bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and characterization of amphiphilic graft copolymers of poly(1,3 dioxolane) macromonomers with styrene and methyl methacrylate
Authors: Bendaikha Hayet , Clisson Gérald , Khoukh Abdelouahad , François Jeanne , Kada Seghier Ould
Published: August 2014

Methacrylate-terminated Poly(1,3 dioxolane) (PDXL) macromonomers were synthesized by cationic ring-opening polymerization in the presence of 2- hydroxypropyl methacrylate (2-HPMA) as transfer agent. Molecular weights, polydispersity index and functionality of the PDXL macromonomers were evaluated by size exclusion chromatography (SEC) and 1H nuclear magnetic resonance spectroscopy (1H-NMR). Copolymerizations of PDXL macromonomers, of different molecular weights, with styrene (St) and methyl methacrylate (MMA) were carried out using various feed molar ratios. The resulting polymers confirmed the grafting of PDXL with PS and PMMA by SEC and 1H-NMR Monomer reactivity ratios between the macromonomers and the comonomers were estimated from the copolymerization results. Macromonomer reactivity depends on the comonomer considered. Glass transition temperatures of the copolymers were found to decrease with an increase in the amount of PDXL in the copolymers. The values of Tg depend on the composition and the size of the PDXL grafts.
Compatibilization of NR/EVA blends by natural rubber grafted poly(dimethyl(methacryloyloxymethyl)phosphonate) compatibilizer
Authors: Intharapat Punyanich. , Derouet Daniel , Gohier Frédéric , Nakason Charoen
Published: August 2014

Graft copolymer of natural rubber (NR) and poly(dimethyl (methacryloyloxymethyl) phosphonate (PDMMMP) (i.e., NR-g-PDMMMP) was prepared and used as a blend compatibilizer in 50/50 NR/EVA simple blends. Influence of various loading levels of NR-g-PDMMMP (i.e., 0, 1, 3, 5, 7, 9, 12 and 15 wt% of NR) on rheological, dynamic, mechanical and morphological properties was investigated. The results showed that the best compatibilization effect was observed in the blend with a loading level of NR-g-PDMMMP at 7 wt%. That is, the highest complex viscosity, tensile strength, elongation at break as well as the lowest values of tension set and tan δ value (i.e., damping factor) were observed. This indicates the highest mechanical strength and the supreme elastic response of the material. Morphological properties of 50/50 NR/EVA blends with any loading levels of NR-g-PDMMMP compatibilizer showed co-continuous phase system. However, in the NR/EVA blend with NR-g-PDMMMP at a loading level of 7 wt%, the finest phase morphology was observed. The 50/50 NR/EVA blend with lower and higher loading amounts of NR-g-PDMMMP compatibilizer exhibited inferior dynamic, mechanical properties as well as larger phase morphologies.
Determination of vinyl acetate propagation rate coefficients via high frequency pulsed laser polymerization
Authors: Junkers Thomas , Voll Dominik , Barner-Kowollik Christopher
Published: August 2014

New data on the propagation rate coefficient, kp, of vinyl acetate (VAc) are obtained via the IUPAC recommended method of pulsed laser polymerization - size exclusion chromatography (PLP-SEC) operated at 500 Hz laser repetition rate. An apparent dependency of the experiment’s outcome on the laser pulsing rate is identified with kp being about 25 % larger at 500 Hz compared to 100 Hz. The temperature dependence of kp was determined to fit ln kp = 17.12 - 2621 K/T; data is in generally good agreement with literature values when the previous underestimation of kp by 100 Hz laser pulsing experiments is taken into account.
Konjac glucomannan nanocrystals prepared by acid hydrolysis
Authors: Huang Jin , Gao Shanjun , Shen Xiaomeng
Published: August 2014

