|
| ||
|
|
||
ABC Triblock Copolymer (abc + triblock_copolymer)
Kinds of ABC Triblock Copolymer Selected AbstractsA Novel ABC Triblock Copolymer with Very Low Surface Energy: Poly(dimethylsiloxane)- block -Poly(methyl methacrylate)- block -Poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate)MACROMOLECULAR REACTION ENGINEERING, Issue 5 2008Zhenghong Luo Abstract Poly(dimethylsiloxane)- block -poly(methyl methacrylate)- block -poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) was successfully synthesized via ATRP. The chemical composition and structure of the copolymer was characterized by NMR and FT-IR spectroscopy and molecular weight measurement. Gel permeation chromatography was used to study the molecular weight distribution of the triblock copolymer. The surface properties of the resulting copolymer were investigated. The effects of fluorine content and bulk structure on surface energy were investigated by static water contact angle measurements. Surface composition was studied by XPS. [source] Synthesis of Amphiphilic ABC Triblock Copolymers with PEO as the Middle BlockMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Surbhi Mahajan Abstract Summary: Stepwise anionic polymerization, catalytic hydrogenation, and atom transfer radical polymerization were performed to synthesize an amphiphilic ABC triblock copolymer, poly(ethylene- alt -propylene)- block -poly(ethylene oxide)- block -poly(hexyl methacrylate) (PEP- b -PEO- b -PHMA), with hydrophilic PEO as the middle block. The resulting block copolymers have well-defined molecular weights and narrow molecular weight distributions as revealed by 1H NMR spectroscopy and gel permeation chromatography. GPC chromatograms of an ABC triblock copolymer, PEP- b -PEO- b -PHMA, and its intermediate precursors exhibiting narrow polydispersities. [source] Encapsulation of nanomaterials using an intermediary layer cross-linkable ABC triblock copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2009Jin Sook Kim Abstract For the preparation of core-shell nanoparticles containing functional nanomaterials, a photo-cross-linkable amphiphilic ABC triblock copolymer, poly(ethylene glycol)- b -poly(2-cinnamoyloxyethyl methacrylate)- b -poly(methyl methacrylate) (PEG-PCEMA-PMMA), was synthesized. This triblock copolymer was then used to encapsulate Au nanoparticles or pyrene. The triblock copolymer of PEG- b -poly(2-hydroxyethyl methacrylate)- b -PMMA (PEG-PHEMA-PMMA) (Mn = 15,800 g/mol, Mw/Mn = 1.58) was first synthesized by activators generated by electron transfer atom transfer radical polymerization. Its middle block was then functionalized with cinnamoyl chloride. The degrees of polymerization of the PEG, PHEMA, and PMMA blocks were 45, 13, and 98, respectively. PMMA-tethered Au nanoparticles (with an average diameter of 3.0 nm) or pyrene was successfully encapsulated within the PEG-PCEMA-PMMA micelles. The intermediary layers of the micelles were then cross-linked by UV irradiation. The spherical structures of the PEG-PCEMA-PMMA micelles containing Au nanoparticles or pyrene were not changed by the photo-cross-linking process and they showed excellent colloidal stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4963,4970, 2009 [source] Synthesis of Amphiphilic ABC Triblock Copolymers with PEO as the Middle BlockMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Surbhi Mahajan Abstract Summary: Stepwise anionic polymerization, catalytic hydrogenation, and atom transfer radical polymerization were performed to synthesize an amphiphilic ABC triblock copolymer, poly(ethylene- alt -propylene)- block -poly(ethylene oxide)- block -poly(hexyl methacrylate) (PEP- b -PEO- b -PHMA), with hydrophilic PEO as the middle block. The resulting block copolymers have well-defined molecular weights and narrow molecular weight distributions as revealed by 1H NMR spectroscopy and gel permeation chromatography. GPC chromatograms of an ABC triblock copolymer, PEP- b -PEO- b -PHMA, and its intermediate precursors exhibiting narrow polydispersities. [source] Morphology of ABCD Tetrablock Copolymers Predicted by Self-Consistent Field TheoryMACROMOLECULAR THEORY AND SIMULATIONS, Issue 4 2005Rong Wang Abstract Summary: We studied the two-dimensional (2D) microphase-separated morphology of linear ABCD tetrablock copolymers by self-consistent field theory. By