bluuebunny/crossref_metadata_2025 huggingface dataset:
Water-Flooding Fluid Diversion Copolymeric Microsphere Prepared by Inverse Suspension Polymerization
Authors: Zhiyu Huang , Hongsheng Lu , Tailiang Zhang
Published: August 2014

In order to enhance oil recovery in high-temperature and high-salinity oil reservoirs, the copolymeric microspheres containing acrylamide (AM), acrylonitrile (AN) and AMPS was synthesized by inverse suspension polymerization. The copolymeric microsphere was very uniform and the size could be changed according to the condition of polymerization. The lab-scale studies showed that the copolymeric microsphere exhibit good salt-tolerance and thermal-stability when immersed in 20×105 mg/L NaCl(or KCl) solution, 7500 mg/L CaCl2 (or MgCl2) solution or 2000 mg/L FeCl3 solution, respectively. The copolymeric microsphere showed satisfactory absorbency rates. The sand-pipes experiments confirmed that the average toughness index was 1.059. It could enhance the oil recovery by about 3% compared with the corresponding irregular copolymeric particle.
Analysis of Water Adsorption on Chitosan and Its Blends with Hydroxypropylcellulose
Authors: Mucha Maria , Wańkowicz Kazimierz , Balcerzak Jacek
Published: August 2014

Chitosan (CH) and hydroxypropylcellulose (HPC) adsorb water easily by hydrogen bonds formed with hydroxyl and amide groups present in their structures. Heat of adsorption is a thermodynamic parameter which is used to estimate the type of adsorbate molecule bond on a solid surface, among the others. Adsorption of water from vapour phase on chitosan, hydroxypropylcellulose and blends of both biopolymers in the form of films were carried out. Isotherms of water adsorption in the samples were described by the GAB equation. Correlations between mass fraction of chitosan in the sample (wf) and the values of GAB coefficients were obtained. From parameter c in the GAB equation mean heat of adsorption of the first monomolecular layer of water molecules E1, and pure molar heat of adsorption q were determined.
On the use of hyperbranched aramids as support of Pt nanoparticles
Authors: Monticelli Orietta , Chincarini Andrea
Published: August 2014

A hyperbranched (HB) aromatic polyamide (aramid) synthesized from A2 (p-phenylenediamine) + B3 (trimesic acid) reactants has been used as Pt nanoparticle support. TEM measurements verified the possibility to obtain a high metallic dispersion (MD) using H2PtCl6 as metal precursor. The amount of Pt retained by the polymer support turned out to be lower than the Pd loading deposited on the same HB aramid from a different metal precursor, i.e. PdCl2, under the same exchange and reduction conditions, namely by the procedure reported in a previous paper of ours [1]. Moreover, Pt nanoparticle diameters have been found to depend on the reducing agent used. As compared to bubbling H2, NaBH4 allowed obtaining of metal particles characterized by smaller dimensions.
Comparison Of Reaction Pathway And Product Analysis For Hydroxyalkylation Of Parabanic Acid With Oxiranes And Alkylene Carbonates
Authors: Zarzyka-Niemiec Iwona
Published: August 2014

Reactions of parabanic acid (PA) with ethylene and propylene oxides and carbonates lead to oligomeric products with hydroxyalkyl groups in both cases. The parabanic acid ring undergoes scissions during reactions depending on kind of reagent and reaction conditions. In some cases the trioxoimidazolidine ring remains untouched. Using the MALDI ToF technique the product analysis was performed. The by-products were determined quantitatively by GC. The thermostability of oligomeric products was also determined.
Poly(methyl acrylate) plus Mesoporous Silica Nanohybrids: Mechanical and Thermophysical Properties
Authors: Pérez León D. , Giraldo Luis F. , Brostow Witold , López Betty L.
Published: August 2014

A mesoporous silica MCM-48 is used as a reinforcement agent for poly(methyl acrylate) (PMA). Methyl acrylate is introduced into the mesoporous silica that has an interconnected porous structure, allowing monomer diffusion into the pores before the polymerization reaction. In order to improve the silica plus polymer adhesion and to decrease the silica agglomeration, the silanol groups of the silica are functionalized with methyl groups without decreasing significantly the pore size. The silica is characterized by nitrogen adsorption, scanning electronic microscopy (SEM) and infrared (IR) spectroscopy. The nanohybrids so obtained are analyzed by tensile testing, thermogravimetry (TGA), differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA). The highest improvement of mechanical and thermophysical properties is achieved for nanohybrids containing 5 wt. % mesoporous silica. At 10 % silica, agglomeration of the filler takes place and the dispersed phase is less effective in reinforcing the polymer matrix.
Molten Salt as a Green Reaction Medium: Synthesis of Polyureas Containing 4-phenylurazole Moiety in the Main Chain in the Presence of Tetrabutylammonium bromide as an Ionic Liquid
Authors: Mallakpour Shadpour , Dinari Mohammad
Published: August 2014

Ionic Liquids (IL)s have been generating increased interest over the last decade. ILs were initially introduced as an alternative green reaction media because of their unique chemical and physical properties of nonvolatility, nonflammability, thermal stability, and controlled miscibility. The step-growth polymerization reactions of 4-phenylurazole (PHU) with various diisocyanates such as hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), and toluylene-2,4-diisocyanate (TDI) were performed in the presence of tetrabutylammonium bromide (TBAB) as a reaction medium with or without dibutyltin dilurate (DBTDL) as a catalyst. The polymerization reaction gave similar results in the presence or absence of DBTDL, indicating that, the catalyst is not needed in this process. The resulting polyureas showed high yields and moderate inherent viscosities in a range of 0.23-0.29 dL/g in N,N-dimethylformamide (DMF) at 25 °C and they are soluble in most polar aprotic organic solvents. This method was compared with the polymerization reaction in conventional solvent such as, N,N-dimethylacetamide (DMAc). In the case of using TBAB, higher yields and inherent viscosities were obtained. All of the above polymers were characterized by FT-IR and thermogravimetric analysis (TGA).
Synthesis, characterization and properties of polymers containing simultaneously the imine and amide moieties.
Authors: Sánchez Christian , Bustos Carlos , Alvarado Fabiola , Schott Eduardo , Gatica Nicolas , Bernede Jean-Christian
Published: August 2014

