bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the shrinkage of dental polymeric composites
Authors: Boguszewski Tomasz , Swieszkowski Wojciech , Lewandowska Malgorzata , Kurzydlowski Krzysztof J.
Published: August 2014

The aim of this study was to investigate the influence of size and shape of ceramic filler in dental composites on polymerization shrinkage. Moreover, the influence of resin shrinkage itself on the whole composite shrinkage was investigated. In 3D linear elastic finite element analyses, the process of shrinkage of dental resin/ceramic composites during polymerization was simulated using the ANSYS software. Composites were modelled with volumetric content of ceramics ranging from 0 up to 45%. Aggregates with different shape and size were analysed. Quantitative estimates have been obtained of the reduction in composite shrinkage with increasing content of ceramic aggregate or decreasing shrinkage of the resin. It has been found that by adjusting aggregate size and resin shrinkage a lower shrinkage of the dental composite may be obtained.
Starch-based multiphase polymer materials
Authors: Kozłowska Anna , Kozłowski Marek , Iwańczuk Andrzej
Published: August 2014

Biocomposites prepared by melt blending were investigated. The blends were composed of synthetic and natural macromolecules, including poly(vinyl alcohol), aliphatic-aromatic polyester and thermoplastic starch. Mechanical properties of the composites, their microstructure, melt rheology and thermal characteristics are presented. Influence of water on the properties as well as the degradation rate of the materials has been estimated as a function of their composition. Such materials may find applications for packaging as well as in medicine and biology as polymeric scaffolds, drug delivery systems etc.
Structural study of semi-crystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate) by means of linear correlation and interface distribution functions
Authors: Fatnassi Mohamed , Larbi Fadhel Ben Cheikh , Dubault André , Halary Jean Louis
Published: August 2014

In this article small-angle X-ray scattering (SAXS) is used to characterize the structural parameters of semi-crystalline blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate). Different blend compositions from 100 to 50 wt.-% of PVDF were investigated. The samples were considered to be isotropic. As two-dimensional SAXS patterns with cylindrical symmetry were examined, a single direction in the SAXS pattern plane was chosen to collect and plot absolute intensities versus the scattering vector. Using the one-dimensional (linear) electron density correlation and interface distribution functions obtained, respectively, from the Fourier-transformed Lorentz-corrected experimental scattering intensity and from the interference function, structural parameters such as the minimal value and the most probable value of the long period, the average lamellar thickness, and the volume crystallinity were determined.
Power-law distribution of molecular weights of nonlinear emulsion polymers
Authors: Tobita Hidetaka
Published: August 2014

It is shown that power-law distributed polymers can be synthesized via nonlinear emulsion polymerization. Theoretical simulation results demonstrate that emulsion polymers formed with polymer transfer reactions during interval II approach a power-law distribution as polymerization proceeds. The exponent α of the weight fraction distribution, W(M) ~ M -α, satisfies the simple relationship α = 1/Pb, where Pb is the probability that the chain end is connected to a backbone chain. This relationship can be used to estimate the polymer transfer constant on the basis of the measured molecular weight distribution. The branched polymer structure is significantly different from randomly branched polymers. The expected branching density of the large-polymer limit is equal to that for Pb = 1 of randomly branched polymers, irrespective of the magnitude of Pb in the emulsion polymers. A preliminary investigation shows that power-law distributed polymers can also be synthesized via crosslinking emulsion polymerization.
Synthesis and characterization of novel organosoluble aromatic copolyimides
Authors: Yang Jintian , Huang Wei , Zhou Yongfeng , Yan Deyue , Wang Xiaohang
Published: August 2014

A series of novel aromatic copolyimides was synthesized from pyromellitic dianhydride with the commercial diamine 4,4’-methylenebisaniline (MBA) and the diamine 4,4’-methylenebis(2-tert-butylaniline) (MBTBA) specially designed by ourselves. The solubility of the copolyimides in conventional solvents decreased with the mole ratio of MBTBA to MBA. When MBTBA/MBA was larger than 8/2, the copolyimides are soluble in low boiling point solvents (such as chloroform and tetrahydrofuran) and can form a transparent, flexible, tough film by solution casting. When MBTBA/MBA was between 7/3 and 5/5, the copolyimides are only soluble in dipolar aprotic solvents (such as dimethylformamide and N-methyl-2-pyrrolidone) and form films, too. The copolyimide was precipitated in m-cresol in the polymerization process when MBTBA/MBA was lower than 5/5. The number-average molecular weights of the soluble copolyimides measured by gel permeation chromatography were larger than 5.0·104 and the polydispersity index was higher than 1.5. Only one glass transition of these copolyimides was detected at around 350°C. The copolyimides did not show appreciable decomposition up to 400°C under air and 550°C under nitrogen, and their thermal stability increased a little with the introduction of MBA into the polymer chains.
Adsorption of monodisperse polybutadienes on carbon black, 3 Displacement of pre-adsorbed molecules by the same polymer. Conformational and molecular weight effects
Authors: Vuillaume Kathy , Haidar Bassel , Vidal Alain
Published: August 2014

Displacement of pre-adsorbed macromolecules by the same polymer, polybutadiene, of the same or of different molecular weight was studied in solution and in the bulk. The effect of polymer concentration on pre-adsorption and displacement processes was determined. Displacement was investigated by gel permeation chromatography and by determination of the amount of bound polymer before and after displacement. A conformational factor was established as a major driving force - besides molecular weight - in the displacement process. Polymer chains adsorbed in flat conformation had the highest adsorption stability and could not be displaced by any other molecular weight of the same polymer.
Self-organization of poly(N-isopropylacrylamide)-carrying microspheres into two-dimensional colloidal thin films
Authors: Tsuji Sakiko , Kawaguchi Haruma
Published: August 2014

