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Tobias Rudolph Adam Nunns Steffi Stumpf Christian Pietsch Felix H. Schacher 《Macromolecular rapid communications》2015,36(18):1651-1657
The step‐wise solution self‐assembly of double crystalline organometallic poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) diblock copolymers is demonstrated. Two block copolymers are obtained by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), featuring PFDMS/PiPrOx weight fractions of 46/54 (PFDMS30‐b‐PiPrOx75) and 30/70 (PFDMS30‐b‐PiPrOx155). Nonsolvent induced crystallization of PFDMS in acetone leads in both cases to cylindrical micelles with a PFDMS core. Afterward, the structures are transferred into water for sequential temperature‐induced crystallization of the PiPrOx corona, leading to hierarchical double crystalline superstructures, which are investigated using scanning electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry.
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Summary: A poly(aspartic acid)‐block‐polylactide (PAsp‐block‐PLA) diblock copolymer was synthesized through the polymerization of β‐benzyl‐L ‐aspartate‐N‐carboxyanhydride [Asp(OBzl)‐NCA] with amino‐terminating polylactide (NH2‐PLA) as a macroinitiator. The chain length of the PAsp segment could be easily controlled by changing the monomer/initiator ratio. Dynamic light scattering measurements of PAsp‐block‐PLA aqueous solutions revealed the formation of polymeric micelles. Changes in the micelles as a function of pH were investigated.
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A novel approach is employed to produce core–corona nanospheres, which introduces a stereoregular hydrophilic part to an amphiphilic block copolymer. The resultant morphology is reported using isotactic‐poly(methacrylic acid)‐block‐poly(butyl acrylate). Infrared spectroscopy revealed a supramolecular interaction, and X ray diffraction revealed the crystallization of the outer isotactic‐poly(methacrylic acid) part. The nanostructure, which looks like a nanosized ‘grape’, was formed when nanospheres and nanofibers coexisted simultaneously and partially fused.
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Yung Chang Ching‐Yi Chen Wen‐Chang Chen 《Journal of Polymer Science.Polymer Physics》2004,42(24):4466-4477
Porous poly(methyl silsesquioxane) (PMSSQ) films were prepared from PMSSQ/amphiphilic block copolymer (ABC) hybrids, and this was followed by spin coating and multistep baking. The ABCs were poly(styrene‐block‐acrylic acid) (PS‐b‐PAA) and poly(styrene‐block‐3‐trimethoxysilylpropyl methacrylate) (PS‐b‐PMSMA), which were synthesized by living polymerization. The chemical bonding between the ABCs and PMSSQ resulted in significant differences in the morphologies and properties of the hybrids and their porous derivatives. Both intramolecular and intermolecular hydrogen bonding existed in the PMSSQ/PS‐b‐PAA hybrid and led to macrophase separation. Through the modification of the chemical structure from the poly(acrylic acid) segment to PMSMA, covalent bonding between PMSSQ and PMSMA occurred and prevented the macrophase separation and initial pyrolysis of the ABC. Modulated differential scanning calorimetry results also suggested a significant difference in the miscibility of the two hybrid systems. The chemical bonding resulted in higher retardation of the symmetry‐to‐nonsymmetry Si? O? Si structural transformation for PMSSQ/PS‐b‐PMSMA than for PMSSQ/PS‐b‐PAA according to Fourier transform infrared studies. The pore size of the nanoporous thin film from the PMSSQ/PS‐b‐PMSMA hybrid was estimated by transmission electron microscopy to be less than 15 nm. The refractive index and dielectric constant of the prepared porous films decreased from 1.354 to 1.226 and from 2.603 to 1.843 as the PS‐b‐PMSMA loading increased from 0 to 50 wt %, respectively. This study suggests that chemical bonding in hybrid materials plays a significant role in the preparation of low‐dielectric‐constant nanoporous films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4466–4477, 2004 相似文献
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Yong Zhang Zhijie Zhang Qian Wang Caihong Xu Zemin Xie 《Macromolecular rapid communications》2006,27(17):1476-1482
Summary: Amphiphilic triblock copolymers (PEOx‐b‐PDMSy‐b‐PEOx) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.
