515 results match your criteria Macromolecules[Journal]


Effect of Intra- versus Intermolecular Cross-Linking on the Supramolecular Folding of a Polymer Chain.

Macromolecules 2018 Nov 29;51(21):8853-8861. Epub 2018 Oct 29.

Institute for Complex Molecular Systems, Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.

Anfinsen's famous experiment showed that the restoration of catalytic activity of a completely unfolded ribonuclease A is only possible when the correct order of events is followed during the refolding process. Inspired by this work, the effect of structural constraints induced by covalent cross-links on the folding of a synthetic polymer chain via hydrogen-bonding interactions is investigated. Hereto, methacrylate-based monomers comprising either benzene-1,3,5-tricarboxamide (BTA)-based or coumarin-based pendants are copolymerized with -butyl methacrylate in various ratios via reversible addition-fragmentation chain-transfer (RAFT) polymerization. Read More

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November 2018

Critical Dependence of Molecular Weight on Thermoresponsive Behavior of Diblock Copolymer Worm Gels in Aqueous Solution.

Macromolecules 2018 Nov 16;51(21):8357-8371. Epub 2018 Oct 16.

Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, U.K.

Reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate was used to prepare three poly(glycerol monomethacrylate) -poly(2-hydroxypropyl methacrylate) (denoted G -H  or PGMA-PHPMA) diblock copolymers, namely G-H, G-H, and G-H. A master phase diagram was used to select each copolymer composition to ensure that a pure worm phase was obtained in each case, as confirmed by transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS) studies. The latter technique indicated a mean worm cross-sectional diameter (or worm width) ranging from 11 to 20 nm as the mean degree of polymerization (DP) of the hydrophobic PHPMA block was increased from 80 to 200. Read More

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November 2018
4 Reads

Hydration and Temperature Response of Water Mobility in Poly(diallyldimethylammonium)-Poly(sodium 4-styrenesulfonate) Complexes.

Macromolecules 2018 Oct 11;51(20):8268-8277. Epub 2018 Oct 11.

Department of Chemistry and Materials Science and Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland.

The combination of all-atom molecular dynamics simulations with differential scanning calorimetry (DSC) has been exploited to investigate the influence of temperature and hydration on the water distribution and mobility in poly(diallyldimethylammonium) (PDADMA) and poly(sodium 4-styrenesulfonate) (PSS) complexes. The findings show that the vast majority of the water molecules hydrating the polyelectrolyte complexes (PECs) with 18-30 wt % hydration are effectively immobilized due to the strong interactions between the PE charge groups and water. Temperature and hydration were found to decrease similarly the fraction of strongly bound water. Read More

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October 2018
3 Reads

Rapid and Quantitative De--butylation for Poly(acrylic acid) Block Copolymers and Influence on Relaxation of Thermoassociated Transient Networks.

Macromolecules 2018 Oct 12;51(20):8316-8323. Epub 2018 Oct 12.

Laboratory of Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708WE Wageningen, The Netherlands.

The synthesis of charged polymers often requires the polymerization of protected monomers, followed by a polymer-analogous reaction to the polyelectrolyte product. We present a mild, facile method to cleave -butyl groups from poly(-butyl acrylate) blocks that yields poly(acrylic acid) (pAA) blocks free of traces of the ester. The reaction utilizes a slight excess of HCl in hexafluoroisopropanol (HFIP) at room temperature and runs to completion within 4 h. Read More

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October 2018

Synthesis of Well-Defined Pyrrolidone-Based Homopolymers and Stimulus-Responsive Diblock Copolymers via RAFT Aqueous Solution Polymerization of 2-(-Acryloyloxy)ethylpyrrolidone.

Macromolecules 2018 Oct 25;51(19):7756-7766. Epub 2018 Sep 25.

Dainton Building, Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.

Poly(-vinylpyrrolidone) (PNVP) is a well-known, highly polar, nonionic water-soluble polymer. However, -vinylpyrrolidone (NVP) usually exhibits strongly non-ideal behavior when copolymerized with methacrylic or styrenic monomers. Moreover, NVP is not particularly well-controlled under living radical polymerization conditions. Read More

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October 2018
7 Reads

Aqueous Phase Separation Behavior of Highly Syndiotactic, High Molecular Weight Polymers with Densely Packed Hydroxy-Containing Side Groups.

Macromolecules 2018 Sep 11;51(18):7248-7256. Epub 2018 Sep 11.