A simple method to fabricate colloidal thin films with periodical structures was investigated. In this study, poly(N-isopropylacrylamide) (PNIPAM) microgel and polystyrene particles with PNIPAM chains on the surface (hairy particles) are used as components. Aqueous dispersions of these PNIPAM-carrying particles spontaneously form monolayers as water evaporates. After the medium is completely evaporated, periodical structures remain on the substrate. This paper focuses on the effect of graft chain density of the hairy particles on film formation.
Surface sulfate groups on poly(methyl methacrylate) and poly(vinyl acetate) particles from soap-free emulsion polymerization
Authors: Saiga Tadanobu , Suzuki Atsushi , Kikuchi Kenji , Okaya Takuji
Published: August 2014

The amounts of sulfate groups on the particle surfaces of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) obtained in soap-free emulsion polymerization were determined. Polymerization was carried out at low monomer concentration using ammonium persulfate as an initiator. After the ionexchange procedure, conductometric titration was carried out. Amounts of surface sulfate groups were lower and particle diameter was larger in the PMMA system compared with PVAc. A large and remarkable difference appeared in the ratio of surface sulfate groups to decomposed sulfate radicals, viz. 90% for the PVAc system and 50% for PMMA. The ratios of sulfate groups per polymer molecule on PMMA and PVAc particles (functionality) were calculated. The functionality of the PMMA system was 70% of the theoretical value, while it was close to 100% in the PVAc system. This large difference might arise from the weak reactivity of the sulfate radical with MMA compared with that of VAc, due to the strong electrophilic nature of the radical. A side reaction of the sulfate radical with MMA is assumed. On the basis of these experimental results, the instability of the emulsion polymerization of acrylic monomers using poly(vinyl alcohol) (PVA) as a protective colloid is discussed in terms of the instability of the soap-free particles formed after the consumption of free PVA in water by the grafting reaction.
Gelation of thermoplastic polyurethane/2-butanone solutions
Authors: Florez Sonia , Muñoz María Eugenia , Santamaría Anton
Published: August 2014

New features of thermoplastic polyurethane (PUR)/2-butanone gels are investigated, using dynamic viscoelastic measurements and differential scanning calorimetry. The work is focused on the effect of the hard-segments content on the gelation process. In the case of PUR with the highest hard-segment fraction (30%), soft segments are not able to crystallize on cooling from solution; consequently, gels are not formed. The copolymer with the lowest hard-segment content (12%) gives the shortest gel times. This is attributed to the low solution viscosity of this copolymer, which enhances the crystallization rate. All gels melt at 7°C, giving rise to a viscoelastic solution in a thermoreversible process. The critical gelation concentration is below the critical concentration for polymer chain entanglements.
Thermal Oligomerisation of Cardanol
Authors: Rodrigues Francisco Helder A. , Souza José Roberto R. , França Francisco Célio F. , Ricardo Nágila M. P. S. , Feitosa Judith P. A.
Published: August 2014

Cardanol was extracted from technical Cashew Nut Shell Liquid (CNSL), a naturally occurring meta-substituted long chain phenol and oligomerized by heating at 140 °C. Products were characterized by rheology, infrared and 1H NMR spectroscopy and thermogravimetric analysis (TGA). Increase in viscosity and the flow activation energy was found with increasing time of heating. The relative absorbance of double bond of the hydrocarbon chain decreased with time of heating and indicated that the oligomerization is taking place through the unsaturation of the side chain. Decrease in internal double bond as well as in vinyl bond, observed by 1H NMR, pointed out to the participation of these two kinds of unsaturation as well as monoene, diene and triene. The oligomerization is a slow process. With 40 h of heating, the average molecular weight increases only by 46%. Great differences were found in TGA curves of cardanol with different times of oligomerization. Thermal stability increases with time of heating. The degree of oligomerization could be determined from relative mass loss of the first event of TG, or from flow activation energy.
Synthesis and Characterization of a Novel Triblock Copolymer Containing Double-hydrophilic Blocks and Poly(fluoroalkyl methacrylate) Block via Oxyanioninitiated Polymerization
Authors: Xu Jie , Ni Peihong , Mao Jiang
Published: August 2014

A new triblock copolymer consisted of a double-hydrophilic diblock and a fluorinated block, namely poly(ethylene glycol)-b-poly[2-(dimethyl amino)-ethylmethacrylate]-b-poly(2,2,3,3,4,4,5,5-octafluoropentylmeth acrylate) (MePEG-b-PDMAEMA-b-POFPMA), was synthesized via oxyanioninitiated copolymerization. The hydroxyl group of poly(ethylene glycol) monomethyl ether (MePEG) reacted with potassium methylsulfinyl carbanion (DMSO-K+) and converted into a potassium alcoholate macroinitiator (MePEG-K). It could initiate DMAEMA monomer to yield a hydrophilichydrophilic diblock copolymer. If not quenched, the living chain could be subsequently used to initiate a second fed monomer such as OFPMA to produce a new triblock copolymer MePEG-b-PDMAEMA-b-POFPMA. As a comparison, the analogous triblock copolymers with different lengths of PDMAEMA and identical length of POFPMA were prepared. These copolymers were characterized by the measurements of 1H NMR, 19F NMR, and gel permeation chromatography (GPC). The results indicated that they had relatively low polydispersities (Mw/Mn̅ :1.25 −1.27) . The comparison of the critical aggregation concentration (CAC) of diblock copolymer MePEG-b- PDMAEMA and triblock copolymer MePEG-b-PDMAEMA-b-POFPMA has been investigated by measurements of surface tension and electrical conductivity. It was also found that the lower critical solution temperatures (LCSTs) of the di- and triblock copolymers varied with different factors, including the chemical structure, the length of DMAEMA block, and the concentration of the aqueous solution.
Molecular weight and contraction factors of hyperbranched poly(urea-urethane)s
Authors: Lederer Albena , Elrehim Mona Abd , Schallausky Falko , Voigt Dieter , Voit Brigitte
Published: August 2014

