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991.
Zhiping Peng Guangzhao Li Xinxing Liu Zhen Tong 《Journal of polymer science. Part A, Polymer chemistry》2008,46(17):5869-5878
A doubly hydrophilic triblock copolymer of poly(N,N‐dimethylamino‐2‐ethyl methacrylate)‐b‐Poly(ethylene glycol)‐b‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) (PDMAEMA‐b‐PEG‐b‐PDMAEMA) with well‐defined structure and narrow molecular weight distribution (Mw/Mn = 1.21) was synthesized in aqueous medium via atom transfer radical polymerization (ATRP) of N,N‐dimethylamino‐2‐ethylmethacrylate (DMAEMA) initiated by the PEG macroinitiator. The macroinitiator and triblock copolymer were characterized with 1H NMR and gel permeation chromatography (GPC). Fluorescence spectroscopy, dynamic light scattering (DSL), transmittance measurement, and rheological characterization were applied to investigate pH‐ and temperature‐induced micellization in the dilute solution of 1 mg/mL when pH > 13 and gelation in the concentrated solution of 25 wt % at pH = 14 and temperatures beyond 80 °C. The unimer of Rh = 3.7 ± 0.8 nm coexisted with micelle of Rh = 45.6 ± 6.5 nm at pH 14. Phase separation occurred in dilute aqueous solution of the triblock copolymer of 1 mg/mL at about 50 °C. Large aggregates with Rh = 300–450 nm were formed after phase separation, which became even larger as Rh = 750–1000 nm with increasing temperature. The gelation temperature determined by rheology measurement was about 80 °C at pH 14 for the 25 wt % aqueous solution of the triblock copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5869–5878, 2008 相似文献
992.
Chong Cheng Karen L. Wooley Ezat Khoshdel 《Journal of polymer science. Part A, Polymer chemistry》2005,43(20):4754-4770
Hyperbranched fluorocopolymers were synthesized by the atom transfer radical self‐condensing vinyl copolymerization (ATR–SCVCP) of an inimer, either p‐chloromethylstyrene (CMS) or p‐bromomethylstyrene (BMS), with 2,3,4,5,6‐pentafluorostyrene (PFS), with 2,2′‐bipyridine together with CuCl or CuBr as the ligand/catalyst system. The reaction conditions were studied to provide for control over the copolymer compositions, molecular weights, degrees of branching, and properties, as characterized by 1H, 13C, and 19F NMR spectroscopy, gel permeation chromatography, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and solubility tests. Copolymers having number‐average molecular weights from 2.9 to 260 kDa and polydispersities (weight‐average molecular weight/number‐average molecular weight) from 1.8 to 4.8 were obtained. The molar fractions of PFS units increased with increases in the feed ratio of PFS to the inimer. The degrees of branching were typically about 30% with the feed of 1.0 or 2.0 equiv of PFS with respect to the inimer, although slight variations could be achieved through the variation of the inimer composition. Under similar reaction conditions with CuCl as the catalyst, ATR–SCVCP of BMS with PFS led to higher degrees of branching than ATR–SCVCP of CMS with PFS. Solubility tests indicated that the polymers prepared under conditions that avoided extensive biradical coupling were soluble in a broad range of organic solvents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4754–4770, 2005 相似文献
993.
Sukhdeep Kaur Gurmeet Singh Virendra K. Gupta 《Journal of polymer science. Part A, Polymer chemistry》2008,46(22):7299-7309
Ethylene polymerizations were performed using catalyst based on titanium tetrachloride (TiCl4) supported on synthesized poly(methyl acrylate‐co‐1‐octene) (PMO). Three catalysts were synthesized by varying TiCl4/PMO weight ratio in chlorobenzene resulting in incorporation of titanium in different percentage as determined by UV‐vis spectroscopy. The coordination of titanium with the copolymer matrix was confirmed by FTIR studies. The catalysts morphology as observed by SEM was found to be round shaped with even distributions of titanium and chlorine on the surface of catalyst. Their performance was evaluated for atmospheric polymerization of ethylene in n‐hexane using triethylaluminum as cocatalyst. Catalyst with titanium incorporation corresponding to 2.8 wt % showed maximum activity. Polyethylenes obtained were characterized for melting temperature, molecular weight, morphology and microstructure. The polymeric support utilized for TiCl4 was synthesized using activators regenerated by electron transfer (ARGET) Atom Transfer Radical Polymerization (ATRP) of methyl acrylate (MA) and 1‐octene (Oct) with Cu(0)/CuBr2/tris(2‐(dimethylamino)ethyl)amine (Me6TREN) as catalyst and ethyl 2‐bromoisobutyrate (EBriB) as initiator at 80 °C. The copolymer poly(methyl acrylate‐1‐octene; PMO) obtained showed monomodal curve in Gel Permeation Chromatography (GPC) with polydispersity of 1.37 and copolymer composition (1H NMR; FMA) of 0.75. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7299–7309, 2008 相似文献
994.
Bianca S. Shemper 《European Polymer Journal》2004,40(4):651-665
The synthesis of a fluorinated macroinitiator for copper-catalyzed atom transfer radical polymerization (ATRP) is reported, as well as its use for the controlled living polymerization of poly(propylene glycol) methacrylate (PPGM) in MEK at 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer and the molecular weight of the polymer estimated by NMR spectroscopy was in close agreement with the theoretical molecular weight, as expected for controlled processes. The statistical copolymerization of PPGM or methyl ether poly(ethylene glycol) methacrylate (MPEGMA) with a perfluoroalkyl ethyl methacrylate by copper-mediated ATRP was also investigated and led to copolymers with essentially random incorporation of monomers. The syntheses and characterization of star-like homopolymers of MPEGMA or the fluorinated monomer via ATRP are also reported, as well as an amphiphilic star-like block copolymer containing ethyleneglycol units as the core and fluorinated moieties in the shell. The micellar behavior of this copolymer was investigated as a function of the external environment. 相似文献
995.
