The copolymerization of trimeric monomer b with DFBP and BHPS gave a series of copolymers 1b (M_n = 26,200–45,900). The copolymers were then sulfonated with chlorosulfonic acid to give ionomers 3a with hydrophilic multiblock segments and ionomers 3b with segments containing clusters of 18 sulfonic acid groups. The proton exchange membranes cast from ionomers 3a and 3b were characterized with regard to thermal stability, water uptake, proton conductivity, and morphology. Transmission electron microscopy images of 3a‐1 and 3b‐1 revealed a phase separation similar to that of Nafion that may explain their higher proton conductivities compared with randomly sulfonated copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4762–4773, 2009     

RAFT synthesis of polystyrene‐block‐poly(polyethylene glycol monomethyl ether acrylate) for zinc phthalocyanine‐loaded polymeric micelles as photodynamic therapy photosensitizers

A series of polystyrene‐block‐poly(polyethylene glycol monomethyl ether acrylate) (PSt_m‐b‐PPEGA_n) polymers were systematically synthesized as carriers for zinc phthalocyanine (ZnPc) for photodynamic therapy via reversible addition and fragmentation chain transfer polymerization. The degree of polymerization of the styrene (m) and PEGA units (n) of the resulting block copolymers were characterized to be n = 174, 40, and 18 for m = 52; and n = 200, 84, and 31 for m = 30. All the block copolymers formed micelles in water. The critical micelle concentration (CMC) of the PSt_m‐b‐PPEGA_n was determined by fluorometry using pyrene as a hydrophobic probe. The CMC value increased from 4.5 to 20 mg·L⁻¹ with an increase in the mole fraction of PEGA units. The median diameters of the micelles increased from 19 to 31 nm for PSt₅₂‐b‐PPEGA_n and from 15 to 23 nm for PSt₃₀‐b‐PPEGA_n with increasing n value. ZnPc‐loaded micelles were prepared by dialysis of the block copolymer in the presence of ZnPc followed by removal of large aggregates by filtration. The encapsulation efficiency was dramatically changed in the range of 0–68%. The light‐dose‐dependent cytotoxicity of the ZnPc‐loaded PSt₃₀‐b‐PPEGA₂₀₀ was clearly established in HeLa cell lines; while no cytotoxicity was confirmed under the dark. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 560–570     

Functional polysilanes of relevance for the synthesis of Au and Au–Pd nanoparticle assemblies—a study on the role of polymer‐supported thioether side chains

Linear polysilanes, [{PhHSi}_x{Ph(RSCH₂CH₂CH₂)Si}_1?x]_n [R = n‐dodecyl ( 1 ), n‐hexyl ( 2 ), n‐butyl ( 3 )], have been synthesized and their reactivity with HAuCl₄·3H₂O (Polymer:Au = 10:1, RT, toluene) examined to gain an insight into the role of polymer‐supported thioether groups in the stabilization of in situ generated gold nanoparticles (AuNPs). The method allows a simple approach for expeditious synthesis of assemblies of AuNPs comprising of well‐separated individual nanoparticles of average diameter 4.5 ± 1.9 nm. In this regard, polysilane 1 with dodecyl side chains serves as a superior matrix than 2 and 3 and confers long shelf‐life stability to the nanoparticle assembly. The structural attributes are preserved in Au–Pd bimetallic nanoparticles which have been synthesized from the polymer‐gold nanoassembly. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of sulfonated poly(diphenylacetylene)s with high CO2 permselectivity

High‐molecular‐weight poly[1‐phenyl‐2‐(4‐t‐butylphenyl)acetylene], poly[1‐phenyl‐2‐(4‐trimethylsilylphenyl) acetylene], and their copolymers were synthesized by the polymerization with TaCl₅–n‐Bu₄Sn. The obtained polymers were sulfonated by using acetyl sulfate to give sulfonated poly(diphenylacetylene)s with different degrees of substitution. The degrees of sulfonation of poly[1‐phenyl‐2‐(4‐t‐butylphenyl)acetylene] and copolymers were in the range of 0.57–0.85. When poly[1‐phenyl‐2‐(4‐trimethylsilylphenyl)acetylene] was sulfonated, the sulfonated poly(diphenylacetylene) with the highest degree of sulfonation was obtained among all the polymers in this study. Its degree of sulfonation was 1.55. All the sulfonated polymers exhibited high CO₂ permselectivity, and their CO₂/N₂ separation factor were over 31. The sulfonated poly(diphenylacetylene) with the highest degree of sulfonation showed the highest CO₂/N₂ separation factor of 75. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6463–6471, 2009     

