bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the ion permeability of poly(p-xylylene) films
Authors: Hanefeld Phillip , Sittner Frank , Ensinger Wolgang , Greiner Andreas
Published: August 2014

The ion permeability of poly(p-xylylene) (PPX, parylene-N®) thin films was investigated using a cyclovoltammetric setup. Iron rods of different surface roughness were coated with PPX films of different thickness (140 - 700 nm) by vapour phase deposition (Gorham process). The presence of pinholes in PPX films deposited as described was analyzed by ion permeability according to cyclovoltammetric measurements. Current densities were directly related to the area of iron not covered by the polymer. It was found that films deposited on iron surfaces by the Gorham process showed significant ion permeability for film thicknesses below 500 nm and no permeability at all for films equal to or thicker than 700 nm, which indicated the absence of pinholes of PPX films of 700 nm thickness. Furthermore, films of 140 nm were deposited on iron surfaces of different roughness (the mean roughness was measured to be 102 nm, 103 nm and 105 nm). Current density increased by the increase in roughness, which confirmed that pinhole formation correlated with surface roughness.
Chemistry and Applications of Phosphorylated Chitin and Chitosan
Authors: Jayakumar R. , Reis R. L. , Mano J. F.
Published: August 2014

Chitin and chitosan are natural based non-toxic, biodegradable and biocompatible polymers and have been used in biomedical areas in the form of sutures, wound healing materials and artificial skin, and for the sustained release of drugs as well as in various industrial applications. However, practical use of these polymers has been mainly confined to the unmodified forms. Recently, there has been a growing interest in chemical modification of chitin and chitosan to improve their solubility and widen their applications. Among them, phosphorylated chitin and chitosan have attracted considerable interest because of their various advantages: anti-inflammatory property, ability to form metal complexes, blood compatibility and formation of anionic polyelectrolyte hydrogels. The purpose of this review is to take a closer look of different synthetic methods of phosphorylated chitin and chitosan and their potential applications in environmental, food, fuel cell, and biomedical fields. Based on current research and existing products, some new and futuristic approaches in this context area are discussed.
Development of Fast Gradient Separations for Different Polymethacrylates
Authors: Brüll Adele , Pasch Harald , Bashir Mubasher
Published: August 2014

Liquid chromatography of polymers is traditionally a slow technique with analysis times of typically 30 min per sample. To adapt liquid chromatographic techniques to combinatorial materials research the sample throughput must be significantly increased. Preferably, the analysis time per sample is to be reduced to a few minutes. Short analysis times can be achieved using high resolution stationary phases, high flow rates, and fast gradients. The present work demonstrates that gradient HPLC of polymethacrylates can be accomplished in less than 2 min. The fast separation of poly(methyl methacrylate), poly(i-propyl methacrylate), poly(n-butyl methacrylate), poly(tbutyl methacrylate), and poly(n-decyl methacrylate) is conducted on a short monolithic stationary phase using a flow rate of up to 7 mL/min. The optimization of the gradient is conducted by running a number of linear gradients and by simulating an optimum step gradient. Further modification of the simulated gradient results in the desired short analysis times.
Direct Polyesterification of Pyridine-2,6-Dicarboxylic Acid and Poly(ethylene glycol) using Picryl Chloride as Condensing Agent
Authors: Doan Nhung T.H. , Montembault Véronique , Soutif Jean-Claude
Published: August 2014

High molecular weight polyesters derived from pyridine-2,6-dicarboxylic acid and poly(ethylene glycol) have been synthesized under mild conditions (room temperature, atmospheric pressure) in the presence of picryl chloride and pyridine. Reaction conditions including solvent, trap agent, reaction time and amount of reagents were investigated using poly(ethylene glycol) 400 as dialcohol comonomer. Detailed analysis of the MALDI-TOF mass spectra of the obtained polyesters has revealed a predominant fraction of macrocycles for a picryl chloride/acid functions molar ratio lower than 1.5. The reaction yielded the most favourable results using 1.5 equivalents of picryl chloride with respect to the acid functions and 4-(N,N-dimethylamino)pyridine as HCl scavenger. The molecular weights of the polyesters at the peak maximum of the SEC trace are in the range of 4 800-80 000 depending on the nature of the comonomer poly(ethylene glycol). Syntheses of an aliphatic and aromatic polyester were also examined.
Plasma polymerization of tetrafluoroethylene – towards CF2 dominated fluorocarbon films
Authors: Nitschke Mirko , Uhlmann Steffi , Schulze Roland , Werner Carsten
Published: August 2014

Fluorocarbon films with an exceptionally high CF2 content were obtained by plasma polymerization using a low pressure radio frequency discharge operated with a mixture of argon and tetrafluoroethylene. Substrates were placed in a remote position downstream the discharge. Gas pressure, discharge power, substrate position, gas composition and substrate temperature were changed to alter the chemical structure of the plasma polymers. The properties of the films were characterized by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry and contact angle goniometry. A pronounced increase of the CF2 content was obtained for elevated substrate temperatures and increased amounts of tetrafluoroethylene in the process gas. Applied as a model surface in studies of interfacial phenomena on polytetrafluoroethylene (PTFE), transparent PTFE-like thin films enable the use of numerous optical techniques not applicable to common PTFE foils.
Synthesis and some Mechanical Properties of Polysulfobetaine – Polyacrylamide Double Networks
Authors: Georgiev George , Dyankova Konstantina , Vassileva Elena , Friedrich Klaus
Published: August 2014