We present the synthesis of polymers by means of self-condensation of ethyl 3-aminophenyl acetate, using HCl as catalyst at high temperature and reduced pressure. This polymer was fractionated by successive precipitation from mixtures of methanol/diethylether of different polarity, yielding three polymeric fractions: Poly A, Poly B and Poly C. Likewise, under the same conditions, 3- aminophenyl acetic acid yields only one polymeric fraction, Poly D. These polymers were characterized by elemental analysis, IR and, in some cases, by 1H-NMR and X-Ray Photoelectron Spectroscopy (XPS). The obtained results show that polymers can be classified as hybrid materials, because in the backbone, they contain simultaneously the amide and imine groups and, at the end of the chain, they have amine and carboxylic acid functions. High solubility of some of these polymers in DMF or methanol has permitted the determination of viscosities and the preparation of films. Poly B and Poly C films exhibit amorphous morphology; and Poly D display spherullitic-type semi-crystallization pattern. The polymers can absorb solvents and they can swell up forming large-sized gels in DMF and methanol. Besides these polymers have high thermal stability that reaches a weight loss of 11.60% at 353 °C.
Gas sensing property of a conducting copolymer
Authors: Ak Metin , Yigitsoy Basak , Yagci Yusuf , Toppare Levent
Published: August 2014

A bifunctional amido thiophene, namely hexamethylene (bis-3-thiophene acetamide) (HMTA) was synthesized and its copolymer with pyrrole was electrochemically prepared in water/PTSA solvent/electrolyte medium. Sensory behavior of this copolymer against ammonia, methanol, dichloromethane (DCM) and n-hexane vapors was investigated. The methanol vapor, which can form hydrogen bonds with the polar groups on the copolymer surface, showed the maximum response. DCM, which is less polar, yielded relatively lower response than methanol. Hexane, being the non-polar vapor, showed the lowest response.
Mechanism of sintering of polyoxymethylene powders investigated by small-angle X-ray scattering
Authors: Sixou Bruno , Jebawi Kassem Al , Seguela Roland , Vigier Gérard
Published: August 2014

The structural reorganization of polyoxymethylene powders during sintering has been investigated through a detailed analysis of the SAXS data in order to determine the origin of the mechanical property improvement with regard to the compression-moulded counterpart. Two approaches afford a quantitative evaluation of the structural parameter evolutions. On one hand, the correlation and interface distribution functions were calculated for the samples submitted to various thermo-mechanical treatments. On the other hand, the Hosemann’s paracrystalline model modified with Reinhold distributions of the crystal and amorphous phase thicknesses was used to evaluate the disorder in the lamella stacking. Both approaches suggest that a more perfect and regular crystalline structure with thicker and wider crystals develops in the sintered samples as compared with the parent powders and the material crystallized from the melt. Theses morphological modifications are discussed in relation to the very high stiffness and brittleness of the sintered materials. Two possible mechanisms of coalescence of the powder grains via the crystalline phase are proposed to account for these specific mechanical properties of the sintered materials.
High temperature reaction between poly(glycolic acid) and ε-caprolactone in ionic liquids
Authors: Dali Souad , Lefebvre Hervé , Gharbi Rachid El , Fradet Alain
Published: August 2014

ε-Caprolactone (CL) was reacted with PGA oligomers in ionic liquids in the presence of Ti(OBu)4, both ring-opening polymerization initiator and polyesterification catalyst. 1H and 13C NMR studies showed that the fast polymerization of CL was followed by simultaneous slow polyesterification and ester-interchange reactions leading to random PGA/CL copolyesters after 6 h reaction. The nature of the catalyst and the ionic liquid did not influence much reaction rate. Hydroxyacetyl end-groups appeared to be much less reactive than the corresponding hydroxycaproyl end-groups, which were consumed at the beginning of reaction. The 50/50 and 60/40 oxyacetyl (G)/oxycaproyl (L) (mass-%) copolyesters were amorphous, while copolyesters containing larger amounts of G units were semi-crystalline. The variations of the Tg of all copolyesters versus composition follow the Flory-Fox law.
Rheological Properties of Calcium Carbonate-Epoxidized Natural Rubber Composites Prepared In Latex State
Authors: Lohakul A. , Kaesaman A. , Rungvichaniwat A. , Nakason C.
Published: August 2014

Epoxidized natural rubber was prepared by performic acid epoxidation. It was then blended with calcium carbonate dispersion in latex state, which was later coagulated and dried. Rheological properties in terms of Mooney viscosity and shear flow properties were determined. We found that at a given shear rate, the Mooney viscosities, shear stress and shear viscosity increased with increasing levels of epoxide groups in the ENR molecules and increasing loading levels as well as decreasing particle sizes of CaCO3. This is attributed to increased level of chemical interaction between polar functional groups in the ENR molecules with increase in the epoxide content. This gives rise to greater chemical interaction between the ENR and CaCO3 interface upon increase in amount of CaCO3. Greater surface areas of the smaller filler particles also caused higher chemical interaction between difference phases.
Copolymerization of two bromine containing methacrylate monomers with methylmethacrylate. Determination of reactivity ratios by in situ quantitative 1H NMR monitoring
Authors: Cameliu Ichim Ionut , Rusu Marius Ciprian , Rusu Mihai , Marcel Popa , Delaite Christelle , Riess Gerard
Published: August 2014

