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Linear Poly (linear + poly)
Selected AbstractsMultiply Shaped Silica Mediated by Aggregates of Linear Poly(ethyleneimine),ADVANCED MATERIALS, Issue 7 2005J.-J. Yuan A new method for biomimetic silica fabrication is reported. Organized poly(ethyleneimine) rapidly catalyzes and directs the shape of silica in the hydrolysis of tetramethoxysilane under ambient conditions. The resultant silica displays a diversity of controllable morphologies, such as flower, plate, bundle, leaf, and sphere (see Figure, scale bar represents 1,,m). [source] Rapid and Precise Release from Nano-Tracted Poly(N -isopropylacrylamide) Hydrogels Containing Linear Poly(acrylic acid)MACROMOLECULAR BIOSCIENCE, Issue 11 2006Taka-aki Asoh Abstract Summary: We investigated the rapid and precise molecular release from hydrogels in response to dual stimuli. To achieve precise on/off drug release using thermoresponsive poly(N -isopropylacrylamide) hydrogels, we prepared nano-structured semi-IPNs, which consisted of thermosensitive PNIPAAm networks penetrated by pH-responsive poly(acrylic acid) (PAAc) linear chains and perforated to create nano-tracts as a molecular pathway. The present nano-tracted semi-IPNs show a rapid deswelling response to both temperature and pH. Model drug releases were investigated when simultaneous changes in temperature and pH were applied. We observed that the cationic drug was rapidly released and then abruptly discontinued from the nano-tracted semi-IPNs in response to the dual stimuli, and clear release and stopping cycles were repeatedly observed on successive steps. Moreover, the release rates and amount of drug released were controllable by the deswelling speed of the gels and the PAAc content inside the gels. This novel release system using the nano-tracted semi-IPNs may be useful for the high performance, pulsed release of molecules. Release profiles of MB from semi-IPNs at pH,=,5.5, 20,°C (white region) and pH,=,2, 40,°C (gray region). [source] Electroactive Linear,Hyperbranched Block Copolymers Based on Linear Poly(ferrocenylsilane)s and Hyperbranched Poly(carbosilane)sCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2009Frederik Wurm Dipl.-Chem. Abstract A convenient two-step protocol is presented for synthesis of linear-hyperbranched diblock copolymers consisting of a linear, organometallic poly(ferrocenylsilane) (PFS) block and hyperbranched poly(carbosilane) (hbPCS) segments. Linear PFS diblock copolymers were synthesized through photolytic ring-opening polymerization of dimethyl[1]silaferrocenophane as the first block and methylvinyl[1]silaferrocenophane as the second. These block copolymers served as polyfunctional cores in a subsequent hydrosilylation polyaddition of different silane-based AB2 monomers. Three AB2 monomers (methyldiallylsilane; methyldiundecenylsilane, and ferrocenyldiallylsilane) were investigated; they introduced structural diversity to the hyperbranched block and showed variable reactivity for the hydrosilylation reaction. In the case with the additional ferrocene moiety in the ferrocenyldiallylsilane monomer, an electroactive hyperbranched block was generated. No slow monomer addition was necessary for molecular-weight control of the hyperbranching polyaddition, as the core had much higher functionality and reactivity than the carbosilane monomers. Different block ratios were targeted and hybrid block copolymers with narrow polydispersity (<1.2) were obtained. All the resulting polymers were investigated and characterized by size exclusion chromatography, NMR spectroscopy, cyclic voltammetry, and TEM, and exhibited strongly anisotropic aggregation. [source] New sets of solubility parameters of linear and crosslinked aromatic polyamidesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Stefano Fiori Abstract As generally accepted, also in the case of polyamides linear and crosslinked polymeric materials are believed to be characterized by the same solution properties and, consequently, by the same solubility parameters. However, despite their great practical importance, a thorough study aimed to determine the best solvent media able to dissolve linear aromatic polyamides has not been performed yet or, at least, has not been published. In this study, we report on our study on the solubility parameters of linear and crosslinked aromatic polyamides. We demonstrate that the assumption of considering these two classes as having the same solubility properties can lead to dramatically erroneous results. Two new different sets for linear and crosslinked aromatic polyamides are proposed. Namely, linear poly(p -phenylene terephthalamide) is characterized by ,p, ,d, and ,H equal to 8.6, 18.4, and 11.3, respectively; by contrast, the corresponding values of the crosslinked aromatic polyamides taken into consideration are: 11.5, 16.8, and 10.2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation of normal-phase HPLC stationary phase based on