Konjac Glucomannan (KGM) nanocrystals were prepared from the disruption of KGM by acid hydrolysis. Effect of hydrolysis time on the degree of hydrolysis of KGM and the size of nanocrystals were investigated. Results from Infrared spectroscopy (IR) showed that KGM nanocrystals were still composed of mannose and glucose like the raw KGM. Results from X-ray diffractometer (XRD) revealed that the amorphous state of raw KGM had changed into a typical β-type crystalline state of KGM nanocrystals. Results from transmission electron microscopy (TEM) indicated that irregularly oval shape nanocrystals with the mean size of 15-40 nm were observed.
Comparison of Matrix Assisted Laser Desorption/ Ionization Mass Spectrometry with Electrospray Ionisation Mass Spectrometry for the characterisation of semitelechelic polyethylene oxide
Authors: De Winter Julien , Vachaudez Magali , Coulembier Olivier , Dubois Philippe , Flammang Robert , Gerbaux Pascal
Published: August 2014

MALDI-MS methodology is nowadays considered as a very reliable technique to determine the chemical structures and the molecular weight distribution of a synthetic polymer. At variance, ESI-MS occupies only a small segment in the analysis of polymers mainly because of the formation of multiple charged ion distributions, which interfere with the molecular distribution in the mass spectra of synthetic polymers. In the present communication, we want to demonstrate that, when applied to fragile polymer samples, both techniques can lead to misinterpretation since in source decomposition of the ionized oligomers can sometimes not be avoided. An accurate knowledge of the source parameters and their influences is therefore a prerequisite prior to start the analysis of the MS data. Moreover, we would like to propose that the best MS methodology to analyze fragile synthetic polymers is to associate the data obtained by both the MALDI-MS and ESI-MS techniques.
Mechanical and hygrothermal aging study on quaternary polyamide 6/maleated styrene-ethylene-butylenestyrene/ clay/short glass fiber hybrid composites
Authors: Rua Yonghong , Tjong Sie Chin
Published: August 2014

Elastomer toughened PA6 hybrids reinforced with short glass fiber and organoclay were fabricated by melt mixing and injection molding. The structure, mechanical and hygrothermal aging behaviors of such hybrids were investigated. XRD patterns showed the absence of clay diffraction peaks in low angle region. TEM observation showed that the organoclay platelets are fully exfoliated in the PA6 matrix of hybrids. Mechanical tests demonstrated that the incorporation of organoclay into PA6/SEBS-g-MA/SGF composite lead to a significant enhancement in the elastic modulus of hybrids. However, the clay additions reduced the tensile ductility and fracture toughness of hybrids. The tensile stiffness and strength of the clay reinforced hybrids deteriorated but the tensile ductility enhanced markedly upon exposure to hygrothermal aging.
In situ formation of silver nanoparticles based on dendriticlinear amphiphilic block copolymer micellar templates
Authors: Wang Huiqing , Shao Ziqiang , Wang Wenjun , Wang Feijun
Published: August 2014

Dendritic-linear amphiphilic block copolymer, G1-b-PEG, was synthesized through a convergent method. The first generation benzylic dendritic polyether, G1-Cl, was synthesized, and benzylic dendritic polyether, G1-Cl, was used to react with linear monohydroxyl terminated MPEG in alkaline solution via a convergent method. The copolymer was characterized by 1H-NMR. The amphiphilic block copolymer could self-assemble into micelles in aqueous solution, which were used as templates to prepare dispersed silver nanoparticles in water. The morphology and structure of the hybrids were characterized by transmission electron microscopy (TEM) and ultraviolet spectroscopy (UV), 1H-NMR. An absorbance peak at 406 nm appeared after reduction in the UV spectrum. The average diameter of G1-B-PEG /Ag hybrid micelles was 186 nm, and the sliver nanoparticles are stable in aqueous solution due to the stabilization of the dendritic-linear micelles.
Synthesis and characterization of temperature/pH-sensitive hydroxypropylcellulose/ sodium alginate hydrogel
Authors: Li Hui , Gong Guo-li
Published: August 2014

