Initial Monomer Research Articles

Solid-Phase Synthesis of a Seventh-Generation Inverse Poly(amidoamine) Dendrimer: Importance of the Loading Ratio on the Resin.

Here, this study overcomes the current barriers to efficient solid-phase synthesis of high-generation dendrimers by decreasing the loading ratio on the resin. G7 inverse poly(amidoamine) dendrimer is now prepared, for the first time, through a solid-phase synthesis using only 50% of the available reactive sites and by choosing a large resin. This preparation takes only 15 d to afford highly pure product in 80% yield with precipitation being the only purification procedure used. The results clearly show the amount of the initial monomer loaded on the resin to be a vital factor for the ability to use solid-phase synthesis to produce large dendrimers. This finding also sets stage for the applications of solid-phase synthesis for the preparation of other macromolecules.

Chemical Functionalization of Graphene Oxide by Poly(styrene sulfonate) Using Atom Transfer Radical and Free Radical Polymerization: A Comparative Study

ABSTRACTPoly(sodium styrenesulfonate)-functionalized graphene was prepared from graphene oxide, using atom transfer radical polymerization and free radical polymerization. In atom transfer radical polymerization route, the amine-functionalized GO was synthesized through hydroxyl group reaction of GO with 3-amino propyltriethoxysilane. Atom transfer radical polymerization initiator was grafted onto modified GO (GO-NH2) by reaction of 2-bromo-2-methylpropionyl bromide with amine groups, then styrene sulfonate monomers were polymerized on the surface of GO sheets by in situ atom transfer radical polymerization. In free radical polymerization route, the poly(sodium 4-styrenesulfonate) chains were grafted on GO sheets in presence of Azobis-Isobutyronitrile as an initiator and styrene sulfonate monomer in water medium. The resulting modified GO was characterized using range of techniques. Thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy results indicated the successful graft of polymer chains on GO sheets. Thermogravimetric analysis showed that the amount of grafted polymer was 22.5 and 31 wt% in the free radical polymerization and atom transfer radical polymerization methods, respectively. The thickness of polymer grafted on GO sheets was 2.1 nm (free radical polymerization method) and 6 nm (atom transfer radical polymerization method) that was measured by atomic force microscopy analysis. X-ray diffractometer and transmission electron microscopy indicated that after grafting of poly(sodium 4-styrenesulfonate), the modified GO sheets still retained isolated and exfoliated, and also the dispersibility was enhanced.

Modeling and analytical simulation of anterior polymerization in the presence of an inert material

The ability to fabricate advanced materials with specific properties efficiently requires a complete understanding of the polymerization kinetics and the effect of several preparative variables such as temperature, monomer and initiator. This paper presents an analytical method for describing anterior polymerization in two adjacent thin layers. Both the initial temperatures and initial monomer and initiator concentrations are assumed to depend on the space variable. We prove the existence and uniqueness of solution of the model by actual solution method. The equations are solved using parameter-expanding method and eigenfunctions expansion technique. The results obtained were discussed. The study shows that the Frank-Kamenetskii number and frequency factors of the two reactions have significant effects on the propagation of the polymerization wave.Keywords: Polymerization, anterior polymerization, polymers, Arrhenius kinetics, parameter-expanding method, eigenfunctions expansion technique

Handcuffing reversal is facilitated by proteases and replication initiator monomers.

Specific nucleoprotein complexes are formed strictly to prevent over-initiation of DNA replication. An example of those is the so-called handcuff complex, in which two plasmid molecules are coupled together with plasmid-encoded replication initiation protein (Rep). In this work, we elucidate the mechanism of the handcuff complex disruption. In vitro tests, including dissociation progress analysis, demonstrate that the dimeric variants of plasmid RK2 replication initiation protein TrfA are involved in assembling the plasmid handcuff complex which, as we found, reveals high stability. Particular proteases, namely Lon and ClpAP, disrupt the handcuff by degrading TrfA, thus affecting plasmid stability. Moreover, our data demonstrate that TrfA monomers are able to dissociate handcuffed plasmid molecules. Those monomers displace TrfA molecules, which are involved in handcuff formation, and through interaction with the uncoupled plasmid replication origins they re-initiate DNA synthesis. We discuss the relevance of both Rep monomers and host proteases for plasmid maintenance under vegetative and stress conditions.

