Showing papers in "Journal of Polymer Science Part A in 2010"
TL;DR: In this paper, the impact of thiol-ene chemistry on polymer and materials science over the past five years is reviewed, and the utility of the reactions for network formation, polymer functionalization, dendrimer synthesis and the decoration of three-dimensional objects is discussed.
Abstract: As a tribute to Professor Charlie Hoyle, we take the opportunity to review the impact of thiol-ene chemistry on polymer and materials science over the past 5 years. During this time, a renaissance in thiol-ene chemistry has occurred with recent progress demonstrating its unique advantages when compared with traditional coupling and functionalization strategies. Additionally, the robust nature of thiol-ene chemistry allows for the preparation of well-defined materials with few structural limitations and synthetic requirements. To illustrate these features, the utility of thiol-ene reactions for network formation, polymer functionalization, dendrimer synthesis, and the decoration of three-dimensional objects is discussed. Also, the development of the closely related thiol-yne chemistry is described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 743–750, 2010
790 citations
TL;DR: In this paper, the synthesis of cyclic polymers including cyclic homo-polymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentia- tion between synthetic methods and synthetic strategies.
Abstract: Syntheses of cyclic polymers including cyclic homo- polymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentia- tion between synthetic methods and synthetic strategies (e.g., polycondensation, ring-ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classi- fied as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed. V C 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 251-284, 2010
363 citations
TL;DR: In this article, multi-walled carbon nanotubes (MWCNTs)-core/thiophene polymer-sheath composite nanocables were synthesized by chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) with oxidant (FeCl3) in the presence of cationic surfactant, deceyltrimethyl ammonium bromide (DTAB).
Abstract: Multi-walled carbon nanotubes (MWCNTs)-core/thiophene polymer-sheath composite nanocables were synthesized by chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) with oxidant (FeCl3) in the presence of cationic surfactant, deceyltrimethyl ammonium bromide (DTAB). In the polymerization process, DTAB surfactant molecules were adsorbed on the surface of MWCNTs and forms MWCNTs-DTAB soft template. Upon the addition of EDOT and oxidant, the polymerization take place on the surface of MWCNTs and PEDOT is gradually deposited on the surface of MWCNTs. The resulting MWCNTs-PEDOT nanocomposites have the nanocable structure. Nanocomposites were characterized by HRTEM, FE-SEM, XRD, XPS, TGA, FTIR and PL, respectively. The π-π interactions between PEDOT and MWCNTs enhancing the thermal and electrical properties of the nanocomposites with loading of MWCNTs. The temperature dependence conductivity measurements show that the conductivity of the nanocomposite decrease with a decrease of temperature, and conductivity-temperature relationship is well fit by the quasi-one dimensional variable range hopping mode. The mechanism for the formation of composite nanocables was explained on the basis of self- assembly of micelles. The reported self-assembly strategy for the synthesis of PEDOT-coated MWCNTs in micellar medium is a rapid, versatile, potentially scalable, stable, and making it useful for further exploitation in a varies types of applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1477–1484, 2010
278 citations
TL;DR: In this paper, the results from the Preparative Macromolecular Chemistry group from the Karlsruhe Institute of Technology (KIT) and the Polymer Chemistry Research group from Ghent University (UGent) were compared.
Abstract: In this work, we report our findings on the use of radical thiol-ene chemistry for polymer–polymer conjugation. The manuscript combines the results from the Preparative Macromolecular Chemistry group from the Karlsruhe Institute of Technology (KIT) and the Polymer Chemistry Research group from Ghent University (UGent), which allowed for an investigation over a very broad range of reaction conditions. In particular, thermal and UV initiation methods for the radical thiol-ene process were compared. In the KIT group, the process was studied as a tool for the synthesis of star polymers by coupling multifunctional thiol core molecules with poly(n-butyl acrylate) macromonomers (MM), employing thermally decomposing initiators. The product purity and thus reaction efficiency was assessed via electrospray ionization mass spectrometry. Although the reactions with 10 or 5 equivalents of thiol with respect to macromonomer were successful, the coupling reaction with a one-to-one ratio of MM to thiol yielded only a fraction of the targeted product, besides a number of side products. A systematic parameter study such as a variation of the concentration and nature of the initiator and the influence of thiol-to-ene ratio was carried out. Further experiments with poly(styrene) and poly(isobornyl acrylate) containing a vinylic end group confirmed that thermal thiol-ene conjugation is far from quantitative in terms of achieving macromolecular star formation. In parallel, the UGent group has been focusing on photo-initiated thiol-ene chemistry for the synthesis of functional polymers on one hand and block copolymers consisting of poly(styrene) (PS) and poly(vinyl acetate) (PVAc) on the other hand. Various functionalization reactions showed an overall efficient thiol-ene process for conjugation reactions of polymers with low molecular weight compounds (∼90% coupling yield). However, while SEC and FT-IR analysis of the conjugated PS-PVAc products indicated qualitative evidence for a successful polymer–polymer conjugation, 1H NMR and elemental analysis revealed a low conjugation efficiency of about 23% for a thiol-to-ene ratio equal to one. Blank reactions using typical thiol-ene conditions indicated that bimolecular termination reactions occur as competitive side reactions explaining why a molecular weight increase is observed even though the thiol-ene reaction was not successful. The extensive study of both research groups indicates that radical thiol-ene chemistry should not be proposed as a straightforward conjugation tool for polymer–polymer conjugation reactions. Head-to-head coupling is a major reaction pathway, which interrupts the propagation cycle of the thiol-ene process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1699–1713, 2010
248 citations
TL;DR: In this article, pyrene-terminated PNIPAAm was synthesized using reversible addition fragmentation chain transfer (RAFT) polymerization via a pyrene functional RAFT agent, and aqueous solutions of the graphene-polymer composites were stable and thermosensitive.
