Vinyl End Groups Research Articles

P71 Vascular endothelial growth factor (VEGF) inhibition and erythropoiesis – a missing link?

Herein, we have designed a novel multilayer system composed of poly(methyl methacrylate) [poly(MMA)] brush, biotin, streptavidin and protein-A on a silicon substrate to attach on anti-immunoglobulin G (anti-IgG). poly(MMA) brush with vinyl end-group was first synthesized by the interface-mediated catalytic chain transfer polymerization. The brush was then modified with cysteamine molecules to generate the polymer chains with amine end-group via a thiol-ene click chemistry. The amine end-groups of poly(MMA) chains were also modified with biotin units to ensure selective connection points for streptavidin molecules. Finally, a multilayer system on the silicon substrate was formed by using streptavidin and protein-A molecules, respectively. This multilayer system was employed to attach anti-IgG molecules in a highly oriented manner and provide anti-IgG molecular functional configuration on the multilayer. High reproducibility of the amount of anti-IgG adsorption and homogeneous anti-IgG adsorption layer on the silicon surface could be provided by this multilayer system. The multilayer system with protein A may be opened the door for designing an efficient immunoassay protein chip.

Cyclic poly(ε‐caprolactone) synthesized by combination of ring‐opening polymerization with ring‐closing metathesis, ring closing enyne metathesis, or “click” reaction

AbstractThis article described the synthesis of cyclic poly(ε‐caprolactone) (PCL) via ring‐closing metathesis (RCM), ring closing enyne metathesis (RCEM), and “click” reaction of different difunctional linear PCL. Linear PCL precursors were prepared by ring‐opening polymerization (ROP) of ε‐caprolactone in bulk using 10‐undecen‐1‐ol or propargyl alcohol as the initiator, followed by reacting with corresponding acyl chloride containing vinyl or azido end group. The subsequent end‐to‐end intramolecular coupling reactions were performed under high dilution conditions. The successful transformation of linear PCL precursor to cyclic PCL was confirmed by Gel permeation chromatography, 1H NMR, and Fourier transform infrared measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3022–3033, 2009

O‐Acylated 2‐Phosphanylphenol Derivatives – Useful Ligands in the Nickel‐Catalyzed Polymerization of Ethylene

AbstractThe title ligands were prepared by O‐acylation of 2‐diphenylphosphanyl‐4‐methylphenol (1) or directly by double lithiation of 2‐bromo‐4‐methylphenol and stepwise coupling with ClPPh2 and ClP(O)Ph2 or RC(O)Cl (R = Me, tBu, Ph, 4‐MeOC6H4) to afford diphenylphosphinate 2 and carboxylic esters 3a–d. X‐ray crystal structure analyses of 3b–d show conformations in which the P‐phenyl substituents are rotated away from the ester group and the C(O)O π planes are nearly perpendicular to the phenol ring π plane. O‐Acylated phosphanylphenols 2 and 3a–d form highly active catalysts with Ni(1,5‐cod)2 (as does 1) for polymerization of ethylene, whereas phosphanylphenyl ethers do not give catalysts under the same conditions. The reason is the cleavage of the O‐acyl bond upon heating with nickel(0) precursor compounds in the presence of ethylene. The precursors are P‐coordinated Ni0 complexes, which are formed at room temperature, such as 4d obtained from 3d and Ni(cod)2 (in a 2:1 molar ratio), and characterized by multinuclear NMR spectroscopy. Upon heating in the presence of ethylene, the precatalysts are activated. Catalysts 2Ni and 3a–dNi convert ethylene nearly quantitatively, 2Ni slowly, and 3a–dNi rapidly, into linear polyethylene with vinyl and methyl end groups, and in the latter case, C(O)R end groups are also detectable. This proves insertion of Ni0 into the O–C(O)R bond of 3a–d ligands for formation of the primary catalyst. Termination of the first chain growing cycle by β‐hydride elimination changes the mechanism to the phosphanylphenolate–NiH initiated polymerization providing the main body of the polymer. A small retardation in the ethylene consumption rate with 3a–dNi catalysts relative to that observed for 1Ni and stabilization of the catalyst, which gives rise to reproducibly high ethylene conversion, is observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The Effect of the Impurities in Refinery Process from Fermentation Broth on Lactic Acid Polymerization

