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1.
You‐Cui Xu Chang‐Ming Dong 《Journal of polymer science. Part A, Polymer chemistry》2012,50(6):1216-1225
Dendron‐like poly(ε‐benzyloxycarbonyl‐L ‐lysine)/linear poly(ethylene oxide) block copolymers (i.e., Dm‐PZLys‐b‐PEO, m = 0 and 3; Dm are the propargyl focal point poly(amido amine) dendrons having 2m primary amine groups) were for the first time synthesized by combining ring‐opening polymerization (ROP) of ε‐benzyloxycarbonyl‐L ‐lysine N‐carboxyanhydride (Z‐Lys‐NCA) and click chemistry, where Dm‐PZLys homopolypeptides were click conjugated with azide‐terminated PEO. Their molecular structures and physical properties were characterized in detail by FTIR, 1H NMR, gel permeation chromatography, differential scanning calorimetry, polarized optical microscopy, and wide angle X‐ray diffraction. Both homopolypeptides and copolymers presented a liquid crystalline phase transition for PZLys block, and the transition was irreversible. Moreover, the degree of crystallinity of PEO block within linear copolymers decreased from 96.2% to 20.4% with increasing PZLys composition, whereas that within dendritic copolymers decreased to zero. The secondary conformation of PZLys progressively changed from β‐sheet to α‐helix with increasing the chain length. These copolymers self‐assembled into spherical nanoparticles in aqueous solution, and the anticancer drug doxorubicin‐loaded nanoparticles gave a similar morphology compared with their blank counterparts. The drug‐loaded nanoparticles showed a triphasic drug‐release profile at aqueous pH 7.4 or 5.5 and 37 °C and sustained a longer drug‐release period for about 2 months. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
2.
Siao‐Wei Yeh Yao‐Te Chang Chia‐Hung Chou Kung‐Hwa Wei 《Macromolecular rapid communications》2004,25(19):1679-1686
Summary: Polystyrene‐block‐poly(ethylene oxide) (SEO) block copolymer thin films, in which CdS clusters have been sequestered into the PEO domains of the SEO block copolymers, are found to induce the morphological transformation of PEO from cylinders to spheres, as shown by using atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). This transformation is caused by the presence of hydrogen‐bonding interactions between surface‐hydroxylated CdS and PEO, as confirmed by nuclear magnetic resonance (NMR) studies.
Morphological transformation of PEO cylinders into CdS/PEO spheres by hydrogen‐bonding interactions between surface‐hydroxylated CdS and PEO. 相似文献
3.
《Journal of Polymer Science.Polymer Physics》2018,56(4):330-339
Numerical self‐consistent field (SCF) lattice computations allow a priori determination of the equilibrium morphology and size of supramolecular structures originating from the self‐assembly of neutral block copolymers in selective solvents. The self‐assembly behavior of poly(ethylene oxide)‐block‐poly‐ε‐caprolactone (PEO‐PCL) block copolymers in water was studied as a function of the block composition, resulting in equilibrium structure and size diagrams. Guided by the theoretical SCF predictions, PEO‐PCL block copolymers of various compositions have been synthesized and assembled in water. The size and morphology of the resulting structures have been characterized by small‐angle X‐ray scattering, cryogenic transmission electron microscopy, and multiangle dynamic light scattering. The experimental results are consistent with the SCF computations. These findings show that SCF is applicable to build up roadmaps for amphiphilic polymers in solution, where control over size and shape are required, which is relevant, for instance, when designing spherical micelles for drug delivery systems © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 330–339 相似文献
4.
Jakub K. Wegrzyn Tim Stephan Ryan Lau Robert B. Grubbs 《Journal of polymer science. Part A, Polymer chemistry》2005,43(14):2977-2984
Amphiphilic poly(ethylene oxide)‐block‐poly(isoprene) (PEO‐b‐PI) diblock copolymers were prepared by nitroxide‐mediated polymerization of isoprene from alkoxyamine‐terminal poly(ethylene oxide) (PEO). PEO monomethyl ether (Mn ≈ 5200 g/mol) was functionalized by esterification with 2‐bromopropionyl bromide with subsequent copper‐mediated replacement of the terminal bromine with 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐nitroxide. The resulting PEO‐alkoxyamine macroinitiator was used to initiate polymerization of isoprene in bulk and in solution at 125 °C to yield PEO‐b‐PI block copolymers with narrow molecular weight distributions (Mw/Mn ≤ 1.1). Polymerizations were first order in isoprene through 35% conversion. Micellar aggregates of PEO‐b‐PI in aqueous solution were crosslinked by treatment with a water‐soluble redox initiating system, and persistent micellar structures were observed in the dry state by AFM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2977–2984, 2005 相似文献
5.