Donor–acceptor copolymers based on phenanthrene as electron‐donating unit: Synthesis and photovoltaic performances

Using 9,10‐bis(dodecyloxy)phenanthrene as electron‐donating unit and 4,7‐dithienyl‐5,6‐bis(dodecyloxy)benzothiadiazole, 4,7‐dithienyl‐5,6‐bis(octyloxy)benzoxadiazole, 5,8‐dithienyl‐2,3‐bis(para‐octyloxyphenyl)quinoxaline, and 5,8‐dithienyl‐2,3‐bis(meta‐octyloxyphenyl)quinoxaline as electron‐accepting unit, four D–A copolymers PPA‐DTBT , PPA‐DTBX , PPA‐ p ‐DTQ , and PPA‐ m ‐DTQ , respectively, were successfully synthesized as new polymeric donors for photovoltaic cells. All the alternating copolymers can show two absorption bands, both in solutions and thin films. The optical bandgaps of the polymers are quite close, which are between 1.93 and 2.00 eV. The HOMO and LUMO levels of the polymers are also comparable of ?5.52 ± 0.03 eV and ?3.57 ± 0.03 eV, respectively. Thus, using the dialkoxyphenanthrene as the D unit could afford D–A copolymers with deep‐lying HOMO levels, which would be an important factor to achieve high open‐circuit voltages (V_oc) in bulk‐heterojunction solar cells. With the copolymers as the donor and PC₇₁BM as the acceptor, the resulting solar cells could display good V_oc between 0.86 and 0.88 V. Among the four copolymers, PPA‐DTBT containing the dialkoxybenzothiadiazole unit showed the best power conversion efficiency of 3.03% because of its relatively higher hole mobility and better phase separation. The results suggest that dialkoxyphenanthrene is a valuable electron‐donating unit in the constructions of D–A copolymers for efficient solar cells with high V_oc. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4966–4974     

Multiarm star block copolymers via Diels‐Alder click reaction

Two types of multiarm star block copolymers: (polystyrene)_m‐poly(divinylbenzene)‐poly(methyl methacrylate)_n, (PS)_m‐polyDVB‐(PMMA)_n and (polystyrene)_m‐poly(divinylbenzene)‐poly(tert‐butyl acrylate)_k, (PS)_m‐polyDVB‐(PtBA)_k were successfully prepared via a combination of cross‐linking and Diels–Alder click reactions based on “arm‐first” methodology. For this purpose, multiarm star polymer with anthracene functionality as reactive periphery groups was prepared by a cross‐linking reaction of divinyl benzene using α‐anthracene end functionalized polystyrene (PS‐Anth) as a macroinitiator. Thus, obtained multiarm star polymer was then reacted with furan protected maleimide‐end functionalized polymers: PMMA‐MI or PtBA‐MI at reflux temperature of toluene for 48 h resulting in the corresponding multiarm star block copolymers via Diels–Alder click reaction. The multiarm star and multiarm star block copolymers were characterized by using ¹H NMR, SEC, Viscotek triple detection SEC (TD‐SEC) and UV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 178–187, 2009     

Three Series of Sulfo‐Functionalized Mixed‐Linker CAU‐10 Analogues: Sorption Properties,Proton Conductivity,and Catalytic Activity