Polylactic acid (PLA) is synthesized by direct polycondensation without catalyst (NC-DP) method using a lactic acid (HLa) solution which had been refined by concentration, esterification and hydrolysis of fermented broth from fresh cassava roots (FCR). Higher polymerization rates and earlier thermal degradation had been observed, compared with those from a pure lactic acid solution. It is due to residual impurities in refining process, such as butanol (BuOH) and butyl lactate (BuLa), which act as an external catalyst. Additionally, it has been found that thermal degradation of PLA containing these impurities occurs via random scission with vinyl end groups, in regard to specific scission for PLA from a pure HLa solution.

Modification of Monodisperse Colloidal Silica by Radical Copolymerizatoin of Cationic Surface Active Vinyl Monomers

Adsorption and polymer modification of colloidal silica by radical copolymerization of surface active monomers, i.e., polymerizable surfactant having a vinyl end group, were investigated. Radical copolymerization of amide ammonium monomer and ammonium-type cross-linker (monomer) using a initiator of 2,2′ -azobis(2-amidinopropane) dihydrochloride on colloidal silica successfully led to the formation of monodispersed cross-linked polymer/SiO2 composites, which is stable in organic solvents. Addition of carboxylic acid monomer to the reaction system of two ammonium monomers gave homogeneously polymer-coated silica composites having carboxyl groups. The composites show ξ-potential of –36mV and 0mV in water and ethanol, respectively.

Synthesis, characterization and photopolymerization of vinyl functionalized poly (ε-caprolactone)

Vinyl functionalized poly (e-caprolactone) with molar mass ranging from 500-5000 Da were synthesized by ring opening polymerization and further photopolymerized. One-step synthesis and functionalization is achieved based on ring opening polymerization (ROP). Hydroxyl butyl vinyl ether (HBVE) was employed to play the role as the initiator of ROP, and photo-curable functional group. The presence of CH2=CH peak in Fourier Transform Infrared (FTIR) spectra con- firmed that vinyl end groups were successfully attached to poly (e-caprolactone) (PCL) macromolecule. Kinetic parameters of cationic photopolymerization of vinyl functionalized PCL were investigated. The activation energy was estimated at 11.33 kJ/mol, by assuming the cationic system followed second-order autocatalytic model.

Synthesis of polyaspartate macromonomer having a vinyl end group and application to dispersion copolymerization of styrene

Sodium polyaspartate (PAspNa) macromonomer with an acryloyl end group was synthesized for dispersion polymerization. At first, a poly(succinimide) (PSI) derivative with a hydroxyphthalimide end group was synthesized by polycondensation of l-aspartic acid and 4-hydroxyphthalic acid. Then, the PSI derivative was end-capped with an acryloyl group by a reaction with acrlyloyl chloride. Finally, a PAspNa derivative with a vinyl end group was synthesized by a hydrolysis of succinimide units by sodium hydroxide. The synthesized macromonomer was applied as a polymerizable stabilizer in dispersion copolymerization of styrene in a mixture of ethanol and water. The PAspNa macromonomer acted as an effective stabilizer and gave sub-micron-sized polymeric particles in dispersion polymerization in polar medium.

On the Nonsingle-Site Character of Bis(2-Dimethylsilyl-indenyl)zirconium(IV) Dichloride/MAO and Bis(2-Trimethylsilyl-indenyl)zirconium(IV) Dichloride/MAO: Polymerization Characteristics and Mechanistic Implications

Ethene polymerization with bis(2-dimethylsilyl-indenyl)zirconium(IV) dichloride (1)/MAO and bis(2-trimethylsilyl-indenyl)zirconium(IV) dichloride (2)/MAO and ethene-co-1-hexene polymerization with 1/MAO are presented. The end group analysis of homopolymers reveals a pronounced dependence of the termination rate on temperature changes. In combination with the high molecular weights obtained, these results are in accord with theoretical predictions. Gel permeation chromatography, Fourier transform infrared, and 13C NMR analyses of copolymerization products from 1/MAO as a function of comonomer concentration at two different temperature series denote its tendency to form inhomogeneous polymer blends. Thermal analysis and fractionation results of one such blend indicate an inhomogeneity in the enchainment process and the existence of multiple active sites of differing geometry. These indications are further supported by AMBER force field and density functional theory studies of the catalyst precursors and the active site of 1/MAO. For this system, delta-agostic interactions for the stabilization of the zirconium cation are favored over beta-agostic interactions, which, in contrast to the situation in studies on bis-Cp systems, is a sparsely populated species. The gap in activation enthalphies for beta-hydride transfer and elimination is marginalized for these bulky zirconocenes, and conceptually new mechanisms for the isomerization of the vinyl end groups are discussed. Further, unexpected activation of the silicon-hydrogen bond within the ligand framework is observed with an activation enthalpy as low as 14 kcal/mol.