Poly(ethylene imine)‐graft‐poly(ethylene oxide) (PEI‐g‐PEO) copolymers were synthesized via Michael addition reaction between acryl‐terminated poly(ethylene oxide) methyl ether (PEO) and poly(ethylene imine) (PEI). The brush‐like copolymers were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the crystallinity of the PEO side chains in the copolymers remained unaffected by the PEI backbone whereas the crystal structure of PEO side chains was altered to some extent by the PEI backbone. The crystallization behavior of PEO blocks in the copolymers suggests that the bush‐shaped copolymers are microphase‐separated in the molten state. The PEO side chains of the copolymers were selectively complexed with α‐cyclodextrin (α‐CD) to afford hydrophobic side chains (i.e., PEO/α‐CD inclusion complexes). The X‐ray diffraction (XRD) shows that the inclusion complexes (ICs) of the PEO side chains displayed a channel‐type crystalline structure. It is identified that the stoichiometry of the inclusion complexation of the PEI‐g‐PEO with α‐CD is close to that of the control PEO with α‐CD. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2296–2306, 2008 相似文献
6.
Catherine Bianchi Bruno Grassl Bernard Franois Christine Dagron‐Lartigau 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4337-4350
Water‐soluble and photoluminescent block copolymers [poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) (PEO‐b‐PPV)] were synthesized, in two steps, by the addition of α‐halo‐α′‐alkylsulfinyl‐p‐xylene from activated poly(ethylene oxide) (PEO) chains in tetrahydrofuran at 25 °C. This copolymerization, which was derived from the Vanderzande poly(p‐phenylene vinylene) (PPV) synthesis, led to partly converted PEO‐b‐PPV block copolymers mixed with unreacted PEO chains. The yield, length, and composition of these added sequences depended on the experimental conditions, namely, the order of reagent addition, the nature of the monomers, and the addition of an extra base. The addition of lithium tert‐butoxide increased the length of the PPV precursor sequence and reduced spontaneous conversion. The conversion into PPV could be achieved in a second step by a thermal treatment. A spectral analysis of the reactive medium and the composition of the resulting polymers revealed new evidence for an anionic mechanism of the copolymerization process under our experimental conditions. Moreover, the photoluminescence yields were strongly dependant on the conjugation length and on the solvent, with a maximum (70%) in tetrahydrofuran and a minimum (<1%) in water. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4337–4350, 2005 相似文献
7.
Disulfide‐centered star‐shaped polypeptide‐PEO block copolymers for reduction‐triggered drug release
Xiao Chang Lisha Liu Yanfei Guan Chang‐Ming Dong 《Journal of polymer science. Part A, Polymer chemistry》2014,52(14):2000-2010
Disulfide‐centered star‐shaped poly(ε‐benzyloxycarbonyl‐l ‐lysine)‐b‐poly(ethylene oxide) block copolymers (i.e., A2B4 type Cy‐PZlys‐b‐PEO) were synthesized by the combination of ring‐opening polymerization and thiol‐yne chemistry. Their molecular structures and physical properties were characterized in detail by FTIR, 1H NMR, gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscope. Despite mainly exhibiting an α‐helix conformation, the inner PZlys blocks within copolymers greatly prohibited the crystallinity of the outer PEO blocks and presented a liquid crystal phase transition behavior in solid state. These block copolymers Cy‐PZlys‐b‐PEO self‐assembled into nearly spherical micelles in aqueous solution, which had a hydrophobic disulfide‐centered PZlys core surrounded by a hydrophilic PEO corona. As monitored by means of DLS and TEM, these micelles were progressively reduced to smaller micelles in 10 mM 1,4‐dithiothreitol at 37 °C and finally became ones with a half size, demonstrating a reduction‐sensitivity. Despite a good drug‐loading property, the DOX‐loaded micelles of Cy‐PZlys‐b‐PEO exhibited a reduction‐triggered drug release profile with an improved burst‐release behavior compared with the linear counterpart. Importantly, this work provides a versatile strategy for the synthesis of the disulfide‐centered star‐shaped polypeptide block copolymers potential for intracellular glutathione‐triggered drug delivery systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2000–2010 相似文献
8.