Bart Dervaux Wim Van Camp Lieven Van Renterghem Filip E. Du Prez 《Journal of polymer science. Part A, Polymer chemistry》2008,46(5):1649-1661
For the first time, a detailed study of the atom transfer radical polymerization of isobornyl acrylate (iBA) is reported. On the basis of these results, well‐defined PiBA‐containing block copolymers were synthesized, focussing on the preparation of amphiphilic poly(acrylic acid) (PAA) containing block copolymers. The precursor monomers 1‐ethoxyethyl acrylate (EEA) as well as tert‐butyl acrylate have been used to synthesize the PAA‐segments of the PiBA‐b‐PAA block copolymers. Finally, the synthesis of “block‐like” copolymers of PiBA and PEEA via a one‐pot procedure was investigated. By optimizing the copper and ligand concentration, and choosing the appropriate solvent, a controlled polymerization behaviour was obtained in all cases, as evidenced by a detailed kinetic analysis, GPC, NMR, and MALDI‐TOF data. Thermogravimetric analysis confirmed the quantitative transformation of the precursor polymer PEEA to the corresponding PAA‐containing copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1649–1661, 2008 相似文献
996.
Jianguo Cheng Li Wang Jia Huo Haojie Yu Qiang Yang Libo Deng 《Journal of Polymer Science.Polymer Physics》2008,46(15):1529-1535
Carbon black nanoparticle grafted with poly(N‐isopropylacrylamide) (CB‐g‐PNIPAAm) was synthesized by surface‐initiated atom transfer radical polymerization (SI‐ATRP). The temperature‐responsive behavior of CB‐g‐PNIPAAm was proved by temperature‐variable 1H NMR. A temperature‐dependent conductive composite was prepared by blending CB‐g‐PNIPAAm with epoxy resin. The relationship between temperature and resistivity of the composite was studied: the composite exhibited a negative temperature coefficient (NTC) phenomenon. Possible mechanism for the NTC phenomenon was suggested. The results showed that resultant composites can be used in intelligent temperature‐switching. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1529–1535, 2008 相似文献
997.
Mehmet Cokun Mehmet Mürit Temüz 《Journal of polymer science. Part A, Polymer chemistry》2003,41(5):668-673
Poly(styrene‐graft‐ethyl methacrylate) graft copolymer was prepared by atom transfer radical polymerization (ATRP) with poly(styrene‐co‐p‐chloromethyl styrene)s in various compositions as macroinitiator in the presence of CuCl/1,2‐dipiperidinoethane at 130 °C in N,N‐dimethylformamide. Both macroinitiators and graft copolymers were characterized by elemental analysis, IR, 1H and 13C NMR, and differential scanning calorimetry. 1,2‐Dipiperidinoethane was an effective ligand of CuCl for ATRP in the graft copolymerization. The controlled growth of the side chain provided the graft copolymers with polydispersities of 1.60–2.05 in the case of poly(styrene‐co‐p‐chloromethyl styrene) (62:38) macroinitiator. Thermal stabilities of poly(styrene‐graft‐ethyl methacrylate) graft copolymers were investigated by thermogravimetric analysis as compared with those of the macroinitiators. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 668–673, 2003 相似文献
998.
Ivaylo Dimitrov Katja Jankova Søren Hvilsted 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):7827-7834
Novel, fluorinated copolymers with different architectures bearing sulfopropyl groups were synthesized in a three‐step procedure. The first step involved atom transfer radical polymerization (ATRP) of aromatic fluorinated monomers followed by two modification reactions performed on the polymer chain: demethylation and sulfopropylation. As a result two types of fluorinated copolymers were obtained. The first one was synthesized by ATRP of 2,3,5,6‐tetrafluoro‐4‐methoxystyrene (TFMS). After the modification steps copolymers with randomly distributed sulfopropyl groups along the backbone were obtained. The second type of copolymers has diblock architecture with one of the blocks being sulfopropylated. They were synthesized via ATRP of 2,3,4,5,6‐pentafluorostyrene (FS) initiated by a PTFMS‐macroinitiator followed by demethylation and sulfopropylation of the TFMS‐block. The copolymers were characterized by size‐exclusion chromatography, FTIR, and 1H NMR spectroscopy. Their thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analyses. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7827–7834, 2008 相似文献
999.
Chao Liu Mugang Pan Yi Zhang Junlian Huang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6754-6761
The star block copolymers with polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) as side chains and hyperbranched polyglycerol (HPG) as core were synthesized by combination of atom transfer radical polymerization (ATRP) with the “atom transfer nitroxide radical coupling” (“ATNRC”) reaction. The multiarm PS with bromide end groups originated from the HPG core (HPG‐g‐(PS‐Br)n) was synthesized by ATRP first, and the heterofunctional PEO with α‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy group and ω‐hydroxyl group (TEMPO‐PEO) was prepared by anionic polymerization separately using 4‐hydroxyl‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (HTEMPO) as parents compound. Then ATNRC reaction was conducted between the TEMPO groups in PEO and bromide groups in HPG‐g‐(PS‐Br)n in the presence of CuBr and pentamethyldiethylenetriamine (PMDETA). The obtained star block copolymers and intermediates were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, fourier transform‐infrared in detail. Those results showed that the efficiency of ATNRC in the preparation of multiarm star polymers was satisfactory (>90%) even if the density of coupling cites on HPG was high. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6754–6761, 2008 相似文献
1000.