bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of cis-5-norbornene-2,3- dicarboxylic anhydride-chitosan
Authors: Ishak Ku Marsilla Ku , Ahmad Zulkifli , Akil Hazizan Md 
Published: August 2014

AbstractChitosan was chemically modified with bulky structure, cis-5- norbornene-2,3-dicarboxylic anhydride and the characteristics of this modified chitosan was studied. Fourier Transform Infrared results show that the anhydride monomer was successfully bound to amine group of chitosan. Thermal analysis of the modified structure provides N-acylated chitosan with improved thermal stability whereas X-ray Diffraction Analysis reveals reduction in crystallinity level after modification. Scanning Electron Microscope micrograph shows the physical nature and microstructure of N-acylated chitosan with less agglomeration
Diffusion coefficients in systems LDPE+cyclohexane and LDPE+benzene
Authors: Randová Alena , Bartovská Lidmila , Hovorka Štěpán , Bartovský Tomáš , Izák Pavel , Poloncarzová Magda , Fries Karel 
Published: August 2014

AbstractThe swelling of the low density polyethylene in organic liquids (cyclohexane and benzene) was studied. The area of swelling was measured as a function of temperature and time. The experimental data were used for calculating the diffusion coefficients and the activation energies of this process.
Effects of comonomer content, comonomer distribution and crystallization condition on crystallinity and dimension of crystal lattice of ethylene-propylene copolymers
Authors: Du Zi-Xiu , Xu Jun-Ting , Dong Qi , Fan Zhi-Qiang 
Published: August 2014

AbstractIn the present work, the crystallinity and dimension of crystal lattice of two series of ethylene-propylene copolymers with different propylene contents, which were prepared by a fluorinated bis(phenoxyimine) Ti catalyst (FI-EP copolymers) and a conventional Ziegler-Natta catalyst (ZN-EP copolymers), respectively, were studied. It is found that the overall propylene content and crystallization condition have more marked effects on the crystallinity of the FI-EP copolymers with a random comonomer distribution than that of the ZN-EP copolymers with a heterogeneous comonomer distribution. The dimension of a-axis of the PE crystals increases more rapidly with the overall propylene content in the FI-EP copolymers, indicating that more propylene units are included into the PE crystals, whereas the a-axis of the PE crystals remains unchanged for all the ZNEP copolymers. Quenching of the samples leads to more propylene units getting included into the PE crystals. The effects of comonomer content and crystallization condition on crystallinity and dimension of crystal lattice of FI-EP and ZN-EP copolymers can be explained in terms of their different comonomer distributions.
ATRP of MMA initiated by 2-bromoisobutyric acid 4-(2- benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) and its fluorescent property in the presence of metal ions
Authors: Gu Pei-Yang , Xu Qing-Feng , Ge Jian-Feng , Liang Zhang , Lu Jian-Mei , Wang Li-Hua 
Published: August 2014

Abstract2-Bromoisobutyric acid 4-(2-benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) was used for the heterogeneous atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) with a copper(I)bromide/2,2’-bipyridine catalytic system. Factors such as the reaction temperature and mole ratio of catalyst to initiator, which could affect the ATRP system, were discussed in the paper. The functional end group was characterized via UV-vis and 1H NMR spectroscopy. The rates of polymerizations exhibited first-order kinetics with respect to the monomer, and a linear increase in the number-average molecular weight with increasing monomer conversion was observed for these initiation systems. The polydispersity indices (PDI) of the polymer were relatively low (1.07- 1.23) up to high conversions. This PMMA with BPBVE as end group shows strong emission at blue-light area whether in solution or in solid. In particularly, emission was decreased (or quenched) with appearance of metal cations (Zn2+, Co2+, Ni2+, Pb2+, Mn2+, Cu2+, Fe3+, Ag+) in DMF solution.
Sacrificial functional polystyrene core template to fabricate cross-linked chitosan microcapsules
Authors: Liu Weijun , Xu Dandan 
Published: August 2014