Double polymer networks (DNs) with poly(N-(3-sulfopropyl)-Nmethacroyloxyethyl- N,N-dimethylammonium betaine) component as a high density cross-linking agent were synthesized by thermoinitiated cross-linking polymerization. Good mechanical properties of the produced DNs were established. These, in combination with an excellent biocompatibility of polyzwitterions, open a possibility for wide biomedical applications of these materials. It is also shown that the mechanical properties could be controlled by the factors (cross-linking agent and monomer concentrations, temperature and time for the cross-linking polymerization, order of single network formation) influencing the junction point densities of the two single networks and on the microphase separation taking place during the formation of the second single network. Specific dipole-dipole interaction between polyzwitterion monomer units as a reason for this separation is a distinct peculiarity of poly(N-(3-sulfopropyl)-N-methacroyloxyethyl-N,Ndimethylammoniumbetaine)/ poly(acrylamide) double networks in comparison to poly(2-acrylamido-2-methylpropanesulfonic-acid)/poly(acrylamide) ones.
Synthesis and absorbency of gelatin-graft-poly(sodium acrylate-co-acrylamide) superabsorbent hydrogel with saltand pH-responsiveness properties
Authors: Pourjavadi Ali , Sadeghi Mohammad , Mahmodi Hashemi Mohammad , Hosseinzadeh Hossein
Published: August 2014

In this article, we synthesize a novel gelatin-based superabsorbent hydrogel via graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto gelatin backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N'-methylene bisacrylamide (MBA) as a crosslinker. The hydrogel structures were confirmed by FTIR spectroscopy. The effect of grafting variables, i.e. concentration of MBA and APS, AA/AAm weight ratio, and reaction time and temperature, was systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The swelling behavior of these absorbent polymers was also investigated in various salt solutions. Results indicated that the swelling capacity decreased with an increase in the ionic strength of the swelling medium. Furthermore, the swelling of superabsorbing hydrogels was examined in solutions with pH values ranging between 1.0 and 13.0. It showed a reversible pH-responsive behavior at pHs 2.0 and 7.0. This on-off switching behavior makes the synthesized hydrogels an excellent candidate for controlled delivery of bioactive agents. Finally, the swelling kinetics of the synthesized hydrogels with various particle sizes was preliminarily investigated.
Preparation and Characterization of Core-Shell Latex Containing PDMS in the Shell
Authors: Zhang Baotan , Liu Bailing , Cao Shunsheng , Deng Xiaobo
Published: August 2014

In this paper, the composite latex particles with a polyacrylate (PA) core and a polydimethylsiloxane (PDMS) shell via 3-(methacryloxypropyl)- trimethoxy silane (MPS) as the medium to link the core and shell were prepared by semicontinuous seeded emulsion polymerization and were characterized by transmission electron microscopy (TEM), FT-IR, particle size analyzer and X-ray photoelectron spectroscopy (XPS). The TEM images indicated that the particles containing organic siloxane (D-40) displayed an evident core/shell structure. Additionally, the study by FT-IR and XPS also revealed that D4 could be grafted onto the surface of polyacrylate core because there appeared the characteristic peaks of Si-O-Si group and Si 2s and Si 2p in the spectra of FT-IR and XPS respectively. Besides, the atomic ratio of C/Si on the surface of the core/shell particles (D-40) was close to the ratio of C/Si in the latex of pure PDMS that could prove the PA particles were fully covered by PDMS and the properties of PDMS should be embodied in a maximal level. In order to testify the result, the surface properties of the films produced from the core/shell particles were also investigated by the static contact angle method. Compared with the copolymer of PA, the core/shell particles were more effective to create hydrophobic surface, so, the introduction of D4 was capable of obvious increase in water repellency.
Synthesis of Well-defined Carbazole Group Labelled Polymer via RAFT Polymerization and Study on the Optical Properties
Authors: Zhou Di , Zhu Xiulin , Zhu Jian , Hu Lihua , Cheng Zhenping
Published: August 2014

Benzyl 9H-carbazole-9-carbodithioate (BCC) was synthesized and characterized. The single-crystal structure of BCC was first reported. The RAFT polymerizations of styrene and acrylates using BCC as the RAFT agent under conventional polymerization conditions were investigated. The results showed that the BCC was an effective RAFT agent for the polymerizations of styrene and acrylates. The well-controlled polymers were labelled with carbazole group, which was confirmed by 1H NMR and the chain extension of the obtained polymer. Azo modified poly(methyl acrylate) (PMA) was synthesized through a postpolymerization azo-coupling scheme. The optical properties of obtained polymer were also characterized. The results showed that the carbazole group labelled polymer exhibited fluorescence and the azo polymer exhibited UV absorption behaviour in N,N-dimethyl formamide (DMF).
Preparation of a Novel Cellular Fiber: Control of Cell Density of the Fiber
Authors: Linfeng Guo , Xiong Chunyan , Zhu Jiangjiang , Wang Yimin
Published: August 2014