Abstract: Thermosensitive graphene-polymer composites have been prepared by attaching poly(N-isopropylacrylamide) (PNIPAAm) onto the basal plane of graphene sheets via pi-pi stacking. Pyrene-terminated PNIPAAm was synthesized using reversible addition fragmentation chain transfer (RAFT) polymerization via a pyrene-functional RAFT agent. Aqueous solutions of the graphene-polymer composites were stable and thermosensitive. The lower critical solution temperature (LCST) of pyrene-terminated PNIPAAm was measured to be 33 degrees C. When the pyrene-functional polymer was attached to graphene the resultant composites were also thermosensitive in aqueous solutions exhibiting a reversible suspension behavior at 24 degrees C. Atomic force microscopy (AFM) analysis revealed that the thickness Of a graphene-PNIPAAm (M-n: 10,000 and PDI: 1.1) sheet was similar to 5.0 nm. The surface coverage of polymer chains on the graphene basal plane was calculated to be 7.2 x 10 (11) mol cm(-2). The graphene-PNIPAAm composite material was successfully characterized using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR) spectroscopy, and thermogravimetric analysis (TGA). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 425-433, 2010
220 citations
TL;DR: In this paper, the singleelectron transfer living radical polymerization (SET-LRP) of water-soluble monomers, N,N-dimethylacrylamide (DMA), initiated with 2-methylchloropropionate (MCP) in dipolar aprotic and protie solvents is reported.
Abstract: The single-electron transfer living radical polymerization (SET-LRP) of water-soluble monomers, N,N-dimethylacrylamide (DMA) and N-isopropylacrylamide (NIPAM), initiated with 2-methylchloropropionate (MCP) in dipolar aprotic and protie solvents is reported. The radical polymerization of acrylamides is characterized by higher rate constants of propagation and bimolecular termination than acrylates. Therefore, the addition of CuCl Is required to mediate deactivation in the early stages of the reaction. Through the use of Cu(0)-wire/Me-TREN catalysis, conditions were optimized to minimize the amount of externally added CuCl required to maintain a linear evolution of molecular weight and narrow molecular weight distribution. By using less CuCl additive, the amount of soluble copper species that must ultimately be removed from the reaction mixture is reduced.
177 citations
TL;DR: The miniemulsions process represents a versatile tool for the formation of polymeric nanoparticles consisting of different kinds of polymer as obtained by a variety of polymerization types ranging from radical, anionic, cationic, enzymatic polymerization to polyaddition, and polycondensation.
Abstract: The miniemulsions process represents a versatile tool for the formation of polymeric nanoparticles consisting of different kinds of polymer as obtained by a variety of polymerization types ranging from radical, anionic, cationic, enzymatic polymerization to polyaddition, and polycondensation. The process perfectly allows the encapsulation of hydrophilic and hydrophobic liquids and solids in polymeric shells, molecularly dissolved dyes or other components. In combination with a specific functionalization of the nanoparticles' or nanocapsules' surfaces and the possibility to release substances in a defined way from the interior, complex nanoparticles or nanocapsules are obtained, which are ideally suited for application in biomedical application as marker and targeted drug-delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 493–515, 2010
163 citations
TL;DR: In this article, a new route to covalently bonded polymer-graphene nanocomposites and the subsequent enhancement in thermal and mechanical properties of the resultant nan composites was described.
