Home About us Contact
|
Home About us Contact | ||
|
|
||
Random Copolymers (random + copolymer)
Selected AbstractsSynthesis and Characterization of Biodegradable Poly(, -caprolactone)-Polyglycolide-Poly(ethylene glycol) Monomethyl Ether Random CopolymerMACROMOLECULAR MATERIALS & ENGINEERING, Issue 6 2004Shaobing Zhou Abstract Summary: Poly(, -caprolactone)-polyglycolide-poly(ethylene glycol) monomethyl ether random copolymers were synthesized from , -caprolactone (, -CL), glycolide (GA) and poly(ethylene glycol) monomethyl ether (MPEG) using stannous octoate as catalyst at 160,°C by bulk polymerization. The copolymers with different composition were synthesized by adjusting the weight ration of reaction mixture. The resultant copolymer with a weight ratio (10:15:75) of MPEG2000, GA, and CL was characterized by IR, 1H NMR, GPC and DSC. The new biodegradable copolymer has potential for medical applications since it is combined with properties of PCL, PGA and MPEG. [source] Effect of Comonomer Ethylene on Plateau Modulus of Crystal-line Ethylene-propylene Random Copolymer with Broad Molecular Weight DistributionCHINESE JOURNAL OF CHEMISTRY, Issue 6 2005Ding Jian Abstract Ethylene-propylene random copolymer with ultra-high molecular weight (UHPPR) and broad molecular weight distribution (MWD) was prepared with Ziegler-Natta catalyst. The viscoelastic behavior of UHPPR has been investigated by means of oscillatory rheometer at 180, 200 and 220 °C. The loss modulus (G, curves of 180 and 200 °C present a pronounced maximum at 38.10 and 84.70 r/s, respectively. For the first time, this makes it possible to directly determine the plateau modulus () of crystalline ethylene-propylene random copolymer with broad MWD in a certain experimental temperature G,(,) curve. The plateau modulus of UHPPR is 4.51×105 and 3.67×105 Pa at 180 and 200 °C respectively, increasing with random incorporation of comonomer ethylene into the molecular chains and being independent of molecular weight. [source] FTIR Microanalysis and Phase Behaviour of Ethylene/1-Hexene Random CopolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2007Mariano Pracella Abstract Ethylene/1-hexene random copolymers with 1-hexene content in the range of 1,5 mol-%, synthesised in the presence of new heterogeneous catalyst systems based on bis-carboxylato and -bis-chloro-carboxylato titanium chelate complexes, have been characterised by FTIR microspectroscopy (FTIR-M), DSC calorimetry and X-ray scattering. The co-monomer content and sequence distribution in the various samples were determined by means of both FTIR-M and 13C NMR spectroscopy. The deformation bands of methyl groups in the region of 1,400,1,330 cm,1 were used for the structural analysis of these copolymers. The effect of composition on the crystallinity and phase transitions of copolymers was analysed both in 1,500,1,300 and 760,690 cm,1 frequency ranges as a function of the annealing temperature. A neat variation of the absorbance ratio of methyl band at 1,378 cm,1 was recorded between 110 and 130,°C corresponding to the melting range of the copolymer crystals. The crystallisation behaviour of the copolymers was examined by DSC in dynamic and isothermal conditions; the isothermal kinetics were analysed according to the Avrami model. A marked decrease in the bulk crystallisation rate, accompanied by changes in the nucleation and growth of crystals, was found with an increase in the co-monomer content. The melting behaviour of isothermally crystallised samples was also investigated and the melting temperatures of the copolymers at equilibrium conditions were related to the composition; the experimental data were consistent with the Flory exclusion model of side branches from the crystalline phase. The lowering of crystal growth rate in the copolymers has been accounted for by an increase in the free energy of formation of critical size nuclei due to the effect of the side branches. [source] QSPR Analysis of Copolymers by Recursive Neural Networks: Prediction of the Glass Transition Temperature of (Meth)acrylic Random CopolymersMOLECULAR INFORMATICS, Issue 8-9 2010Carlo Giuseppe Bertinetto Abstract The glass transition temperature (Tg) of acrylic and methacrylic random copolymers was investigated by means of Quantitative Structure-Property Relationship (QSPR) methodology based on Recursive Neural Networks (RNN). This method can directly take molecular structures as input, in the form of labelled trees, without needing predefined descriptors. It was applied to three data sets containing up to 615 polymers (340 homopolymers and 275,copolymers). The adopted representation was able to account for the structure of the repeating unit as well as average macromolecular