Parametric investigation of polymethacrylate monolith synthesis and stability via thermogravimetric characterisation

AbstractPolymethacrylate monoliths are synthetic adsorbents with macroporous and mesoporous interconnected channels that can be engineered to target the hydrodynamic features of a wide range of molecular species. However, rigorous study into the effect of synthesis conditions on their thermal stability is limited. This work attempts to characterise the influence of key synthesis process variables on the stability of polymethacrylate monoliths using thermogravimetric analysis at a heating rate of 10 °C/min. Experimental results showed that the thermal stability of polymethacrylate monoliths increased with decreasing polymerisation temperature from 85 to 65 °C. Increasing the total porogen (P) to monomer (M) ratio increased the thermal stability of the monolith by >62% and >50% for P40/M60–P60/M40 and P60/M40–P80/M20, respectively. The impact of the initiator concentration, monomer variation, biporogen ratio, washing and activation of the monoliths was investigated. Nuclear magnetic resonance analyses conducted confirmed the hydrolysis of epoxy moieties on the monolith. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Effect of transfer agent, temperature and initial monomer concentration on branching in poly(acrylic acid): A study by 13C NMR spectroscopy and capillary electrophoresis

Branching has been investigated in poly(acrylic acid) synthesized by conventional radical polymerization with and without chain transfer agent (CTA) at different temperatures and initial monomer concentrations. The average number of branches per monomer unit (i.e. degree of branching) was quantified by solution-state 13C NMR spectroscopy. The heterogeneity of branching (dispersity of the electrophoretic mobility distributions) was measured by capillary electrophoresis in the critical conditions (CE-CC). The degree of branching (DB) increases with the reaction temperature due to a rise in the frequency of reactions leading to branches, while the heterogeneity of branching remains steady. DB is lower in polymer synthesized with CTA. This decrease is due to either the CTA quenching the mid-chain radicals or a reduction of the rate of chain transfer to polymer relative to (chain-end) propagation. No influence of initial monomer concentration on DB and on the heterogeneity of branching was observed.

Rheological Properties in Aqueous Solution for Hydrophobically Modified Polyacrylamides Prepared in Inverse Emulsion Polymerization

Inverse emulsion polymerization technique was employed to synthesize hydrophobically modified polyacrylamide polymers with hydrophobe contents near to feed composition. Three different structures were obtained: multisticker, telechelic, and combined. N-Dimethyl-acrylamide (DMAM), n-dodecylacrylamide (DAM), and n-hexadecylacrylamide (HDAM) were used as hydrophobic comonomers. The effect of the hydrophobe length of comonomer, the initial monomer, and surfactant concentrations on shear viscosity was studied. Results show that the molecular weight of copolymer increases with initial monomer concentration and by increasing emulsifier concentration it remained almost constant. Shear viscosity measurements results show that the length of the hydrophobic comonomer augments the hydrophobic interactions causing an increase in viscosity and that the polymer thickening ability is higher for combined polymers.

Фізико-хімічні властивості кополімерів на основі фторалкілакрилатів і метилметакрилату.

In the process of radical copolymerization of 1,1,3-trihydroperfluoropentanol, 1,1,5-trihydroperfluoropentanol, 1,1,5-trihydroperfluoropentanol with methyl methacrylate the rate of reaction and the composition of copolymer significantly depend on the associative nature of peralkylates. Dependence of the rate of copolymerization of the composition of the initial monomer mixture is interpreted in terms of the model about the associates-the blanks, in which the mutual arrangement of the molecules of the monomer is favorable for the growth response of the polymer chain. The experimentally determined composition of copolymers were used to calculate copolymerization constants in the temperature range of 65–90 °C by the Mayo–Lewis method. At low temperatures, the copolymer is enriched by the fluorinated component, at higher values the azeotrope is observed. The equilibrium swelling degree of the synthesized copolymers in physiological solution at 37 °C varies between 0.04–0.48 %. The glass transition temperature of the copolymers depending on the composition is in the range of 72–86 °С

Kinetic control in the temperature-dependent sequential growth of surface-confined supramolecular copolymers.

We report the sequential growth of supramolecular copolymers on gold surfaces, using oppositely charged dendritic peptide amphiphiles. By including water-solubilising thermoresponsive chains in the monomer design, we observed non-linear effects in the temperature-dependent sequential growth. The step-wise copolymerisation process is characterised using temperature dependent SPR and QCM-D measurements. At higher temperatures, dehydration of peripheral oligoethylene glycol chains supports copolymer growth due to more favourable comonomer interactions. Both monomers incorporate methionine amino acids but remarkably, desorption of the copolymers via competing sulphur gold interactions with the initial monomer layer is not observed. The surface-confined supramolecular copolymers remain kinetically trapped on the metal surface at near neutral pH and form viscoelastic films with a tuneable thickness.