monodisperse hydrophilic polymeric beads and their applicationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Bolin Gong Abstract The monodisperse, 5.0 ,m hydrophilic macroporous poly(glycidymethacrylate- co -ethylenedimethacrylate) beads were first prepared based on monosized linear poly(glycidylmethacrylate) beads as seed by using a single-step swelling and polymerization method. The seed beads prepared by dispersion polymerization exhibited good absorption of the monomer phase. The pore size distribution of the beads was evaluated by mercury instrusion method. The surface area was calculated from the BET isotherms of nitrogen adsorption and desorption. The beads were modified to be a normal-phase liquid chromatographic (NPLC) stationary phase for high performance liquid chromatography (HPLC) in the following steps. First, the beads were completely hydrolyzed. Second, hydrolyzed particles were reacted with epichlorihydrin followed by another hydrolysis of the newly introduced epoxide groups. The retention properties of the NPLC stationary phase were easily modulated by changes in the composition of the mobile phase. The performance of theses beads was demonstrated with the separation of a variety of polar compounds. The satisfactory results were obtained. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Star polymers by cross-linking of linear poly(benzyl- L -glutamate) macromonomers via free-radical and RAFT polymerization.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010A simple route toward peptide-stabilized nanoparticles Abstract Poly(benzyl- L -glutamate) (PBLG) macromonomers were synthesized by N -carboxyanhydride (NCA) polymerization initiated with 4-vinyl benzylamine. MALDI-ToF analysis confirmed the presence of styrenic end-groups in the PBLG. Free-radical and RAFT polymerization of the macromonomer in the presence of divinyl benzene produced star polymers of various molecular weights, polydispersity, and yield depending on the reaction conditions applied. The highest molecular weight (Mw) of 10,170,000 g/mol was obtained in a free-radical multibatch approach. It was shown that the PBLG star polymers can be deprotected to obtain poly(glutamic acid) star polymers, which form water soluble pH responsive nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Divergent synthesis of dendrimer-like macromolecules through a combination of atom transfer radical polymerization and click reactionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2007Qingchun Liu Abstract This article describes a divergent strategy to prepare dendrimer-like macromolecules from vinyl monomers through a combination of atom transfer radical polymerization (ATRP) and click reaction. Firstly, star-shaped polystyrene (PS) with three arms was prepared through ATRP of styrene starting from a three-arm initiator. Next, the terminal bromides of the star-shaped PS were substituted with azido groups. Afterwards, the azido-terminated star-shaped PS was reacted with propargyl 2,2-bis((2,-bromo-2,-methylpropanoyloxy)methyl)propionate (PBMP) via click reaction. Star-shaped PS with six terminal bromide groups was afforded and served as the initiator for the polymerization of styrene to afford the second-generation dendrimer-like PS. Iterative process of the aforementioned sequence of reactions could allow the preparation of the third-generation dendrimer-like PS. When the second-generation dendrimer-like PS with 12 bromide groups used as an initiator for the polymerization of tert -butyl acrylate, the third-generation dendrimer-like block copolymer with a PS core and a poly (tert -butyl acrylate) (PtBA) corona was afforded. Subsequently PtBA segments were selectively hydrolyzed with hydrochloric acid, resulting an amphiphilic branched copolymer with inner dendritic PS and outer linear poly(acrylic acid) (PAA). Following the same polymerization procedures, the dendrimer-like PS and PS- block -PtBA copolymers of second generation originating from six-arm initiator were also synthesized. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3330,3341, 2007 [source] Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2006Yan-Xin Liu Abstract Multiwall carbon nanotube (MWNT) was grafted with polyacrylate- g -poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid-treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X-ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880,6887, 2006 [source] Synthesis, crystallization, and morphology of star-shaped poly(,-caprolactone)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005Jing-Liang Wang Abstract Six-arm star-shaped poly(,-caprolactone) (sPCL) was successfully synthesized via the ring-opening polymerization of ,-caprolactone with a commercial dipentaerythritol as the initiator and stannous octoate (SnOct2) as the catalyst in bulk at 120 °C. The effects of the molar ratios of both the monomer to the initiator and the monomer to the catalyst on the molecular weight of the polymer were investigated