Elution fractionations of broadly molar mass-distributed, hyperbranched poly(urea-urethane)s with OH- and Ph- end groups were carried out to obtain a number of macromolecular samples possessing different molar masses at the same chemical structure. The characterization of the polymers was performed by SEC, MALLS, 1H-NMR, MALDI-TOF-MS and viscosity measurements. Modifications of the OH-end groups of the polymers were carried out. We observed a strong influence of the end groups on the solution behaviour of the hyperbranched samples. The molecular shape of the hyperbranched polymers in solution was compared to their linear analogue using the Kuhn-Mark-Houwink- Sakurada relationship. The calculated contraction factors between 0,15 and 0,7 depending on the molar masses correspond to a very compact structure of the modified branched polymers at high molar masses.
Dynamic Dilution Effects in Polymeric Networks
Authors: Larsen Anne Ladegaard , Sommer-Larsen Peter , Hassager Ole
Published: August 2014

The relaxation processes occurring in slightly and well-entangled polydimetylsiloxane (PDMS) networks are investigated. Swelling experiments are performed in order to determine the sol fractions. The low-frequency linear rheology of the two types of networks reveal two significant relaxation processes, namely the reptation of linear species within the network and the arm withdrawal process of star arms in the sol fraction and of dangling single-chain ends attached to the network. The relaxation spectra are influenced by the stoichiometry to a large extent due to dynamic dilution effects caused by the change in the amount of dangling arms and solubles with stoichiometry. The star arm relaxation is suppressed by washing out the sol fraction which is seen as a clear example of the dynamic dilution effect arising from the small amount of non-reactive PDMS.
Synthesis and characterization of hyperbranched poly (sulfone-amine) modified β-cyclodextrin
Authors: Chen Liang , He Peng , Jia Zhifeng , Zhu Xinyuan , Yan Deyue
Published: August 2014

An economical strategy to prepare hyperbranched poly(sulfone-amine) modified β-cyclodextrins (HPSA-m-CDs) from natural β-cyclodextrin (β-CD) and other commercially available materials has been reported. The final product has many good properties of hyperbranched poly(sulfone-amine)s (good solubility, low viscosity etc.), while its inclusion ability can also be well kept. It is a feasible approach to prepare functionalized modified cyclodextrin at very low cost, and may have potential applications in the fields of catalysis, drug delivery, food additives, etc.
Fractional isolation and structural characterisation of hemicellulosic polymers from delignified and ultrasonic irradiated sugarcane bagasse
Authors: Ren Jui-Li , Geng Zeng-Chao , Liu Chan-Fu , Xu Feng , Sun Jin-Xia , Sun Run-Cang
Published: August 2014

Hemicellulose-type polysaccharides were isolated from the delignified and ultrasonic irradiated sugarcane bagasse by a sequential two-step alkaline extraction. It was found that the successive extractions with 15% and 18% KOH for 2 h, 15% and 18% NaOH for 2 h, 8% and 10% KOH for 15 h, and with 8% and 10% NaOH for 15 h resulted in a total dissolution of 89.6%, 92.8%, 94.9%, and 97.3% of the original hemicelluloses, respectively. Sugar analysis revealed that xylose was the predominant sugar composition of all the hemicelluloses, comprising 57.4- 68.6% of the total sugars. Arabinose (12.3-18.4%) and glucose (10.8- 14.6%) appeared as the second and third major sugar constituents. Galactose (3.9-8.7%), uronic acids, mainly 4-O-methyl-glucuronic acid (2.7-5.8%), rhamnose (1.2-2.6%), and mannose (0.2-1.3%) were observed as minor constituents. The structural studies by 13C-NMR spectroscopy showed that L-arabino (4-O-methyl-D-glucurono) xylans were the major constituents of the hemicellulosic polymers. Furthermore, the current results also showed that the four alkali-soluble hemicellulosic fractions, isolated during the first step treatment with relatively lower concentrations of alkalis, were more branched and acidic, and had larger molecular weights (Mw, 23100-34500), but lower thermal stability than the other four alkali-soluble hemicellulosic preparations (Mw, 21700-28700), extracted during the second stage treatment with relatively higher concentrations of alkalis.
Preparation and characterization of sulfone-based polyimide nanofoams grafted with poly(propylene glycol)
Authors: Mehdipour-Ataei Shahram , Saidi Samaneh
Published: August 2014