A new cellular fiber was obtained by a post-treatment of spun fibers. Cellular polymers such as poly(ethylene terephthalate) show great promise for different engineering applications due to their high density property. Recent study has shown that some high density cellular polymers possess long fatigue life and/or equivalent strengths as compared with commercial-type neat polymers. However, only few studies have focused on the process of cellular polymer fibers to date. In this paper, the effect on a cellular structure of cellular PET fibers (hereafter called “CPET fibers”) subjected to different forming processes is discussed. An ultra saturating gas method was used to fabricate the CPET fibers with different cell densities. Inert gas nitrogen (N2) was saturated in PET fiber at high pressure to form a polymer/gas system. A pressure vessel was then discharged and polymer/gas solutions were foamed at a temperature controlled medium. The effect on the fiber’s cellular structure, particularly on the fiber cell density with different processing parameters such as pressure, saturation time, foaming temperature and time was investigated in detail. Experimental results showed that the cell density of the CPET fibers increased with increasing the pressure, saturation time, foaming temperature and time. The saturation time and pressure are key factors that affect the density of cells formed inside the CPET fibers. The foaming time however showed no substantial influence on the cell density of the fibers when held longer than 10s.
HPLC separation of ibuprofen and mefenamic acid using molecularly imprinted polymer as stationary phase
Authors: Hung Chin-Yin , Huang Yun-Tzu , Huang Han-Hung , Hwang Ching-Chiang
Published: August 2014

A simple high-performance liquid chromatographic method for the assay of ibuprofen and mefenamic acid in tablets is described. This method was developed by using self-prepared molecularly imprinted polymers (MIPs) as the stationary phase. MIPs are synthesized using non-covalent method by the free radical polymerization of template, functional monomer and an excess of crosslink monomers resulting in organic materials. The resulting bulk material was then ground into 25~44μm particles and packed into analytical columns. The effect of functional monomers/crosslinking ratio and the concentration of acetonitrile in the mobile phase were studied. Ibuprofen and mefenamic acid were efficiently resolved on the polymer. The retention time of ibuprofen and mefenamic acid were approximately 19.69±0.36min and 46.27±1.23min, respectively. Linearity was observed from 3.13-8.33g/l for ibuprofen and 0.3-0.9g/l for mefenamic acid, with the coefficients of determination (r2) of 0.9977 and 0.9958. The limits of detection (LOD) of ibuprofen and mefenamic acid were found to be respectively 0.42g/l and 0.06g/l, while the limits of quantitation (LOQ) were 1.41g/l and 0.20g/l, respectively. The self-prepared MIP was successfully applied to the commercial tablet analysis and the result showed a good accuracy with -1.33 ~ -1.8% and -0.8 ~ +1.33% for ibuprofen and mefenamic acid.
Role of magnesium complexes in the anionic polymerization of hexano-6-lactam
Authors: Arnoldová Petra , Brus Jiří , Prokopová Irena , Brožek Jiří
Published: August 2014

The course of anionic hexano-6-lactam polymerization initiated with magnesium compounds differs in some parameters from that initiated with lactam alkali salts. This may be attributed to the coordination of magnesium compounds with functional groups on polymer chains. Supposed coordination effects were proved on model compounds of N-ethylacetamide and N-butyryl-hexano-6-lactam with magnesium bromide. Based on interpretation of Raman and NMR spectra, the interaction between magnesium bromide and both types of ligands as an electron donating coordination of carbonyl groups was proposed. N-butyryl-hexano-6-lactam is more distinctly coordinated to magnesium atom through the carbonyl group located in the cyclic constitution unit.
High-throughput experimentation applied to atom transfer radical polymerization: Automated optimization of the copper catalysts removal from polymers
Authors: Zhang Huiqi , Abeln Caroline H. , Fijten Martin W. M. , Schubert Ulrich S.
Published: August 2014

Combinatorial chemistry and high-throughput experimentation have drawn great attention in recent years because of their significant advantages in increasing the research productivity. One of the emerging fields is their application in polymer science. Herein we describe the high-throughput optimization of purification conditions for polymers prepared via atom transfer radical polymerization using an automated synthesizer. The effects of the column materials, column lengths and eluent volumes on the purification efficiency as well as the molecular weights of the obtained purified polymers were systematically investigated for the first time. The optimum purification conditions for the removal of copper catalysts are provided. As a result an online high-throughput purification workflow using SPE cartridges is now available for the utilization in automated parallel synthesizers for ATRP screening experiment.
Atom transfer rearrangement radical polymerization of (2,4,6-trihalophenolato) Fe(II) / Ce(III) / Ce(IV) complexes in solid state
Authors: Çelik Güler Bayraklı , Sultan Wadie , Kısakürek Duygu
Published: August 2014

The synthesis of poly(dihalophenylene oxide)s by thermal decomposition of Fe(II), Ce(III) and Ce(IV) phenolato complexes with pyridine as neutral ligands were achieved at different temperature ranges (140o - 250oC) with different time intervals (3 - 48 hr) via atom transfer rearrangement radical polymerization (ATRRP). The complexes were characterized by FTIR, DSC, UV-Visible, mass spectroscopy, magnetic susceptibility and elemental analyses. Structural analyses of polymers were performed by 1H and 13C-NMR, FTIR spectroscopic analyses, Tg by DSC and the molecular weights by viscometrical method. 1H-NMR spectra of polymers are quite similar in pattern except the relative intensities of two main peaks, all having branched structures. The lowest percent conversion values were observed for polymers synthesized from Fe(III) complexes compared to Ce(III) and Ce(IV) complexes. The glass transition temperature of the polymers were quite high indicating they are rigid polymers (162o to 187 oC).
Ethylene Polymerization over Transition Metal Supported Catalysts. III. Vanadium
Authors: Matos Inês , Zhang Yingjun , Fonseca Isabel , Lemos Francisco , Lemos Manda , Freire Filipe , Fernandes Anabela C. , Botelho do Rego Ana M. , Valente Anabela , Mano João F. , Henriques Rui T. , Marques Maria M.
Published: August 2014