Abstract: This report describes a new route to covalently bonded polymer–graphene nanocomposites and the subsequent enhancement in thermal and mechanical properties of the resultant nanocomposites. At first, the graphite is oxidized by the modified Hummers method followed by functionalization with Octadecylamine (ODA). The ODA functionalized graphite oxides are reacted with methacryloyl chloride to incorporate polymerizable CC functionality at the nanographene platelet surfaces, which were subsequently employed in in situ polymerization of methylmethacrylate to obtain covalently bonded poly(methyl methacrylate) (PMMA)–graphene nanocomposites. The obtained nanocomposites show significant enhancement in thermal and mechanical properties compared with neat PMMA. Thus, even with 0.5 wt % graphene nanosheets, the Tg increased from 119 °C for neat PMMA to 131 °C for PMMA–graphene nanocomposite, and the respective storage modulus increased from 1.29 to 2 GPa. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4262–4267, 2010
159 citations
TL;DR: In this article, a simple method for the activation of the Cu(0) wire used as catalyst in singleelectron transfer living radical polymerization (SET-LRP) is reported.
Abstract: A simple method for the activation of the Cu(0) wire used as catalyst in single-electron transfer living radical polymerization (SET-LRP) is reported. The surface of Cu(0) stored in air is coated with a layer of CuO. It is well established that CuO is a less reactive catalyst for SET-LRP than Cu(0). We report here the activation of the Cu(0) wire under nitrogen by the reduction of CuO from its surface to Cu(0) by treatment with hydrazine hydrate. The kinetics of SET-LRP of methyl acrylate (MA) catalyzed with activated Cu(0) wire in dimethyl sulfoxide (DMSO) at 25 °C demonstrated a dramatic acceleration of the polymerization and the absence of the induction period observed during SET-LRP catalyzed with nonactivated Cu(0) in several laboratories. Exposure of the activated Cu(0) wire to air results in a lower apparent rate constant of propagation because of gradual oxidation of Cu(0) to CuO. This dramatic acceleration of SET-LRP is similar to that observed with commercial Cu(0) nanopowder except that the polymerization provides excellent molecular weight evolution, very narrow molecular weight distribution and high polymer chain-end functionality.
155 citations
TL;DR: In this article, a series of water-soluble thermoresponsive hyperbranched copoly(oligoethylene glycol)s were synthesized by copolymerization of di(ethylene gels) methacrylate (DEGMA) and oligo(ethylenes glycol), with EGD-MA used as the crosslinker via reversible addition fragmentation chain transfer polymerization.
Abstract: A series of water-soluble thermoresponsive hyperbranched copoly(oligoethylene glycol)s were synthesized by copolymerization of di(ethylene glycol) methacrylate (DEGMA) and oligo(ethylene glycol) methacrylate (OEG-MA, M-w = 475 g/mol), with ethylene glycol dimethacrylate (EGD-MA) used as the crosslinker, via reversible addition fragmentation chain transfer polymerization. Polymers were characterized by size exclusion chromatography and nuclear magnetic resonance analyses. According to the monomer composition, that is, the ratio of OEG-MA: DEG-MA: EGD-MA, the lower critical solution temperature (LCST) could be tuned from 25 degrees C to 90 degrees C. The thermoresponsive properties of these hyperbranched copolymers were studied carefully and compared with their linear analogs. It was found that molecular architecture influences thermoresponsive behavior, with a decrease of around 5-10 degrees C in the LCST of the hyperbranched polymers compared with the LCST of linear chains. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2783-2792, 2010
150 citations
TL;DR: In this article, the authors demonstrate that SET-LRP of methyl acrylate can be conducted in the presence of air, and the addition of a small amount of reducing agent hydrazine hydrate to the reaction mixture reduces Cu2O generated by the oxidation of Cu(0) with air, regenerating Cu( 0) and allowing for the synthesis of polymers with predictable molecular weight and perfect retention of chain end functionality.