Ten mixed‐linker metal–organic frameworks [Al(OH)(m‐BDC‐X)_1?y(m‐BDC‐SO₃H)_y] (H₂BDC=1,3‐benzenedicarboxylic acid; X=H, NO₂, OH) exhibiting the CAU‐10‐type structure were synthesized. The compounds can be grouped into three series according to the combination of ligands employed. The three series of compounds were obtained by employing different ratios of m‐H₂BDC‐X and m‐H₂BDC‐SO₃Li. The resulting compounds, which are denoted CAU‐10‐H/Sx, ‐N/Sx and ‐O/Sx, show exceptionally high thermal stability for sulfonated materials of up to 350 °C. Detailed characterization with special focus on polarity and acidity was performed, and the impact of the additional SO₃H groups is clearly demonstrated by changes in the sorption affinities/capacities towards several gases and water vapor. In addition, selected samples were evaluated for proton conductivity and as catalysts for the gas‐phase dehydration of ethanol to ethylene. While only very low proton conductivities were observed, a pronounced increase in catalytic activity was achieved. Although reactions were performed at temperatures of 250 and 300 °C for more than 40 h, no desulfonation and no loss of crystallinity were observed, and stable ethanol conversion resulted. This demonstrates the high stability of this material.     

Polymethylene‐b‐polystyrene diblock copolymer: Synthesis,property, and application

The design and synthesis of well‐defined polymethylene‐b‐polystyrene (PM‐b‐PS, M_n = 1.3 × 10⁴–3.0 × 10⁴ g/mol; M_w/M_n (GPC) = 1.08–1.18) diblock copolymers by the combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) was successfully achieved. The ¹H NMR spectrum and GPC traces of PM‐b‐PS indicated the successful extension of PS segment on the PM macroinitiator. The micellization behavior of such diblock copolymers in tetrahydrofuran were characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM) techniques. The average aggregate sizes of PM‐b‐PS diblock copolymers with the same length of PM segment in tetrahydrofuran solution (1.0 mg mL^?1) increases from 104.2 nm to 167.7 nm when the molecular weight of PS segment increases. The spherical precipitated aggregates of PM‐b‐PS diblock copolymers with an average diameter of 600 nm were observed by AFM. Honeycomb porous films with the average diameter of 3.0 μm and 6.0 μm, respectively, were successfully fabricated using the solution of PM‐b‐PS diblock copolymers in carbon disulfide via the breath‐figure (BF) method under a static humid condition. The cross‐sections of low density polyethylene (LDPE)/polystyrene (PS)/PM‐b‐PS and LDPE/polycarbonate (PC)/PM‐b‐PS blends were observed by scanning electron microscope and reveal that the PM‐b‐PS diblock copolymers are effective compatilizers for LDPE/PS and LDPE/PC blends. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1894–1900, 2010     

Stimuli‐responsive 4‐acryloylmorpholine/4‐acryloylpiperidine copolymers via nitroxide mediated polymerization

4‐acryloylmorpholine/4‐acryloylpiperidine statistical copolymers were synthesized by nitroxide mediated polymerization (NMP) with BlocBuilder unimolecular initiator in dimethylformamide solution at 120 °C. The copolymers had narrow molecular weight distributions (dispersity ? = 1.25–1.35, number average molecular weights M _n = 8.5–13.7 kg mol^?1). The copolymer microstructure was essentially statistical (reactivity ratios r _4AP = 0.81 ± 0.73, r _4AM = 0.73 ± 0.68 based on non‐linear fitting of the Mayo‐Lewis equation). Cloud point temperatures (CPT) in aqueous media were tuned from 11 °C to 92 °C, merely by adjusting the initial monomer composition. Using NMP permitted sharper control of the CPT transitions, compared to the similar copolymer made using conventional radical polymerization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2160–2170     

Synthesis and characterization of poly(ethylene oxide)/polylactide/polylysine tri‐arm star copolymers for gene delivery

Amphiphilic cationic poly(ethylene oxide)‐S(polylysine)‐poly(d ,l ‐lactide) (mPEO‐S(CK_n)‐PLA) tri‐arm star copolymers were synthesized by a combination of ring opening polymerization (ROP) and a thiol–disulfide exchange. The mPEO‐S(CK_n)‐PLA copolymers were found to be non‐cytotoxic and could effectively condense GFP plasmid DNA into nanometer‐sized complexes, as characterized by dynamic light scattering (DLS), suitable for endocytotic cellular uptake. In vitro DNA transfection studies showed that the amphiphilic structure is capable of DNA transfection and GFP expression. Addition of chloroquine into the medium further enhanced the DNA transfection efficiency. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 635–644     