characteristics, such as stereoregularity and molar composition. The best result, obtained on a data set focused on copolymers, showed a Mean Average Residual (MAR) of 4.9,K, a standard error of prediction (S) of 6.1,K and a squared correlation coefficient (R2) of 0.98 for the test set, with an optimal rate with respect to the training error. Through the treatment of homopolymers and copolymers both as separated and merged data sets, we also showed that the proposed approach is particularly suited for generalizing prediction of polymer properties to various types of chemical structures in a uniform setting. [source] Photocurable Shape-Memory Copolymers of , -Caprolactone and L -LactideMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Minoru Nagata Abstract Biodegradable and photocurable block copolymers of , -caprolactone and L -lactide were synthesized by polycondensation of PLLA diol (,=,10,000,g,·,mol,1), PCL diol (,=,10,000,g,·,mol,1), and a chain extender bearing a coumarin group. The effect of copolymer composition on the thermal and mechanical properties of the photocured copolymers was studied by means of DSC and cyclic tensile tests. An increase in Young's modulus and a decrease in the tensile strain with increasing PLLA content was observed for the block copolymers. Block copolymers with high PCL content showed good to excellent shape-memory properties. Random copolymers exhibited Rf and Rr values above 90% at 45,°C for an extremely large tensile strain of 1,000%. [source] Well-defined diblock and triblock copolymers for KrF lithographyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Ting-Yu Lee Abstract One of the major components of a photoresist formulation is polymer resin. Well-defined diblock and random copolymer of tert -butyl acrylate (tBA) and 4-acetoxystyrene (StyOAc), as well as triblock and random tertpolymer of tBA, StyOAc, and Sty were prepared by reversible addition fragmentation chain transfer polymerization (RAFT) process. The polymers all possess Mw about ten thousand and PDI less than 1.23. After hydrolysis under basic condition, the hydroxystyrene (StyOH) analogs are obtained and then are formulated as photoresist. Lithographic evaluation under KrF excimer laser shows that random copolymer based photoresist exhibits better S/L patterns according to SEM images. However, the lithographic performance of the terpolymer based resists is similar. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Emulsion polymerization of styrene with amphiphilic random copolymer as surfactant: Predominant droplet nucleationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Li Liu Abstract Amphiphilic random copolymer consisting of monomeric units of poly (butyl acrylate) and poly (maleic acid salt) was synthesized and characterized. The emulsion polymerization kinetics of styrene stabilized by this copolymer was investigated. The influencing factors, including polymeric surfactant concentration, initiator concentration and polymerization temperature, were systematically studied. The kinetic data show that the polymerization rate (RP) increased with the increase of the polymeric surfactant concentration ([S]) and polymerization temperature (T). At the higher [S], droplets nucleation and micelle nucleation coexisted in the polymerization system; at the lower [S], only the droplets nucleation process existed. The polymerization did not follow Smith-Ewart Case II kinetics. Dynamic light scatter and transmission electron microscope were utilized to measure the sizes and shapes of the particles, respectively. It would be speculated that a kind of large heterogeneous particles with multiple-active-sites was formed in the polymerization system. The increasing of RP with increasing initiator concentration ([KPS]) was rapid at a medium [KPS], but the slowly increasing was observed at a lower or higher [KPS]. It was attributed to the barrier effect of the polymeric surfactant around the monomer droplets. The polymerization activation energy was 60.29 kJ/mol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Hierarchy crystallization structure of a polypropylene random copolymer injection-molded bar induced by a nucleating agentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Yong Wang Abstract In this work, the effect of a nucleating agent on the crystallization structure of an injection-molded bar of a polypropylene random copolymer (PPR) with sorbitol derivatives [1,2,3,4-dibenzylidene sorbitol (DBS)] has been studied. The results show that pure PPR forms a simple skin,core crystallization structure. However, PPR/DBS forms an interesting and complicated hierarchy crystallization structure: there is a transition layer between the skin layer and the