A route to thermally stable polyimide nanofoams was developed. Nanofoams were prepared from graft copolymers consisting of thermally stable and thermally labile blocks as continuous and disperse phase, respectively. The copolymers were synthesized via reaction of sulfone-based diamines with aromatic dianhydrides through the poly (amic acid) precursor, followed by thermal imidization. Foam formation was achieved by thermolysis of thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Polyimide precursors and nanofoams were subjected to a variety of characterization including FT-IR, thermal gravimetric analysis (TGA), dielectric constant, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The nanofoams showed good processability, high thermal stability, and low dielectric constant which are prerequisites for application in electronic industry.
A New Accurate Neural Network Quantitative Structure- Property Relationship for Prediction of θ (Lower Critical Solution Temperature) of Polymer Solutions
Authors: Gharagheizi Farhad
Published: August 2014

In this study, a new neural network quantitative structure-property relationship model for prediction of θ (LCST ) of polymer solutions is presented. The parameters of this model are eight molecular descriptors which are calculated only from the chemical structure of polymer and solvent. These eight molecular descriptors were selected from 3328 molecular descriptors of polymer and solvent available in polymer solution by genetic algorithm-based multivariate linear regression (GA-MLR) technique. The obtained neural network model can predict the θ (LCST ) of 169 polymer solutions with mean relative error of 1.67% and squared correlation coefficient of 0.9736.
Preparation, Characterization and Swelling Behaviours of a Novel Multifunctional Superabsorbent Composite Based on Ca-Montmorillonite and Sodium Humate
Authors: Zheng Yian , Wang Aiqin
Published: August 2014

In this work, a novel water-managing superabsorbent composite was prepared by graft copolymerization reaction using acrylic acid (AA) and acrylamide (AM) as the monomers, calcium montmorillonite (Ca-MMT) as an inorganic component and sodium humate (SH) as fertilizer, and well characterized by means of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effects of the reaction temperature, neutralization degree of AA, amount of crosslinker, initiator, Ca-MMT and SH on water absorbencies were systematically investigated. The water absorbencies of the superabsorbent composite synthesized under optimal conditions with a Ca-MMT content of 20 wt% and an SH content of 30 wt% are 615 g g-1 and 45 g g-1 in distilled water and in 0.9 wt% NaCl solution, respectively. The swelling behaviours of the superabsorbent composite in various cationic salt solutions (NaCl, CaCl2 and FeCl3) were also investigated and it was found that at the same saline concentration (> 0.1 mmol L-1), the effect of three cationic salt solutions on the swelling capability has the following order: NaCl < CaCl2 < FeCl3. Here, it is worthy to point out that the water absorbency and swelling behaviours of the developed composite were improved by introducing simultaneously Ca-MMT and SH into PAA-AM network in comparison with that of incorporated single with Ca-MMT or SH.
Novel results and potential applications of bitumen used as an additive for polyethylene
Authors: Goikoetxeaundia Goretti , Mateos Alexander , González Oscar , Muñoz María Eugenia , Santamaría Anton , Martínez Inmaculada
Published: August 2014

A metallocene catalysed linear low density polyethylene (mLLDPE) was mixed with very low amounts of bitumen (1-2%) as an additive. Bitumen interacts with mLLDPE giving rise to a dying effect, which turns the originally white mLLDPE extrudates into black. No slippage is observed during extrusion and sharkskin is postponed as bitumen is added. “Melt strength” values of the blends, determined in melt spinning experiments, are very similar to those of mLLDPE. Accordingly good performance is expected in film-blowing process. Tensile modulus values are higher than 109 Pa. Bitumen emerges as an alternative to carbon black powder currently used to obtain black polymer films.
Thermotropic Behaviour of Liquid Crystalline Poly[n-(4’- cyanophenyl-4’’-phenoxy)alkyl acrylate] Gels in the Dry and Swollen States
Authors: Vendamme Richard
Published: August 2014

This paper reports the thermotropic behaviour of various side-chain liquid crystalline (LC) networks and gels of poly[n-(4’-cyanophenyl-4’’-phenoxy)alkyl acrylate]. Increasing the aliphatic spacer length tend to increase the melting temperature of the pure LC polymers. On the other hand, increasing the crosslinking density lead to a decrease and broadening of the melting transition temperature. Swelling of a liquid crystalline elastomer in a low molar weight liquid crystal (LMWLC) leads to the formation of a LC gel, with thermotropic properties drastically different from the original LC polymers and solvents. The thermotropic behaviour of such an LC gel is determined by several parameters, such as the concentration of LMWLC inside the gel and the compatibility between the two types of mesogens.
Synthesis and complete NMR characterization of methacrylateendcapped poly(ortho-esters)
Authors: Paesen Bert , Baekelandt Tom , Heller Jorge , Martins José C. , Schacht Etienne H.
Published: August 2014

In this paper a synthesis method for low molecular weight poly(orthoesters) with photo crosslinkable methacrylate endgroups is presented. Using this procedure, the molecular weight could be controlled and the desired endgroup functionality was introduced in a single reaction step. The detailed characterization of the molecular structure of bismethacrylate endcapped poly(ortho-esters) using NMR affords a re-evaluation of previous assignments reported for similar poly(ortho-ester) polymers. In addition, the use of diffusion filtered 1D 1H NMR spectroscopy as a simple but effective analysis tool that allows to distinguish resonance contributions from impurities and low molecular weight compounds, most probably the result of degradation, from those of the full size polymer, is demonstrated.
Structure and Mechanical Properties of Carboxylated Styrene-Butadiene Rubber (XSBR)/Pristine Clay Nanocomposites
Authors: Abdollahi Mahdi , Rahmatpour Ali , Khanli Homayon Hossein
Published: August 2014