The polymerization of ethylene in the presence of vanadium catalysts supported on zeolite NaY, HY and charcoal was examined. The catalysts were prepared by the incipient wetness method and characterized by a variety of techniques to determine the oxidation state of the vanadium species inside the zeolite. In all the catalysts that were prepared vanadium is not in a single oxidation state. These catalysts were active in the polymerization of ethylene with activities of the order of magnitude 105 gPE/molV.[M].h for the zeolite catalysts and 103 gPE/molV.[M].h for the charcoal systems. No polymer could be obtained in the absence of alkylaluminum or aluminoxane in the experimental conditions used. The kinetics of ethylene polymerization reactions using the vanadium catalysts was studied. A kinetic model based on a proposed mechanism for these reactions was used to fit the experimental data. The application of this model resulted in very good fittings and the kinetic rate constants of each elementary step could be estimated. Since the polyethylene that was produced is closely bound to the zeolite catalysts, the thermal and mechanical properties of the PE/zeolite composites were measured, indicating that the presence of zeolite improved the mechanical properties of the polymers produced.
The Synthesis and Crystallization of Poly(vinylidene fluoride) in Supercritical CO2
Authors: Shi Zhendong , Zheng Zhen , Su Xiaoli , Wang Xinling
Published: August 2014

A series of poly(vinylidene fluoride)s (PVDFs) is synthesized in supercritical carbon dioxide (sc-CO2). The influences of polymerization pressure, molecular weight distribution and H-H defect concentration on the crystallization of PVDF have been studied in combination with differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXRD) and Fourier transform infrared spectroscopy (FT-IR) measurements. The result shows that the morphology, molecular weights, polydispersity and head-to-head (H-H) defect concentrations of the PVDFs are affected by the reaction pressure and good solubility generated from sc-CO2. Especially, the sc-CO2 polymerization has greatly improved the crystallization mode of the obtained PVDFs such as the complete degree of crystallinity, crystallinity and the crystal phase. This will create more comprehensive application fields for PVDF.
Water expandable polystyrene (WEPS): Part 4. Synthesis of the water expandable blend of polystyrene and poly(2,6- dimethyl-1,4-phenylene ether)
Authors: Snijders Emile A. , Nelissen Laurent , Lemstra Piet J.
Published: August 2014

In previous studies, we discussed the use of water as an environmentally benign blowing agent for foaming of polystyrene beads, resulting in so-called WEPS, viz. water expandable polystyrene foam. Several grades of precursors to WEPS have been prepared by varying the water content and the molar mass, to control the melt strength of the polystyrene matrix. Additionally, we have used (endcapped) poly(2,6-dimethyl-1,4-phenylene ether) (PPE) to control both the meltviscosity and the glass transition temperature Tg. The advantage of using the blend PS/PPE is that the processing window for foaming is increased in view of the difference between the Tg and the boiling point of water. Using the novel WEPS route with some adjustments, for the first time a water expandable homogeneous blend of polystyrene and end-capped PPE was successfully obtained.
Mechanical properties of thin microcellular PET sheet
Authors: Guan Rong , Banglong Xiang , Yinglin Li , Zhaoxin Xiao , Deping Lu , Gongwu Song
Published: August 2014

In this paper, the thin microcellular poly(ethylene terephthalate)(PET) sheets, having the controlled structures, were prepared by compression molding. The effects of the processing conditions on the microcellular PET tensile properties have been investigated. By comparing the importance of the individual processing parameters, the saturation time was the most important factor to determine tensile modulus, whereas the saturation time and the upper-plate temperature were the most important processing parameters that influence the tensile strength and specific tensile strength. The effects of the microstructure on the tensile properties of microcellular PET were also investigated systematically. The results indicated that the tensile modulus and strength increased with increasing foam density, but decreased slightly with increasing cell size. Following the experimental data, a new model was built to relate the tensile modulus and tensile strength with the foam density and the cell size.
A new way of step-mass-thermal transferring to control phase inversion for polyacrylonitrile(PAN)/DMSO/water system
Authors: Bing-Xin Jiang , Huan-Qin Zhu , Zhan-He Du , Cheng-Xun Wu
Published: August 2014

The step-mass-thermal transferring meant that for PAN/DMSO/water system, the kinetic of phase inversion and droplet ripening was controlled by employing several consecutive coagulation baths with different concentrations and temperatures. In this way, the morphology of fiber could be adjusted based on modelling. The phase diagram of PAN/DMSO/water was calculated based on Flory-Huggins theory. The mass and thermal transferring was calculated according to Fick’s second law and Fourier heat equation respectively.
Novel blocked functionality copolymers as surface coatings in DNA microarray technology
Authors: Viganò M. , Levi M. , Chiari M. , Damin F. , Turri S.
Published: August 2014