Effect of interface on thermodynamic behavior of liquid crystalline type amphiphilic di‐block copolymers

In PEO_m‐b‐PMA(Az)_n amphiphilic diblock copolymers, nanoscale structures exhibit an hexagonal‐packed PEO_m cylinders arrangement. To precisely investigate the role of interfacial interactions between hydrophilic PEO_m and hydrophobic PMA(Az)_n including mesogene sequences in the side chains, at the isotropic transition, polymer systems are submitted to thermal and barometric effects under hydrostatic pressure. The thermodynamic investigation is based on the original coupled calorimetric‐PVT technique, yielding scanning transitiometry. Three phase diagrams can be represented versus pressure: (1) isotropic temperature described by Clapeyron equation (T_iso vs. P), (2) change of volume of the system (ΔV_iso vs. P), (3) entropy of the system (ΔS_iso vs. P). In presence of mercury as pressure transmitting fluid, (dT_iso/dP) as well as ΔV_iso and ΔS_iso are larger for a PMA(Az)_n homopolymer compared to those for the investigated copolymer. Additional calculations of ΔS_iso using thermal and mechanical effects give consistent results. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1354–1364, 2007     

Silica spheres coated with C18‐modified gold nanoparticles for capillary LC and pressurized CEC separations

Nonporous monodispersed silica spheres of 1.3 μm were coated with gold nanoparticles (AuNPs) and subsequently coated with n‐octadecanethiol. By transmission electron microscopy analysis, the average diameter of the AuNPs on the silica spheres was determined to be 12 nm. The chromatographic and electrochromatographic properties of self‐assembled n‐octadecanethiol AuNP‐coated silica microspheres (C18‐AuNPs‐SiO₂) were investigated using a group of nonpolar PAHs. The stationary phase appears to display a characteristic reversed‐phase behavior. Higher separation efficiency and shorter separation times were obtained using pressurized CEC (pCEC) compared with capillary LC (CLC). A maximum column efficiency of about 2.5×10⁵ plates per meter and less than 18 min separation time for benzene were obtained in pCEC while only 66 507 plates per meter and an analysis time of nearly 100 min were observed in CLC mode. A chemical stability test of the C18‐AuNPs‐SiO₂ stationary phase under extremely high and low pH conditions demonstrated that it is stable at pH 12 and 1 for at least 60 h. The results confirm that C18‐AuNPs‐SiO₂ possesses a high rigidity to withstand high packing pressures and can be used as a good stationary phase for CLC and pCEC.     

XPS C 1s binding energies for fluorocarbon–hydrocarbon microblock copolymers

Fluorocarbon–hydrocarbon microblock copolymers –(CF₂)_n–(CH₂)_m– (n = 4, 6, 8; m = 6, 8, 10) were synthesized. Binding energies of the C 1s and F 1s peaks of these copolymers were measured using x‐ray photoelectron spectroscopy. The binding energy of the C 1s peaks of the carbon atoms of the hydrocarbon segments was set at 285.0 eV as the binding energy reference. Unexpectedly, the binding energy of the C 1s peak corresponding to the CF₂ group of the microblock copolymers was determined to be ～291.4 eV, which is ～0.8 eV lower than that of the CF₂ group of tetrafluoroethylene. Copyright © 2003 John Wiley & Sons, Ltd.     

Controllable ring‐opening copolymerization of L‐lactide and (3S)‐benzyloxymethyl‐(6S)‐methyl‐morpholine‐2,5‐dione initiated by a biogenic compound creatinine acetate