An important method used to make medical implants radiologically visible is based on introduction of radiopaque bromine or iodine containing methacrylic monomers. Thus, 2-(2-bromopropionyloxy) propyl methacrylate (BPPM) and 2-(2-bromoisobutyryloxy) propyl methacrylate (BIPM) were synthesized with the aim to use them as radiopaque agents. The free radical initiated copolymerization of BPPM and BIPM with methyl methacrylate (MMA) were performed directly in a thermostatic cell of the NMR spectrometer. The copolymer compositions obtained from 1H NMR spectra led to the determination of the reactivity ratios (rMMA = 1.08 ± 0.12; rBPPM = 1.01 ± 0.13 and rMMA = 0.95 ± 0.09; rBIPM = 0.95 ± 0.1). The reactivity ratios of these two monomers is similar to that of MMA suggesting that the length of the bromine containing monomers side chain does not affect significantly the reactivity of the methacrylic double bond. From the results we conclude the copolymers to have random structure.
Structure and properties of styrene-butadiene rubber/ pristine clay nanocomposites prepared by latex compounding method
Authors: Abdollahi Mahdi , Rahmatpour Ali , Aalaie Jamal , Khanli Homayon Hossein
Published: August 2014

Styrene- butadiene rubber (SBR)/ clay nanocomposites were prepared by mixing the SBR latex with aqueous clay dispersion and co-coagulating the mixture. Tapping mode AFM and XRD were applied to characterize the structure of nanocomposites. It was found that fully exfoliated structure could be obtained by this method only when the low loading of layered silicate (< 10 phr) is used. With increasing the clay content, both non-exfoliated (stacked layers) and exfoliated structures can be observed simultaneously in the nanocomposites. The results of mechanical tests on the vulcanized pure SBR and SBR/ clay nanocomposites showed that the nanocomposites presents better mechanical properties than clayfree SBR vulcanizate. Furthermore, initial modulus, tensile strength, tensile strain at break, hardness (shore A) and tear strength increased with increasing the clay content, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/ clay nanocomposites. Compared to the clay free SBR vulcanizate, the nanocomposite vulcanizates exhibit a lower tanδ peak value, higher storage modulus and higher tanδ value at the rubbery region (0-60 °C) which indicate that the elastic responses of pure SBR towards deformation are strongly influenced by the presence of nanodisperced natural sodium montmorillonite layers especially completely exfoliated silicate layers.
Preparation of highly stable polypyrrole dispersions in the mixed aqueous solution of sodium dodecyl sulfate and polyvinyl pyrrolidone
Authors: Shuangxi Xing , Guoku Zhao
Published: August 2014

Polypyrrole (PPy) dispersions with high stability were prepared in the mixed aqueous solution comprising an anionic surfactant (sodium dodecyl sulfate, SDS) and a polymeric stabilizer (polyvinyl pyrrolidone, PVP). By choosing proper mass ratios of the surfactant to the monomer, stable dispersions could be obtained owing to the interaction between the two components. The structure, morphology, stability, particle size, polydispersity index and conductivity of the samples obtained from different conditions were investigated. The PPy dispersions prepared from mixed aqueous solutions were much more stable than those from single component solution.
Preparation of (tri-isopropoxidesilane)-acrylate latex and the properties of its film formed in room temperature
Authors: Xi Chen , Tianying Guo , Guang jie Hao , Moudao Song , Banghua Zhang
Published: August 2014

The vinyl (tri-isopropoxide silane)-co-methyl methacrylate-co-n-butyl acrylate-co-styrene latex was prepared by emulsion polymerization. The crosslinked structure was formed in the copolymer latex film and the crosslinking degree of the copolymer latex film increases with the increasing vinyl triisopropoxide silane content. The tensile stress and water repellent property were also strengthened, when the vinyl tri-isopropoxide silane was introduced into the copolymer latex film.
Polymer Characterization by Electrospray-Mass- Spectrometry – shifting the upper mass limit
Authors: Kehr Seda , Luftmann Heinrich
Published: August 2014

The described approach allows the determination of homopolymer characteristics from complex electrospray mass spectra of multicharged ions in the range of 5000 to 20000. It makes mass spectrometric characterizations possible where compounds are fragmented under MALDI conditions. The determination is accomplished by simulation of the observed complex mass spectra with an Excel based computer program (PolyCalc). The parameters molecular weight (M), reduced sum of end groups (EG), mean molecular weights and polydispersity (Mn, Mw, PDI) are obtained by recursive iteration.
Temperature-responsive hydrogels containing new LCST methacrylate macromonomers
Authors: Korytkowska-Wałach Anna , Porwoł Anna , Gibas Mirosław
Published: August 2014

A series of hydrogels were synthesized: homopolymers of new temperature-sensitive methacrylate macromonomers of ether-ester structure, derived from monomethacrylate of tetraethylene glycol via Michael-type addition - oligo(TTEGMMA), and copolymers of oligo(TTEGMMA) with N-isopropylacrylamide (NIPAAm) or 2-hydroxyethyl methacrylate (HEMA). Hydrogels based on oligo(TTEGMMA) demonstrate broad volume phase transition. Combination of oligo(TTEGMMA) with NIPAAm or HEMA yielded hydrogels having narrower phase transition and lower gel transition temperature (LGTT) up to 43 °C at the most, which is in the range of interest for most biomedical applications.
Preparation of azobenzene-terminated polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization
Authors: Wan Xiaoming , Zhang Zhengbiao , Zhu Xiulin , Zhu Jian , Cheng Zhenping
Published: August 2014