Coordination radical polymerization of methyl methacrylate, initiated by the azobis(isobutyronitrile)–tri-n-butylborane binary system

A procedure for coordination radical polymerization of methyl methacrylate in the bulk, initiated by the azobis(isobutyronitrile)–tri-n-butylborane binary system at 60°С, was developed. Butyl radicals participating in the initiation step were detected by EPR. These radicals are generated by complexation of cyanoisopropyl radicals with trialkylborane. The radical at the boron atom transforms from the C-centered to N-centered structure with the subsequent SR2 reaction and fast generation of n-butyl radicals. As found by NMR and confirmed by kinetic studies, the tri-n-butylborane–initiator–monomer system stimulates generation of propagating poly(methyl methacrylate) radicals.

Ferrogels based on entrapped metallic iron nanoparticles in a polyacrylamide network: extended Derjaguin-Landau-Verwey-Overbeek consideration, interfacial interactions and magnetodeformation.

A new kind of ferrogel with entrapped metallic iron nanoparticles causing unusual magnetodeformation is presented. Crosslinked polyacrylamide (PAAm) based ferrogels embedded with iron nanoparticles (MNPs) were synthesized by free radical polymerization in aqueous medium. Spherical iron MNPs with average diameter 66 nm were synthesized by the electrical explosion of wire and modified by interfacial adsorption of linear polyacrylamide (LPAAm). Extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) calculations based on the superposing of van der Waals, electrostatic, steric, and magnetic contributions showed that polymeric encapsulation of nanoparticles by LPAAm is one of the most suitable pathways for preparing stable aqueous dispersions of iron nanoparticles. Microcalorimetry confirmed the presence of strong interfacial adhesion forces between LPAAm chains and the surface of iron nanoparticles. By keeping the same crosslinking density of a polymer network (i.e. 100 : 1, monomer to crosslinker ratio) and varying the initial monomer concentration, an influence of the extent of polymer network reticulation on the mechanical properties and subsequently, magneto-elastic properties was demonstrated. It was found that the upper limit of the shear modulus for the synthesis of a new kind of polyacrylamide based ferrogel to exhibit any usable magnetodeformation under the application of a uniform external magnetic field of 420 mT is ca. 1 kPa. Magnetodeformation of cylindrical ferrogel samples was observed in the form of an overall volume contraction accompanied by a homogeneous decrease in all dimensions. The deformation was found to be maximum (around 10%) for the aspect ratio of 1/1 and it was lower and similar for the samples with 1/2 and 2/1 aspect ratios. Such a type of magnetic response is significantly different from the behavior observed in the existing reports on ferroelastomers.

Surface charge-bias impact of amine-contained pseudozwitterionic biointerfaces on the human blood compatibility

This work discusses the impact of the charge bias and the hydrophilicity on the human blood compatibility of pseudozwitterionic biomaterial gels. Four series of hydrogels were prepared, all containing negatively-charged 3-sulfopropyl methacrylate (SA), and either acrylamide, N-isopropylacrylamide, 2-dimethylaminoethyl methacrylate (DMAEMA) or [2-(methacryloyloxy)ethyl]trimethylammonium (TMA), to form SnAm, SnNm, SnDm or SnTm hydrogels, respectively. An XPS analysis proved that the polymerization was well controlled from the initial monomer ratios. All gels present high surface hydrophilicity, but varying bulk hydration, depending on the nature/content of the comonomer, and on the immersion medium. The most negative interfaces (pure SA, S7A3, S5A5) showed significant fibrinogen adsorption, ascribed to the interactions of the αC domains of the protein with the gels, then correlated to considerable platelet adhesion; but low leukocyte/erythrocyte attachments were measured. Positive gels (excess of DMAEMA or TMA) are not hemocompatible. They mediate protein adsorption and the adhesion of human blood cells, through electrostatic attractive interactions. The neutral interfaces (zeta potential between −10mV and +10mV) are blood-inert only if they present a high surface and bulk hydrophilicity. Overall, this study presents a map of the hemocompatible behavior of hydrogels as a function of their surface charge-bias, essential to the design of blood-contacting devices.