Carboxylated styrene- butadiene rubber (XSBR)/clay nanocomposites were prepared by mixing the XSBR latex with aqueous clay dispersion and cocoagulating the mixture. TEM and XRD were applied to characterize the structure of nanocomposites. Fully exfoliated structure was observed for the nanocomposites containing equal to or less than 10 phr (weight parts per hundred) clay. With increasing the clay content to 20 phr, both non-exfoliated (stacked layers) and exfoliated structures can be observed simultaneously in the nanocomposites. The results of mechanical tests on the vulcanized clay-free XSBR and XSBR/clay nanocomposites showed that the nanocomposites present better mechanical properties than clay-free XSBR vulcanizate. Furthermore, modulus, tensile strength, tensile strain at break and hardness (shore A) increased with increasing the clay content, indicating the nanoreinforcement effect of clay on the mechanical properties of XSBR/ clay nanocomposites.
New epoxy-ionic liquid dispersions. Room temperature ionic liquid as lubricant of epoxy resin-stainless steel contacts
Authors: Sanes José , Carrión-Vilches Francisco-José , Bermúdez María-Dolores
Published: August 2014

Room-temperature 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (IL) reduces friction and wear of epoxy resin/AISI 316L stainless steel contacts when used as neat external lubricant. In order to study the internal lubricant performance of IL, variable concentration epoxy+IL dispersions containing 0.5-3.3 wt.% IL were obtained by mechanical mixing and casting. SEM cryofracture and EDS show dispersed rounded IL particles within the epoxy matrix. The new dispersions have slightly lower Tg and hardness values than the unmodified resin. Fracture modes and tensile strength are similar for epoxy and epoxy+2.7%IL, although the elongation at break reduces in presence of IL. Pin-on-disc tests show that dry friction coefficients decrease exponentially as the IL proportion increases and wear resistance improves in several orders of magnitude for a critical IL concentration of 2.7 wt.%. Wear mechanisms are discussed on the basis of SEM and AFM observations. The surface modification of the new dispersions gives lower static and dynamic friction coefficients when sliding against steel or polytetrafluoroethylene sheets under mild conditions.
Synthesis of α,ω-bis(3-aminopropyldiethoxylsilane) Poly(tri fluoropropylmethyl)siloxanes
Authors: Shi Zhendong , Wang Xinling
Published: August 2014

High molecular weight α,ω-bis(3-aminopropyldiethoxylsilane) poly(tri fluoropropylmethyl)siloxanes (APTFPMS) were prepared via a “one-step” process, based on the ring-opening polymerization of 1,3,5-tris(trifluoropropylmethyl) cyclotrisiloxane (F3) in the presence of water and 3-aminopropyltriethoxysilane (APTES). GPC, FT-IR and 1H NMR confirmed the structure of the polymers. It was found that the amount of APTES had significant influence on the reaction rate and the molecular weights of polymers decreased with the increasing amount of water. It was probably because both water and the amino group of APTES favoured generation of hydroxyl ions, which efficiently initiate the polymerization of F3 to achieve APTFPMS. In order to verify this mechanism, another “two-step” process was also performed: Firstly the α,ω-dihydroxylated poly(trifluoropropylmethyl) siloxanes were synthesized from F3 catalyzed by both diaminoethane and water, then reacted with APTES to achieve APTFPMS. All the syntheses had high yields and the molecular weight of the polymers ranged from 2000 to 25000.
Synthesis and characterization of the polyacrylate latex functionalized by fluorine and silicon
Authors: Ding Xiaofeng , Guan Rong , Chen Peizhi
Published: August 2014

Novel functionalized polyacrylate latex with fluorine and silicon was prepared by semi-continuous dropping technique. 19F NMR, elemental analysis of the silicon (EAS) and FT-IR measurements prove that 2,2,2-trifluoroethyl methacrylate (TFEMA) and α,ω-bis(hydroxyl)polydimethylsiloxane (PDMSH) is successfully polymerized. TEM demonstrates that the functionalized latex particles were spherical, uniform and stable. Contact angle measurement and surface energy estimation show that the highest water contact of the functionalized latex films were 118.3° and the surface energy was as low as 11.7 mJ/m2. Water absorption ratio measurement reveals that the water resistance of the functionalized latex films is improved. The heat resistance of the functionalized latex films does not show a large difference from that of the original polyacrylate in our investigated systems.
Preparation, Morphology and Thermal Properties of Rubber-Modified Polyester Resins
Authors: Munyati M O , Lovell P A
Published: August 2014

The preparation of polyester resin blends consisting of an unsaturated polyester resin matrix and rubbery particles comprising three radially-alternating glassy and rubbery layers is described. The morphology of the resin blends was examined by transmission electron microscopy (TEM) while thermal properties were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The results show that the particles were prepared with good control of particle size and morphology. DMTA results showed no reduction in the Tg of the matrix whilst the shear modulus of modified materials was found to be lower than that of the matrix material.
Synthesis of Imidazole End-Capped Poly(n-butyl methacrylate)s via Atom Transfer Radical Polymerization with a new functional initiator containing imidazolium group
Authors: Zhu Aihua , Wang Zhi , Xie Meiran , Zhang Yiqun
Published: August 2014