Ring‐opening copolymerization (ROCP) of L ‐lactide (L ‐LA) and (3S)‐benzyloxymethyl‐(6S)‐methyl‐morpholine‐2,5‐dione [(3S, 6S)‐BMMD] initiated by creatinine acetate, a biogenic organic compound, was performed in the bulk at 130 °C. The copolymerization was well controlled as evidenced by that both the measured values of number‐average molecular weight (M_n,NMR(OH) and M_n,NMR(COOH)) and serine molar fraction (F_Bz.ser) of synthesized copolymers were close to the corresponding theoretical values; and that the higher isotacticity of synthesized copolymers (85–86%) and lower racemization degree of the ROCP. After removing O‐benzyls of the copolymers with Et₃SiH/Et₃N/CH₂Cl₂ under catalysis of PdCl₂, functional biodegradable copolymers of L ‐lactic acid (L ‐Lac) and L ‐Ser with designed molar fraction of serine (F_ser 1.35%, 3.57%, 5.41%), narrow molecular weight distribution (polydispersity index 1.10–1.36), and improved hydrophilicity (θ_stat 82.3–89.6°) were finally obtained. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of well‐defined,amphiphilic poly(N‐isopropylacrylamide)‐ b‐[2‐hydroxyethyl methacrylate‐poly(ϵ‐caprolactone)]n graft copolymers by RAFT polymerization and macromonomer method

The well‐defined, thermosensitive and biodegradable graft copolymers, poly(N‐isopropylacrylamide)‐b‐[2‐hydroxyethyl methacrylate‐poly(ε‐caprolactone)]_n (PNIPAAm‐b‐(HEMA‐PCL)_n) (n = 3 or 9), were synthesized by combining reversible addition‐fragmentation chain transfer polymerization and macromonomer method. The copolymers were able to self‐assemble into micelles in water with low critical micellar concentration and demonstrated temperature sensitivity with a lower critical solution temperature at around 36 °C. Transmission electron microscopy shows that the micelles exhibit a nanosized spherical morphology within a size range of 30–100 nm. The PNIPAAm‐b‐(HEMA‐PCL)₃ copolymer exhibited biodegradation and low cytotoxicity. The paclitaxel‐loaded PNIPAAm‐b‐(HEMA‐PCL)₃ micelles displayed thermosensitive controlled release behavior, which indicates potential as drug carriers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5354–5364, 2007     

Electrolytes for quasi solid‐state dye‐sensitized solar cells based on block copolymers

The first use of PS_n‐b‐PEO_m‐b‐PS_n block copolymers (PS = polystyrene, PEO = poly(ethylene oxide)) as solid hosts for iodine/iodide electrolytes in dye‐sensitized solar cells (DSSCs) is described. Using the benchmark photosensitizer N719, DSSC based on the quasi solid‐state electrolytes afforded efficiencies up to 6.7%, to be compared with an efficiency of 7.3% obtained in similar conditions with a conventional iodine/iodide liquid electrolyte. By varying the PS:PEO relative volume ratio in the block copolymers different properties and morphologies were obtained. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 719–727     

Synthesis,micellar structures,and multifunctional sensory properties of poly(3‐hexylthiophene)‐block‐poly(2‐(dimethylamino)ethyl methacrylate) rod‐coil diblock copolymers

We report the synthesis, micellar structures, and multifunctional sensory properties of new conjugated rod‐coil block copolymers, poly(3‐hexylthiophene)‐block‐poly(2‐(di methylamino)ethylmethacrylate)(P3HT‐b‐PDMAEMA). The new copolymers, synthesized by atom transfer radical polymerization of P3HT macroinitiator, consisted PDMAEMA coil lengths of 43, 65, and 124 repeating units. All the P3HT‐b‐PDMAEMA copolymers exhibit a similar low critical solution temperature in water around 33 °C. The micellar structures of the synthesized polymers were characterized by AFM, TEM, and dynamic light scattering, by varying temperature, pH, and water/THF composition. The micelles of P3HT₂₀‐b‐PDMAEMA₄₃ in water had a reversible size change from 75 ± 5 nm to 132 ± 5 nm on heating from 25 to 55 °C and reduced to the original size during cooling. In addition, the micellar size also showed a significant pH dependence, changing from 67 ± 8 nm (pH = 12) to 222 ± 6 nm (pH = 4), depending on the protonation of the PDMAEMA blocks and their electrostatic repulsion. The micellar structure of three P3HT‐b‐PDMAEMA copolymers changed from spheres, to vesicles, and finally to larger sphere micelles as the solvent composition varied from 0 to 100 wt % water in the mixed solvent. The different micellar structures of P3HT₂₀‐b‐PDMAEMA₄₃ solution led to a red‐shift on the absorption or photoluminescence spectra and exhibited the emission colors of yellow, orange, red, and dark red with increasing the water content. This study suggested that new copolymers had potential applications as multifunctional sensory materials toward temperature, pH, and solvent. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Polymethylene‐block‐polystyrene copolymers: A new synthetic approach using a combination of polyhomologation and reversible addition‐fragmentation chain‐transfer polymerization and their microfibers and microspheres fabricated through electrospinning process