Three azobenzene-based dithiocarbamates, 2-(phenylazo-phenoxycarbonyl) prop-2-yl 9H-carbazole-9-carbodithioate (APCDT), 2-(4-nitro-phenylazophenoxy- carbonyl)prop-2-yl 9H-carbazole-9-carbodithioate (ANPCDT), 2-(4-cyanophenylazo- phenoxy-carbonyl)pro-2-yl 9H-carbazole-9-carbodithioate (ACPCDT), were synthesized and used as RAFT agents in the polymerizations of styrene (St) and methyl methacrylate (MMA). The results showed that APCDT, ACPCDT and ANPCDT were effective RAFT agents for the polymerization of St. In the case of MMA, the polymerization showed hybrid behavior. The different substitutes on azobenzene moiety in dithiocarbamates did not show obvious influence on the controllability of the polymerizations. The UV and fluorescence spectra of RAFT agents and obtained azobenzene-terminated polymers were investigated
Synthesis of poly(methyl methacrylate)-b-poly(acrylic acid) by DPE method
Authors: Chen Dong , Liu Ruixue , Fu Zhifeng , Shi Yan
Published: August 2014

Amphiphilic diblock copolymer poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) was prepared by 1,1-diphenylethene (DPE) method. Firstly, free radical polymerization of methyl methacrylate was carried out with AIBN as initiator in the presence of DPE, giving a DPE-containing PMMA precursor with controlled molecular weight. tert-Butyl acrylate (tBA) was then polymerized in the presence of the PMMA precursor, and PMMA-b-PtBA diblock copolymer with controlled molecular weight was prepared. Finally, amphiphilic diblock copolymer PMMA-b-PAA was obtained by hydrolysis of PMMA-b-PtBA. The formation of PMMA-b-PAA was confirmed by 1H NMR spectrum and gel permeation chromatography. Transmission electron microscopy and dynamic light scattering were used to detect the self-assembly behavior of the amphiphilic diblock polymers in methanol.
Chitosan based antimicrobial films for food packaging applications
Authors: Tripathi Shipra , Mehrotra G. K. , Dutta P. K.
Published: August 2014

Antimicrobial packaging is one of the most promising active packaging systems. Antimicrobial packaging is the packaging system that is able to kill or inhibit spoilage and pathogenic microorganisms that are contaminating foods. A tremendous effort has been made over the last decade to develop and test films with antimicrobial properties to improve food safety and shelf life. For food preservation, chitosan films are very effective. Chitosan has widely been used in antimicrobial films, to provide edible protective coating, dipping and spraying for the food products due to its antimicrobial properties. Chitosan can be formed into fibers, films, gels, sponges, beads or nanoparticles. Chitosan films have been used as a packaging material for the quality preservation of a variety of food. Chitosan has great potential for a wide range of applications due to its biodegradability, biocompatibility, antimicrobial activity, non-toxicity and versatile chemical and physical properties. The present review outlines the preparation and antimicrobial activity of chitosan based films.
Bovine serum albumin imprinted calcium phosphate /polyacrylate/alginate multi-hybrid polymer microspheres in inverse-phase suspension
Authors: Zhao Kong Yin , Kan Bo Hong , Wei Jun Fu , Cheng Guo Xiang , Chen Li
Published: August 2014

Macromolecularly imprinted calcium phosphate/polyacrylate/alginate (CP/PA/A) multi-hybrid polymer microspheres with the surface and embedded imprinting of bovine serum albumin were prepared with sodium alginate (SA), (NH4)2HPO4 and sodium polyacrylate (SPA) by using CaCl2 as gelling agent in inverse-phase suspension. Infrared spectrum analysis demonstrated that multihybrid components were produced in the microspheres. Rebinding dynamic of both imprinted microspheres proved a higher BSA rebinding relative to those nonimprinted ones. The specific surface area of CP/PA/A microspheres increased when compared with non-imprinted ones. The specific rebinding peak and imprinting efficiency cross point have appeared in rebinding dynamic curves, which showed remarkable difference in rebinding behaviours between surface and embedding imprinted microspheres.
Second Order Nonlinear Optical Properties of Multifunctional Chiral Azobenzene Polymers
Authors: Angiolini Luigi , Benelli Tiziana , Bozio Renato , Cozzuol Matteo , Giorgini Loris , Pedron Danilo , Salatelli Elisabetta
Published: August 2014

Corona poling behaviours of optically active photochromic copolymers derived from methyl methacrylate (MMA) and the methacrylic ester of (S)-3- hydroxy pyrrolidine linked through the nitrogen atom to the highly conjugated photochromic 4'-(β-cyano-β-(methylsulfonyl)vinyl)-4-azobenzene moiety, have been investigated with the aim to evaluate the effect on the non-linear optical (NLO) properties originated by the presence of inactive side-chain MMA groups along the main chain. The NLO properties of in situ corona poled polymeric films have been studied by second harmonic generation (SHG) measurements. The d33 values of the investigated polymers were determined to be in the range 10-86 pm/V after corona poling. The temporal and thermal stability of the optimal SHG signals obtained after corona poling process of all the macromolecular materials has been investigated and compared. The results indicate that the maximum of these properties can be obtained at a molar content of photochromic units around 20- 40%.
Novel blocked mercaptosilane (3-propionylthio-1- propyltrimethoxylsilane) for natural rubber/silica composite reinforcement in various curing systems
Authors: Peng Hualong , Liu Lan , Luo Yuanfang , Jia Demin , Fu Weiwen
Published: August 2014