Abstract: Single Electron Transfer-Living Radical Polymerization (SET-LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with well defined topology. In SET-LRP, certain combinations of solvents and ligands facilitate the disproportionation of in situ generated Cu(I) species into “nascent” Cu(0) and Cu(II) species. A combination of heterogeneous and “nascent” Cu(0) activation yields polymers with very high chain end functionality. Under suitable conditions the tolerance toward oxygen must be increased since Cu(0), the activator in SET-LRP, acts as an oxygen scavenger in all inert gas purification systems. Here we demonstrate that SET-LRP of methyl acrylate can be conducted in the presence of air. The addition of a small amount of reducing agent hydrazine hydrate to the reaction mixture reduces Cu2O generated by the oxidation of Cu(0) with air, regenerating Cu(0) and allowing for the synthesis of polymers with predictable molecular weight and perfect retention of chain end functionality. The kinetics plots obtained under these conditions were identical to these generated by degassed samples. High conversions were achieved within a very short reaction time. In these SET-LRP experiments, the reagents were not deoxygenated or subjected to standard degassing procedures such as freeze-pump-thaw or nitrogen sparging. This simple SET-LRP procedure provides an efficient and economical approach to the synthesis of functional macromolecules. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1190–1196, 2010
TL;DR: In this paper, the synthesis of polyethylene/graphite nanocomposites by in situ polymerization was achieved using the catalytic system Cp2ZrCl2 (bis(cyclopentadienyl)zirconium(IV) dichloride)/methylaluminoxane (MAO).
Abstract: The synthesis of polyethylene/graphite nanocomposites by in situ polymerization was achieved using the catalytic system Cp2ZrCl2 (bis(cyclopentadienyl)zirconium(IV) dichloride)/methylaluminoxane (MAO). Graphite with nano dimensions, previously treated with MAO, was added into the reactor as filler at percentages of 1, 2, and 5% (w/w). XRD analysis showed that the chemical and thermal treatments employed preserve the structure of the graphite sheets. The formation of graphite nanosheets and nanocomposites was confirmed by TEM and AFM. TEM micrographics showed that the polyethylene grew between the graphene nanosheets, giving intercalated and exfoliated graphite nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 692–698, 2010
TL;DR: In this paper, the synthesis of poly(methyl methacrylate) via SET-LRP in dimethyl sulfoxide (DMSO) by using CCl4 as initiator is demonstrated.
Abstract: Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The synthesis of poly(methyl methacrylate) via SET-LRP in dimethyl sulfoxide (DMSO) by using CCl4 as initiator is demonstrated in this work. Resorting to a rather simple Cu(0)/Me6-TREN catalyst a method was established that allowed for the straightforward design of well-defined poly(methyl methacrylate). The reactions were performed at various temperatures (25, 50, 60, and 80 °C) and complete monomer conversion could be achieved. The polymerizations obeyed first order kinetic, the molecular weights increased linearly with conversion and the polymers exhibited narrow molecular weight distributions all indicating the livingness of the process. By providing a small amount of hydrazine to the reaction mixture the polymerization could be conducted in presence of air omitting the need for any elaborated deoxygenation procedures. This methodology offers an elegant way to synthesize functionalized poly(methyl methacrylate) with perfect control over the polymerization process as well as molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2243–2250, 2010
TL;DR: In this article, a very small "nascent" Cu(0) species formed via disproportionation in SET-LRP of methyl acrylate (MA) was used as a mimics of the very active catalysts in the single-electron transfer living radical polymerization of MA.
Abstract: Cu(0) was prepared via disproportionation of Cu(I)Br in the presence of MeTREN in various solvents in a glove box. The resulting nanopowders were used as mimics of "nascent" Cu(0) catalyst in the single-electron transfer living radical polymerization (SET-LRP) of methyl acrylate (MA), providing faster polymerization than any commercial Cu(0) powder, Cu(0) wire, or Cu(I)Br and achieving 80% conversion in only 5 min reaction time. Despite the high rate, a living polymerization was observed with linear evolution of molecular weight, narrow polydispersity, no induction period, and high retention of chain-end functionality. In addition to providing an unprecedentedly fast, yet controlled LRP of MA, these studies suggest that the very small "nascent" Cu(0) species formed via disproportionation in SET-LRP are the most active catalysts. Thus, when bulk Cu(0) powder or wire may be the most abundant catalyst and dictates the overall kinetics, any Cu(0) produced via disproportionation will be rapidly consumed and contributes to the overall catalytic cycle.
TL;DR: In this article, the synthesis of crosslinked polyacrylate polyHIPEs based on Pickering HIPEs stabilized using silane-modified silica nanoparticles is described and the effects of the synthesis parameters on the porous structure are discussed.