Thermal properties of europium nitrate hexahydrate Eu(NO3)3·6H2O

The hexahydrate of europium nitrate hexahydrate Eu(NO3)3·6H2O shows no phase transitions in the range of −40 to 76 °C when it melts in its own water of crystallization. It was shown that the thermal decomposition is a complex step-wise process, which starts with the simultaneous condensation of 6 mol of the initial monomer Eu(NO3)3·6H2O into a cyclic cluster 6[Eu(NO3)3·6H2O]. This hexamer gradually loses water and nitric acid, and a series of intermediate amorphous oxynitrates is formed. The removal of HNO3 azeotrope is essentially a continuous process occurring in the liquid phase. At higher temperatures, oxynitrates undergo further degradation, lose water, nitrogen dioxide, and oxygen, and finally, after having lost lattice water, are transformed into europium oxide. All mass losses are satisfactorily accounted for under the proposed scheme of thermal decomposition.

Formation of porous matrices from lactide and ε-caprolactone copolymers in supercritical carbon dioxide medium

A series of lactide and e-caprolactone copolymers containing 4–24 mol % of e-caprolactone with 20- to 30-kDa molecular weights are synthesized. Based on them, porous materials are produced by foaming in supercritical carbon dioxide. The pore size was shown to decrease with increasing e-caprolactone content in copolymer, while the porosity of the entire sample was not altered. The resulting pore size also decreases if 7 wt % polyethylene glycol is added to the initial monomer mixture. The Young’s modulus of the porous samples decreases with increasing e-caprolactone content and when polyethylene glycol is added.

Switching from Controlled Ring-Opening Polymerization (cROP) to Controlled Ring-Closing Depolymerization (cRCDP) by Adjusting the Reaction Parameters That Determine the Ceiling Temperature.

Full control over the ceiling temperature (Tc) enables a selective transition between the monomeric and polymeric state. This is exemplified by the conversion of the monomer 2-allyloxymethyl-2-ethyl-trimethylene carbonate (AOMEC) to poly(AOMEC) and back to AOMEC within 10 h by controlling the reaction from conditions that favor ring-opening polymerization (Tc > T0) (where T0 is the reaction temperature) to conditions that favor ring-closing depolymerization (Tc < T0). The ring-closing depolymerization (RCDP) mirrors the polymerization behavior with a clear relation between the monomer concentration and the molecular weight of the polymer, indicating that RCDP occurs at the chain end. The Tc of the polymerization system is highly dependent on the nature of the solvent, for example, in toluene, the Tc of AOMEC is 234 °C and in acetonitrile Tc = 142 °C at the same initial monomer concentration of 2 M. The control over the monomer to polymer equilibrium sets new standards for the selective degradation of polymers, the controlled release of active components, monomer synthesis and material recycling. In particular, the knowledge of the monomer to polymer equilibrium of polymers in solution under selected environmental conditions is of paramount importance for in vivo applications, where the polymer chain is subjected to both high dilution and a high polarity medium in the presence of catalysts, that is, very different conditions from which the polymer was formed.

Influence of Sonication on Morphological Properties of Poly(Vinyl Acetate) Particles Produced Through Suspension Polymerization

SummaryThe use of polymers for various medical purposes has increased significantly over the past few years, including vascular embolization procedures. The main challenge in this particular case is the development of embolic agents with suitable properties in order to render the application safer and reproducible. In this context, particle density plays a fundamental role in vascular embolization performance, since off‐spec values can lead to undesired sedimentation of particles during the medical procedure. The influence of sonication power on the morphology of polymer particles produced through suspension polymerizations was investigated in the present work, as well as the effects of adding polymer material into the initial monomer dispersion on the final morphological properties of the product. It is shown in particular that the investigated morphological properties (density, shape, porosity) depend on the operation conditions on manners that have not been discussed in the literature.

Influences of monomer self‐association on the radical solution homopolymerization of N‐[3‐(dimethylamino)propyl](meth)acrylamide

ABSTRACTThe specific dependencies of the initial reduced polymerization rate on the initial monomer concentration were introduced for the radical homopolymerization of N‐[3‐(dimethylamino)propyl]acrylamide (DMAPA) and N‐[3‐(dimethylamino)propyl]methacrylamide (DMAPMA) in toluene, DMF, and water at 60 °С. The degree of the monomer self‐association and the ratio of the amides constituting various types of associates were evaluated using FT‐IR spectroscopy and computer simulation for the solutions of DMAPA and DMAPMA in toluene with different monomer concentrations. The hypothesis linking the type of predominant pre‐reaction monomer assemblies and the revealed concentration effects was proposed for the homopolymerization of aminoamide monomers and explaining unconventional experimental data. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44412.