A series of temperature and pH responsive hydrogels were synthesized by using hydroxypropylcellulose (HPC) as temperature natural sensitive material, sodium alginate (SA) as pH sensitive material. The effect of SA to LCST has been studied and the mechanism of the influence has been presented. In addition, the swelling ratio and controlling factor of swelling process were all researched in this paper. The main results obtained are as follows: the LCST decreased gradually as SA was added into HPC; the HPC/SA hydrogel responded to both temperature and pH value of the medium; the swelling ratio reached maximum value at pH value of 6.
Rheological characterization of polystyrene melts dissolved with supercritical nitrogen fluid during microcellular injection moulding
Authors: Chen Shia-Chung , Chung Ming-Hsiu , Lin Yu-Wan , Hsu Ping-Shun , Hwang Shyh- Shin , Hsu Pe-ming
Published: August 2014

There are several benefits of using the supercritical fluid microcellular injection moulding process. The part weight, melt temperature, viscosity, moulding pressure, shrink/warpage, and cooling/cycle time are all significantly reduced. The purpose of this study is to investigate the rheological behaviour of PS melt dissolved SCF of nitrogen during Microcellular Injection Moulding process applied with Gas Counter Pressure (GCP) technology. The application of gas into the mould cavity prior to the melt filling provides a counter force against the melt front advancement, restricting the foaming process during the melt filling stage. A slit cavity is designed to measure the pressure drop of polystyrene mixed with 0.4wt% supercritical nitrogen fluid under different mould temperatures (185°C, 195°C, and 205°C), injection speeds (5, 10, and 15 mm/s) as well as counter pressures (0, 150, 300 bars). It was found that melt viscosity is reduced by up to 30% when GCP is increased from 50 to 150 bar as compared to conventional injection moulding. The non-nucleation mixture melt obtained by using a GCP of 300 bar has 32~49% lower viscosity. In addition, the glass transition temperature, Tg, was found to be reduced from 96 °C to 50 °C when the applied GCP is 300 bar.
Synthesis and characterization of novel benzoxazines containing nitrile and allyl groups and their polymers
Authors: Zhang Hongchun , Lu Zaijun
Published: August 2014

A p-cyanophenol and allylamine based benzoxazine has been synthesized and characterized. This benzoxazine has nitrile and allyl functionalities that can polymerize, resulting in a highly crosslinked material. The DSC spectra of novel benzoxazine monomer reveal that incorporation of the nitrile and allyl group greatly decreases the ring-opening temperature of oxazine rings (140°C). The IR spectra of curing process indicate that the polymerization of oxazine ring accompany with the curing reaction of allyl and nitrile groups. Benzoxazine monomers with one or none of the two functionalities were also prepared to study structure effect on thermal properties of resulted polymer. The comparison of results confirms that introducing the two functionalities improved glass transition temperature (238 °C), thermal stability of polybenzoxazine (T5%=340 °C), and char yield (57%).
MgH2/PEG initiating system for ring opening polymerization of lactone and lactide
Authors: Guerrouani Nadia , Mas André , Schué François
Published: August 2014

Dihydroxy-terminated poly(ethylene glycol) and MgH2 form an efficient initiating system for the ring opening polymerization of ε-caprolactone and Llactide. Polycaprolactone-block-polyethylene glycol-block-polycaprolactone and polylactide-block-polyethylene glycol-block-polylactide were synthesized in bulk at 120 °C for 16 h under argon. MgH2 provided a faster polymerization rate compared with other initiating systems based on non toxic metals used under vacuum. Molecular weight of copolymers varied according to the monomer / ethylene oxide units ratio. The developed procedure led to easy polymerization with better control of the design, molecular weight and polydispersity of the final material. Copolymers were characterized by SEC, DSC, 1H and 13C NMR and IR. Micelles in aqueous solutions were prepared by finding balance between hydrophobic polyester and hydrophilic polyethylene glycol blocks. Interest for this method is since the use of MgH2, environmental chemical, absence of solvent and vacuum techniques and the possible recovery of solid material without further operation.
Interfacial properties of all-polypropylene composites
Authors: Houshyar Shadi , Shanks Robert A.
Published: August 2014