Abstract: A polyHIPE is a highly porous polymer synthesized from monomers within the external phase of a high internal phase emulsion (HIPE). The large amount of difficult to remove surfactant needed for HIPE stabilization can affect the properties of the resulting polymer. A Pickering emulsion is a surfactant-free emulsion stabilized by solid particles that preferentially migrate to the interface. In this article, the synthesis of crosslinked polyacrylate polyHIPEs based on Pickering HIPEs stabilized using silane-modified silica nanoparticles is described and the effects of the synthesis parameters on the porous structure are discussed. The silane chemistry, silane content, and nanoparticle content had significant effects on the size of the polyhedral, relatively closed-cell polyHIPE voids that resulted from aqueous-phase initiation. Increasing the mixing intensity reduced the wall thickness and produced a more open-cell structure. The locus of initiation had a significant effect on polyHIPE morphology. Organic-phase initiation yielded larger, more spherical voids from the more extensive coalescence before the structure could be "locked-in" at the gel point. Most significantly, the nanoparticles were located within the polymer walls rather than at the interface, as might be expected. The void walls were shown to be an assembly of nanoparticle agglomerate shells that become embedded within the polymer.
TL;DR: In this article, the authors describe the synthesis, the spectroscopic and the thermal characterization of linear and crosslinked polymers as well as a number of corresponding model compounds, containing Diels-Alder adducts derived from furan and maleimide groups.
Abstract: This study describes the synthesis, the spectroscopic, and the thermal characterization of linear and crosslinked polymers as well as a number of corresponding model compounds, containing Diels-Alder adducts derived from furan and maleimide groups. The thermal reversibility (rDA, DA) of structurally varied model compounds, polymeric and network structures were studied by differential scanning calorimetry, where possible in combination with 1H NMR spectroscopy. It was established that the endo and exo DA stereoisomers show significantly different thermal responses: the rDA of the endo DA-adducts typically takes place at 20-40 K lower temperatures than that of the corresponding exo DA-adducts in all cases, with the exception of some aromatic maleimides. Although In situ isomerization was observed to a limited extent and only In some cases, this effect is not expected to influence the thermoremendability of DA-crosslinked networks being dependent on two separate stereoisomeric rDA steps.
TL;DR: In this article, a very small amount of acrylonitrile (AN, 2.2−8.8 mol %) was used as a comonomer for the SG1-based polymerization of methyl methacrylate.
Abstract: Nitroxide-mediated controlled/living free-radical polymerization of methyl methacrylate initiated by the SG1-based alkoxyamine BlocBuilder was successfully performed in bulk at 80―99 °C with the help of a very small amount of acrylonitrile (AN, 2.2―8.8 mol %) as a comonomer. Well-defined PMMA-rich P(MMA-co-AN) copolymers were prepared with the number-average molar mass, M n , in the 6.1―32 kg mol ―1 range and polydispersity indexes as low as 1.24. Incorporation of AN in the copolymers was demonstrated by 1 H and 13 C NMR spectroscopy, and its effect on the chain thermal properties was evaluated by DSC and TGA analyses. Investigation of chain-end functionalization by an alkoxyamine group was performed by means of 31 P NMR spectroscopy and chain extensions from a P(MMA-co-AN)-SG1 macroinitiator. It demonstrated the very high proportion of SG1-terminated polymer chains, which opened the door to block copolymer synthesis with a high quality of control.
TL;DR: In this article, the authors examined acac complexes of transition metals in the 4th period as catalysts for the ring-opening polymerization of benzoxazine and found that acac complex of manganese, iron, and cobalt exhibited the highest activity, comparable or slightly higher than that exhibited by p-toluenesulfonic acid.
Abstract: Acetylacetonato (acac) complexes of transition metals in the 4th period were examined as catalysts for the ring-opening polymerization of benzoxazine. This examination revealed that acac complexes of manganese, iron, and cobalt exhibited the highest activity, which was comparable or slightly higher than that exhibited by p-toluenesulfonic acid. By replacing acac ligand by hexafluoroacetylacetonato (F 6 -acac) ligand, the activity of manganese and iron complexes was remarkably enhanced. These metal F 6 -acac complexes were tolerant to moisture to allow their use under air without special caution. Another advantage was their negligible effect to promote unfavorable weight loss during the polymerization.
TL;DR: A series of well-defined amphiphilic triblock copolymers [polyethylene glycol monomethyl ether]-block poly(e-caprolactone)-block poly[2-(dimethylamino)ethyl methacrylate] were prepared by a combination of ring-opening polymerization and atom transfer radical polymerization.