New copolymers made of 2-(dimethyl amino) ethyl methacrylate (DMAEM) and isocyanate ethyl methacrylate blocked with methyl ethyl ketoxime (IEMB) was synthesized in various composition ratios in order to obtain water reducible copolymers after acidification. They were characterized by infrared spectroscopy, chemical titration for the determination of amine equivalent weight, and by differential scanning calorimetry (DSC). Calorimetric analysis showed the presence of a former broad endothermal peak followed by a latter, stronger exothermal one, which can be respectively attributed to the deblocking of isocyanate groups and to their subsequent reactions. Some copolymer compositions were dip coated onto microscope glass slides and surfaces were characterized by static and dynamic contact angles, revealing a clear effect of the salifying agent and a likely surface rearrangement of polar groups while in contact with water. Finally, oligonucleotides surface immobilization and molecular recognition capability of the coated glass slides were positively assessed by hybridization tests with fluorescently labelled complementary probes.
Preparation of polyaniline/Fe2O3 composite dispersions in the presence of dodecylbenzene sulfonic acid
Authors: Yan Wu , Shuangxi Xing , Shengyu Jing , Teili Zhou , Chun Zhao
Published: August 2014

We reported a chemical approach for the in-situ preparation of conducting polyaniline (PANI)/Fe2O3 composite dispersions using dodecylbenzene sulfonic (DBSA) acid both as dopant and surfactant. The PANI/Fe2O3 composite dispersions were characterized by X-ray diffraction, UV-vis and FT-IR spectra and conductivity measurement. The dispersions showed good stability and existed without precipitate for at least half a year. The gas-sensing behavior of the composite film to 100 ppm of NH3 was studied through monitoring the change of the resistance.
Preliminary testing of silicone-urethane elastomers as substrates in human cell culture
Authors: Lewandowska-Szumieł Malgorzata , Kozakiewicz Janusz , Mrówka Piotr , Jurkowska Agnieszka , Sienkiewicz-Łatka Edyta , Przybylski Jarosław , Okrój Wiesława , Walkowiak Bogdan
Published: August 2014

Silicone-urethanes, polymers combining the characteristics of two widely used biomaterials, i.e. polyurethanes and silicones, are highly valued in many applications, including medical implants. To assess properties of these materials in contact with living cells, a set of different silicone-urethane materials, candidates for tissue engineering scaffolds, was synthesized and characterized. Two different oligomeric siloxane diols: Tegomer-2111 (Teg) and KF-6001 (KF), and two different types of diisocyanate, MDI and IPDI, were used in synthesis. Blood platelets adhesion to surfaces of selected materials showed a higher thrombogenicity of material based on Teg. Human fibroblasts were used in in vitro biocompatibility tests. The viability of cells cultured on silicone-urethanes was tested by XTT assay. Teg-based silicone-urethanes showed a significantly higher biocompatibility than those based on KF. Materials based on MDI compared to IPDI were found to be significantly more favoured by cells, not necessarily due to the type of diisocyanate but maybe also because of the necessity of using potentially toxic catalyst which accompanies the use of IPDI. Our studies indicate that silicone-urethanes are potent materials for tissue engineering products development. On the basis of the observations performed in cell culture, Tegomer- 2111 as oligomeric siloxane diol and MDI as diisocyanate are recommended as starting materials for silicone-urethane scaffolds synthesis.
Second-order nonlinear optical properties of polyphosphazenes containing multi-dipolar and imidazolebased chromophores
Authors: Yang Pan , Xiaozhen Tang
Published: August 2014

The synthesis and second-order nonlinearity study of several new polyphosphazenes were described, which are composed of a new type of Yshaped nonlinear optical (NLO) chromophores attached onto polyphosphazene. They were obtained via a post-azo coupling reaction. The resulting materials were characterized by means of 1H NMR, 31P NMR, FT-IR, UV-vis, GPC and DSC. Chromophore contents up to 14 mol% have been realized. The polymers have high glass-transition temperatures, good optical transparency, and the poled film of P3- P8 revealed a resonant d33 value in the range of 11-42 pm/V by second harmonic generation (SHG) measurements.
Guar gum as filler in unsaturated polyester composites
Authors: Shenoy Mohan , D’Melo Dawid John
Published: August 2014

Guar gum is a natural polysaccharide that has been explored for various applications. However, there is a limited number of studies in which guar gum has been used as a filler in a polymer. The effect of acetylation of guar gum on its properties as a filler in an unsaturated polyester matrix was studied. The rheology of the uncured composition indicated increased polymer-filler interaction with increased ester content. The tensile and flexural properties increased with the acetylation degree of guar gum; however the impact resistance of the composites was reduced. Excessive esterfication of guar gum was detrimental to the mechanical properties of the composites due to reduced hydrogen bonding resulting in the filler phase having lower integrity. The chemical properties of the composites were also studied as well as the effects of acetylation. Thus, an increase in the hydrophobic nature of guar gum resulted in an increase in the polymer-filler adhesion and interaction but at the same time reduced the hydrogen bonding leading to reduced cohesion of the filler particles. This resulted in reduced mechanical properties of the composites as compared to lower acetylated guar gum based composites.
Bimodality and Increased Amount of Crosslinker Enhances Tensile Properties of the Silicone Networks
Authors: Shah Gul Bali
Published: August 2014