core zone. In this transition layer, the crystallization structure consists of some perfect spherulites and many tiny crystallites. Further research suggests that the formation of the hierarchy crystallization structure depends on not only the content of the nucleating agent in the PPR matrix but also the mold temperature during the injection-molding processing. The crystallization behavior of PPR/DBS during the cooling process has been characterized with polarization optical microscopy and differential scanning calorimetry. The results suggest that there are different mechanisms in the crystallization process of PPR/DBS. The formation of a three-dimensional DBS network under a certain condition might be the main reason for the complicated hierarchy crystallization structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of sequence distribution of PES/PEES random, block, and alternative copolymers on excimer formation in solutionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Xiao-Ming Zhou Abstract Three copolymers of poly(ether sulfone) and poly(ether ether sulfone) with the same composition but different sequence distribution were synthesized by three kinds of methods. Their molecular aggregation in dichloromethane was studied by fluorescence spectrophotometer and electron microscope. The experimental results revealed that the formation of intermolecular excimers in alternative copolymer (A50) dichloromethane solution were observed at a A50 concentration about 1.6 × 10,2 g/mL by the fluorescence analysis, but the formation of intermolecular excimers in dichloromethane were not found for random copolymer (R50) and block copolymer (B50). The electron micrograph of three copolymer films, heat-treated at 200°C for 7 days, presented a diffraction micrograph, which suggest that three copolymer molecular aggregation is changed from a randomly coiled amorphous phase to an ordered one, and the order structure of alternative copolymer (A50) was the most distinct in three copolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Influence of the copolymer architecture and composition on the response and mechanical properties of pH-sensitive fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Anasuya Sahoo Abstract A series of copolymers based on acrylonitrile (AN) and acrylic acid (AA) with varying architecture and composition were synthesized using free radical polymerization. The distribution of monomers in the copolymer chains could be successfully controlled by regulating the addition of more reactive monomer (AA). Copolymers having nearly random distribution of comonomer moieties to block type distribution with different composition (10,50 mol % AA) were synthesized to investigate the effect of polymer architecture and composition on pH response and mechanical properties of resultant structures. These copolymers were solution spun from dimethylformamide-water system, drawn in coagulation bath, and annealed at 120°C for 2 h to make pH-sensitive fibers which were structurally stable without the need of chemical crosslinking. The fibers from block copolymers showed significantly better tensile strength (34.3 MPa), higher retractive forces (0.26 MPa), and enhanced pH response (swelling 3890%) in comparison with fibers from random copolymer (13.55 MPa, 0.058 MPa, and 1723%, respectively). The tensile strength and retractive forces could be further improved to a value of 72 MPa and 0.36 MPa, respectively, by changing the composition of the block copolymer while retaining the swelling percentage similar to the random copolymer mentioned above. It is proposed that on processing to fibers, the block copolymers could form a segregated domain structure with separate domains of AA and AN, where AN domains were responsible for high structural integrity by providing connectivity among polymer chains, while AA domains showed improved response to changing pH of the environment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Kinetics and monomer reactivity ratios of N -vinylpyrrolidone and ,-terpineolJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Sarika Yadav Abstract The radical copolymerization of ,-terpineol with N -vinylpyrrolidone (N -VP) in dioxane at (80 ± 0.1)°C for 1 h in the presence of benzoylperoxide follows ideal kinetic and results in the formation of random copolymer as evidenced from the value of reactivity ratios as r1 (N -VP) = 0.23 and r2 (,-terpineol) = 0.025, which have been calculated by the Kelen-Tüdos method. The overall activation energy is computed to be 28 kJ/mol. The FTIR spectrum of the copolymer shows the presence of bands at 3507 cm,1 due to alcoholic group and 1717 cm,1 due to > CO group. The Alfrey-Price parameters for ,-terpineol has been calculated as 0.024 and ,2.66. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 476,481, 2007 [source] Poly(methyl methacrylate) copolymers containing pendant carbazole and oxadiazole moieties for applications in single-layer organic light emitting devicesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2008David D. Evanoff Jr. Abstract Methyl methacrylate derived monomers functionalized with pendant carbazole and oxadiazole moieties were synthesized and could be copolymerized to form a random copolymer. The glass transition temperature of the copolymers could be predicted with a Fox equation and ranged from 140 to 191 °C. The photoluminescent characteristics of the copolymers, both in solution and in solid films, exhibited emission that was a combination of sharp and broad peaks, suggestive of monomeric and chromophore aggregation emission. These trends were also apparent in the electroluminescent response of the copolymers, where the appearance of an electromer emission was evident and was tentatively assigned to the carbazole moieties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7882,7897, 2008 [source] Preparation and characterization of biodegradable poly(trimethylenecarbonate-,-caprolactone)-block-poly(p -dioxanone) copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005J.-T. Hong Abstract A series of poly(trimethylenecarbonate-,-caprolactone)-block-poly(p- dioxanone) copolymers were prepared with varying feed rations by using two step polymerization reactions. Poly(trimethylenecarbonate)(,-caprolactone) random copolymer was synthesized with stannous-2-ethylhexanoate and followed by adding p- dioxanone monomer as the other block. The ring opening polymerization was carried out at high temperature and long reaction time to get high molecular weight polymers. The monofilament fibers were obtained using conventional melting spun methods. The copolymers were identified by 1H and 13C NMR spectroscopy and gel permeation chromatography (GPC). The physicochemical properties, such as viscosity, molecular weight, melting point, glass transition temperature, and crystallinity, were studied. The hydrolytic degradation of copolymers was studied in a phosphate buffer solution, pH = 7.2, 37 °C, and a biological absorbable test was performed in rats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2790,2799, 2005 [source] Comprehensive 2-D chromatography of random and block methacrylate copolymersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2010Monique van Hulst Abstract A comprehensive 2-D separation method was developed for the characterization of methacrylate copolymers. In both dimensions conditions were employed that give a critical separation for the homopolymer of one of the monomers in the copolymer, and exclusion behaviour for the other. The 2-D separation was realized by using a normal-phase column in one dimension and a reversed phase column in the other, and by precisely tuning the compositions of the two mobile phases employed. In the normal-phase dimension mixtures of THF and n -hexane or n -heptane were used as mobile phase, and in the reversed-phase dimension mixtures of ACN and THF. Moreover, stationary phase particles had to be selected for both columns that gave an exclusion window appropriate for the molecular size of the sample polymers to be characterized. The 2-D critical chromatography principle was tested with a polystyrene (PS)-polymethylmethacrylate (PMMA) block copolymer and with block and random polybutylmethacrylate (PBMA)-PMMA copolymers. Ideally, the retention time for a copolymer in both dimensions of this system would depend on the size of only one of the blocks, or on the contribution of only one of the monomers to the size of a random copolymer. However, it was found that the elution of the PS-PMMA block copolymer depended on the size of both blocks, even when the corresponding homopolymer of one of the monomers showed critical elution behaviour. Therefore, the method could not be calibrated for block sizes by using homopolymer standards alone. Still, it was shown that the method can be used to determine differences between samples (PS-PMMA and PBMA-PMMA) with respect to total molecular size or block sizes separately, or to average size and chemical composition for random copolymers. Block and random PBMA-PMMA copolymers showed a distinctly different pattern in the 2-D plots obtained with 2-D critical chromatography. This difference was shown to be related to the different procedures followed in the polymerization process, and the different molecular distributions resulting from these. [source] Studies on Preparation and Fluorescent Properties of a Novel Photo-Sensitive Nanoparticle Composed of Europium Ion