Abstract: A series of well-defined amphiphilic triblock copolymers [polyethylene glycol monomethyl ether]-block-poly(e-caprolactone)-block-poly[2-(dimethylamino)ethyl methacrylate] (mPEG-b-PCL-b-PDMAEMA or abbreviated as mPEG-b-PCL-b-PDMA) were prepared by a combination of ring-opening polymerization and atom transfer radical polymerization. The chemical structures and compositions of these copolymers have been characterized by Fourier transform infrared spectroscopy, 1H NMR, and thermogravimetric analysis. The molecular weights of the triblock copolymers were obtained by calculating from 1H NMR spectra and gel permeation chromatography measurements. Subsequently, the self-assembly behavior of these copolymers was investigated by fluorescence probe method and transmission electron microscopy, which indicated that these amphiphilic triblock copolymers possess distinct pH-dependent critical aggregation concentrations and can self-assemble into micelles or vesicles in PBS buffer solution, depending on the length of PDMA in the copolymer. Agarose gel retardation assays demonstrated that these cationic nanoparticles can effectively condense plasmid DNA. Cell toxicity tests indicated that these triblock copolymers displayed lower cytotoxicity than that of branched polyethylenimine with molecular weight of 25 kDa. In addition, in vitro release of Naproxen from these nanoparticles in pH buffer solutions was conducted, demonstrating that higher PCL content would result in the higher drug loading content and lower release rate. These biodegradable and biocompatible cationic copolymers have potential applications in drug and gene delivery. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1079–1091, 2010
TL;DR: The ability to tailor the surface chemistry of the composite nanoparticles and incorporate steric stabilizing groups using simple thiol-ene chemistry is demonstrated.
Abstract: A simple and modular synthetic approach, based on miniemulsion polymerization, has been developed for the fabrication of composite polymer-metal nanoparticle materials. The procedure produces well-defined composite structures consisting of gold, silver or MnFe(2)O(4) nanoparticles (∼10 nm in diameter) encapsulated within larger spherical nanoparticles of poly(divinylbenzene) (∼100 nm in diameter). This methodology readily permits the incorporation of multiple metal domains into a single polymeric particle, while still preserving the useful optical and magnetic properties of the metal nanoparticles. The morphology of the composite particles is retained upon increasing the inorganic content, and also upon redispersion in organic solvents. Finally, the ability to tailor the surface chemistry of the composite nanoparticles and incorporate steric stabilizing groups using simple thiol-ene chemistry is demonstrated.
TL;DR: In this article, the authors describe recent developments in polymer synthesis via these two kinds of polymerizations to afford various functional polymers having completely different structures, poly(N-acylethylenimine)s via CROP and 2-amino-2-deoxy sugar unit-containing oligo and polysaccharides via EROPA, respectively.
Abstract: Chemistry of 2-oxazolines is involved in the polymer synthesis fields of cationic ring-opening polymerization (CROP) and enzymatic ring-opening polyaddition (EROPA), although both polymerizations look like a quite different class of reaction. The key for the polymerization to proceed is combination of the catalyst (initiator) and the design of monomers. This article describes recent developments in polymer synthesis via these two kinds of polymerizations to afford various functional polymers having completely different structures, poly(N-acylethylenimine)s via CROP and 2-amino-2-deoxy sugar unit-containing oligo and polysaccharides via EROPA, respectively. From the viewpoint of reaction mode, an acid-catalyzed ring-opening polyaddition (ROPA) is considered to be a crossing where CROP and EROPA meet. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1251–1270, 2010
TL;DR: In this article, a linear unsaturated terminal diisocyanate, 1,16-diisocynatohexadec-8-ene (HDEDI), was synthesized from oleic acid via Curtius rearrangement.
Abstract: A novel long chain linear unsaturated terminal diisocyanate, 1,16-diisocyanatohexadec-8-ene (HDEDI) was synthesized from oleic acid via Curtius rearrangement. Its chemical structure was identified by FTIR, 1H NMR, 13C NMR, and HRMS. This diisocyanate was used as a starting material for the preparation of entirely bio-based polyurethanes (PUs) by reacting it with canola diol and canola polyol, respectively. The physical properties and crystalline structure of the PUs prepared from this diisocyanate were compared to their counterparts prepared from similar fatty acid-derived diisocyanate, 1,7-heptamethylene diisocyanate (HPMDI). The HDEDI based PUs demonstrated various different properties compared to those of HPMDI based PUs. For example, HDEDI based PUs exhibited a triclinic crystal form; whereas HPMDI based PUs exhibited a hexagonal crystal lattice. In addition, canola polyol-HDEDI PU demonstrated a higher tensile strength at break than that of canola polyol-HPMDI, attributed to the higher degree of hydrogen bonding associated with the former sample. Nevertheless, lower Young's modulus and higher elongation in canola polyol-HDEDI PU were obtained because of the flexibility of the long chain introduced by the HDEDI diisocyanate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3302–3310, 2010
TL;DR: Three types of poly(N-vinylcaprolactam)-based temperature-sensitive microgel particles were synthesized by emulsion polymerization and the driving force for the model drug to penetrate into the micro gel particles is H-bonding associations.