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C Guinto Gamys Jean‐Marc Schumers Clment Mugemana Charles‐Andr Fustin Jean‐Franois Gohy 《Macromolecular rapid communications》2013,34(12):962-982
This review deals with nanoporous materials made from the self‐assembly of block copolymers with a special interest in the chemical functions covering the surface of their nanopores. A detailed overview of the existing methods and strategies to generate well‐defined organic functional groups covering the surface of the pore walls is provided. This further enables to finely tune the affinity of the pore walls and to perform well‐defined chemical reactions onto them, which is essential for further dedicated applications.
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Christoph H. Braun Benjamin Schpf Chheng Ngov Cyril Brochon Georges Hadziioannou Edward J. W. Crossland Sabine Ludwigs 《Macromolecular rapid communications》2011,32(11):813-819
We report the synthesis of a series of block copolymers consisting of a rod‐like semiconducting poly(2,5‐di(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene) (DEH‐PPV) block and a flexible poly(lactic acid) (PLA) block that can be selectively degraded under mild conditions. Such selectively degradable block copolymers are designed as self‐assembling templates for bulk heterojunction donor–acceptor layers in organic solar cells. A lamellar microphase‐separated domain structure was identified for block copolymers with PLA volume fractions between 29 and 79% in bulk and thin films using SAXS, TEM, and AFM. Depending on the ratio of the two blocks we find either lamellae oriented parallel or perpendicular to the substrate in thin films.
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Wing Yan Tam Chris S. K. Mak Alan Man Ching Ng Aleksandra B. Djurii Wai Kin Chan 《Macromolecular rapid communications》2009,30(8):622-626
The synthesis of poly(N‐vinylcarbazole)‐based block copolymers functionalized with rhenium diimine complexes or pendant terpyridine ligands is reported. The copolymers are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and they exhibit interesting morphological properties as a result of the phase separation between different blocks. The rhenium complex polymer block may function as a photosensitizer, while the terpyridine‐containing polymer block can be used as the template for nanofabrication by selective deposition of zinc complexes.
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Cdric Bergerbit Florian Baffie Arne Wolpers Pierre‐Yves Dugas Olivier Boyron Manel Taam Muriel Lansalot Vincent Monteil Franck D'Agosto 《Angewandte Chemie (International ed. in English)》2020,59(26):10385-10390
Poly(ethylene oxide) (PEO) with dithiocarbamate chain ends (PEO–SC(=S)?N(CH3)Ph and PEO–SC(=S)?NPh2, named PEO‐1 and PEO‐2 , respectively) were used as macromolecular chain‐transfer agents (macro‐CTAs) to mediate the reversible addition–fragmentation chain transfer (RAFT) polymerization of ethylene in dimethyl carbonate (DMC) under relatively mild conditions (80 °C, 80 bar). While only a slow consumption of PEO‐1 was observed, the rapid consumption of PEO‐2 led to a clean chain extension and the formation of a polyethylene (PE) segment. Upon polymerization, the resulting block copolymers PEO‐b‐PE self‐assembled into nanometric objects according to a polymerization‐induced self‐assembly (PISA). 相似文献
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Huiping Bi Shouwen Chen Xinbing Chen Kangcheng Chen Nobutaka Endo Mitsuru Higa Kenichi Okamoto Lianjun Wang 《Macromolecular rapid communications》2009,30(21):1852-1856
Novel poly(2‐(3‐sulfo)benzoyl‐1,4‐phenylene)‐block‐polynaphthalimide (PSP‐b‐PI) copolymers were successfully synthesized by Ni(0)‐catalyzed copolymerization of 2,5‐dichloro‐3′‐sulfo‐benzophenone and dichloro‐terminated naphthalimide oligomer. The membranes exhibited a microphase‐separated structure and good hydrolytic stability at 130 °C. They showed a fairly strong anisotropy of membrane swelling with much smaller in‐plane swelling, but a rather weak anisotropy of proton conductivity. The membranes had a fairly high through‐plane conductivity in water and even under low relative humidity. The PSP‐b‐PI copolymer with an IEC of 1.5 meq · g−1 showed high PEFC performance due to the high through‐plane conductivity.