Polymerization strategies to overcome limiting monomer conversion in silicone-acrylic miniemulsion polymerization

The limiting conversion phenomenon observed in high solid content silicone-modified acrylic miniemulsion polymerizations was investigated. It was found that the limiting conversion was mainly due to the formation of inactive radicals upon propagation of butyl acrylate radicals with the vinyl end groups of the polydimethylsiloxane. Polymerization strategies that allowed overcoming this problem and achieving high monomer conversion were implemented.

A Shortcut To Organize Self-Assembled Monolayers of Cobalt Ferrite Nanoparticles on Silicon

We report a successful synthetic strategy to covalently assemble a monolayer of CoFe2O4 nanoparticles on a silicon substrate using undecanoate as molecular linker. The nanocrystals of ferrite are coated with a protecting layer of undecanoate which beyond stabilizing the nanoparticles allows their organization on silicon directly reacting with Si–H surface through its vinyl end group. The organic coat was obtained during the synthesis of cobalt ferrite using sodium undecanoate as protective agent. This synthetic strategy avoids the exchange monolayer reaction generally required to bind the NPs on the substrate. The structural and magnetic characterizations of monolayer self-assembled nanoparticles on silicon surface are reported.

Synthesis and Thermally Enhanced Photoinduced Orientation of Liquid Crystalline Polymer Possessing Vinyl End Group

Methacrylate polymer liquid crystals containing p-substituted 4-cinnamoyloxybiphenyl (CB) side group were synthesized. Two vinyl end groups were introduced to investigate the influence of the end group on the photoinduced reorientation behavior. Thermally enhanced photoinduced orientation of polymer thin films was performed by irradiating with linearly polarized ultraviolet (LPUV) light and annealing. The reorientation behavior was evaluated by measuring the polarization absorption spectroscopy. When the degree of the photoreaction was around 10 mol%, the reorientation direction was parallel to the polarization of LPUV light for both polymer films. On the other hand, when the degree of the photoreaction was low, out-of-plane orientation was observed for the polymer with the longer end group.

Synthesis and mesomorphic properties of fluorinated Schiff's base liquid crystals containing vinyl end groups

Abstract Three kinds of fluorinated Schiff's base esters, 4-allyloxy-2-X-6-X-benzoic acid 4-[(2, 3, 4-trifluorophenylimino)-methyl]phenyl ester, where X=H or F, were synthesized and characterized. Their chemical structures were identified by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance ( 1H NMR). Their mesomorphic properties were studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). It was found that all the three compounds exhibited enantiotropic nematic phases only. And their clearing point temperature and thermal range of mesophase decreased with the number of fluorine atoms on the rigid core of the compounds; while their melting point temperature showed no distinct regularity.

Effect of silane‐coupling agents on interfacial properties of CF/PI composites

AbstractIn this article, to form a structure‐controlled interface, carbon fiber (CF) surfaces were first activated by plasma technique and then hydroxylated by LiAlH4 treatment, and then were reacted with a suit of silane‐coupling agents terminated with desired functional groups to form thin films, which further reacted with polyimide (PI) resin to generate a strong adhesion interface. The morphology, structure, and composition of CF surfaces before and after treatment were investigated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS), respectively. The results of FTIR and XPS analysis showed that silane‐coupling agents were successfully chemisorbed onto the CF surfaces by the hydrolysis and condensation reactions. The interfacial shear strength of the CF/PI microcomposites was evaluated by the microbond technique. The results showed that the types of the interfacial functional groups, especially the vinyl end groups in vinyltriethoxysilane (VS), which can react with PI resin, had very significant influence on the improvement of the interfacial adhesion properties of composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Simulation and Optimization of Wiped-Film Poly-Ethylene Terephthalate (PET) Reactor Using Multiobjective Differential Evolution (MODE)