AbstractIn this work, biocompatible and biodegradable chitosan microcapsules are successfully prepared in abundance and easily via using carboxylfunctionalized polystyrene (PS) particles as core template and the chitosan crosslinked with gultaraldehyde as the shell. Firstly, the monodisperse functionalized PS particles are made by emulsifier-free emulsion polymerization. The structure and morphology of the carboxyl-functionalized PS particles are characterized by FTIR, FESEM and TEM. Secondly, microcapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized PS particles and by removing the core template. The microcapsules are characterized by FESEM and TEM. The results revealed that the latex particles are removed by exposure to solvent and the microcapsules exhibited the hollow structure. This work confirmed that the microcapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized PS particles and by removing the core template.
Thermal and mechanical properties of polymethyl mathacrylate reinforced by polyhedral oligomeric silsesquioxane
Authors: Yang Benghong , Li Meng , Song Bangping , Wu Yun 
Published: August 2014

AbstractA series of Inorganic/organic nanocomposites were prepared by blending cage-like carboxyl-bearing polyhedral oligomeric silsesquioxane (carboxyl-POSS) with polymethyl mathacrylate (PMMA) in THF solvent. FTIR and 29Si-NMR were employed to characterize the structures of the nanocomposites. SEM images showed that the as-prepared films were smooth and no aggregation of carboxyl-POSS was observed. TGA and DSC results showed that the incorporation of small amount of nanosize carboxyl-POSS enhanced the thermal stability of PMMA. When 1.0 wt% of carboxyl-POSS was incorporated into PMMA matrix, the Tg and Td increased by 16.9 °C and 21.0 °C, respectively. However, higher POSS contents (>1.0 wt%) would deteriorate the thermal and mechanical properties of the nanocomposites.
Structural design of PNIPA-based intelligent hydrogels via porous silica templates
Authors: Komarova Galina , Maurer Xiaoou Liu , Starodubtsev Sergey , Potemkin Igor , Hüsing Nicola , Khokhlov Alexei 
Published: August 2014

AbstractIntelligent temperature-sensitive hydrogels have been synthesized using a hierarchically organized, porous silica gel as template. The organic gels were obtained by three-dimensional copolymerization of N-isopropylacrylamide and N,N’- bis(acryloyl)cystamine in the free volume of a monolith of a porous silica gel. After characterization, the silica matrix was dissolved in alkali. Unexpectedly, the remaining organic polymer showed similar properties to a gel obtained in homogeneous solution. The shape of the inorganic mould was retained in the purely organic hydrogel even after dissolution of the inorganic part and it showed the ability to collapse under enhanced temperatures. The collapse rate of the gel prepared via the template synthesis was much higher compared to gels prepared conventionally.
Growth of large-scaled polypyrrole fibers using polyacrylamide as modifier
Authors: Tang Qunwei , Sun Xiaoming , Li Qinghua , Lin Jianming , Wu Jihuai 
Published: August 2014

AbstractWe first report a novel route to synthesize centimeter-scaled polypyrrole (PPy) fiber in the presence of oligo-polyacrylamide. The Fourier transform infrared and ultraviolet-visible spectra reveal that the fiber is in high conductive state. The PPy fibers have a uniform diameter of 300 μm, and length varying from several millimeters to 4 cm. The temperature dependence of electrical conductivity reveal that the transport properties of PPy fibers should be dominantly characterized by phonon-assisted hopping mechanism. Polymer-directed crystal growth may provide promising routes to rational synthesis of various ordered organic materials with complex form and structural specialization.
Evaluation of crosslinked chitosan hydrogels as carriers for prolonged delivery of some novel nitric oxide donor compounds based on theophylline and paracetamol
Authors: Cojocariu Anca , Profire Lenuta , Cheaburu Catalina , Oprea Ana-Maria , Vasile Cornelia 
Published: August 2014

AbstractThe hydrogels of crosslinked chitosan with different glutaraldehyde amounts have been “in vitro” tested as carriers for prolonged release of some drugs for inflammatory and bronchopulomonary diseases. These hydrogels have been loaded with two novel nitric oxide donors, derivatives of 7-[2-nitroxyacethyloxy- 3-(4-acethyl-amino-phenoxy)-propyl]-8-R-1,3-dimethyl-xanthine compounds (R=H, NO2 for 65 and respectively 77 compounds) designed as multitarget drugs and parent compounds as paracetamol, theophylline, two xanthine derivatives 7-[2- hydroxy-3-(4-acethyl-amino-phenoxy)-propyl]-8-R-1,3-dimethyl-xanthine derivatives with (R=H, NO2 for D1 and respectively D2) and their release was evaluated in an acidic solution (pH=2.2) simulating the gastric fluid. Results have been correlated with the swelling behaviour which was also followed in acidic media with pH=2.2. The relationships between the release profiles and kinetics and matrix characteristics and/or drug properties have been established.
Carbon black/polypyrrole/nitrile rubber conducting composites: synergistic properties and compounding conductivity effect
Authors: Chiu Hsien-Tang , Chiang Tzong-Yiing , Chang Chi-Yung , Kuo Ming-Tai 
Published: August 2014