The effect of bimodality i.e. blending short and long chain (0 to 80 % w/w) silicone prepolymers, and that of concentration of the crosslinker on the tensile properties such as percent elongation at break (%Eb), ultimate tensile strength (UTS), 100 % modulus and elastic modulus (E) has been investigated. It was found out that the greater amount of crosslinker used for crosslinking provide an additional reinforcement to the silicone network whereas bimodality further significantly accentuates this effect. Remarkably, the %Eb of the silicone networks was found to increase to an average of 2.4 times than that of the monomodal network, cured in each of the three series of bimodal networks cured with 3.9, 9.1 and 12.3% of crosslinker. The optimum property in each case was observed at about 70 mol % of P100. The over all order of sensitivity of these properties up to about 70 mol % of short chain prepolymer has been observed to be as: %Eb > UTS > 100% modulus > elastic modulus. It has been shown that in addition to the previously published reports the tensile properties are acutely dependent not only upon the degree of crosslinking and primary molecular weight; but also on bimodality and crosslinker concentration for preparation of the unfilled silicone polymer networks. The concept of phase inversion (or phase transition) associated with the optimum properties in polymer blends has for the first time been applied to the bimodal polymer networks. It has been observed that the maxima in tensile properties generally corresponds to phase inversion which takes place at 0.5 volume fraction (70 mol %) of short chain (P100) prepolymer which is in accordance with the literature for other systems.
Synthesis and Characterization of Porous Crosslinked Copolymers for Oil Spill Sorption
Authors: Abdel-Azim Abdel-Azim A. , Abdul-Raheim A. Mahmoud , Atta Ayman Mohamady , Brostow Witold , El-Kafrawy A. Fawzy
Published: August 2014

Cinnamoyloxy ethyl methacrylate (CEMA) was copolymerized with different monomer feed ratios of octadecyl acrylate (ODA) and crosslinked using azobisisobutyronitrile (AIBN) as the initiator and N,N’,N”-trisacryloyl melanine (AM) or N,N’,N”,-trismethacryloylmelanine (MM) crosslinkers. The networks are characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). For crosslinked CEMA/ODA copolymer sol fraction values are lower when MM is used rather than AM. The thermal stability of crosslinked network increases with increasing ODA concentration and also in the presence of MM crosslinker, a consequence of higher crosslinking density. SEM results show a porous structure; micropores are formed when ODA contents increases. According to DMA results, the flexibility of the network is enhanced by incorporation of MM rather than AM. Since our crosslinked networks are both flexible and porous, they are applicable as oil sorber networks to alleviate pollution from oil spills.
Particle Morphology of Epoxidised Natural Rubber Latex Prevulcanized by Peroxide System
Authors: Suteewong Teeraporn , Tangboriboonrat Pramuan
Published: August 2014

Epoxidised natural rubber (ENR) latex could be prevulcanized by employing tert-butyl hydroperoxide/fructose system. By applying the phase transfer/bulk polymerization/ transmission electron microscopy (TEM) technique, the uniform crosslink distribution in peroxide-prevulcanized (PP) ENR particle was observed. However, the membrane layer of protein-lipid complex, originally existing at rubber particle surface, could not be detected. Results implied that the alkoxy radicals penetrated throughout the rubber phase. The diffusion rate of radicals should be equal to that of vulcanization. Under TEM, the uniform mesh-like particle and cluster of the rubber chains were observed in PP(NR/ENR) while micrographs of PP-NR/PP-ENR blends showed only the crosslinked particles whose structure correlated well with that of PP-NR.
Study of Mechanical Properties and Morphology of PA 6/PO Blends Compatibilized by PO Grafted with Itaconic Acid
Authors: Xijun Liu , Zhaohua Jiang , Wenming Zhu
Published: August 2014

Two different types of polyolefine (PO) grafted with itaconic acid as a reactive compatibilizer, polypropylene (PP) grafted with itaconic acid (PP-g-ITA) and high density polyethylene (HDPE) grafted with itaconic acid (HDPE-g-ITA), PP and HDPE grafted with copolymer of itaconic acid and styrene (PP-g-(ITA-St) and HDPE-g-(ITA-St)) were prepared by melt graft technique through reactive type twin-screw extruder. FT-IR and thermal analysis were used to characterize the structure of the graft copolymer. The graft ratio (GR) and melt flow rate (MFR) were determined by non-aqueous titration and melt flow rate analyzer. The effect of the concentration of monomer and initiator dosage on GR and MFR of graft copolymer were studied. Then polyamide 6 (PA 6) blends, PA 6/PP (PA 6/HDPE), that compatibilized with PP-g-ITA (HDPE-g-ITA) were prepared. The morphology of the blends was analyzed by SEM, DSC and Molau tests and the mechanical properties of which were characterized by tensile, impact, and bend tests. The results of mechanical property showed that the impact strength of blends was increased by 50% and 70% after PP-g-ITA and HDPE-g-ITA was used as compatibilizer, but the MFR of blends was decreased. The SEM photographs indicated that the accession of compatibilizer obviously improved binding state between two phases in blends, the size of dispersed phase was reduced evidently and the interface became indistinct. DSC results demonstrated that in the case of PP-g-ITA, glass temperature (Tg) of PA 6 matrix in blends was ascended, melt point (Tm) was improved a little, crystallinity (Xc) was decreased, Tm and Xc of PP phase was increased; With the accession of HDPE-g-ITA, Tm of PA 6 matrix and HDPE phase had almost no change, Xc of PA 6 matrix was decreased and Xc of HDPE phase was increased.
Modeling of Precipitation Polymerization I: The Method of Finite Molecular Weight Moments
Authors: Bouhendi H. , Haddadi-Asl V. , Rafizadeh M. , Safinejad A.
Published: August 2014