The multiobjective differential evolution (MODE), which is an extension of the Differential Evolution (DE), is applied to solve the multiobjective optimization problem (MOOP) of wet film Poly-Ethylene Terephthalate (PET) reactor considering minimization of acid end group and vinyl end group as the main objectives. The objective function is modified to solve five different possible cases. The results show that a Pareto set (a set of equally good solutions) is obtained for the cases when two of the parameters (residence time of the polymeric reaction mass, θ, and the speed of the wiped-film agitator, N) are considered as decision variables, unlike a unique solution obtained using Nondominated Sorting Genetic Algorithm (NSGA). The Pareto optimal front provides wide-ranging optimal sets of operating conditions. And an appropriate set of operating conditions can be selected based on the requirements of the user.

A Surface Functional Monomer-Directing Strategy for Highly Dense Imprinting of TNT at Surface of Silica Nanoparticles

This paper reports a surface functional monomer-directing strategy for the highly dense imprinting of 2,4,6-trinitrotoluene (TNT) molecules at the surface of silica nanoparticles. It has been demonstrated that the vinyl functional monomer layer of the silica surface can not only direct the selective occurrence of imprinting polymerization at the surface of silica through the copolymerization of vinyl end groups with functional monomers, but also drive TNT templates into the formed polymer shells through the charge-transfer complexing interactions between TNT and the functional monomer layer. The two basic processes lead to the formation of uniform core-shell TNT-imprinted nanoparticles with a controllable shell thickness and a high density of effective recognition sites. The high capacity and fast kinetics to uptake TNT molecules show that the density of effective imprinted sites in the nanoshells is nearly 5 times that of traditional imprinted particles. A critical value of shell thickness for the maximum rebinding capacity was determined by testing the evolution of rebinding capacity with shell thickness, which provides new insights into the effectiveness of molecular imprinting and the form of imprinted materials. These results reported here not only can find many applications in molecularly imprinting techniques but also can form the basis of a new strategy for preparing various polymer-coating layers on silica support.

Proton (3 MeV) and copper (120 MeV) ion irradiation effects in low-density polyethylene (LDPE)

Low-density polyethylene (LDPE) was irradiated with proton (3 MeV) and copper (120 MeV) ions to analyze the induced modifications with respect to optical and structural properties. In the present investigation, the fluence for proton irradiation was varied up to 2×10 15 protons cm −2, while that for copper beam was kept in the range of 1×10 1 to 1×10 13 ions cm −2 to study the swift heavy ion-induced modifications in LDPE. Ultraviolet–visible (UV–vis), FTIR and X-ray diffraction (XRD) techniques were utilized to study the induced changes. The analysis of UV–vis absorption studies reveals that there is decrease of optical energy gap up to 43% on proton irradiation (at 2×10 15 ions cm −2), whereas the copper beam (at 1×10 13 ions cm −2) leads to a decrease of 51%. FTIR analysis indicated the presence of unsaturations due to vinyl end groups in the irradiated sample. The formation of O H and C O groups has also been observed. XRD analysis revealed that the semi-crystalline LDPE losses its crystallinity on swift ion irradiation. It was found that the proton beam (2×10 15 ions cm −2) decreased the crystallite size by 23% whereas this decrease is of 31% in case of the copper ion-irradiated LDPE at 1×10 13 ions cm −2.

Evaluation of Philips and Ziegler–Natta high-density polyethylene degradation during processing in an internal mixer using the chain scission and branching distribution function analysis