Yakai Feng Shifeng Zhang 《Journal of polymer science. Part A, Polymer chemistry》2005,43(20):4819-4827
AB‐type block copolymers with poly(trimethylene carbonate) [poly(TMC); A] and poly(ethylene oxide) [PEO; B; number‐average molecular weight (Mn) = 5000] blocks [poly(TMC)‐b‐PEO] were synthesized via the ring‐opening polymerization of trimethylene carbonate (TMC) in the presence of monohydroxy PEO with stannous octoate as a catalyst. Mn of the resulting copolymers increased with increasing TMC content in the feed at a constant molar ratio of the monomer to the catalyst (monomer/catalyst = 125). The thermal properties of the AB diblock copolymers were investigated with differential scanning calorimetry. The melting temperature of the PEO blocks was lower than that of the homopolymer, and the crystallinity of the PEO block decreased as the length of the poly(TMC) blocks increased. The glass‐transition temperature of the poly(TMC) blocks was dependent on the diblock copolymer composition upon first heating. The static contact angle decreased sharply with increasing PEO content in the diblock copolymers. Compared with poly(TMC), poly(TMC)‐b‐PEO had a higher Young's modulus and lower elongation at break. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4819–4827, 2005 相似文献
9.
Lin Sun Lin‐Jing Shen Ming‐Qiang Zhu Chang‐Ming Dong Yen Wei 《Journal of polymer science. Part A, Polymer chemistry》2010,48(20):4583-4593
Biocompatible and biodegradable ABC and ABCBA triblock and pentablock copolymers composed of poly(ε‐caprolactone) (PCL), poly(L ‐lactide) (PLA), and poly(ethylene glycol) (PEO) with controlled molecular weights and low polydispersities were synthesized by a click conjugation between alkyne‐terminated PCL‐b‐PLA and azide‐terminated PEO. Their molecular structures, physicochemical and self‐assembly properties were thoroughly characterized by means of FT‐IR, 1H‐NMR, gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, dynamic light scattering, and transmission electron microscopy. These copolymers formed microphase‐separated crystalline materials in solid state, where the crystallization of PCL block was greatly restricted by both PEO and PLA blocks. These copolymers self‐assembled into starlike and flowerlike micelles with a spherical morphology, and the micelles were stable over 27 days in aqueous solution at 37 °C. The doxorubicin (DOX) drug‐loaded nanoparticles showed a bigger size with a similar spherical morphology compared to blank nanoparticles, demonstrating a biphasic drug‐release profile in buffer solution and at 37 °C. Moreover, the DOX‐loaded nanoparticles fabricated from the pentablock copolymer sustained a longer drug‐release period (25 days) at pH 7.4 than those of the triblock copolymer. The blank nanoparticles showed good cell viability, whereas the DOX‐loaded nanoparticles killed fewer cells than free DOX, suggesting a controlled drug‐release effect. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
10.
Mingxiao Deng Xuesi Chen Longhai Piao Xuefei Zhang Zhongli Dai Xiabin Jing 《Journal of polymer science. Part A, Polymer chemistry》2004,42(4):950-959
Biodegradable, amphiphilic, four‐armed poly(?‐caprolactone)‐block‐poly(ethylene oxide) (PCL‐b‐PEO) copolymers were synthesized by ring‐opening polymerization of ethylene oxide in the presence of four‐armed poly(?‐caprolactone) (PCL) with terminal OH groups with diethylzinc (ZnEt2) as a catalyst. The chemical structure of PCL‐b‐PEO copolymer was confirmed by 1H NMR and 13C NMR. The hydroxyl end groups of the four‐armed PCL were successfully substituted by PEO blocks in the copolymer. The monomodal profile of molecular weight distribution by gel permeation chromatography provided further evidence for the four‐armed architecture of the copolymer. Physicochemical properties of the four‐armed block copolymers differed from their starting four‐armed PCL precursor. The melting points were between those of PCL precursor and linear poly(ethylene glycol). The length of the outer PEO blocks exhibited an obvious effect on the crystallizability of the block copolymer. The degree of swelling of the four‐armed block copolymer increased with PEO length and PEO content. The micelle formation of the four‐armed block copolymer was examined by a fluorescent probe technique, and the existence of the critical micelle concentration (cmc) confirmed the amphiphilic nature of the resulting copolymer. The cmc value increased with increasing PEO length. The absolute cmc values were higher than those for linear amphiphilic block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 950–959, 2004 相似文献
11.