In present work, the effect of novel blocked mercaptosilane(3- propionylthio-1-propyltrimethoxylsilane) (called hereafter PXT) on structure and dynamic mechanical properties of natural rubber/silica (NR/silica) composites was studied in efficient, semi-efficient and conventional vulcanization systems. Equilibrium swelling method investigation indicates that PXT is able to enhance crosslinking density of composites. The investigation of properties shows that PXT can strengthen the reinforcement of silica for NR vulcanizates and substantially enhance the resistance to flex cracking and abrasion of NR/silica composites. Since PXT possess two functionally active end groups which can chemically react with both silica and rubber, at 2 phr of the PXT content, NR/silica composites possess optimum comprehensive dynamic mechanical properties.
Fine structure and physical properties of poly(butylene terephthalate) sheets prepared by roll drawing
Authors: Lee Sunhee , Nakayama Kazuo , Cho Hyunhok
Published: August 2014

PBT sheets were extruded from T-die using a single extruder and were winded by a take-up roller controlled at 50°C and with speed at 1.2 m/min. Oriented PBT sheets were prepared with various winding roll speeds at 3.6, 4.8 and 6.0 m/min. Fine structure and physical properties of PBT sheets thus obtained were investigated by measuring the molecular orientation, crystal structure, dynamic visco-elasticity, thermal and mechanical properties, sonic modulus, etc. PBT melts were found to be readily crystallizable in the sheet. In the case of roll drawing, the DRmax of PBT sheet was 5. The PBT sheets prepared from winding speed at 6 m/min showed polymorphism of both α- and β-form crystallites with crystallinity of about 24%. In the tri-directional WAXD patterns, the PBT sheets by the roll drawing method turned out to be oriented in the uniplanar-axial form. For the roll drawn PBT sheets with various winding speeds, large orientation effects were observed in the winding direction together with improved thermal and mechanical properties.
Cerium oxide hollow nanospheres prepared by polymermonomer self-assembly
Authors: Gao Yongyi , Ding Xiaobin , Zheng Zhaohui , Peng Yuxing
Published: August 2014

In this paper, cerium oxide hollow nanospheres have been prepared via a polymer-monomer self-assembly route; it may be possible to extend this approach to fabricate other metal oxide hollow nanospheres. In this method, cerium oxide hollow nanospheres were fabricated by calcining hollow polymer spheres which were prepared via addition of ceric ammonium nitrate (CAN) into self-assembled micelles which were prepared through dissolving chitosan (CS) in methacrylic acid (MAA) solution.
Polymer-silica hybrids latexes dyed with Rhodamine B
Authors: Nistor Cristina Lavinia , Donescu Dan , Purcar Violeta , Petcu Cristian , Serban Sever , Ghiurea Marius , Corobea Mihai Cosmin
Published: August 2014

Synthesis of latexes based on polystyrene (PSt) and polybutylacrylate (PBuA) dyed with Rhodamine B (RhB), by polymerization in ternary microemulsions, is discussed in this paper. Silica was generated through the solgel process of methacryloxypropyl-trimethoxysilane (MPTS) and glycidyloxypropyltrimethoxysilane (GMPS). MPTS copolymerizes, through its double bounds, with St or BuA. GMPS can form covalent bonds with RhB by opening of the oxyranic cycle. The smallest average diameter of the particles was obtained for latexes prepared with MPTS+GMPS couple. Latexes with RhB prepared in the presence of an organophilic layered silicate (Cloisite 20 A) were used for comparing the influence of the inorganic fillers on microemulsion properties. By St and BuA copolymerization with MPTS hybrids which can react by sol-gel process with GMPS, a coupling agent for RhB, were prepared. By using RhB as molecular sample, polarity modifications for polymer-inorganic latexes were put in evidence.
Fabrication and electrical conducting behavior of carbon nanofiber reinforced high-density polyethylene/ polystyrene nanocomposites with low percolation threshold
Authors: Liang Guodong , Bao Suping , Tjong Sie Chin
Published: August 2014

Ternary high-density polyethylene/polystyrene/carbon nanofiber nano composites were fabricated by melt-compounding. The effect of melt compounding sequences on electrical conducting behavior of such composites was examined. Two compounding sequences were adopted in this study. Route I consisted of an initial melt mixing of HDPE and PS, followed by blending with CNFs. Route II involved an initial formation of the PS/CNF master batch, followed by blending with HDPE. The results showed that CNFs were dispersed in HDPE phase of Route I prepared HDPE/PS/CNF nanocomposites whilst they resided in PS phase of Route II formed nanocomposites. Electrical measurement showed that Route II prepared nanocomposites had a low percolation concentration of 1.1 vol% CNF.
Synthesis and characterization of novel β-cyclodextrin cored poly(α-caprolactone)s by anionic ring opening polymerization
Authors: Guo Yingzhi , Yu Changjiang , Gu Zhongwei
Published: August 2014