Precipitation polymerization method is a non homogeneous method in which polymer chains are separated from continuous phase as polymer particles. In this method, all polymerization reactions occur in continuous and polymer dispersed phases based on simultaneous polymerization theory. Hunkeler theory is a perfect "simultaneous polymerization" theory that predicts molecular weights and the rate of polymerization for precipitation polymerization of hydrophilic monomers. In this paper, finite moment method is used to predict features of precipitation polymerization. This model is able to predict number and weight average degree of polymerization in dispersed and continuous phases, polydispersity index (PDI) for two phases and volume fraction of primary and secondary particles. Experimental results are in agreement with the properties of dispersed phase; weight and number average degree of polymerization in the dispersed phase is more than that of degrees of polymerization in the continuous phase. The PDI of polymer formed in the dispersed phase is equal to 2 and that of PDI in the continuous phase is less than 2. Furthermore Hunkeler mathematical model is reviewed critically.
Novel acrylic copolymers: synthesis, characterization and antimicrobial studies.
Authors: Patel Hetal , Patel Mitesh , Patel Kirit , Patel Rajni
Published: August 2014

The monomer 2,4-dichloro phenyl acrylate (2,4-DCPA) was synthesized from 2,4-dichlorophenol and characterized by conventional methods. The homopolymers of 2,4-DCPA and its copolymers with 8-quinolinyl methacrylate (8- QMA) in different feed ratio were prepared by free radical polymerization using dimethyl formamide (DMF) as a solvent and 2,2’-azobisisobutyronitrile (AIBN) as an initiator. The resulting polymers were characterized by Infrared Spectroscopy. UV spectral data were employed to obtain the reactivity ratios of the monomers, 2,4-DCPA and 8-QMA. The results showed that 2,4-DCPA is more reactive than 8- QMA. Average molecular weights and intrinsic viscosities determined by Vapour pressure osmometer (VPO) lies in the range of 7900 to 10890 and 0.021-0.036 dl.g-1 respectively. Thermal analysis shows that thermal stability of copolymers increases with the increase of 2,4-DCPA. The copolymers also showed antimicrobial activity which increased with increase in 8-QMA content.
Influence of Electron Beam Irradiation on PP/Clay Nanocomposites Prepared by Melt Blending
Authors: Nejad Shahryar Jafari , Ahmadi Seyed Javad , Abolghasemi Hossein , Mohaddespour Ahmad
Published: August 2014

In this research, the melt blending technique was used to prepare various polypropylene (PP) based nanocomposites. A commercial organoclay (denoted 15A) served as the filler for PP matrix, and the maleic anhydride modified PP was used as compatibilizer. The specimens were subjected to electron beam (EB) irradiation. The purpose of the study focuses on the influences of EB irradiation on the thermal stability and mechanical properties of the nanocomposites. The morphology of the nanocomposites was studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD and SEM results showed that these nanocomposites are best described as intercalated systems. PP/Clay nanocomposites showed good thermal stability in the TGA analysis. TGA data at 500KGy showed that the EB irradiation has negative effect on thermal stability of the nanocomposites. Mechanical testing showed that the EB irradiation strongly influences the mechanical properties (tensile strength, Young’s modulus and hardness) of PP/Clay nanocomposites. The value of tensile strength decreases remarkably for all specimens with increasing irradiation dose up to about 550 KGy, but this reduction for nanocomposites with 3% clay is less than that of the pure PP/PP-g-MA blend. In higher irradiation doses, reduction in tensile strength of PP nanocomposites is less than that of the pure PP/PP-g-MA blend. Optimum irradiation dose of Young’s modulus for PP/Clay nanocomposites with 5% clay is 450 KGy. The hardness of the nanocomposites with 5% clay was found to decrease with increase in irradiation dose.
Studies of silicon-containing maleimide polymers. Part II: Synthesis and properties of poly(styrene-co-brominecontaining maleimide).
Authors: Chia-Yu Chiang , Ruey-Shi Tsai , Wei-Jye Shu
Published: August 2014

Soluble copolymers of a series of bromine-containing (N-maleimido phenoxy) silane (BMS) monomers with styrene (St) were synthesized by radical polymerization in toluene using 2,2’-azobisisobutyronitrile (AIBN) as initiator. The comonomer reactivity ratios were calculated by the conventional Fineman-Ross and Kelen-Tüdos methods and a nonlinear least-squares Tidwell-Mortimer method. The glass transition temperatures (Tg’s) and thermal degradation of copolymers were determined by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) respectively. The introduction of silane side-chain into maleimide (MI) monomers changed the comonomer reactivity ratio with styrene from alternating to azeotropic copolymerization. The curves of Tg’s versus the different compositions of the above synthesized St-BMS copolymers matched a modified Tg’s equation as a increase in the effect of weight ratio on alternating-segment, and an S-shaped curve of deviation in comparison with the Fox’s equation. The MIsegments within these copolymers exhibited a good compatibility and, the flame retardancy of polystyrene could be enhanced via the introduction of Si/Brcontaining maleimide.
Temperature Dependent Dynamic Mechanical Properties of Hydrogenated Nitrile Butadiene Rubber and the Effect of Peroxide Cross-linkers
Authors: Likozar Blaž , Krajnc Matjaž
Published: August 2014