Junxian Wu Yonathan S Thio Frank S. Bates 《Journal of Polymer Science.Polymer Physics》2005,43(15):1950-1965
Amphiphilic poly(n‐butylene oxide)‐b‐poly(ethylene oxide) (PBO–PEO) diblock copolymers of various compositions were synthesized and studied as modifiers for epoxy resins. In blends of PBO–PEO, epoxy resin, and curing agent, the copolymers formed well‐defined microstructures that persisted upon curing of the epoxy. The resulting morphologies were vesicles, worm‐like micelles, and spherical micelles (in order of increasing size of PEO block), as well as transitional morphologies. Addition of 5% by weight of these block copolymers improved the fracture toughness of the epoxy by as much as 19 times with relatively small reduction in the elastic modulus. The highest level of toughness was measured in a system containing branched worm‐like micelles. Close examination of the fracture surfaces of these compositions suggests that although all the dispersed morphologies played a similar role to inclusions in particle‐toughened thermosets, crack deflection toughening contributed to the significantly higher levels of toughness in the worm‐like micelle systems. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Chem 43: 1950–1965, 2005 相似文献
12.
Controlling domain orientation of liquid crystalline block copolymer in thin films through tuning mesogenic chemical structures
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He‐Lou Xie Xiao Li Jiaxing Ren Camille Bishop Christopher G. Arges Paul F. Nealey 《Journal of Polymer Science.Polymer Physics》2017,55(6):532-541
Controlling the macroscopic orientation of nanoscale periodic structures of amphiphilic liquid crystalline block copolymers (LC BCPs) is important to a variety of technical applications (e.g., lithium conducting polymer electrolytes). To study LC BCP domain orientation, a series of LC BCPs containing a poly(ethylene oxide) (PEO) block as a conventional hydrophilic coil block and LC blocks containing azobenzene mesogens is designed and synthesized. LC ordering in thin films of the BCP leads to the formation of highly ordered, microphase‐separated nanostructures, with hexagonally arranged PEO cylinders. Substitution on the tail of the azobenzene mesogen is shown to control the orientation of the PEO cylinders. When the substitution on the mesogenic tails is an alkyl chain, the PEO cylinders have a perpendicular orientation to the substrate surface, provided the thin film is above a critical thickness value. In contrast, when the substitution on the mesogenic tails has an ether group the PEO cylinders assemble parallel to the substrate surface regardless of the film thickness value. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 532–541 相似文献
13.
Sung Chan Park Hyunjung Jung Ken‐ichi Fukukawa Luis M. Campos Kyunghee Lee Kyusoon Shin Craig J. Hawker Jeong Sook Ha Joona Bang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(24):8041-8048
Herein, we present a simple method for producing nanoporous templates with a high degree of lateral ordering by self‐assembly of block copolymers. A key feature of this approach is control of the orientation of polymeric microdomains through the use of hydrophilic additives as structure directing agents. Incorporation of hydrophilic poly(ethylene oxide) (PEO) moieties into poly(styrene‐b‐methyl methacrylate) (PSt‐b‐PMMA) diblock copolymers gives vertical alignment of PMMA cylinders on the substrate after solvent annealing. Because of the miscibility between PEO and PMMA, PEO additives were selectively positioned within PMMA microdomains and by controlling the processing conditions, it was found that ordering of PSt‐b‐PMMA diblock copolymers could be achieved. The perpendicular orientation of PMMA cylinders was achieved by increasing the molecular size of the PEO additives leading to an increased hydrophilicity of the PMMA domains and consequently to control the orientation of microdomains in PSt‐b‐PMMA block copolymer thin films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8041–8048, 2008 相似文献
14.