Preparation and characterization of novel composites, consisting of polypropylene (PP) fibres in a random poly(propylene-co-ethylene) (PPE) matrix, were investigated. These composites possess unique properties, due to chemical compatibility of the two polymers allowing creation of strong physico-chemical interactions and strong interfacial bonds. The difference between the melting temperatures of PP fibre and PPE was exploited in order to establish processing conditions for the composites. Suitable conditions were chosen so that the matrix was a liquid, to ensure good wetting and impregnation of the fibres, though the temperature must not be high enough to melt the fibres. The morphology of the composites was investigated using optical and scanning electron microscopy. Optical microscope images showed that transcrystallization of the matrix was observed on PP fibre surfaces. SEM photographs displayed a thin layer of matrix on the reinforcement, attributed to good impregnation and wetting of the fibres. Adhesion between PPE matrix and PP fibres was characterized using a microbond test inspired by a fibre pull-out technique. The results showed that adhesion was appreciably increased when PP fibres were used instead of glass fibres in the matrix. Nevertheless, thermal processing conditions of the composites caused reduction in mechanical behaviour of the reinforcement.
Preparation and Investigation of chitosan nanoparticles including salicylic acid as a model for an oral drug delivery system
Authors: MojtabaTaghizadeh Seyd , Javan Raveled Safaei
Published: August 2014

The aim of this study was to prepare a biocompatible and biodegradable nanoparticulate drug delivery system to increase the efficiency and bioavailability of oral drugs. Chitosan nanoparticles containing salicylic acid (SA) were prepared by emulsion method. The morphology of nanoparticles was characterized by scanning electron microscopy (SEM). Particle size distribution was examined by laser light scattering. The drug released and drug content was examined by UVspectroscopy. The effects of different initial drug loading on the drug content and drug released were investigated. The nanoparticles were spherical and the average size of them was 300 nm, the drug content was in the range of 20-35%. All the nanoparticles had a burst release initially and the burst release behavior of them conformed best to higuchi model. The release of SA from chitosan nanoparticles was Fickian.
Preparation and characterization of poly(propylene carbonate)/polystyrene composite films by melt-extrusion method
Authors: Huihong Liu , Lisha Pan , Qiang Lin , Nai Xu , Lingbin Lu , Sujuan Pang , Songbao Fu
Published: August 2014

Poly(propylene carbonate) (PPC) is a new biodegradable aliphatic polycarbonate with poor thermal stability and mechanical properties which shows difficulty in forming film by melt-extrusion technology. Through the addition of polystyrene (PS), the melt-extrusion film processability, thermal stability and mechanical properties of PPC was improved largely. PPC/PS films were prepared in the the melt-extrusion process successfully. DSC data showed that there was some degree of miscibility between PPC and PS. SEM showed good dispersion of PS particles into PPC matrix. Improved mechanical properties and thermal stability of PPC/PS blends were attributed to homogeneous dispersing and stronger interfacial interaction of PS and PPC. These results indicate that blending PPC with PS is an efficient and convenient method to improve the properties of PPC, and the composites can be used as a common packaging material for a wide range of applications.
An algorithm for Monte Carlo modeling of hyperbranched polymerization
Authors: Lechowicz Jaromir B. , Galina Henryk
Published: August 2014

A model hyperbranched polymerization involving irreversible reactions between functional groups A and B in a mixture of comonomers ABxand Bn(x = 2, 3,…; n = 1, 2, …) has been studied. An algorithm simulating the reactions in computer memory was developed and converted into computer code. Simulations were applied to optimize the procedure of feeding monomers AB2 and B2.
macroporous hydrogels based on 2-hydroxyethyl methacrylate. Part 7: Methods of preparation and comparison of resulting physical properties
Authors: Přádný Martin , Šlouf Miroslav , Martinová Lenka , Michálek Jiří
Published: August 2014