By anionic ring opening polymerization initiated by cyclodextrin oxyanions generated from NaH and β-cyclodextrin(β-CD), novel biodegradable β- CD cored star-shaped poly(ε-caprolactone)s (s-PCLs) were synthesized and then characterized by means of FTIR, GPC, 1H-NMR. The effects of different feed molar ratios of NaH and β-CD on arm number and on the molecular weight of s-PCLs, and the relationship between the polymerization time and monomer conversion were investigated. Moreover, the physical properties of linear PCL (l-PCL) and s- PCLs with similar molecular weights but different arm number were studied and compared by DSC, SEM and intrinsic viscosity measurement, respectively. It was found that the feed molar ratio of NaH and β-CD is an important factor which influences both the molecular weight and arm number. The melting points and intrinsic viscosities of s-PCLs with similar molecular weights were lower than that of l-PCL, and were found to decrease with increasing arm number. Both SEM and AFM showed that the surface morphology of s-PCL films was different from that of l-PCL. These results indicated that s-PCL with different arms and physical properties could be synthesized using just a β-CD core by adjusting the feed molar ratio of NaH and β-CD
Mechanical behavior of high impact polystyrene based on SB copolymers as a function of synthesis conditions: Part II
Authors: Díaz de León Ramón , Morales Graciela , Acuña Pablo , Soriano Florentino
Published: August 2014

The mechanical properties of different high impact polystyrene (HIPS) were determined by means of impact and tensile tests. Impact strength (IS), yield stress (σy) and Young’s modulus (E) were evaluated as a function of the rubber phase morphological features such as type and particle size (Dp), volume fraction (Φ) and interparticle distance (IPD). In order to evaluate the changes produced in the rubber phase, the initiator, chain transfer agent (CTA), and type and concentration of SB copolymer were varied during the synthesis of HIPS. Transmission electron microscopy was used to analyze the materials’ morphology and the data obtained reveal that the Dp and Φ increases mainly with an increase in the PB content and/or with the use of CTA and decreases with an increase in initiator concentration. In addition, E and yield stress diminishes when increasing the dimensions of the rubber phase (Dp and Φ), contrary to the IS. The IPD/Dp ratio also indicates the dependency of the mechanical properties with respect to the rubber phase features. An increase in IPD/Dp provokes an increases in E and σy, whereas IS diminishes.
Chemical modification of poly(vinylacetylene) via click reaction
Authors: Fengling Qing , Rongxing Yao , Lianjun Wang , Hongqi Li , Weidong Meng
Published: August 2014

Chemical modification of poly(vinylacetylene) (PVacet) was performed through click reactions by which alkyl and fluoroalkyl groups were introduced to the pendent terminal alkynes of PVacet. Novel polymers containing 1,2,3-triazoles were consequently obtained and their structures and properties were characterized by FT-IR, 1H NMR, TGA, DSC and GPC. The polymers modified by alkyl groups had good solubility, thermal stability and reasonable molecular weights. It was also demonstrated that the properties of fluorine-containing polymers were affected by fluorine atoms with hydrophobic and chemical proof properties
Synthesis and characterization of star and brush grafted polysiloxanes, obtained by atom transfer radical polymerization
Authors: Hurduc Nicolae , Sandu Viorel , Ibanescu Constanta , Nor Iulian
Published: August 2014

Star- and brush-polysiloxanes were synthesized via living radical polymerization using two different catalytic systems. The new compounds were characterized by 1H-NMR, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) techniques. CuCl and 2,2’-bipyridyl proved to be the most efficient catalytic system. The type of catalytic system and the reaction conditions control the number of arms for star polymers or the grafted-chain density for brush polymers. The use of chloromethyl styrene as monomer or co-monomer yields homogeneous star- or brush-polysiloxanes, although chloromethyl styrene is an inimer system. The homogeneity of materials was verified by GPC and DSC (TOPEM) methods. For linear grafted polysiloxanes the molecular simulations reflect a tendency of chains to adopt globular conformation for high values of the branching density. The polysiloxanes grafted with styrene/chloromethyl styrene were modified with azobenzene in order to obtain systems able to react to the light stimuli. Rheological behavior of the polymer solutions were evaluated before and after irradiation with UV light. After the UV irradiation a significant viscosity increase was evidenced
Uv-Vis investigations on ion beam irradiated polycarbonate
Authors: Chipara Mircea , Chipara Magdalena Dorina
Published: August 2014

UV-VIS investigations on polycarbonate irradiated with accelerated U ions are reported. The experimental data are consistent with the decrease of the energy gap due to irradiation and indicate the formation of isolated conjugated structures. The relatively weak decrease of the energy gap and the shape of the electron spin resonance lines indicate that the conjugated structures are isolated within the polymeric matrix
Characterization and optical properties of a novel conjugated polynitrile produced by plasma polymerization
Authors: Zhao Xiong-Yan
Published: August 2014

A novel conjugated polynitrile thin film, plasma-polymerized 3- quinolinecarbonitrile (PP3QCN) thin film was prepared by plasma polymerization of 3-quinolinecarbonitrile. Fourier transform infrared (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), and X-ray photoelectron spectroscopy (XPS) studies revealed that extensively conjugated C=N double bonds were formed in the deposited plasma film and the plasma polymerization of 3-quinolinecarbonitrile took place mainly through the opening of the π bonds of C ≡ N functional group under our experimental conditions. Plasma-polymerized 3-quinolinecarbonitrile thin film shows a blue emission with relatively high photoluminescence (PL) intensity at about 475 nm wavelength. The fabricated devices with PP3QCN as electroluminescent layer sandwiched between Indium Tin Oxides (ITO) and aluminium (Al) were also found to show a blue emission.
Poly(aniline)/poly(methylmethacrylate) films obtained from waterborne latex nanoparticles
Authors: Oliveira Melo Luciana , Ponzio Eduardo A. , Carmona-Ribeiro Ana M. , Torresi Roberto M.
Published: August 2014