Well‐defined polymethylene‐block‐polystyrene (PM‐b‐PS) diblock copolymers were synthesized via a combination of polyhomologation of ylides and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization of styrene. Trithiocarbonate‐terminated polymethylenes (PM‐TTCB) (M_n = 1400 g mol^?1; M_w/M_n = 1.09 and M_n = 2100 g mol^?1; M_w/M_n = 1.20) were obtained via an esterification of S?1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetate) trithiocarbonate with hydroxyl‐terminated polymethylene synthesized via polyhomologation of ylides followed by oxidation. Then, a series of PM‐b‐PS (M_n = 5500–34,000 g mol^?1; M_w/M_n = 1.12–1.25) diblock copolymers were obtained by RAFT polymerization of styrene using PM‐TTCB as a macromolecular chain‐transfer agent. The chain structures of all the polymers were characterized by proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography, and Fourier transform infrared spectroscopy. The thiocarbonylthio end‐group of PM‐b‐PS was transformed into thiol group by aminolysis and confirmed by UV–vis spectroscopy. In addition, microfibers and microspheres of such diblock copolymers were fabricated by electrospinning process and observed by scanning electron microscopy (SEM). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2892–2899     

Multiarm star polymers with peripheral dendritic PMMA arms through Diels–Alder click reaction

Dendritic 2‐ and 4‐arm PMMA‐based star polymers with furan‐protected maleimide at their focal point, (PMMA)_2n‐MI and (PMMA)_4n‐MI were efficiently clicked with the peripheral anthracene functionalized multiarm star polymer, (α‐anthryl functionalized‐polystyrene)_m‐poly(divinyl benzene) ((α‐anthryl‐PS)_m‐polyDVB) through the Diels–Alder reaction resulting in corresponding multiarm star block copolymers: (PMMA)_2n‐(PS)_m‐polyDVB and (PMMA)_4n‐(PS)_m‐polyDVB, respectively. Molecular weights (M_w,TDGPC), hydrodynamic radius (R_h), and intrinsic viscosity (η) of the multiarm star polymers were determined using three‐detection GPC (TD‐GPC). The high efficiency of this methodology to obtain such sterically demanding macromolecular constructs was deduced using ¹H‐NMR and UV–vis spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Magneto‐Plasmonic Janus Vesicles for Magnetic Field‐Enhanced Photoacoustic and Magnetic Resonance Imaging of Tumors

Magneto‐plasmonic Janus vesicles (JVs) integrated with gold nanoparticles (AuNPs) and magnetic NPs (MNPs) were prepared asymmetrically in the membrane for in vivo cancer imaging. The hybrid JVs were produced by coassembling a mixture of hydrophobic MNPs, free amphiphilic block copolymers (BCPs), and AuNPs tethered with amphiphilic BCPs. Depending on the size and content of NPs, the JVs acquired spherical or hemispherical shapes. Among them, hemispherical JVs containing 50 nm AuNPs and 15 nm MNPs showed a strong absorption in the near‐infrared (NIR) window and enhanced the transverse relaxation (T₂) contrast effect, as a result of the ordering and dense packing of AuNPs and MNPs in the membrane. The magneto‐plasmonic JVs were used as drug delivery vehicles, from which the release of a payload can be triggered by NIR light and the release rate can be modulated by a magnetic field. Moreover, the JVs were applied as imaging agents for in vivo bimodal photoacoustic (PA) and magnetic resonance (MR) imaging of tumors by intravenous injection. With an external magnetic field, the accumulation of the JVs in tumors was significantly increased, leading to a signal enhancement of approximately 2–3 times in the PA and MR imaging, compared with control groups without a magnetic field.