Well-defined polymer microspheres formed by living dispersion polymerization: precisely functionalized crosslinked polymer microspheres from monomers possessing cumulated double bonds

The precise method for synthesizing well-defined polymer microspheres via π-allylnickel-catalyzed living coordination polymerization of allene derivatives under dispersion polymerization conditions is described. The π-allylnickel-catalyzed living coordination polymerization of allene derivatives such as phenoxyallene was carried out in protic solvents such as methanol in the presence of stabilizers such as polyvinylpyrrolidone to produce polymer microspheres with a narrowly dispersed diameter distribution (Dw/Dn) at a high yield. For example, polymer microspheres with a number-average diameter (Dn) of 1.10 μm and Dw/Dn of 1.01 were obtained at a yield of 97%; these microspheres are composed of a polymer with a controlled molecular weight (Mn=11 700) and narrow molecular weight distribution (Mw/Mn=1.06). The size of the resulting polymer microspheres proved to be affected by polymerization conditions such as the initial monomer concentrations, monomer structures, polymerization media and stabilizers. Unlike conventional dispersion polymerization systems, the use of a bifunctional monomer, 1,4-diallenoxybenzene, for this living dispersion polymerization successfully produced well-defined crosslinked living polymer microspheres that exhibited high solvent tolerance. The postpolymerization of functional allene monomers in the living dispersion polymerization was also successful, resulting in functionalized polymer microspheres that could be applied in solid-phase organic synthesis and solid-supported transition metal catalysis. A controllable process for producing uniform, robust microspheres can make mixed solid-liquid chemical reactions easier to perform. Tiny beads of polymers such as polystyrene are finding increasing use as supports for catalysts in organic synthesis. Now, Ikuyoshi Tomita from the Tokyo Institute of Technology and co-workers have used a ‘living’ coordination mechanism, which polymerizes molecules until directed to stop, to improve the size distribution and modification capabilities of microspheres. Nickel-based catalysts and unsaturated, bifunctional carbon reagents worked together to generate microspheres with cross-linked internal structures for additional strength and solvent tolerance. Furthermore, the microsphere surfaces contained living, growing ends that can attach to additional reagents. Synthetic trials revealed that decorating the microspheres with palladium produced a heterogeneous catalyst that could be recovered and reused multiple times with little loss of activity. The precision synthetic method of well-defined polymer microspheres by the π-allylnickel-catalyzed living coordination polymerization of allene derivatives under the dispersion polymerization conditions is described. Unlike the conventional dispersion polymerization systems, the use of a bifunctional monomer, 1,4-diallenoxybenzene, to this living dispersion polymerization successfully gave well-defined crosslinked living polymer microspheres that exhibit high solvent-tolerant properties. The postpolymerization of functional allene monomers in the living dispersion polymerization also proceeded smoothly to give functionalized polymer microspheres that enabled their applications to the solid-phase organic synthesis and the solid-supported transition metal catalysts.

Monodisperse AIE-Active Conjugated Polymer Nanoparticles via Dispersion Polymerization Using Geminal Cross-Coupling of 1,1-Dibromoolefins.

Monodisperse AIE (aggregation-induced emission)-active conjugated polymer nanoparticles are synthesized by dispersion polymerization using geminal Suzuki cross-coupling of 1,1-dibromoolefins. The size of the nanoparticles can be adjusted by varying the concentration of the initial monomer.

Synthesis, gas transport and dielectric properties of fluorinated poly(arylene ether)s based on decafluorobiphenyl

In this work, the fluorinated poly(arylene ether)s containing meta-phenoxy units based on decafluorobiphenyl and hydroxyl-substituted monomers were synthesized. Two synthetic pathways were investigated in order to prepare polyether based on decafluorobiphenyl and resorcinol. In a first route, such polymer was synthesized by interaction of decafluorobiphenyl with resorcinol. In a second route, the specified polyether was synthesized by interaction of decafluorobiphenyl with 4,4’-bis(3-hydroxyphenoxy)octafluorobiphenyl as initial monomer instead of resorcinol. The molecular weight, mechanical, and thermal properties of the synthesized fluorinated poly(arylene ether)s were studied depending on the structure of macromolecular chains and synthetic route. Gas transport properties for He, H2, O2, N2, CO2 and CH4 gases of the synthesized fluorinated poly(arylene ether)s were investigated. Furthermore, the obtained fluorinated polyether membranes showed low dielectric constants with the values in the range of 2.30–2.75 at room temperature and at 10 kHz frequency.