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Dr. Kyosuke Isoda Dr. Naoki Kanayama Dr. Masahiro Fujita Dr. Tohru Takarada Prof. Dr. Mizuo Maeda 《化学:亚洲杂志》2013,8(12):3079-3084
Temperature‐responsive diblock copolymers made of poly(N‐isopropylacrylamide) (PNIPAAm) generated by reversible addition‐fragmentation chain transfer (RAFT) polymerization and a single‐stranded DNA (ssDNA) self‐assembled into polymer micelles. The micelles consisted of the PNIPAAm core surrounded by the ssDNA corona with a hydrodynamic diameter up to 300 nm in an aqueous medium above the lower critical solution temperature. In a medium of high ionic strength, the formation of the fully matched duplex with the complementary ssDNA on the surface of the polymer micelles induced rapid and spontaneous aggregation. By contrast, the micelles remained dispersed under the identical conditions when single‐base‐substituted ssDNA was added to form the corresponding terminal‐mismatched duplex on the micellar surface. This highly sequence‐selective process took place irrespective of the size of the PNIPAAm core. 相似文献
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Sung‐Wook Choi Yongwoo Kim In Woo Cheong Jung‐Hyun Kim 《Macromolecular rapid communications》2008,29(2):175-180
This paper aims to report the fabrication of biodegradable thin films with micro‐domains of cylindrical nanochannels through the solvent‐induced microphase separation of poly(L ‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(L ‐lactide) (PLA‐b‐PEG‐b‐PLA) triblock copolymers with different block ratios. In our experimental scope, an increase in each of the block lengths of the PLA and PEG blocks led to both a variation in the average number density (146 to 32 per 100 µm2) and the size of the micro‐domains (140 to 427 nm). Analyses by atomic force microscopy (AFM) and fluorescence microscopy indicated that the hydrophilic PEG nanochannels were dispersed in the PLA matrix of the PLA‐b‐PEG‐b‐PLA films. We demonstrated that the micro‐domain morphology could be controlled not only by the block length of PEG, but also by the solvent evaporation conditions.
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Beng H. Tan Chakravarthy S. Gudipati Hazrat Hussain Chaobin He Ye Liu Thomas P. Davis 《Macromolecular rapid communications》2009,30(12):1002-1008
We report the synthesis of a novel pH‐responsive amphiphilic block copolymer poly(dimethylaminoethyl methacrylate)‐block‐poly(pentafluorostyrene) (PDMAEMA‐b‐PPFS) using RAFT‐mediated living radical polymerization. Copolymer micelle formation, in aqueous solution, was investigated using fluorescence spectroscopy, static and dynamic light scattering (SLS and DLS), and transmission electron microscopy (TEM). DLS and SLS measurements revealed that the diblock copolymers form spherical micelles with large aggregation numbers, Nagg ≈ 30 where the dense PPFS core is surrounded by dangling PDMAEMA chains as the micelle corona. The hydrodynamic radii, Rh of these micelles is large, at pH 2–5 as the protonated PDMAEMA segments swell the micelle corona. Above pH 5, the PDMAEMA segments are gradually deprotonated, resulting in a lower osmotic pressure and enhanced hydrophobicity within the micelle, thus decreasing the Rh. However, the radius of gyration, Rg remains independent of pH as the dense PPFS cores predominate.