in detail. The molecular weight of the polymer linearly increased with the molar ratio of the monomer to the initiator, and the molecular weight distribution was very low (weight-average molecular weight/number-average molecular weight = 1.05,1.24). However, the molar ratio of the monomer to the catalyst had no apparent influence on the molecular weight of the polymer. Differential scanning calorimetry analysis indicated that the maximal melting point, cold crystallization temperature, and degree of crystallinity of the sPCL polymers increased with increasing molecular weight, and crystallinities of different sizes and imperfect crystallization possibly did not exist in the sPCL polymers. Furthermore, polarized optical microscopy analysis indicated that the crystallization rate of the polymers was in the order of linear poly(,-caprolactone) (LPCL) > sPCL5 > sPCL1 (sPCL5 had a higher molecular weight than both sPCL1 and LPCL, which had similar molecular weights). Both LPCL and sPCL5 exhibited a good spherulitic morphology with apparent Maltese cross patterns, whereas sPCL1 showed a poor spherulitic morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5449,5457, 2005 [source] Multiple morphologies from a novel diblock copolymer containing dendronized polymethacrylate and linear poly(ethylene oxide)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2005Cai-Xia Cheng Abstract A novel amphiphilic diblock copolymer, consisting of dendronized polymethacrylate- b -poly(ethylene oxide), was synthesized via atom transfer radical polymerization; from it, micellelike aggregates of various morphologies, prepared under near-equilibrium conditions, were studied with transmission electron microscopy and scanning electron microscopy. The effects of various factors on the aggregate morphologies of the amphiphilic copolymer, such as the water content, the copolymer concentration, and the type of common solvent, were investigated systematically. The unique architecture of the block copolymer led to morphological variety and peculiarities such as dendritic and shuttle-shaped aggregates, which could be attributed to the effective packing of the bulky side chains, that is, another driving force for the aggregates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2291,2297, 2005 [source] Novel, biodegradable, functional poly(ester-carbonate)s by copolymerization of trans -4-hydroxy- L -proline with cyclic carbonate bearing a pendent carboxylic groupJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2004Ren-Shen Lee Abstract Water-soluble poly(ester-carbonate) having pendent amino and carboxylic groups on the main-chain carbon is reported for the first time. This article describes the melt ring-opening/condensation reaction of trans -4-hydroxy- N -benzyloxycarbonyl- L -proline (N -CBz-Hpr) with 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) at a wide range of molar fractions. The influence of reaction conditions such as catalyst concentration, polymerization time, and temperature on the number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the copolymers was investigated. The polymerizations were carried out in bulk at 110 °C with 3 wt % stannous octoate as a catalyst for 16 h. The poly(ester-carbonate)s obtained were characterized by Fourier transform infrared spectroscopy, 1H NMR, differential scanning calorimetry, and gel permeation chromatography. The copolymers synthesized exhibited moderate molecular weights (Mn = 6000,14,700 g mol,1) with reasonable molecular weight distributions (Mw/Mn = 1.11,2.23). The values of the glass-transition temperature (Tg) of the copolymers depended on the molar fractions of cyclic carbonate. When the MBC content decreased from 76 to 12 mol %, the Tg increased from 16 to 48 °C. The relationship between the poly(N -CBz-Hpr- co -MBC) Tg and the compositions was in approximation with the Fox equation. In vitro degradation of these poly(N -CBz-Hpr- co -MBC)s was evaluated from weight-loss measurements and the change of Mn and Mw/Mn. Debenzylation of 3 by catalytic hydrogenation led to the corresponding linear poly(ester-carbonate), 4, with pendent amino and carboxylic groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2303,2312, 2004 [source] Synthesis and Characterisation of Poly[oligo(, -caprolactone)L -malate- graft -poly(L -lactide)]MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2010Christian Hahn Abstract Graft copolyesters with a PCL backbone and PLLA side chains were successfully prepared in three steps avoiding transesterification. First , -caprolactone was polymerised with 1,6-hexane diol as initiator to obtain hydroxytelechelic oligo(, -caprolactone)s. These diols were then subjected,in the second step,to polycondensation with L -malic acid yielding in linear poly[oligo(, -caprolactone)L -malate] having secondary hydroxyl functions in the side chain. For both reactions scandium triflate Sc(OTf)3 was used as a catalyst. In the third step various amounts of L -lactide