The synthesis of imidazole end-capped poly(n-butyl methacrylate)s via atom transfer radical polymerization (ATRP) is reported. n-Butyl methacrylate (n- BMA) was polymerized in isopropyl alcohol (IPA) at different temperatures via ATRP using a new N-heterocyclic functional initiator (1-α-bromoisobutylimidazole, BrBI) in the presence of CuBr/2,2’-bipyridine (bpy) as the catalyst. With this new initiating system, a successful ATRP of n-BMA was carried out, and imidazole endcapped polymers with predetermined molecular weights and low polydispersities (1.1<PDI<1.3) were obtained at low polymerization temperature (below 80 °C). Furthermore, the dependence of both the rate of polymerization and PDI on temperature gave the optimal reaction temperature (50 °C). However, at elevated temperature (especially above 80 °C), some different phenomena appeared in the polymerization: the conversion of monomer remains constant after reaching a maximum value (20%-30%), and the higher the temperature, the lower the conversion obtained.
Highly soluble and colorless fluorinated poly(ether imide)s based on 4,4’-(2,5-tolylenedioxy)diphthalic anhydride and trifluoro methyl-substituted aromatic bis(ether amine)s
Authors: Yang Chin-Ping , Hsiao Sheng-Huei , Su Yu-Yang , Lin Chun-Hung , Hsu Mei-Yuan
Published: August 2014

A series of novel fluorinated poly(ether imide)s (PEIs) IVa-h were synthesized from 4,4’-(2,5-tolylenedioxy)diphthalic anhydride (I) and various trifluoromethyl-substituted aromatic bis(ether amine)s (IIa-h) via a conventional two-step method with thermal or chemical imidization of the precursor poly(amic acid)s. These PEIs were readily soluble in a variety of organic solvents; they were soluble with a concentration higher than 10% in amide-type polar solvents, ether type solvents, and chlorinated hydrocarbons. The solution-cast films showed a high optical transparency and low color intensity, with an ultraviolet-visible absorption edge of 371- 377 nm and low b* values (a yellowness index) of 4.9-7.5. These films were strong and tough with tensile strength of 90-103 MPa. They exhibited glass-transition temperatures (Tg) in the range of 207-293oC, with 10% weight loss temperature in excess of 500oC in air or nitrogen atmosphere. They also showed low-dielectric constants (2.95-3.37 at 1 MHz) and low moisture absorption (0.20- 0.67 wt %).
Fabrication of cucurbit[6]uril mediated alginate physical hydrogel beads and their application as a drug carriers
Authors: Huang Xiaoling , Tan Yebang , Zhou Qifeng , Wang Yuexia
Published: August 2014

A novel cucurbit[6]uril (CB[6]) mediated alginate physical hydrogel bead was prepared for the first time, which is based on the electrostatic attraction and ion-dipole interaction between sodium alginate and CB[6]. These alginate/CB[6] gel beads are useful in controlled drug delivery and other biomedical applications. The potential of alginate/CB[6] gel beads as carrier for 5-Fluorouracil (5-Fu) was studied in this paper. The properties of alginate/CB[6] gel beads were studied by FT-IR, XRD and TGA. The process of the formation of alginate/CB[6] gel beads was recorded by Digital cameras. The external morphology of the dried beads were observed using SEM. Alginate/CB[6] gel beads first was formed as a thin film on the surface of the alginate solution droplet, holding its spherical shape. The color of the alginate/CB[6] gel beads changed from almost colorless to white with the increase of gel time, and also the beads became small and compact. The dried alginate/CB[6] gel beads were about 900-1000 μm, irregular spherical and the surface of dried beads showed a corrugated surface having a uniform distribution of regular nodules and cavities.
Carboxyl functionalized poly(methyl methacrylate-acrylic acid-ethylene glycol dimethacrylate) copolymer particles and their amination with amine-nucleophiles
Authors: Ahmad Hasan , Hossain Md. Emtiaz , Rahman M. Abdur , Rahman M. Mahbubor , Miah M. A. Jalil , Tauer Klaus
Published: August 2014

Poly(methyl methacrylate-acrylic acid-ethylene glycol dimethacrylate) copolymer particles abbreviated as P(MMA-AA-EGDM) copolymer particles were prepared by soap-free emulsion copolymerization. The concentration of carboxyl group on/near the surface of particles increased with the increase in acrylic acid (AA) content in the recipe. The carboxyl groups were reacted with amine nucleophiles such ethylene diamine and 1,6-diaminohexane through preactivation with dicyclohexyl carbodiimide as a coupling agent. The modified particles were characterized by electron micrographs and FTIR spectral analysis. Adsorption behaviours of some biomolecules were measured to have idea about=-0 the polarity of the particles surface
Preparation of super HIPS via nanocomposite assemblies in the presence of toughener- intercalant
Authors: Bagcioglu Cuneyt , Sen Sinan , Yagci Yusuf , Nugay Turgut , Nugay Nihan
Published: August 2014

Highly toughened super high-impact polystyrene (HIPS)/organophilic montmorillonite (Org-MMT) nanocomposite was prepared by solution blending method. Organophilic modification of MMT layered silicate was achieved by using a special toughener-intercalant, quaternary ammonium salt of α-tertiary amine functionalized polybutadiene and shown by X-ray diffraction analysis. The resulting HIPS/Org-MMT nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and static and dynamic mechanical analyses. The morphological study of HIPS/Org-MMT nanocomposite showed that nanolayers were exfoliated in nanocomposite and moreover caused much more well dispersed and reduced PS occluded rubber domains. This mechanism was found to be responsible for dramatic increase in toughness of nanocomposites. Additionally, improved thermal and dynamic mechanical properties of the resultant nanocomposite promises to open a new way for highly toughened super HIPSs via nanocomposite assemblies even with a very low degree of clay loading.
Rapid phthaloylation and succinylation of hemicelluloses by microwave irradiation
Authors: Peng Feng , Ren Jun-Li , Sun Xiao-Feng , Xu Feng , Sun Run-Cang , Peng Bai , Sun Jin-Xia
Published: August 2014