Five methods of preparation of macroporous hydrogels are described and compared: precipitation polymerization, polymerization in presence of salt, polymerization in presence of gas-releasing compound, lyophilization and electrospinning. Crosslinked copolymers based on 2-hydroxyethyl methacrylate were selected as model hydrogels. Hydrogels were characterized by SEM microscopy, porosity, communicating/non-communicating pore ratio, pore sizes and their distributions. The advantages and drawbacks of the methods of preparation, modification of hydrogel properties, reproducibility and issues related to their preparation are discussed. The most convenient method was preparation in presence of salts. One type of porous hydrogel was based on a hydrogel matrix composed of nanofibers prepared by electrospinning method. The nanofibers have shown unique properties due to their large specific surface. The least suitable method seems to be the preparation of porous hydrogels by polymerization using gas (nitrogen) releasing initiator, 2,2´-azobisisobutyronitrile. The use of prepared porous hydrogels is intended especially for scaffolds in tissue engineering.
Probing superficial and mechanical behaviors of nanosilica incorporated poly(acrylate) hybrid latexes
Authors: Chen Li , Wang Lifang , Yan Lili , Gu Yuansong , Chen Su
Published: August 2014

We reported the synthesis of nanosilica/poly(acrylate) (PA) core-shell hybrid latexes via emulsion polymerization with nanosilica as the core and acrylic copolymer as the shell. Firstly, the nanosilica was surface-functionalized with the coupling agent 3-aminopropyltriethoxysilane (APTS). Then the nanosilica tethered APTS (SIAP) further connected to acrylate monomer by covalent bond during emulsion polymerization, leading to the formation of nanocomposite PA latexes. The microstructures of obtained nanosilica/PA hybrids (SIAP/PA) were characterized by attenuated Total Reflection Fourier Transform Infrared (ATRFTIR), FT-IR imaging, transmission electron microscopy (TEM) and atomic force microscopy (AFM) in detail. The FT-IR imaging indicated the perfect compatibility between the core and the shell. Additionally, the properties of hybrid films were investigated by water contact angle analysis and mechanical property measurement. The SIAP/PA composites exhibit hydrophobic behavior, enhanced tensile strength (about 1.5 times) and high elongation (1262%).
Tensile behaviour of rubber-modified polyester resin materials
Authors: Munyati M.O. , Lovell P.A.
Published: August 2014

Polymer blends comprising an unsaturated polyester resin and dispersed particles were prepared. Rubbery particles were synthesized by sequential emulsion polymerization and had core-shell morphology. Curing of materials was carried out at ambient temperature and subsequently post cured at elevated temperatures to obtain materials of consistent properties. Materials made of different particle content were prepared and their tensile properties evaluated. Effect of matrix ductility was investigated by inclusion of ethyl acrylate in the polyester resin composition. Deformation mechanisms involved in these materials were examined using transmission electron microscopy (TEM) and real-time small angle X-ray spectroscopy (RT-SAXS). Incorporation of rubbery particles in the polyester resin was found to generally improve the tensile properties of the materials. Furthermore, the deformation mechanisms were found to involve cavitation/debonding processes as evidenced from stress whitening in the failed specimen and from real-time small angle X-ray scattering experiments.
Synthesis of UV-curable resin/ZnO composite films as pH buffering material
Authors: Yin Hui-En , Kuo Kuo-Huai , Chiu Wen-Yen
Published: August 2014