were grafted from the polymer backbone using Zn(oct)2 as catalyst. The successful reaction was confirmed by NMR and SEC (size exclusion chromatography) analysis. Further the thermal properties of the graft copolymers with different graft lengths were determined via differential scanning calorimetry. [source] A Novel Inorganic Polymer as Cathode Material for Secondary Lithium BatteriesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Guo-Xiang Xu Abstract Summary: This paper introduces a new inorganic poly(phosphazene disulfide) material. With unique element composition and molecular structure, the polymer has noncombustible safety and preferable conductivity. When used as cathode material for rechargeable lithium batteries, the polymer's first discharge capacity is as high as 467.9 mAh,·,g,1, which can be retained at 409.9 mAh,·,g,1 after 60 repeated cycles. Therefore, it has a great application potential in the field of lithium batteries. Replacement of the Cl atoms by SS groups by refluxing Na2S2 and linear poly(dichloro-phosphazene). [source] A Defect-Free Ring Polymer: Size-Controlled Cyclic Poly(tetrahydrofuran) Consisting Exclusively of the Monomer Unit,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2008Yasuyuki Tezuka Abstract A series of size-controlled, cyclic poly(tetrahydrofuran)s ( of 4,400,8,600) that consist exclusively of the monomer, i.e., oxytetramethylene, unit (I) have been prepared in high yield through the metathesis polymer cyclization of a telechelic precursor having allyl groups, 1, in the presence of a Grubbs catalyst, and the subsequent hydrogenation of the linking, i.e., 2-butenoxy, unit in the presence of an Adams' catalyst (PtO2). A remarkable topology effect has subsequently been observed upon the isothermal crystallization of these two model polymers, showing distinctive spherulite growth rates and spherulite morphologies in comparison with the relevant linear poly(tetrahydrofuran) counterpart that has ethoxy end groups (II). [source] Self-Assembly of Large Multimolecular Micelles from Hyperbranched Star CopolymersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2007Haiyan Hong Abstract This work focused on the synthesis and aqueous self-assembly of a series of novel hyperbranched star copolymers with a hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) core and many linear poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) arms. The copolymers can synchronously form unimolecular micelles (around 10 nm) and large multimolecular micelles (around 100 nm) in water at room temperature. TEM measurements have provided direct evidence that the large micelles are a kind of multimicelle aggregates (MMAs) with the basic building units of unimolecular micelles. It is the first demonstration of the self-assembly mechanism for the large multimolecular micelles generated from the solution self-assembly of hyperbranched copolymers. [source] Physicochemical characterization of branched chain polymeric polypeptide carriers based on a poly-lysine backboneBIOPOLYMERS, Issue 3 2003I. B. Nagy Abstract A systematic study is reported on the physicochemical characteristics of two branched chain polymers (based on a poly- L -lysine backbone) with a general formula poly[Lys-(DL -Alam - Xi)], where X = Orn (OAK) or N -acetyl-Glu (Ac-EAK) and m , 3, using surface pressure and fluorescence polarization methods. These data are compared with those of the linear poly(L -Lys) from which OAK and Ac-EAK are derived. These two polymers show a moderate surface activity, able to form stable monomolecular layers at the air-water interface. Poly(L -Lys), the most hydrophilic, has the lowest surface activity. The interaction of these polymers with phospholipid bilayers either neutral or negatively charged was studied with vesicles labeled with two fluorescent probes: ANS and DPH. Results indicate that these polymers are able to accommodate in their internal structure, mainly through electrostatic interactions, a certain amount of ANS marker molecules, but fluorescence increases of the ANS-polypeptide complexes were so low that its influence in further polarization measurements could be discarded. After interaction with liposomes, these polymers induce an increase in the polarization of the probes, thus indicating a rigidification of the bilayers. Electrostatic forces seem to be very important in this interaction; cationic polymers are clearly more active, with PG-containing liposomes, than Ac-EAK. Moreover, in these assays poly(L -Lys) behaves as the more active compound. This fact is probably due to its major ability to form ,-helical structures that could insert easily in the bilayers. These results indicate that the polymeric structures studied can be used as carriers for biologically active molecules, because their interactions with bilayers remain soft and have a positive effect on the stability of the membranes. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 323,335, 2003 [source] | |||||||||||||