Rapid phthaloylation and succinylation of wheat straw hemicelluloses with phthaloyl dichloride (PdC) and succinyl chloride (SC) in N,Ndimethylformamide/ lithium chloride (DMF/LiCl) system using N-bromosuccinimide (NBS) as a catalyst was achieved for only 5 minutes at 50 °C by microwave irradiation. The degree of substitution (DS) ranged between 0.43 and 1.47. The effect of the molar ratios of xylose units in hemicelluloses to phthaloyl dichloride or succinyl chloride on the degree of substitution was investigated. It was found that the reactivity of succinyl chloride was higher as compared to Phthaloyl dichloride under similar experimental conditions. 13C NMR studies revealed that the esterification occurred at the C-3 and C-2 positions in the β-D-xylose units of hemicelluloses, but preferentially at C-3 position. However, it should be noted that microwave irradiation did result in more degradation of the macromolecular hemicelluloses than conventional heating technique as shown by a lower thermal stability of the hemicellulosic derivatives obtained by microwave irradiation than those obtained by conventional heating technique.
Electromechanical properties of poly(dimethylsiloxane) and poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) blends
Authors: Wichiansee Wijittra , Sirivat Anuvat
Published: August 2014

Electromechanical properties of crosslinked polydimethylsiloxane (PDMS) and PDMS_PEDOT/PSS blends were investigated as potential actuator materials. Experiments were carried out under the oscillatory shear mode and with applied electric filed strength varying from 0 to 2 kV/mm. The storage modulus, G', of the crosslinked PDMS increases with increasing electric filed strength with a scaling behavior: ΔG' α Eα where the scaling exponent α is equal to 0.88. With PEDOT/PSS particles added at volume fractions of 5, 10, 15, and 20 vol%, the storage modulus G' of the polymer blends, are higher than that of the pristine crosslinked PDMS. The scaling exponent of the scaling behavior decreases from 0.88 to 0.10 as the volume fraction increases from 0 to 20 vol%. The storage modulus sensitivity,, attains maximum values of 8%, 9%, 10%, and 9%, at particle volume fractions of 5, 10, 15, and 20 vol%, respectively at the electric field strength of 2 kV/mm. Temporal response of the crosslinked PDMS system is irreversible, but the response of the PDMS_PEDOT/PSS system is evidently reversible
Electrospinning of poly-L-lactide nanofibers on liquid reservoir collectors
Authors: Röcker Thorsten , Greiner Andreas
Published: August 2014

The electrospinning process of Poly-L-lactide (PLA) solutions using liquid reservoir collectors was studied. As collector liquids, distilled water and sodium chloride solutions of different concentrations were used. A new, non-linear correlation of the fiber diameter and the filling of the collector was found. It was also proved, that the electrical conductivity of the substrate has a strong influence on the electrospinning process and the nanofibers obtained therein, both in diameter and in morphology
Studies on the structure, morphology and thermal properties of HDPE/ petroleum resin blends
Authors: Wu Chifei , Cao Deming , Cao Yuanyi , Gao Yuanji , Guo Weihong
Published: August 2014

The phase structure, crystallization and melting behavior of high density polyethylene (HDPE) blends with hydrogenated petroleum resin P-100 were investigated by polarized optical microscopy (POM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Results of polarized optical microscopy and scanning electron microscopy indicated that the structures of blends had a three-dimensional bi-continuous network. The network sizes depended on the blends composition and crystallization conditions, when the blends were quenched or cooled down slowly below the melting temperature of HDPE from molten state; the network sizes decreased with both the increasing of HDPE content and the decreasing of the quenching temperature. Differential scanning calorimeter analysis revealed that the melting point and crystallization temperature of HDPE in blends shifted to lower temperature with the decreasing of HDPE concentrations. The depression of HDPE melting point and crystallization temperature in blends were attributed to the smaller sizes of HDPE crystallites in presence of petroleum resin. The activation energy values and nucleation activity values indicated HDPE had lower crystallization activation energy and P-100 acted as a more effective nucleating agent only at low HDPE concentration
Synthesis of carboxymethyl-chitosan/acrylic acid hydrogel using silane crosslinker
Authors: Yasin Tariq , Rasool Nadia , Akhter Zareen
Published: August 2014

Novel pH sensitive carboxymethyl (CM) chitosan/acrylic acid hydrogels were prepared. CM-chitosan and acrylic acid (AA) in aqueous solution were copolymerized and crosslinked by using vinyltriethoxysilane (VTESi). Different amounts of AA and crosslinker were incorporated in CM-chitosan/AA hydrogel. IR analysis confirmed the presence of pyranose ring as well as Si-O-Si linkage within the hydrogel. Thermogravimetric analysis showed an increase in the stability of hydrogel either having high AA ratio or high crosslinker ratio. The swelling of the hydrogels was carried out by investigating the effect of time, pH (buffered and nonbuffered) and ionic media. In non-buffered media the overall swelling was found to be high as compared to buffered media. Maximum swelling was observed in hydrogel having mass ratio of 7.0 (AA : CM-chitosan). This hydrogel showed low swelling in low pH similar to that of the stomach and high swelling in neutral pH similar to that of the small intestine and can be used in drug delivery applications
Comparison of conventional and controlled bulk polymerization of styrene by N-methyl-2-pyrrolidone and 1-dodecanethiol
Authors: Krajnc Matjaž , Poljanšek Ida , Likozar Blaž
Published: August 2014