and Cinnamic Acid DerivativeMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2009Dongjian Shi Abstract A novel fluorescent and photo-sensitive nanoparticle was self-assembled from an europium-based random copolymer, europium coordinated poly(methylacrylic acid)- co -poly(cinnamyl acrylate) (PMCFA-Eu3+), which was synthesized from methylacrylic acid (MAA), and Eu3+ -cinnamyl acrylate derivative (CFA) by radical polymerization. DLS and TEM results indicated the formation of spherical nanoparticles with 120,nm in diameter. The PMCFA-Eu3+ complex showed stronger fluorescence than Eu3+, indicating the effective energy transferred from the ligand to Eu3+. Moreover, the photo-crosslinking of the cinnamate groups induced a decrease in the diameter and an increase in the fluorescent properties of the PMCFA-Eu3+ nanoparticles. This functional nanoparticle might be useful as a carrier and a fluorescence probe in biomedical and fluorescent fields. [source] Non-Fluorous Random Copolymeric Stabilizers for Dispersion Polymerizations of MMA in Supercritical CO2MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2006Ha Soo Hwang Abstract Summary: The dispersion polymerization of MMA in supercritical CO2 was successfully carried out utilizing the first non-fluorous random copolymers composed of 3-tris(trimethoxysilyl)propyl methacrylate and 2-dimethylaminoethyl methacrylate, poly(SiMA- co -DMAEMA) as a stabilizer. The resulting high yield (>93%) of micron-sized PMMA was formed in the presence of 5% (w/w to MMA) of copolymeric stabilizers. While the PSiMA and PDMAEMA homopolymer produced nondescript solid and irregular shape aggregate, respectively, the random copolymer of 71% SiMA-content resulted in spherical and uniform powder. SEM image of PMMA particles prepared in supercritical CO2 using poly(SiMA- co -DMAEMA) (71:29) stabilizer. [source] Polymacromonomers with polyolefin branches synthesized by free-radical homopolymerization of polyolefin macromonomer with a methacryloyl end groupMACROMOLECULAR SYMPOSIA, Issue 1 2004Hideyuki Kaneko Abstract Polymacromonomers with polyolefin branches were successfully synthesized by free-radical homopolymerization of polyolefin macromonomer with a methacryloyl end group. Propylene-ethylene random copolymer (PER) with a vinylidene end group was prepared by polymerization using a metallocene catalyst. Then, the unsaturated end group was converted to a hydroxy end group via hydroalumination and oxidation. The PER with the hydroxy end group was easily reacted with methacryloyl chloride to produce methacryloyl-terminated PER (PER macromonomer; PERM). The free-radical polymerization of thus-obtained PERM was done using 2,2,-azobis(isobutyronitorile) (AIBN) as a free-radical initiator. From NMR analyses, the obtained polymers were identified as poly(PERM). Based on gel permeation chromatography (GPC), the estimated degree of polymerization (Dp) of these polymers were about 30. Thus, new class of polymacromonomers with polyolefin branches was synthesized. [source] Synthesis of biodegradable polyhydroxyalcanoate copolymer from a renewable source by alternate feedingPOLYMER ENGINEERING & SCIENCE, Issue 10 2008Silvia M.F. Pereira Polyhydroxyalcanoates copolymers with 3-hydroxybutirate (3HB) and 3-hydroxyvalerate (3HV) co-monomers, P3(HB-co-x%HV), were produced in fed-batch culture by Ralstonia eutropha DSM428 using fructose as a single carbon source in the first step and adding propionic acid in the second step by alternating feeding. Polymer yield was 0.18 g/L with a content of 24 mol% of the 3HV fraction determined by 1H NMR. NMR measurements indicated that the polymer obtained is isotactic. The copolymer attained 35% of crystallinity according to X-ray diffraction measurements, and two (020) planes were observed. Thermal behavior presented melting temperature at 154°C and the crystallization temperature was 65°C. A glass transition temperature was observed at ,10°C. Average molecular weight measured by GPC was 4.9 × 105 Dalton. Isothermal radial growth rates of spherulites of P3(HB-co-24%HV) were studied. All experimental facts and the analysis of the sequence distribution of diads and triads of 3HB and 3HV units led to the conclusion that it is not a completely statistical random copolymer once it contains different types of segments. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers. [source] Synthesis of styrene,maleic anhydride random copolymer and its compatibilization to poly(2,6-dimethyl-1,4-phenylene ether)/brominated epoxy resinPOLYMER INTERNATIONAL, Issue 6 2003Guozheng Liang Abstract Styrene,maleic anhydride random copolymer (R-SMA7.5), with a low content of maleic anhydride (MAH) of about 7.5 mol%, has been prepared, and the copolymer was characterized by fourier-transform infrared (FTIR) and 13C NMR techniques showing that the product contained only random copolymer without blocks. The miscibility between poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and R-SMA, was investigated by differential scanning calorimetry (DSC), showing that PPE was miscible with R-SMA synthesized in our laboratory over the entire composition with low MAH content. A blend of R-SMA18 (MAH content is about 18 mol%) and PPE was also studied by DSC, which showed that PPE was immiscible when R-SMA was the major component, although it was miscible with limited composition. FTIR investigation showed that R-SMA could react with bromide epoxy (BEP) resin at high temperature (180°). The heat-resistance and mechanical properties of R-SMA/PPE/BEP systems were tested and analyzed, and results indicated that R-SMA could improve the miscibility of PPE and BEP with increasing Tg of the BEP phase and decreasing the Tg of the PPE slightly, improving the breaking elongation and breaking energy, which resulted from good miscibility between PPE and BEP with R-SMA as the compatibilizer. Finally, the properties of the composites (copper clad laminate) with R-SMA7.5 are studied and discussed. Copyright © 2003 Society of Chemical Industry [source] Coloration of monodispersed polystyrene nanoparticles prepared via the RAFT reactionPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2006Ju Sung Kim Abstract Highly monodispersed polystyrene (PS) nanoparticles were prepared via the reversible addition fragmentation transfer (RAFT) living radical emulsion polymerization technique using a sur-iniferter, 4-(2-hydroxyethyl)piperazine-1-carbodithioicacid benzylether (HPCB). The monodispersed nanoparticles were colored by various methods, namely random and block copolymeriztion, the end group reaction and the adsorption method. For the coloration of the block and random copolymer monodispersed nanoparticles, a color pre-monomer was previously synthesized with a vinyl functional site. Dynamic light scattering and scanning electron microscopy were the main tools used to analyze the size and distribution of the prepared nanoparticles. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effect of Comonomer Ethylene on Plateau Modulus of Crystal-line Ethylene-propylene Random Copolymer with Broad Molecular Weight DistributionCHINESE JOURNAL OF CHEMISTRY, Issue 6 2005Ding Jian Abstract Ethylene-propylene random copolymer with ultra-high molecular weight (UHPPR) and broad molecular weight distribution (MWD) was prepared with Ziegler-Natta catalyst. The viscoelastic behavior of UHPPR has been investigated by means of oscillatory rheometer at 180, 200 and 220 °C. The loss modulus (G, curves of 180 and 200 °C present a pronounced maximum at 38.10 and 84.70 r/s, respectively. For the first time, this makes it possible to directly determine the plateau modulus () of crystalline ethylene-propylene random copolymer with broad MWD in a certain experimental temperature G,(,) curve. The plateau modulus of UHPPR is 4.51×105 and 3.67×105 Pa at 180 and 200 °C respectively, increasing with random incorporation of comonomer ethylene into the molecular chains and being independent of molecular weight. [source] Random Copolymer Films with Molecular-Scale Compositional Heterogeneities that Interfere with Protein AdsorptionADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Salmaan H. Baxamusa Abstract Smooth surfaces with compositional heterogeneities at a molecular-length scale are presented with the goal of disrupting surface,protein interactions. These surfaces are synthesized by utilizing photoinitiated chemical vapor deposition (piCVD) to deposit thin films of random copolymers consisting of highly hydrophilic and highly hydrophobic comonomers. Swellability, wettability, and surface roughness could be systematically controlled by tuning the copolymer composition. The surface composition was dynamic, and the surface reconstructed based on the hydration state of the film. Proteins adsorbed to the copolymer films less readily than to either of the respective homopolymers, indicating a synergistic effect resulting from the random copolymer presenting molecular-scale compositional heterogeneity. These results provide direct evidence that protein adsorption can be disrupted by such surfaces and a simple analytical model suggests that the heterogeneities occur over areas encompassing 4,5 repeat units of the polymer. The synthetic method used to create these films can be used to coat arbitrary geometries, enabling practical utility in a number of applications. [source] Donor,Acceptor C60 -Containing Polyferrocenylsilanes: Synthesis, Characterization, and Applications