This paper presents the characterization of poly(aniline) (PANI) and poly(methyl methacrylate) (PMMA) coatings obtained by mixing PANI with PMMA aqueous dispersions (latex particles). These dispersions were characterized by using dynamic light scattering for sizing, zeta-potential analysis and thermal analysis. PMMA and PANI/PMMA dispersions show negative charged particles with zeta potential greater than |40| mV, a zeta-average diameter of 64 nm for pure PMMA and a bi-modal particle-size distribution centered at 45 and 120 nm for a mixture with 25% w/w of PANI. Films obtained by casting were characterized by using scanning electron microscopy and they show a conductivity increase upon PANI content reaching a value of 1 mS cm-1 for a film with 25% w/w of PANI. In addition, Raman spectroscopy have shown the presence of the conducting form of PANI in the films and cyclic voltammetry experiments corroborated that they are electroactive in both acid and neutral solutions.
Controlling the phase morphology of immiscible poly(2,6- dimethyl-1,4-phenylene ether)/poly(styrene-co-acrylonitrile) blends via addition of polystyrene
Authors: Göldel Andreas , Ruckdäschel Holger , Müller Axel H.E. , Pötschke Petra , Altstädt Volker
Published: August 2014

The microstructure of melt-processed, immiscible poly(2,6-dimethyl-1,4- phenylene ether)/poly(styrene-co-acrylonitrile) blends (PPE/SAN) was controlled by systematically adjusting the viscosity ratio between both phases. For this purpose, low-viscous polystyrene (PS) was added as a third component, as it shows selective miscibility with PPE and thus allows the varying of the shear viscosity of PPE over a broad range. In order to theoretically predict the phase morphology, a model following Utracki was applied taking into account the viscosity ratio and the respective volume contents of each phase. Detailed transmission electron microscopic investigations of the blend morphologies demonstrated excellent agreement with theory. Moreover, quantitative evaluation of the observed microstructures allowed further description of the degree of blend co-continuity. Thus, desirable compositions of the ternary blend systems could be identified which potentially show enhanced properties such as a high heat deflection temperature, an elevated strength, stiffness, and ease of processing. Finally, a optimum (PPE/PS)/SAN blend system that has been optimised regarding the aforementioned properties was compatibilized by polystyrene-b-poly(1,4-butadiene)-b-poly(methyl methacrylate) triblock terpolymers. Due to the interfacial enrichment of the block copolymer, nanostructured blend morphologies were observed. In the view of these results, pathways to control both the micro- and the nanostructure of PPE/SAN blends are derived, potentially useful to enhance the mechanical as well as thermomechanical property profile.
Study on the effect of galbanic acid on photo-oxidative degradation of linear low density polyethylene (LLDPE) films
Authors: Jahanmardi Reza , Assempour Homa
Published: August 2014

Photo-oxidative degradation of LLDPE films (~ 250 μm thick) containing varying amounts of galbanic acid (a type of coumarin derivatives) was investigated by exposing the films to an artificial sunlight (emitted by 300 W OSRAM Ultra- Vitalux lamps) at 40°C for extended time periods. Photo-oxidative degradation of the neat polymer film and the LLDPE films containing benzophenone (an active photo-initiator for PE) and coumarin alone were also studied under similar conditions for comparison. The rate of photo-oxidation was assessed by measuring tensile properties, gel content, carbonyl index, molecular weight and density. It was shown that galbanic acid was highly effective in accelerating photo-oxidation of LLDPE films and an outstanding acceleration of photo-oxidation was observed for the film containing 0.2 wt % of galbanic acid in comparison with the film containing the same amount of benzophenone. However, the film containing coumarin did not exhibit considerable difference in behaviour in photo-oxidation relative to the neat LLDPE film during the exposure time. On the basis of the obtained results, the prooxidant activity of galbanic acid was described in terms of activity of the functional groups existing in the substituted moiety of its molecules.
Synthesis and swelling characteristics of zwitterionic hydrogel
Authors: Singh Meenakshi , Singh Paresh Kumar , Singh Vinay Kumar
Published: August 2014

Hydrogels comprising of zwitterionic repeat units were synthesized. The amine groups of the poly (ester amine) were quaternized with 1,3-propane sultone. The gelation was observed on treatment with sultone. The hydrophilic gel thus formed is sensitive to temperature, pH, ionic strength and nature of electrolytes in aqueous solution. In absence of any electrolyte, the extent of swelling decreased with temperature, but in the monovalent salt solution the equilibrium swelling diminished with temperature and the contrary behaviour was experiential in bivalent electrolytes.
Effect of the initial water activity on the yields and molecular wWeights of the lipase-catalysed synthesis of aliphatic polyesters in low pressure liquid R-134a
Authors: García-Arrazola Roeb , Gimeno Miquel , Bárzana Eduardo
Published: August 2014

The enzymatic synthesis of the polyester poly(epsilon-caprolactone) (PCL) were evaluated on the basis of the initial water activity (awi) using liquid 1,1,1,2-tetrafluoroethane (R-134a) as solvent media at 2.5 MPa. Polymer yields and molecular weights were directly related to awi and reaction times. The highest molecular weight (Mn) was 83,600 gmol-1, Mw /Mn 1.4, with a 67% yield after 48 h of reaction with the lowest biocatalyst awi preparation (awi <0.16). It is suggested that the enhanced solubility of the growing polymer chains in liquid R-134a may be responsible for the attainment of such high molecular weight. A maximum polymer yield of 99% with Mn 7,246 gmol-1 and Mw/Mn 4.5 was attained when the biocatalyst was adjusted to awi =0.22.
A high mechanical strength hydrogel from polyacrylamide/polyacrylamide with interpenetrating network structure by two-steps synthesis method
Authors: Tang Qunwei , Wu Jihuai , Lin Jianming , Sun Hui , Ao Haiyong
Published: August 2014