varying the interaction parameters and the compositions, we found at least twelve structures, two of which , "four-color" lamellae and "three-color" core-shell hexagonal phase , prove the existing experimental observations. These morphologies were discussed in correlation with the volume fraction of the components and the interaction parameters. A specific behavior of symmetrical tetrablock copolymers, i.e., fA,=,fD and fB,=,fC, is that the stable phases are lamellae, which is different from symmetrical ABC triblock copolymer having order-to-order transition. These results are helpful for the design of new block copolymer-based nanomaterials. [source] Molecule-Responsive Block Copolymer MicellesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2007Yoshihiro Ishihara Abstract Ring-opening metathesis polymerization was used to generate an ABC triblock copolymer, containing complementary diamidopyridine (DAP) and thymine (THY) outer blocks, which assembles into spherical aggregates held together by DAP,THY noncovalent interactions. Addition of THY-containing small guest molecules results in complete opening and deaggregation of the block copolymer micelle. This molecular recognition and macroscopic response shows high selectivity to the guest structure, and tolerates only a small amount of conformational mobility in the THY guest. On the other hand, addition of a small DAP-containing guest does not break the aggregates, but instead, results in new micelles which show a different selectivity profile from the parent morphology. We have examined the effect of a number of structural features in the block copolymers, on both the extent and selectivity of their macroscopic response to guests (that is, opening of the micelle). This study has resulted in a set of structural guidelines, which help in the design of effective molecule-responsive micelles for applications in selective drug delivery, sensing, and surface patterning. [source] Tailoring Macromolecular Expression at Polymersome SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Adam Blanazs Abstract A series of amphiphilic ABC triblock copolymers are synthesized by atom transfer radical polymerization, wherein the ,A' and ,C' blocks are hydrophilic and the pH-sensitive ,B' block can be switched from hydrophilic in acidic solution to hydrophobic at pH 7. Careful addition of base to the molecularly dissolved copolymer in acidic solution readily induces the self-assembly of such triblock copolymers at around neutral pH to form pH-sensitive polymersomes (a.k.a. vesicles) with asymmetric membranes. By systematic variation of the relative volume fractions of the ,A' and ,C' blocks, the chemical nature of the polymer chains expressed at the interior or exterior corona of the polymersomes can be selected. Treatment of primary human dermal fibroblast cells with these asymmetric polymersomes demonstrates the biological consequences of such spatial segregation, with both polymersome cytotoxicity and endocytosis rates being dictated by the nature of the polymersome surface chemistry. The pH-sensitive nature of the polymersomes readily facilitates their dissociation after endocytosis due to the relatively low endosomal pH, which results in the rapid release of an encapsulated dye. Selective binding of anionic substrates such as DNA within the inner cationic polymersome volume, coupled with a biocompatible exterior, leads to potential gene delivery applications for these pH-sensitive asymmetric nanovectors. [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] Highly Defined ABC Triblock Cooligomers and Copolymers Prepared by ROMP Using an N -Heterocyclic-Carbene-Substituted Ruthenium Benzylidene InitiatorMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2003Christian Slugovc Abstract The "3rd generation Grubbs" initiator (H2IMes)(3-bromopyridine)2(Cl)2RuCHPh (1) accomplishes the synthesis of ABC triblock copolymers via living ring-opening metathesis polymerisation (ROMP) of norbornene derivatives. Complete initiation and an outstanding tolerance of functional groups are provided, which is proven by a combined study by means of matrix-assisted laser desorption/ionisation mass spectrometry, gel permeation chromatography and NMR spectroscopy on an ABC triblock cooligomer. Gel permeation chromatograms of oligoA, oligoAB, and oligoABC. [source] | ||||||||||