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Diblock Copolymer Poly (diblock + copolymer_poly)
Selected AbstractsSynthesis of silicon nitride based ceramic nanoparticles by the pyrolysis of silazane block copolymer micellesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2006Kozo Matsumoto Abstract Diblock copolymer poly(1,1,3,N,N,-pentamethyl-3-vinylcyclodisilazane)- block- polystyrene (polyVSA- b -polySt) and triblock copolymer poly(1,1,3,N,N,-pentamethyl-3-vinylcyclodisilazane)- block- polystyrene- block -poly(1,1,3,N,N,-pentamethyl-3-vinylcyclodisilazane) (polyVSA- b -polySt- b -polyVSA), consisting of silazane and nonsilazane segments, were prepared by the living anionic polymerization of 1,1,3,N,N,-pentamethyl-3-vinylcyclodisilazane and styrene. PolyVSA- b -polySt formed micelles having a poly(1,1,3,N,N,-pentamethyl-3-vinylcyclodisilazane) (polyVSA) core in N,N -dimethylformamide, whereas polyVSA- b -polySt and polyVSA- b -polySt- b -polyVSA formed micelles having a polyVSA shell in n -heptane. The micelles with a polyVSA core were core-crosslinked by UV irradiation in the presence of diethoxyacetophenone as a photosensitizer, and the micelles with a polyVSA shell were shell-crosslinked by UV irradiation in the presence of diethoxyacetophenone and 1,6-hexanedithiol. These crosslinked micelles were pyrolyzed at 600 °C in N2 to give spherical ceramic particles. The pyrolysis process was examined by thermogravimetry and thermogravimetry/mass spectrometry. The morphologies of the particles were analyzed by atomic force microscopy and transmission electron microscopy. The chemical composition of the pyrolysis products was analyzed by X-ray fluorescence spectroscopy and Raman scattering spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4696,4707, 2006 [source] Spontaneous Vertical Ordering and Pyrolytic Formation of Nanoscopic Ceramic Patterns from Poly(styrene- b -ferrocenylsilane),ADVANCED MATERIALS, Issue 4 2003K. Temple The rapid generation of nanopatterned surfaces using thin films of the amorphous diblock copolymer poly(styrene- b -ferrocenylethylmethylsilane) (PS- b -PFS) is reported. Spontaneous self-assembly into vertically oriented cylinders of PFS in a PS matrix is observed on a variety of substrates by spin or dip coating, irrespective of the substrate surface polarity. Pyrolysis of the films affords arrays of 20 nm Fe-containing ceramic nanoparticles, (see Figure, AFM, 4 ,m2 scan area). [source] Application of the biodegradable diblock copolymer poly(L -lactide)- block -poly(L -cysteine): Drug delivery and protein conjugationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Jing Sun Abstract A novel approach to self-assembled and shell-crosslinked (SCL) micelles from the diblock copolymer poly(L -lactide)- block -poly(L -cysteine) to be used as drug and protein delivery carriers is described. Rifampicin was used as a model drug. The drug-loaded SCL micelles were obtained by self-assembly of the copolymer in the presence of the drug in aqueous media. Their morphology and size were studied with dynamic light scattering and field emission scanning electron microscopy. The rifampicin loading capacity and encapsulation efficiency were studied with ultraviolet,visible spectrophotometry. The drug-release rate in vitro depended on the oxidizing and reducing environment. Moreover, a straightforward approach to the conjugation of the copolymer with bovine serum albumin (BSA) was developed, and a gel electrophoresis test demonstrated that this conjugated BSA could be reversibly released from the copolymer substrate under reducing conditions. In conclusion, this L -cysteine copolymer can be used in drug delivery and in protein fixation and recovery. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Behaviors of self-assembled diblock copolymer with pendant photosensitive azobenzene segmentsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010Jui-Hsiang Liu Abstract A novel monomer, ethyl 4-[4-(11-methacryloyloxyundecyloxy)phenyl azobenzoyl-oxyl] benzoate, containing a photoisomerizable NN group was synthesized. The monomer was further diblock copolymerized with methyl methacrylate. Amphiphilic diblock copolymer poly(methyl methacrylate- block -ethyl 4-[4-(11-methacryloyloxyundecyloxy)phenyl azobenzoyl-oxyl] benzoate (PMMA - b - PAzoMA) was synthesized using atom transfer radical polymerization. The reverse micelles with spherical construction were obtained with 2 wt % of the diblock copolymer in a THF/H2O mixture of 1:2. Under alternating UV and visible light illumination, reversible changes in micellar structure between sphere and rod-like particles took place as a result of the reversible E-Z photoisomerization of azobenzene segments in PMMA - b - PAzoMA. Microphase separation of the amphiphilic diblock copolymer in thin films was achieved through thermal and solvent aligning methods. The microphases of the annealed thin films were investigated using atom force microscopy topology and scanning electron microscopy analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1142,1148, 2010 [source] Synthesis and characterization of side-chain liquid crystalline ABC triblock copolymers with p -methoxyazobenzene moieties by atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Xiaohua He Abstract 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 [source] A Self-Assembly Approach to Temperature-Responsive Polymer NanocontainersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2004Xiangrong Chen Abstract Summary: Thermosensitive polymer nanocontainers were formed by self-assembly of diblock copolymers poly(2-cinnamoylethyl methacrylate)- block -poly(N -isopropylacrylamide) (PCEMA- block -PNIPAM) and subsequent photo-crosslinking of the PCEMA shells. It was found that the diameter of the nanocontainers ranges from tens of nanometers to thousands of nanometers, depending on the self-assembly conditions. The phase transition of the nanocontainers takes place at 32,°C; the structural changes are reversible in a heating and cooling cycle. Schematic illustration of the structural transition behavior of the thermosensitive polymer nanocontainers. [source] | ||||||||||