A simple two-steps polymerization method was used to prepare a polyacrylamide hydrogel with a full interpenetrating network structure based on the sorption and porous properties of polyacrylamide superabsorbent. In conditions of 10 g acrylamide monomer, 0.04 g crosslinker for the first polymerization and the second polymerization, respectively, and the swelling ratio of 9, the hydrogel possessed a tensile strength of 1.22 MPa and elongation at break of 900 %.
Rheological behaviour of low/high density polyethylene melt flowing through micro-channels
Authors: Chen Chun-Sheng
Published: August 2014

The determination of the proper rheological behaviour of the polymer melt within micro structured geometry is vital for accurately simulating the micro moulding. The paucity of suitable equipments is one of main hurdles in the investigation of micro melt rheology. In the present study, a measurement system for the melt viscosity of low and high density polyethylene polymer melts flowing through micro-channels was established. The capillary flow model with Rabinowitsch correction was used in the calculations of the viscosity based on the measured pressure drop and volumetric flow rate. The effect of the morphology structure on the viscosity characteristics for both the LDPE and HDPE resins within micro-channels was investigated and discussed. It was found that the measured viscosity values for LDPE and HDPE in the test ranges are significantly lower (about 40~56% and 22~29% for LDPE and HDPE, respectively, flowing through a channel size of 150μm) than those obtained with a traditional capillary rheometer. Moreover, both the percentage reduction in the viscosity value and the ratio of the slip velocity to the mean velocity increase as the micro-channel size decreases. It can be observed that the rheological behaviours of the HDPE and LDPE resins in microscopic scale are different from those in macroscopic scale as a result of the wall slip effect. It also revealed that the wall slip occurs more easily for the LDPE resin within micro channels than HDPE resin due to enlarged effect of morphology structure.
Synthesis and characterization of new liquid, branched and random poly(methylhydrosiloxanes)
Authors: Chruściel Jerzy , Fejdyś Marzena , Michalska Zofia , Fortuniak Witold
Published: August 2014

Twelve new liquid branched poly(methylhydrosiloxanes) of random structures (b-r-PMHS), containing triple branching units MeSiO1.5 (T), both Me2SiO (D) and MeHSiO (DH) chain building units (or only mers MeHSiO), and terminal groups Me3SiO0.5, have been prepared by hydrolytic polycondensation method of appropriate organic chlorosilanes in diethyl ether medium at temperatures < 0 °C. Two b-r-PMHS containing structural units: M, D, DH, T and TH have been obtained as well. Volatile low molecular weight oligosiloxanes were removed by vacuum distillation at 125-150 °C. Yields of b-r-PMHS ranged from 57 to 84 wt. %. All polymeric products were characterized by FT-IR, 1H- and 29Si-NMR, and elemental analysis. Their dynamic viscosities were determined in the Brookfield HBDV+IIcP cone-plate viscometer. The molecular weights of b-r-PMHS and polydispersities of MW were analyzed by size exclusion chromatography (SEC).
Effect of LiCl and non-ionic surfactant on morphology of polystyrene electrospun nanofibers
Authors: Fallahi Delaram , Rafizadeh Mehdi , Mohammadi Naser , Vahidi Behrooz
Published: August 2014

Polystyrene fibers were produced by the electrospinning technique. The effects of solution conductivity, surface tension and concentration on morphology and average diameter of electrospun fibers were investigated by scanning electron microscopy (SEM). Solutions of 12, 10, 8, 6% (w/v) polystyrene in dimethylformamide were prepared. Lithium Chloride and a non-ionic surfactant were used to change the conductivity and surface tension of the solutions, respectively. The results indicate that increasing the solution conductivity eliminates the bead formation and increases the fiber diameters. By addition of salt, fine and consistent fibers could be produced from electrospinning of 8% (w/v) PS/DMF solution. Adding 0.1% surfactant reduces the solution surface tension and results in smaller beads and higher fiber diameters. By increasing the amount of surfactant to 0.3%, big beads and thinner fibers are produced.
All furanic polyhydrazides and corresponding polyoxadiazoles
Authors: Afli Aljia , Abid Souhir , El Gharbi Rachid
Published: August 2014

Polyhydrazides based on furanic diacid chlorides and furanic dihydrazides were prepared. The properties of the products are discussed in terms of the backbone structure and the polycondensation technique employed. Their cyclodehydration was carried out by heating in SOCl2 to give new polyoxadiazoles consisting of alternating furanic units and 1,3,4-oxadiazole rings.
Synthesis and structural studies of poly(tetramethyleneoxypropylene p, p´-bibenzoate)
Authors: Martínez-Gómez Aránzazu , Bello Antonio , Pérez Ernesto
Published: August 2014

A smectic main chain polybibenzoate has been synthesized using a mixture of the branched ether-diols: HO(CH2)4OCH(CH3)CH2OH and HO(CH2)4OCH2CH(CH3)OH, as flexible spacers. The mesophase has been identified as SmCalt by optical microscopy and X-ray diffraction experiments. The irregular chemical structure of the polymer, due to the asymmetry of the spacers, produce two important effects: the mesophase is stabilized and the liquid crystallization is slowed down, making possible the freezing of the amorphous glass by supercooling the isotropic melt. Therefore, both the amorphous glass and the smectic glass can be obtained and analyzed. By differential scanning calorimetric measurements it was found that the glass transition of the mesophase appears at lower temperature than the glass transition of the amorphous state. Depending on the temperature and rate of deformation, the molecular orientation in the drawn smectic phase can be perpendicular (anomalous orientation) or parallel (normal orientation) to the stretching direction (or a mixture of both orientations). The morphology of these oriented samples has been studied by scanning electron microscopy.