AbstractElectrically conducting nitrile rubber (NBR) containing electro-conductive carbon black (CB) and polypyrrole as conducting-modifier were prepared by single-step in situ polymerization with mechanical mixing and compression molding (vulcanized). Our result showed CB/NBR and CB/ polypyrrole /NBR conducting composites presents high thermal stability. Thermo-gravimetric analysis showed that the CB 50 phr / polypyrrole 10 phr /NBR of composites formula has highest thermal stability with improved degradation temperature from 422 °C (NBR matrix) to 440 °C at 10% weight loss. CB 50 phr and polypyrrole 10 phr has still optimum volume resistivity values 2.83×1010 to 2.03×103 ohm-cm above the percolation threshold. Therefore, incorporating CB with polypyrrole conducting-modifier showed four causes of advantage i.e. increase in thermal stability, conductive pathways, synergistic properties on thermal stability with reinforcement mechanical properties and compounding conductivity effect within the rubber matrix.
SiO2 Nanofiller impact on crystallization kinetics during adiabatic anionic polymerization of ε-caprolactam
Authors: Davtyan Sevan , Schick Christoph , Tonoyan Anahit , Zohrabyan David 
Published: August 2014

AbstractAnion activated adiabatic polymerization of ε-caprolactam was investigated in the presence of various quantities of nano-SiO2. The parallel processes of crystallization and polymerization are separated first. Based on the crystallization kinetics and electron microscopic investigations it was shown that nano-SiO2 particles are heterogeneous nuclei for the crystallization of poly-ε-caprolactam. Further the time dependence of mean length of amorphous polymer macromolecules is determined experimentally.
Synthesis and characterization of novel thermally stable poly(ether-amide)s containing dinaphthosulfone units in the main chain
Authors: Shockravi Abbas , Mehdipour-Ataei Shahram , Naghdi Shaghayegh 
Published: August 2014

Abstract A New type of sulfone (4) containing 1,1´-thiobis(2- hydroxynaphthalene) diacid as a monomer was synthesized from the reaction of 2-hydroxynaphthalene (1) and sulfur dichloride, followed by reaction with methylchloroactate to obtain diester (2). Oxidation of this product in the presence of hydrogen peroxide followed by basic hydrolysis led to corresponding sulfone diacid (4) in good yield. Six organic-soluble poly(ether-amide)s bearing sulfone groups were synthesized via direct polycondensation of diacid (4) with commercially available aromatic diamines in the presence of calcium chloride as dehydrating agent. The resulting polyamides had inherent viscosity ranging from 0.38 to 0.46 dLg-1 at concentration of 0.5 gdL-1 in N,N-dimethylacetamide at 30 °C. The glass transition temperatures of these polyamides were recorded between 276-327 °C in air atmosphere. These polymers were also characterized by IR, 1H NMR and elemental analysis and their physical properties including viscosity, solubility properties, thermal stability and thermal behaviour were studied. These polyamides showed very good thermal stability and solubility in polar aprotic solvents.
Influences of silane/ether composite external donors on propylene polymerization with MgCl2-supported Ziegler-Natta catalyst in the presence of hydrogen
Authors: Tu Song-tao , Lou Jun-qin , Fu Zhi-sheng , Fan Zhi-qiang 
Published: August 2014

AbstractIn this work, the effects of two silane type external donors, Ph2Si(OCH3)2 (DPDMS) and dicyclopentyldimethoxysilane (DCPDMS) on propylene slurry polymerization in the presence of hydrogen with a MgCl2/TiCl4/DIBP - Al(C2H5)3 catalyst system were investigated, and the tacticity distribution and molecular weight distribution (MWD) of polypropylene (PP) were further regulated by using silane/ether (ROCH3, R = n-Bu, i-C8H17) composite external donors. The tacticity distribution of PP, as revealed by successive self-nucleation and annealing (SSA) thermo analysis of the polymer, is markedly changed by the external donors. DCPDMS shows much stronger effects than DPDMS. Addition of the ether as an auxiliary external donor in MgCl2/TiCl4/DIBP-TEA/silane (DPDMS or DCPDMS) lead to further increase in catalytic activity and isotacticity of PP, and changes in tacticity distribution. By using the composite external donors, PP with both higher isotacticity index, lower molecular weight or narrower molecular weight distribution was prepared at high activity. Effects of the external donors on the active center distribution were discussed based on the results of deconvoluting the MWD curve with multiple Flory “most-probable” distributions, and possible mechanism of the external donor effects was proposed.
Toughening of epoxy resin with poly(methyl methacrylate) grafted silica core-shell particles
Authors: Yang Peng , Zhu Liyuan , Wang Haitao , Du Qiangguo , Zhong Wei 
Published: August 2014