Byoung‐Ki Cho Seung‐Hyun Kim Eunji Lee 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2372-2376
We prepared two block copolymers 1 and 2 consisting of a third‐generation dendron with poly(ethylene oxide) (PEO) peripheries and a linear polystyrene (PS) coil. The PS molecular weights were 2000 g/mol and 8000 g/mol for 1 and 2 , respectively. The differential scanning calorimetry (DSC) data indicated that neither of the block copolymers showed glass transition, implying that there was no microphase separation between the PEO and PS blocks. However, upon doping the block copolymers with lithium triflate (lithium concentration per ethylene oxide unit = 0.2), two distinct glass transitions were seen, corresponding to the salt‐doped PEO and PS blocks, respectively. The morphological analysis using small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) demonstrated that a hexagonal columnar morphology was induced in salt‐doped sample 1‐Li+ , whereas the other sample ( 2‐Li+ ) with a longer PS coil revealed a lamellar structure. In particular, in the SAXS data of 2‐Li+ , an abrupt reduction in the lamellar thickness was observed near the PS glass transition temperature (Tg), in contrast to the SAXS data for 1‐Li+ . This reduction implies that there is a lateral expansion of the molecular section in the lamellar structure, which can be interpreted by the conformational energy stabilization of the long PS coil above Tg. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2372–2376, 2010 相似文献
15.
Xiaohua He Wuqiong Sun Deyue Yan Meiran Xie Yiqun Zhang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(13):4442-4450
A series of novel side‐chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine‐terminated diblock copolymer poly(ethylene oxide)‐block‐polystyrene (PEO‐PS‐Br) was prepared by the ATRP of styrene initiated with the macro‐initiator PEO‐Br, which was obtained from the esterification of PEO and 2‐bromo‐2‐methylpropionyl bromide. An azobenzene‐containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side‐chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)‐block‐polystyrene‐block‐poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] (PEO‐PS‐PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (1H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442–4450, 2008 相似文献
16.
Khalid Ibrahim Paul Starck Barbro Lfgren Jukka Seppl 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5049-5061
The atom transfer radical polymerization of methyl methacrylate (MMA) and n‐butyl methacrylate (n‐BMA) was initiated by a poly(ethylene oxide) chloro telechelic macroinitiator synthesized by esterification of poly(ethylene oxide) (PEO) with 2‐chloro propionyl chloride. The polymerization, carried out in bulk at 90 °C and catalyzed by iron(II) chloride tetrahydrate in the presence of triphenylphosphine ligand (FeCl2 · 4H2O/PPh3), led to A–B–A amphiphilic triblock copolymers with MMA or n‐BMA as the A block and PEO as the B block. A kinetic study showed that the polymerization was first‐order with respect to the monomer concentration. Moreover, the experimental molecular weights of the block copolymers increased linearly with the monomer conversion, and the molecular weight distribution was acceptably narrow at the end of the reaction. These block copolymers turned out to be water‐soluble through the adjustment of the content of PEO blocks (PEO content >90% by mass). When the PEO content was small [monomer/macroinitiator molar ratio (M/I) = 300], the block copolymers were water‐insoluble and showed only one glass‐transition temperature. With an increase in the concentration of PEO (M/I = 100 or 50) in the copolymer, two glass transitions were detected, indicating phase separation. The macroinitiator and the corresponding triblock copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, size exclusion chromatography analysis, dynamic mechanical analysis, and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5049–5061, 2005 相似文献
17.
Zhijie Gu Tatsuya Kanto Kousuke Tsuchiya Takeshi Shimomura Kenji Ogino 《Journal of polymer science. Part A, Polymer chemistry》2011,49(12):2645-2652
Novel block copolymers, poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) (P3HT‐b‐PEO) were synthesized via Suzuki coupling reaction of P3HT and PEO homopolymers. The copolymers were characterized by NMR, gel permeation chromatography, differential scanning calorimeter, and UV–vis measurements. A series of devices based on the block copolymers with a fullerene derivative were evaluated after thermal or solvent annealing. The device using P3HT‐b‐PEO showed higher efficiency than using P3HT blend after thermal annealing. Phase‐separated structures in the thin films of block copolymer blends were investigated by atomic force microscopy to clarify the relationship between morphologies constructed by annealing and the device performance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
18.