The viscoelastic behavior of hydrogenated nitrile butadiene rubber (HNBR) was studied over a range of temperatures and shear frequencies. Dynamic mechanical properties were studied and modelled using the generalized Maxwell model and the Williams-Landel-Ferry equation. A fitting algorithm was developed to provide the best agreement between the experimental data and the model results. In addition to dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) was applied. The HNBR structure was characterized by X-ray diffraction (XRD). The developed model exhibited an excellent agreement with either isothermal or dynamic experiment data, yet only up to the rubbery plateau, after which a structure ordering occurred. This was explained by the cyano group secondary bonding and consequentially the cross-linking between HNBR chains. A molecular modeling simulation was made to confirm the cross-linking. The effect of peroxide cross-linking agents in a compound resembled the one usually observed in the filler formulated compounds.
Porous 4-Vinylpyridine-Divinylbenzene Copolymers– Varying Porosity in Different Bead Sizes of a Single Batch
Authors: Malik Muhammad Arif , Naheed Riffat
Published: August 2014

Ion-exchangers, adsorbents, supported catalysts, etc, derived from porous copolymer beads are employed as medium in fine chemical separation processes. In these processes the exchange of reagents completes earlier in the smaller beads than in the larger beads in the same lot, which reduces the separation efficiency. So, it is potentially advantageous to preferentially introduce the macropores in the larger beads, as the macropores provide fast access to the reagents into the inner portions of the beads. In this study, camphor-a sublimable organic compound was employed as a diluent to create porosity in 4-vinylpyridinedivinylbenzene copolymer beads produced by o/w suspension polymerization technique. Camphor preferentially introduced macropores in the larger beads in the reaction. The results are explained on the basis of removal of diluent by sublimation phenomenon from the polymerizing droplets at a faster rate from the smaller beads as compared to the larger beads in the same batch.
Morphological features of PU/PMMA hybrid latex prepared by Miniemulsion Polymerization
Authors: Li Chien-Yu , Chiu Wen-Yen , Lee Chia-Fen
Published: August 2014

PU/PMMA hybrid particles are synthesized by using the method of twostep miniemulsion polymerization. In the first step, PU prepolymer is synthesized by isophorone diisocyanates (IPDI) and poly(propylene glycol) (PPG) with methyl methacrylate (MMA) as a solvent. Then the oil phase, including the NCOterminated prepolymer, MMA, hexadecane (HD), a chain extender as 1,4- butanediol (BD) or bisphenol A (BisA), a cross-linking agent trimethylol propane (TMP), and a catalyst dibutyltin dilaurate (SnDBL) is dispersed in the water phase containing SDS. Then the mixtures form miniemulsion by ultrasonication. Two kinds of initiators, BPO and KPS, are applied for the polymerization of MMA. The influences of chain extenders, initiators and PU/MMA weight ratios on the morphology of PU/PMMA latex particles are investigated. Conversion of MMA is measured and discussed. Particle sizes are analyzed by dynamic lighting scattering (DLS) and transmission electron microscopy (TEM). The cross section morphology of the hybrid particles is also characterized by TEM. For BD/BPO and BD/KPS systems, when increasing the load of PU component, PU-rich phase is moved to the outside of hybrid particles. A core-shell structure can be observed. However, for BisA/KPS system, while using hydrophobic bisphenol A as chain extender of PU, the boundary of PMMA and PU phases is not clear. A more homogeneous structure of hybrid particles is obtained.
Novel rapid response clay/poly(N-isopropylacrylamide) nanocomposite hydrogels by post treatment with HCl solution
Authors: Yun Ma , Yang Liu , Yongmei Jiang , Hao Yu , Meifang Zhu
Published: August 2014

A series of high clay content Laponite XLS/poly (N-isopropylacrylamide) (PNIPAAm) nanocomposite hydrogels (S-N gels) have been successfully prepared by in-situ ultraviolet (UV) initiated polymerization. The effects of post treatment with HCl solution on swelling/deswelling behaviour of the S-N gels have been investigated in detail. The results indicate that the Laponite XLS/PNIPAAm nanocomposite hydrogels with HCl solution post treatment (S-N-H gels) exhibit great swelling ratio and rapid deswelling response rate; much higher and faster than other reported clay/PNIPAAm nanocomposite hydrogels.
A Novel Poly(amido amine) with Methoxy Carbonyl Groups and High Charge Density: Synthesis and Nanoscopic Selfassembly with Polyanion
Authors: Chuan-bao Wu , Jian-yuan Hao , Deng Xian-mo
Published: August 2014

A novel poly(amido amine) with methoxy carbonyl groups, high charge density and broad nitrogen profile, was synthesized from tetraethylene pentamine (TEPA) and methyl acrylate (MA), and named as PTMA. During synthesis, on one hand, double bond of MA was added with amino group of TEPA by Michael addition reaction and, on the other hand, methoxy carbonyl group of MA was nucleophilicly substituted by amino group of TEPA. There are primary, secondary, tertiary amines and amide groups in PTMA molecule. Acid base titration indicated that the polymer was protonated in the range of both pH 5.0 to pH 7.4 and pH 7.4 to pH 11, which is indicative of not only good self-assembling capability with polyanion but also desirable proton sponge effect as shown by polyethylenimine (PEI). In aqueous solution, PTMA self-assembled with weak anionic polymer, poly(acrylic acid) (PAA), to form nanoparticles. The particle size first increased and then decreased with increasing mass ratio of PTMA to PAA, which is defined as θ. At all examined θ values, self-assembling particles with diameter less than 200 nm were obtained. The UV-Vis absorbance curve of self-assembling complex solution at first day overlapped with that at seventh day, indicating that self-assembling particles were stable.