AbstractStructurally well-defined core-shell particles were prepared by modifying the surface of silica with initiators for atom transfer radical polymerization (ATRP), and followed by using these initiator-modified particles as ATRP macro-initiators for methyl methacrylate. These particles were characterized with Fourier-transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). The tethered polymer chains on the grafted silica particles were cleaved with hydrofluoric acid and measured with gel permeation chromatography (GPC). The results showed that poly(methyl methacrylate) (PMMA) chains grew from the particle surfaces in form of individual particles comprising of a hard silica core and a well-defined, densely grafted outer polymer layer. Diglycidyl ether of bisphenol-A (DGEBA) based epoxy resin was toughened with various doses of the synthesized PMMA-grafted silica particles. Resulting composite materials were characterized by tensile testing, SEM, dynamic mechanical analysis (DMA) and TGA. The results indicated that the incorporation of the core-shell particles improved the toughness of the composites without any significant deterioration of its thermal properties.
Computer simulation study on the structure and physical property of pyrene-functionalized fluorescent film
Authors: Kong Hong-yan , Zhang Lin , Liu Jing 
Published: August 2014

AbstractExperimentally, the fluorescent intensity of the pyrene-functionalized fluorescent film is reduced by introducing nitrobenzene. In order to fulfill the functional reason of this quenching effect, a molecular dynamics simulation is adopted in this paper. The simulation finds that the structural changes of the pyrene molecules in the film are the main reason for the quenching effects. Result reveals that, in the vacuum environment, the distance between a pair of pyrene ring centers distributes from about 4 Å to 10 Å, and a large number of distances populate at 5.3 Å, which is a suitable distance for excimer emission. The introduction of nitrobenzene leads to a decrease of the population of pyrene molecules within that distance, indicating a decrease of excimer emission of the film. In addition, the pyrene molecule rings in the film prone to adopt a quasicoplanar structure in the vacuum, but less likely arrange into a coplanar structure when nitrobenzene is introduced. Study clearly indicates that the structural changes are all caused by the insertion of the incoming nitrobenzene molecules into the previously coplanar pyrene rings. Analysis of structure factor and X-ray scattering also indicates that the structural modification of the pyrene molecules surely reduces the fluorescent intensity of the pyrene-functionalized film in the nitrobenzene environment.
Crystallization behavior of poly(ε-caprolactone) grafted on silicon surface
Authors: Wang Xi , Yang Juping , Zhou Jianjun 
Published: August 2014

AbstractPoly(ε-caprolactone) (PCL) grafted on silicon wafer with different thickness (10 to 100 nm) were prepared by surface-initiated ring-opening polymerization (ROP). The morphologies, crystallinity, and crystallization rate of different thickness thin films have been investigated by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The nascent morphology of the as polymerized 15 nm film was found to be nodular structure form. As the film thickness increased, the nodular structures gradually aggregated to form flat-on lamellae. When the film thickness reached 100 nm, the surface of silicon wafer was covered with a whole layer of flat-on lamellae. The isothermal crystallization study on 100 nm film had shown that the tethered PCL chains could only crystallize in the form of flat-on lamellae. FTIR study had showed that the crystallinity decreased significantly with the film thickness decreasing, while the half-crystallization time increased as the film became thicker. The halfcrystallization time increase of thicker film was supposed to relate with the degree of chain entanglement in the tethered brushes.
Synthesis and characterization of an amphiphilic methoxy poly(l-lactide)-block-poly(glycidylmethacrylate) copolymer as a drug nanocarrier
Authors: Bagheri Massoumeh , Motirasoul Forough 
Published: August 2014