in Photodiode Devices,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2008Masato Nanjo Abstract A series of polyferrocenylsilane (PFS) random copolymers containing covalently bound pendant [C60]fullerene groups, the first well-characterized metallopolymers with pendant C60 units, have been prepared and characterized. The fullerene content of the prepared copolymers ranges from 7 to 24% relative to monomer unit. The desired copolymers were synthesized in three steps: metal-catalyzed ring opening polymerization of sila[1]ferrocenophanes was performed to synthesize random copolymers of poly(ferrocenylmethylphenylsilane -co- ferrocenylchloromethylsilane); the resulting random PFSs were then functionalized by reaction with 11-azido-1-undecanol to give PFSs with pendant azide groups; the desired donor,acceptor C60 -containing PFSs were then synthesized by the reaction of the azide group in the side chains with C60 in toluene at 110,°C. The resulting C60 -containing PFSs are air-stable and soluble in aromatic solvents, chloroform, or THF. The UV-vis spectra of these materials show broad absorption up to 800 nm. Thin films of these materials were examined as the active layer in rare examples of all solid-state sandwich-type diode devices based on ferrocene-fullerene dyads. The devices exhibit photoconducting and photovoltaic responses, with an open circuit potential of ca. 0.3 V under white light illumination. [source] Hierarchical structures formed by partially crystalline polymers in solution: from fundamentals to applications , a combined conventional, focusing and ultra-small-angle neutron scattering studyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Dietmar Schwahn Multilevel aggregates with characteristic sizes covering four orders of magnitude, from 1,nm to 10,µm, are formed upon cooling decane solutions of poly(ethylene-butene) random copolymers (designated as PEB- n, where n is the number of ethyl side branches per 100 backbone C atoms) and wax-containing mixed solutions. The partially crystalline PEB-7.5 copolymers form two distinct morphologies that evolve on a range of length scales. When these polymers are mixed with wax molecules having a crystallization point lower than the polymer aggregation temperature, a hierarchy of morphologies evolves on decreasing the temperature. The multilevel structures were elucidated by combining conventional small-angle neutron scattering, focusing small-angle neutron scattering and ultra-small-angle neutron scattering investigations with microscopy. Contrast-matching analysis of the wax and copolymer components within the common morphologies revealed the wax-crystal modification capacity of the PEB-7.5 copolymers. Since the copolymers limit the growth of wax crystals, they are potential pour-point depressants for the fuel industry. [source] Kinetics and mechanism of the radical copolymerization of 4-vinyl pyridine with methyl acrylate initiated by p -acetylbenzylidene triphenylarsonium ylideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009S. P. Tiwari Abstract The free-radical copolymerization of 4-vinyl pyridine (4-VP) with methyl acrylate (MA) initiated by p -acetylbenzylidene triphenylarsonium ylide at 60 ± 0.1°C with dioxane as an inert solvent yielded random copolymers. The kinetic equation was Rp , [Ylide]0.83[4-VP]0.33 [MA]0.40 (where Rp is the rate of polymerization); in other words, the system followed nonideal kinetics. The values of the energy of activation and kp2/kt (where kp is the rate constant of propagation and kt is the rate constant of termination) were 23.21 kJ/mol and 1.212 × 10,5 mol L,1 s,1, respectively. The reactivity ratios calculated with the Kelen,Tüdos method were 0.14 ± 0.0075 for 4-VP and 0.56 ± 0.0078 for MA. The copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, differential scanning calorimetry, and electron spin resonance methods. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] New straightforward route for the synthesis of some 1-oxa-2-silacyclopentane derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2008Kazem D. Safa Tris(dimethylsilyl)methyl lithium, (HSiMe2)3CLi, reacts with allyl, phenyl, benzyl, n -propyl and n -butyl glycidyl ethers in THF at -5 °C to give 1-oxa-2-silacyclopentane derivatives. It seems that ring closure is facilitated by conversion of the SiH bond into an SiO bond. Glycidyl methacrylate (GM) random copolymers with 4-methyl- and 4-methoxy styrene, synthesized by solution free radical polymerization at 70 (±1) °C with ,,,-azobis(isobutyronitrile) (AIBN) as initiator, contained pendant epoxide functions. Treatment of these with (HSiMe2)3CLi did not lead to intramolecular nucleophilic attack as found for simple epoxides. [source] Synthesis