Abstract: Three types of poly(N-vinylcaprolactam)-based temperature-sensitive microgel particles were synthesized by emulsion polymerization. The uptake of a model drug (calcein) into the particles was analyzed in terms of the amount of calcein absorbed and equilibrium–swelling degree. By incubating the microgels with primary neuronal cell cultures of embrionary rats, cell viability and biocompatibility tests were carried out. The results show that the driving force for the model drug to penetrate into the microgel particles is H-bonding associations. On the other hand, cell death was microgel concentration and incubation period dependent. Microgels can be stored in a dried state and resuspended in water when necessary without changing their swelling–deswelling ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1173–1181, 2010
TL;DR: In this article, the singleelectron transfer living radical polymerization (SET-LRP) of vinyl chloride (VC) initiated with CHBr in dimethylsulfoxide (DMSO) at 25 °C was investigated using Cu(0) powder and Cu( 0) wire as the catalyst.
Abstract: The single-electron transfer living radical polymerization (SET-LRP) of vinyl chloride (VC) initiated with CHBr in dimethylsulfoxide (DMSO) at 25 °C was investigated using Cu(0) powder and Cu(0) wire as the catalyst. It was determined that living kinetics and high conversion are achieved only through the proper calibration of the ratio between Cu(0) and TREN and the concentration of VC in DMSO. For both Cu(0) powder and Cu(0) wire, optimum conversion was achieved with higher levels of TREN than reported In earlier preliminary reports and under more dilute conditions. Using these conditions, 85+% conversion of VC could be achieved with Cu(0) powder and wire to produce white poly(vinyl chloride) (PVC) with M = 20,000 and M /M = 1.4-1.6 in 360 min. The use of Cu(0) wire provides the most effective catalytic system for the LRP of PVC allowing for simple removal and recycling of the catalyst. In the Cu(0) wire-catalyzed SET-LRP of VC, the consumption of Cu(0) was monitored as a function of conversion. From these studies, it is evident that the catalyst can be recycled extensively before significant exchange of Cu(0) into Cu(II)X and change in catalyst surface area is observed.
TL;DR: The SET-LRP reaction, was restarted each time after resealing the reaction vessel and reestablishing the catalytic cycle with the same Cu(0) wire, to produce the same conversion as in the conventional uninterrupted SET−LRP process as mentioned in this paper.
Abstract: Cu(0)-wire/Me6-TREN is a well established catalyst for living radical polymerization via SET–LRP. Here, it is demonstrated that this polymerization is not just living, but it is in fact the first example of immortal living radical polymerization. The immortality of SET–LRP mediated with Cu(0) wire was demonstrated by attempting, in an unsuccessful way, to irreversible interrupt multiple times the polymerization via exposure to O2 from air. SET–LRP indeed stopped each time when the reaction mixture was exposed to air. However, the SET–LRP reaction, was restarted each time after resealing the reaction vessel and reestablishing the catalytic cycle with the same Cu(0) wire, to produce the same conversion as in the conventional uninterrupted SET–LRP process. Despite the interruption by O2, the reactivated SET–LRP had a good control of molecular weight, molecular weight evolution, and molecular weight distribution, with perfect retention of chain-end fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2716–2721, 2010
TL;DR: In this paper, a new soluble donor-acceptor type polyvinyl carbazole)-covalently functionalized graphene oxide (GO-PVK) has been synthesized by reaction of DDAT (S-1-dodecyl-S′-(α,α′-dimethyl-α″-aceticacid)trithiocarbonate)-PVK with GO-toluene-2,4-diisocynate.
Abstract: A new soluble donor-acceptor type poly(N-vinylcarbazole)-covalently functionalized graphene oxide (GO-PVK) has been synthesized by reaction of DDAT (S-1-dodecyl-S′-(α,α′-dimethyl-α″-aceticacid)trithiocarbonate)-PVK with GO-toluene-2,4-diisocynate. The incorporation of sufficient amount of PVK chains makes the modified GO nanosheets readily dispersible in organic solvents. The resulting material exhibits an enhanced solubility of 10 mg/mL in organic solvents. Covalent grafting of PVK onto the edge and surface of GO nanosheets did not change the carbazole absorption in the ultraviolet region, but substantially reduced the absorption intensity of GO in the visible region. The intensity of the emission band of GO-PVK at 437 nm was a little bit quenched when compared with that of DDAT-PVK, suggesting intramolecular quenching from PVK to GO. Such intramolecular quenching process may involve energy or electron transfer between the excited singlet states of the PVK moiety and the GO moiety. The HOMO/LUMO values and the energy bandgap of GO-PVK experimentally estimated by the onset of the redox potentials are −5.60, −3.58, and 2.02 eV, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2642–2649, 2010
TL;DR: In this article, a diallyl functional benzoxazine monomer is synthesized through the Mannich and respective ring closing reactions of 4,4 0 -isopropylidenediphenol (bisphenol A), formal-dehyde, and allyamine.