AbstractPresent research is a preliminary report on the amphiphilic diblock copolymer (mPLA-b-PGMA) comprising hydrophobic methoxy poly(L-lactide) (mPLA) and hydrophilic poly(glycidyl methacrylate) (PGMA) segments was used as a promising drug carrier. Diblock copolymer was synthesized via ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) methods. Methanol first initiated ROP of L-lactide in the presence of tin(II)bis(2-ethylhexanoate) (Sn(oct)2) as a catalyst. The resulting monohydroxyl-terminated polylactic acid (mPLA) was subsequently converted to a bromine-ended macroinitiator (mPLA-Br) by esterification with 2-bromisobutyryl bromide. The copolymer mPLA-b-PGMA was synthesized in a subsequent ATRP of GMA. The obtained polymers were characterized by means of 1H NMR, FTIR, DSC and TGA. The copolymer mPLA-b- PGMA self-assembled into nanoscale micelles in aqueous solutions, as investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The TEM image of polymeric micelles showed that the micelles were spherical in shape and that their diameters were in the range of 80-140 nm. Then by using the naproxen as a hydrophobic model drug, the drug-loaded micelles with 81.18 % loading efficiency and 16.24 % loading capacity were prepared. Moreover, in vitro release study of naproxen was performed using dialysis bag in phosphate-buffered solution at 37°C and pH at 7.4. Accordingly, these polymeric micelles may provide as an effective drug carrier for controlled drug release.
Miscibility of chitosan and poly(ethyleneglycol) blends in buffer solution
Authors: Sudhakar Y.N. , Selvakumar M. 
Published: August 2014

AbstractThe miscibility of chitosan (CS) and poly(ethyleneglycol) (PEG) blends in buffer solution (CH3COOH and CH3COONa) has been investigated by viscosity, density and refractive index studies. Various interaction parameters such as polysolvent and blend-solvent interaction parameters and heat of mixing have been calculated using viscosity and density data. The results indicated the existence of positive interactions in the blend polymer solution and that they are miscible in buffer solution in 90/10 and 80/20 composition ranges. The study also revealed that variation of temperature does not affect the miscibility of chitosan and PEG blends in the buffer solution significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. Thermal behavior was studied using DSC instrument. The result obtained reveal that Chitosan forms a miscible blend with PEG in 90/10 and 80/20 composition ranges.
On the structure alteration of crosslinkable gelatin coupled with methacrylic acid and its hydrogel
Authors: Hu Xiaohong , Li Dan , Zhou Feng , Gao Changyou 
Published: August 2014

AbstractPhysical structures of a crosslinkable gelatin derivative (GM) were studied in terms of alteration of apparent molecular weight, triple helix content and mechanical strength. The GM with a substitution degree (DS) of 49% and 79% was prepared by grafting mechacrylic acid (MA), which was able to form injectable hydrogel by photoinitiating polymerization. The zeta potential was increased along the increase of DS. After modification, the apparent number-average molecular weight (Mn) detected by gel permeation chromatography was decreased to about 2/3 of gelatin, while the apparent weight-average molecular weight (Mw) was changed within a small range. Differential scanning calorimetry and circular dichroism (CD) revealed that ability of triple-helix formation of GM was decreased along with the increase of DS and decrease of GM concentration. After photocrosslinking, the sol-gel transition of GM49 physical-chemical hydrogel still existed, but completely disappeared for its chemical hydrogel. The physical-chemical hydrogel showed a larger storage modulus at 20°C than at 37°C as a result of additional physical crosslinking.
Intercalation of montmorillonite based on dendritic quaternary ammonium: preparation and characterization
Authors: Chen Feng , Xiong Han , Yang Jintao , Cai Weiwei , Zhong Mingqiang 
Published: August 2014

AbstractThree generations of dendritic quaternary ammonium (G1, G2 and G3) were intercalated into montmorillonite (MMT) layered silicates. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the respective intercalations of dendrimer/MMT hybrids exhibited organized characteristics, and the interlayer spacings were 2.83, 2.62 and 2.89 nm for G1/MMT, G2/MMT and G3/MMT, respectively. Moreover, the preparation of dendrimer/MMT hybrids was investigated at different dendrimer/MMT molar ratios regarding the changes of interlayer distance, revealing a conformation change of the intercalating dendrimers. The dendritic structure with low molecular weight (G1) could effectively intercalate the layered silicates and enlarge the basal spacing to 2.83 nm.