of bipolar charge transporting block copolymers and characterization for organic light-emitting diodeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2010Kousuke Tsuchiya Abstract A series of hole and electron transporting random and block copolymers consisting of triphenylamine moiety as a hole transporting unit and oxadiazole moiety as an electron transporting unit have been prepared via a nitroxide mediated radical polymerization. Oxadiazole monomers with t -butyl or trifluoromethyl groups, 2 and 7, respectively, were used for copolymerization. Photoluminescent measurements of polymers revealed that the formation of the exciplex between triphenylamine and oxadiazole units tends to occur in the order of random copolymers, block copolymers, and polymer blends, implying phase-separated morphologies in block or blend systems. The polymers were applied for OLED devices, and we found that the morphology in the polymer layer critically affected device performance. The block copolymer comprising hole and electron transporting units with the composition of 14/86 showed the highest external quantum efficiency over 10%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1461,1468, 2010 [source] Macromolecular brushes synthesized by "grafting from" approach based on "click chemistry" and RAFT polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2010Dongxia Wu Abstract Well-defined macromolecular brushes with poly(N -isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by "grafting from" approach based on click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS) and methyl methacrylate (MMA) (poly(MMA- co -HEMA-TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide-containing polymers. Novel alkyne-terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper-catalyzed 1,3-dipolar cycloaddition (azide-alkyne click chemistry), and macro-RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well-defined structures, controlled molecular weights, and molecular weight distributions (Mw/Mn , 1.23). The RAFT polymerization of NIPAM exhibited pseudo-first-order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self-assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443,453, 2010 [source] Heterograft copolymers via double click reactions using one-pot techniqueJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Aydan Dag Abstract The double click reactions (Cu catalyzed Huisgen and Diels,Alder reactions) were used as a new strategy for the preparation of well-defined heterograft copolymers in one-pot technique. The synthetic strategy to the various stages of this work is outlined: (i) preparing random copolymers of styrene (St) and p -chloromethylstyrene (CMS) (which is a functionalizable monomer) via nitroxide mediated radical polymerization (NMP); (ii) attachment of anthracene functionality to the preformed copolymer by the o -etherification procedure and then conversion of the remaining CH2Cl into azide functionality; (iii) by using double click reactions in one-pot technique, maleimide end-functionalized poly(methyl methacrylate) (PMMA-MI) via atom transfer radical polymerization (ATRP) of MMA and alkyne end-functionalized poly (ethylene glycol) (PEG-alkyne) were introduced onto the copolymer bearing pendant anthryl and azide moieties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6969,6977, 2008 [source] Styrene 4-vinylbenzocyclobutene copolymer for microelectronic applicationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2008Ying-Hung So Abstract Styrene and 4-vinylbenzocyclobutene (vinyl-BCB) random copolymers were prepared by free radical polymerization and studied for suitability as a dielectric material for microelectronic applications. The percentage of vinyl-BCB in the copolymer was varied from 0 to 26 mol % to optimize the physical and mechanical properties of the cured copolymer as well as the cost. Copolymer in which 22 mol % of vinyl-BCB was incorporated along with styrene produced a thermoset polymer which, after cure, did not show a Tg before decomposition at about 350 °C. The polymeric material has a very low dielectric constant, dissipation factor, and water uptake. The fracture toughness of the copolymer was improved with the addition of 20 wt % of a star-shaped polystyrene- block -polybutadiene. Blends of the poly(styrene- co -vinyl-BCB) with the thermoplastic elastomer provided material that maintained high Tg of the cured copolymer with only a slight decrease in thermal stability. The crosslinked styrenic polymer and toughened blends possess many properties that are desirable for high frequency-high speed mobile communication applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2799,2806, 2008 [source] | |||||||||||||