Abstract: Polysiloxanes containing thermally curable benzox- azine units in the main chain have been synthesized. For this purpose, first the diallyl functional benzoxazine monomer is synthesized through the Mannich and respective ring closing reactions of 4,4 0 -isopropylidenediphenol (bisphenol A), formal- dehyde, and allyamine. Subsequent hydrosilylation reaction of the resulting allylic monomer (B-ala) with 1,1,3,3-tetramethyldi- siloxane (TMDS) in the presence of Pt catalyst yields the corre- sponding oligo(B-ala-tetramethyldisiloxane)s (OBTMDS). Using the anionic polymerization route, OBTMDS was then converted to poly(bisbenzoxazinedimethylsiloxane)s (PBDMSs) by react- ing with readily available cyclic oligomer octamethylcyclotetra- siloxane (D4) or decamethylcyclopentasiloxane (D5) in the presence of tetrabutylammonium hydroxide as catalyst. The structures of the precursor diallyl monomer, the intermediate oligomer, and the resulting polymers are confirmed by Fourier transform infrared and 1 H NMR analysis. Curing behavior of the products at various stages has also been studied by differ- ential scanning calorimetry. Flexible transparent films of the PBDMSs are obtained by solvent casting. Thermal properties of the cured polymers are also investigated by thermogravi- metric analysis. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5156-5162, 2010 INTRODUCTION Polybenzoxazines are class of thermosetting resins that can be used in many fields such as electronics and aerospace industries because they have a good combina- tion of several pre-eminent features. They exhibit nearly zero shrinkage upon curing, thermal stability, chemical resistance, low water absorption; for some polybenzoxazines Tg is much higher than cure temperature and no strong acid catalysts are required for curing. The synthesis of polybenzoxazines can be done easily by thermally activated ring opening of the corresponding benzoxazines without generating any byprod-
TL;DR: In this paper, a photo and thermo double-responsive block copolymer was developed to fabricate micelles and reverse mouselles in aqueous solution, which can be used as smart polymeric nanocarriers for controlled encapsulation, triggered release, and re-encapsulation of model drug coumarin 102.
Abstract: A novel photo and thermo double-responsive block copolymer was developed to fabricate micelles and reverse micelles in aqueous solution. The block copolymer was synthesized by ATRP block copolymerization of a spiropyran- containing methacrylate (SPMA) with di(ethylene glycol) methyl ether methacrylate (DEGMMA). By facile control of the photo irradiation and solution temperature, PSPMA-core and PDEGMMA-core micelles can be obtained, respectively. The thermo- and photo-responsive micelles were used as smart polymeric nanocarriers for controlled encapsulation, triggered release, and re-encapsulation of model drug coumarin 102. The double-responsive self-assembly and disassembly were tracked by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2855–2861, 2010
Abstract: Thermally induced polymerizations of a series of 1,3-benzoxazines with a variety of substituents on the nitrogen atom were investigated in detail, particularly in the following three aspects of the polymerization: (1) N-alkyl-1,3-benzoxazines are much more reactive than N-phenyl-1,3-benzoxazine (2) The polymerization rate depended on the bulkiness of the N-substituent The bulkier the substituent was, the slower the polymerization was (3) The polymerizations accompanied weight loss due to the elimination of the corresponding imine (R-N = CH 2 ), and its extent became larger when R was more bulky
TL;DR: In this article, the authors describe the polymerization of methyl methacrylate by SET-LRP in protic solvent mixtures and demonstrate the living polymerization was demonstrated by kinetic evaluation.
Abstract: Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The present article describes the polymerization of methyl methacrylate by SET-LRP in protic solvent mixtures. Herein, the polymerization process was catalyzed by a straightforward Cu(0)wire/Me6-TREN catalyst while initiation was obtained by toluenesulfonyl chloride. All experiments were conducted at 50 °C and the living polymerization was demonstrated by kinetic evaluation of the SET-LRP. The process follows first order kinetic until all monomer is consumed which was typically achieved within 4 h. The molecular weight increased linearly with conversion and the molecular weight distributions were very narrow with Mw/Mn ∼ 1.1. Detailed investigations of the polymer samples by MALDI-TOF confirmed that no termination took place and that the chain end functionality is retained throughout the polymerization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2236–2242, 2010