Controlled radical polymerization of styrene was initiated using Nmethyl- 2-pyrrolidone (NM2P) and 1-dodecanethiol (1DT). This polymerization system exhibited “living” characteristics, namely the molecular weight averages of resulting polymers increased linearly with conversion, which has been determined by gel permeation chromatography (GPC) analysis. The polymer was additionally characterized with Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. Kinetics of controlled radical polymerization has been studied and the temperature dependency of overall polymerization rate constant has been determined. A comparison of conventional bulk radical and controlled bulk radical polymerization of styrene has been explored. Conventional radical polymerization was initiated with 2,2’-azobis(2- methylpropionitrile) (AIBN), whereas 1-dodecanethiol was applied as a chain transfer agent. The reaction rate of controlled radical polymerization was slower than the reaction rate of conventional radical polymerization initiated with AIBN. Consequentially, the activation energy and the pre-exponential factor were lower in the case of controlled polymerization in comparison to the ones observed in the conventional - AIBN initiated - system. Furthermore, by comparing the controlled to the conventional radical polymerization lower polydispersities were observed. Macromolecular structure analysis suggested a more linear chain structure in the controlled radical polymerization system. The thermal properties of polymer products have also been studied and the corresponding glass transition temperatures were higher upon comparison of the conventional and the AIBN initiated system, respectively
Ruthenium(II) Ions triggered direct supramolecular polymerization of bis-terpyridine poly(ethylene glycol): New Insights on synthesis and optimization
Authors: Chiper Manuela , Hoogenboom Richard , Schubert Ulrich S.
Published: August 2014

In order to obtain linear and high molecular weight Ru(II) coordination polymers, we investigated the reaction conditions for the direct one-step metallopolymerization of bis-terpyridine poly(ethylene glycol) 3 with RuCl3 in the presence of reducing agents. Here we discuss the direct synthesis method, the optimization and the purification of the water soluble Ru(II) chain extended poly(ethylene glycol). The optimization of the metallo-polymerization was monitored by SEC. For the highest molecular weight Ru(II) coordination polymer 4 obtained in this study, full characterization was performed by 1H-NMR and UV-Vis spectroscopy as well as SEC proof for the formation and the stability of the designed structure
Use of the SPME-GC-MS technique to study the thermal degradation of isotactic polypropylene: Effects of temperature and reaction time, and analysis of the reaction mechanism
Authors: Bortoluzzi Janina H. , Cristiano Rodrigo , Gallardo Hugo A. , Carasek Eduardo , Soldi Valdir
Published: August 2014

Commercial fibers covered with poly(dimethylsiloxane) were used to pre-concentrate (solid phase microextraction technique) products evolved from the thermal degradation of isotactic polypropylene. Although the analysis by GC-MS indicated the formation of more than one hundred evolved products (ca. forty were identified), only twenty nine formed at 470°C (the temperature of maximum degradation rate for isotactic polypropylene) were analyzed. The main compounds identified were 2,4-dimethyl-1-heptene, 2-methyl-1-pentene, 2,3-dimethyl hexane, n-pentane and 1,3,5-trimethyl cyclohexane. The analysis at 470°C, using different degradation times, also indicated that the compounds 2-methyl-1-pentene and 2,4- dimethyl-1-heptene (major products) were formed at 15 and 25 minutes, respectively. The mechanism proposed for the formation of the major compounds was based on radical formation through chain cleavage (allyl and secondary radicals), followed by a chain decomposition process via hydrogen radical addition or cyclization to a thermodynamically stable six-membered ring.
Chain Extender and Diisocyanate Amount Effects on the Thermal, Mechanical and Wettability Properties of Some Polyurethane Elastomers
Authors: Vlad Stelian , Oprea Stefan
Published: August 2014

The aim of this study was to investigate the effect of chain extender and diisocyanate amount on the thermal, mechanical and wettability properties of some polyurethanes. The chain extender nature caused the increase of the thermal stability due to the higher stability of the double and triple bonds respectively in contrast to simple bonds. Tg of the polyurethanes based on PCL/MDI decreased when the unsaturated grade from chain extenders increased. The double and triple bonds content from polyurethane structure was responsible for this behavior. The hard segment contents and the chain extenders nature also influenced the wettability. The results showed that the thermal, mechanical and wettability properties of the final products might be controlled by fine control of the amount of the MDI and the nature of the chain extenders
First approach on transfection ability of novel amphiphilic water soluble degradable poly(ε-caprolactone)-g-poly(Llysine) copolymers
Authors: Nottelet Benjamin , Vendrell Julie , Coudane Jean , Vert Michel
Published: August 2014

The potential of novel amphiphilic water soluble and degradable poly(ε- caprolactone)-g-poly(L-lysine) as carriers for DNA transfection has been investigated. Two graft copolymers having the same proportion of lysine units but different structures have been synthesized following two grafting techniques. The chemical composition of these copolymers, their expected architectures and their behaviour in aqueous solutions have been studied. The benefits resulting from the use of these degradable polycationic structures as well as their ability to form polyplexes are discussed. Finally, preliminary transfection assays of MCF-7 cells by pRL-TK plasmid using poly(ε-caprolactone)-g-poly(L-lysine) copolymers as carriers are reported.