UV-curable Resin/ZnO composite film, which has advantages including UV-curable property and pH buffering ability, was prepared through incorporation of pre-made ZnO nanoparticles and UV-curable resin. The resins we used in this paper were R1 and R10. R1 was Bisphenol A epoxy diacrylate (EA) dissolved in propylene glycol monomethyl ether acetate (PGMEA), and R10 was synthesized by EA, pyromellitic dianhydride (PMDA) and 2-hydroxyethyl methacrylate (HEMA), and then followed by characterization using FTIR and GPC. The ZnO nanoparticles were prepared from Zinc acetate and Sodium hydroxide in 1-butanol by hydrothermal method. “Physical Adsorption” and “Mixture Coating” were two ways to prepare the Resin/ZnO composite film. Then, the pH buffering ability of the Resin/ZnO composite film was evaluated by soaking the film in the pH4 or pH10 solution, and the variation of pH value was recorded with time. The result shows that F10/ZnO composite film obtained from R10/ZnO by “Physical Adsorption” method could be a good buffering material to justify either pH4 or pH10 solution to pH7.4 in 5 min and F10/ZnO composite film by “Mixture Coating” method could be a long time pH buffering material.
Effect of marble particle size and gamma irradiation on mechanical properties of polymer concrete
Authors: Martínez-Barrera Gonzalo , Brostow Witold
Published: August 2014

Effects of gamma radiation and the marble particle size on compressive properties and the dynamic elastic modulus of polymer concretes (PCs) were studied. The PCs had a composition of 30 % of unsaturated polyester resin and 70 wt. % of marble as aggregate. Different types of PC were developed with the combination of one, two or three marble-particle sizes. The materials were submitted to 5, 10, 50, 100 and 150 kGy of radiation doses. Both the compressive properties and the dynamic elastic modulus values depend on the combination of the marble-particle sizes and the applied radiation dose. Higher numbers of dispersed particles per unit volume provide more resistance to crack propagation. On the other hand, longer particles give more reinforcement. As a result of these two competing effects, medium size marble particles provide the highest compression modulus
Fabrication and characterization of collagen (shell) /thermoplastic polyurethane (core) composite nanofibers by coaxial electrospinning
Authors: Chen Rui , Qiang Li Xiao , Ke Qin Fei , He Chuang Long , Mo Xiu Mei
Published: August 2014

Coaxial-electrospinning is a new method used in tissue engineering and drug delivery field. It can spin nanofibers with shell-core structure through electrospinning of two polymer solutions. In this study, collagen was used as the outer layer or the shell and thermoplastic polyurethane (TPU) was used as the inner layers or the core. A series of tests were conducted to characterize the compound nanofiber and its membrane. Morphology and microscopy of the ultrafine fibers were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), whereas the fiber diameter distribution was understood using image visualization software (ImageJ) and measurements of solution viscosity and conductivity. Mechanical measurements were carried out by applying tensile test loads to samples which were prepared from electrospun ultra fine non-woven fiber mats. The results demonstrated that these composite nanofibers had the characters of native extracellular matrix and they could be designed as the scaffold for tissue engineering and functional biomaterials.
Flexible plasticized PLA with high crystallinity obtained by controlling the annealing temperature
Authors: Ran Xiang-Hai , Jia Zhi-Yuan , Yang Yu-Ming , Dong Li-Song
Published: August 2014

In this study, plasticized polylactide (PLA) was prepared by blending PLA with high stereoregularity and poly(ethylene glycol-co-propylene glycol) (PEPG) in a batch wise mixer and pressed into films. The influence of annealing temperature on the thermal properties and tensile properties of quenched plasticized PLA was investigated by DSC, DMA and tensile tests. It was found that plasticized PLA after cold crystallization can keep its high flexibility with an elongation at break over 300% by choosing a proper annealing temperature. The difference of crystallization morphology formed at the different annealing temperature was thought as a possible reason for this result.
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

Chitosan 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

The 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

In 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

2-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

In 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

A 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

Intelligent 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

We 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

The 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

Electrically 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

Anion 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

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

In 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

Structurally 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

Experimentally, 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

Poly(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

Present 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

The 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

Physical 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

Three 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.