Jung Kwon Oh Hongchen Dong Rui Zhang Krzysztof Matyjaszewski Helmut Schlaad 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4764-4772
Atom transfer radical polymerization with activators generated by electron transfer initiating/catalytic system (AGET ATRP) of 2‐hydroxyethyl methacrylate (HEMA) was carried out in inverse miniemulsion. Water‐soluble ascorbic acid as a reducing agent and mono‐ and difunctional poly(ethylene oxide)‐based bromoisobutyrate (PEO‐Br) as a macroinitiator were used in the presence of CuBr2/tris[(2‐pyridyl)methyl]amine (TPMA) and CuCl2/TPMA complexes. The use of poly(ethylene‐co‐butylene)‐block‐poly(ethylene oxide) as a polymer surfactant resulted in the formation of stable HEMA cyclohexane inverse dispersion and PHEMA colloidal particles. All polymerizations were well‐controlled, allowing for the preparation of well‐defined PEO‐PHEMA and PHEMA‐PEO‐PHEMA block copolymers with relatively high molecular weight (DP > 200) and narrow molecular weight distribution (Mw/Mn < 1.3). These block copolymers self‐assembled to form micellar nanoparticles being 10–20 nm in diameter with uniform size distribution, and aggregation number of ~10 confirmed by atomic force microscopy and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4764–4772, 2007 相似文献
19.
Takeshi Mori Takushi Watanabe Keiji Minagawa Masami Tanaka 《Journal of polymer science. Part A, Polymer chemistry》2005,43(8):1569-1578
Rod–coil amphiphilic diblock copolymers, consisting of oligo(p‐phenylenevinylene) (OPV) as a rod and hydrophobic block and poly(ethylene oxide) (PEO) as a coil and hydrophilic block, were synthesized by a convergent method. The aggregation behavior of the block copolymers in a selective solvent (tetrahydrofuran/H2O) was probed with the absorption and emission of the OPV block. With increasing H2O concentration, the absorption maximum was blueshifted, the emission from the molecularly dissolved OPV decreased, and that from the aggregated OPV increased. This indicated that the OPV blocks formed H‐type aggregates in which the OPV blocks aligned in a parallel orientation with one another. The transmission electron microscopy observation revealed that the block copolymers with PEO weight fractions of 41 and 62 wt % formed cylindrical aggregates with a diameter of 6–8 nm and a length of several hundreds nanometers, whereas the block copolymer with 79 wt % PEO formed distorted spherical aggregates with an average diameter of 13 nm. Furthermore, the solubilization of an OPV homooligomer with the block copolymer was studied. When the total polymer concentration was less than 0.1 wt %, the block copolymer solubilized OPV with a 50 mol % concentration. The structure of the aggregates was a cylinder with a relatively large diameter distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1569–1578, 2005 相似文献
20.
J. M. Dean P. M. Lipic R. B. Grubbs R. F. Cook F. S. Bates 《Journal of Polymer Science.Polymer Physics》2001,39(23):2996-3010
Amphiphilic block copolymers provide a unique means for toughening epoxy resins because they can self‐assemble into different inclusion shapes before epoxy curing. The two examples reported here are spherical micelles and vesicles, which form in blends containing epoxy and symmetric or asymmetric poly(ethylene oxide)–poly(ethylene‐alt‐propylene) (PEO–PEP) block copolymer with PEO volume fractions of 0.5 and 0.26, respectively. The vesicles and spherical micelles were characterized by transmission electron microscopy and small‐angle X‐ray scattering (SAXS), respectively. SAXS data from the spherical micelles were fit to the Percus–Yevick model for a liquid‐like packing of spheres with hard‐core interactions. Mechanical properties of spherical‐micelle‐modified and vesicle‐modified epoxies in the dilute limit are compared. The glass‐transition temperature and Young's (storage) modulus were tested with dynamic mechanical spectroscopy, and compact‐tension experiments were performed to determine the critical plane‐strain energy release rate for fracture. Vesicles were most effective in improving the epoxy fracture resistance. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2996–3010, 2001 相似文献