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Rong‐Ming Ho Tsai‐Ming Chung Jing‐Cherng Tsai Jing‐Chang Kuo Benjamin S. Hsiao Igors Sics 《Macromolecular rapid communications》2005,26(2):107-111
Summary: Various crystalline textures have been identified in a crystallizable block copolymer system, polystyrene‐block‐[syndiotactic poly(propylene)] (PS‐sPP), having a glass‐transition temperature of PS (Tg,PS) located in the midst of the sPP crystallization window. A confined morphology for the crystallization of sPP was observed while the crystallization temperature of sPP (Tc,sPP) was less than Tg,PS. A further increase in Tc,sPP could lead to a breakout in nanostructure. This study revealed the Tg effect on crystallization‐induced morphological changes of block copolymers from confinement to breakout.
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Lithium‐Salt‐Containing High‐Molecular‐Weight Polystyrene‐block‐Polyethylene Oxide Block Copolymer Films 下载免费PDF全文
Dr. Ezzeldin Metwalli Majid Rasool Simon Brunner Prof. Dr. Peter Müller‐Buschbaum 《Chemphyschem》2015,16(13):2882-2889
Ionic conductivity in relation to the morphology of lithium‐doped high‐molecular‐weight polystyrene‐block‐polyethylene oxide (PS‐b‐PEO) diblock copolymer films was investigated as solid‐state membranes for lithium‐ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt‐doping level and the temperature. The PEO crystallites completely vanished at a salt‐doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS‐b‐PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded‐like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt‐doping level. 相似文献
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Ian W. Hamley Ben M. D. O'Driscoll Gudrun Lotze Claire Moulton Jürgen Allgaier Henrich Frielinghaus 《Macromolecular rapid communications》2009,30(24):2141-2146
The phase diagram of a series of poly(1,2‐octylene oxide)–poly(ethylene oxide) (POO–PEO) diblock copolymers is determined by small‐angle X‐ray scattering. The Flory–Huggins interaction parameter was measured by small‐angle neutron scattering. The phase diagram is highly asymmetric due to large conformational asymmetry that results from the hexyl side chains in the POO block. Non‐lamellar phases (hexagonal and gyroid) are observed near fPEO = 0.5, and the lamellar phase is observed for fPEO ≥ 0.5.
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Block copolymers create various types of nano‐structures, e. g., spheres, rods, cubes, and lamellae. This review discloses the dynamic macromolecular organization of block copolymers comprising poly(L ‐lactide) (PLLA) and poly(oxyethylene) (PEG) that allows to simulate elaborate biological systems. The block copolymers, AB‐ (PLLA‐PEG) and ABA‐type (PLLA‐PEG‐PLLA), are synthesized by ordinary lactide polymerization to have a controlled block length. They are dispersed into an aqueous medium to prepare nano‐scale particles, consisting of hydrophobic PLLA and hydrophilic PEG in the core and shell, respectively. Then, the particles are placed on a flat substrate by the casting method. The particles are detected as discoids by AFM, having shrunk with loss of water. Heat‐treatment of these particles at 60°C (above Tg of PLLA) gives rise to a collapse into small fragments, which then aggregate into bands with nano‐size width and thickness. The PLLA‐PEG bands align parallel to each other, while the PLLA‐PEG‐PLLA bands form a characteristic network resembling the neuron system created in animal tissue. As analyzed by TEM diffraction, each is composed of α‐crystal of PLLA whose c‐axis (molecular axis) is perpendicular to the substrate surface. Based on this fact, a doubly twisted chain structure of PLLA is proposed in addition to a plausible mechanism for the self‐organization of the block copolymers. Derivatives of the PLLA‐PEG block copolymers can form far more interesting nano‐architectures. An equimolar mixture of enantiomeric copolymers, PLLA‐PEG‐PLLA and PDLA‐PEG‐PDLA, forms a hydrogel that is thermo‐responsive. The terminal‐modified poly(L ‐lactide)‐block‐polyoxyethylene monocinnamate (PLLA‐PEG‐C) forms a highly stabilized nanofiber by the photo‐reaction of the cinnamates placed in the outer layer of the nanobands. 相似文献