The oxidative and thermo-mechanical degradation of HDPE was studied during processing in an internal mixer under two conditions: totally and partially filled chambers, which provides lower and higher concentrations of oxygen, respectively. Two types of HDPEs, Phillips and Ziegler–Natta, having different levels of terminal vinyl unsaturations were analyzed. Materials were processed at 160, 200, and 240 °C. Standard rheograms using a partially filled chamber showed that the torque is much more unstable in comparison to a totally filled chamber which provides an environment depleted of oxygen. Carbonyl and transvinylene group concentrations increased, whereas vinyl group concentration decreased with temperature and oxygen availability. Average number of chain scission and branching ( n s) was calculated from MWD curves and its plotting versus functional groups' concentration showed that chain scission or branching takes place depending upon oxygen content and vinyl groups' consumption. Chain scission and branching distribution function (CSBDF) values showed that longer chains undergo chain scission easier than shorter ones due to their higher probability of entanglements. This yields macroradicals that react with the vinyl terminal unsaturations of other chains producing chain branching. Shorter chains are more mobile, not suffering scission but instead are used for grafting the macroradicals, increasing the molecular weight. Increase in the oxygen concentration, temperature, and vinyl end groups' content facilitates the thermo-mechanical degradation reducing the amount of both, longer chains via chain scission and shorter chains via chain branching, narrowing the polydispersity. Phillips HDPE produces a higher level of chain branching than the Ziegler–Natta's type at the same processing condition.

New reaction for the preparation of liquid rubber

AbstractThe article reports on the noncatalytic transformation of a polybutadiene (number‐average molecular weight = 128,000) into a functionalized liquid rubber via the carboxidation of the polymer CC bonds by nitrous oxide. The reaction was conducted in a benzene solution at 160–230 °C and a pressure of 3–6 MPa. The carboxidation mechanism was determined. The main route (95%) of the reaction proceeded without cleavage of CC bonds and led to the formation of ketone groups in the polymer backbone. A minor route (5%) of the reaction proceeded with the cleavage of CC bonds, yielding two smaller fragments containing aldehyde and vinyl end groups. The availability of the cleavage route could lead to a dramatic decrease in the molecular weight, which, depending on the carboxidation degree, could be 1–2 orders of magnitude less than that of the initial material. Thus, the carboxidation of more than 15% of the polybutadiene CC bonds transformed it into a CO‐functionalized liquid rubber with a narrow molecular weight distribution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2510–2520, 2006

LONG-CHAIN HIGHLY BRANCHED POLYETHYLENE PREPARED WITH BINARY α-DIIMINE NICKEL/MAO CATALYSTS

Long-chain branched polyethylene was prepared by a bianary catalyst systemCat 1:bis(α- naphthalidine)-butanediimine) NiBr_2 and Cat 2:bis(2,6-diisopropylphenyl)-acenaphthenediimine NiBr_2.The binary catalyst system showed a good synergic effect.Its polymerization activity (4.6×10~5g PE/mol Ni·h)was higher than that of either single catalyst.The resultant highly branched (94.8～144.5/1000C) PE was confirmed by ~13 C-NMR to contain a significant amount (27～42/1000C) of long chain branches (n≥6).The GPC results showed that the molecular weight distribution of the polyethylene obtained with this binary catalyst system was very narrow.The explanation for this is that ethylene oligomerizes in the Cat 1 active site,and the produced vinyl end group oligomers serving as comonomers in situ copolymerize with the growing polyethylene chain in the active site of Cat 2.

In situ FTIR spectroscopic study of the recently detected low‐temperature‐induced structural changes in isotactic polypropylene

AbstractThe in situ Fourier transform infrared spectroscopic study of isotactic polypropylene showed that structural changes are induced at liquid nitrogen temperature, and start to show up in the FTIR spectra with heating from −196 to +200 °C. This structural change leads to the detection of an abnormal behavior in the MIR absorption spectra of the investigated sample. Lowering the temperature brought the chains closer together and so increased the interchain interaction. At −196 °C splitting of some regularity bands assigned to helical chains within the crystalline region was observed, showing that the regularity of the chains increases because of cooling. Heating the samples from liquid nitrogen temperature caused an opposite conformational disordering, which resulted in the appearance of several new broad bands in the ranges: 600–700, 1614–1640, and 3050–3550 cm−1. These structural changes might be due to both twisting and folding of the chains, which gave rise to bands assigned to the various bending modes of CH2 molecules, in addition to the rotational isomers (conformers) resulting from rotation of the vinyl and alkyne end groups. Moreover, our experimental study of the behavior of several regularity bands suggests that at temperatures in the vicinity of +120 °C another high temperature structural change resulting from the disordering of helical sequences in the noncrystalline region takes place. Differential scanning calorimetry thermograms of the thermally treated and an untreated sample were found to confirm the obtained results. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2829–2842, 2005