Van 't Hoff Institute for Molecular Sciences (HIMS), Department of Homogeneous and Supramolecular Catalysis, Universiteit van Amsterdam, P.O. Box 94720, 1090 GS Amsterdam, Netherlands.

Herein we describe the Rh-catalyzed C1 polymerization of silyl-protected diazoacetates of the general formula HC(=N)C(=O)O(CH) OSiR, where = 2-5. After polymerization and subsequent desilylation, polymers bearing a hydroxy-containing side group on backbone carbon are obtained. The molecular weight of the desired polymers can be controlled via chain transfer with methanol during the polymerization. Read More

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September 2018
1 Read

Time-Dependent ATR-FTIR Spectroscopic Studies on Solvent Diffusion and Film Swelling in Oil Paint Model Systems.

Macromolecules 2018 Sep 7;51(18):7134-7144. Epub 2018 Sep 7.

Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090GD Amsterdam, The Netherlands.

In the restoration of paintings, solvent diffusion and swelling of polymeric oil paint binding media are important factors to consider. Common cleaning methods with organic solvents or aqueous solutions could lead to undesirable physicochemical changes in the paint in the long term, though the extent of this effect is not yet clear. We used tailored nonporous model systems for aged oil paint to measure paint swelling and solvent diffusion for a wide range of relevant solvents. Read More

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September 2018
1 Read

UV-Blocking Synthetic Biopolymer from Biomass-Based Bifuran Diester and Ethylene Glycol.

Macromolecules 2018 Mar 21;51(5):1822-1829. Epub 2018 Feb 21.

Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland.

A furan-based synthetic biopolymer composed of a bifuran monomer and ethylene glycol was synthesized through melt polycondensation, and the resulting polyester was found to have promising thermal and mechanical properties. The bifuran monomer, dimethyl 2,2'-bifuran-5,5'-dicarboxylate, was prepared using a palladium-catalyzed, phosphine ligand-free direct coupling protocol. A titanium-catalyzed polycondensation procedure was found effective at polymerizing the bifuran monomer with ethylene glycol. Read More

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Two Robust Strategies toward Hydrogels from Quenched Block Copolymer Nanofibrillar Micelles.

Macromolecules 2018 Aug 24;51(15):5788-5797. Epub 2018 Jul 24.

Advanced Soft Matter Group, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.

While the formation of (tri)block copolymer hydrogels has been extensively investigated, such studies mostly focused on equilibrium self-assembling whereas the use of preformed structures as building blocks such as out of equilibrium, quenched, nanofibrillar micelles is still a challenge. Here, we demonstrate that quenched, ultralong polystyrene--poly(ethylene oxide) (PS--PEO) micelles can be used as robust precursors of hydrogels. Two cross-linking strategies, (i) thermal fusion of micellar cores and (ii) chemical cross-linking of preformed micellar coronas were studied. Read More

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August 2018
1 Read

Crystal Growth in Polyethylene by Molecular Dynamics: The Crystal Edge and Lamellar Thickness.

Macromolecules 2018 Jul 28;51(13):4865-4873. Epub 2018 Jun 28.

VTT Technical Research Centre of Finland Ltd., Espoo, Finland.

We carried out large-scale atomistic molecular dynamics simulations to study the growth of twin lamellar crystals of polyethylene initiated by small crystal seeds. By examining the size distribution of the stems-straight crystalline polymer segments-we show that the crystal edge has a parabolic profile. At the growth front, there is a layer of stems too short to be stable, and new stable stems are formed within this layer, leading to crystal growth. Read More

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July 2018
4 Reads

Blob Size Controls Diffusion of Free Polymer in a Chemically Identical Brush in Semidilute Solution.

Macromolecules 2018 Aug 10;51(16):6312-6317. Epub 2018 Aug 10.

Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, U.K.

The diffusion of rhodamine-labeled poly(ethylene glycol) (r-PEG) within surface-grafted poly(ethylene glycol) (s-PEG) layers in aqueous solution at 18 °C was measured by fluorescence correlation spectroscopy. The diffusion coefficient of r-PEG within s-PEG was controlled by the grafting density, σ, and scaled as σ. It is proposed that a characteristic blob size associated with the grafted (brush) layer defines the region through which the r-PEG diffusion occurs. Read More

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Semicrystalline Block Copolymers in Rigid Confining Nanopores.

Macromolecules 2017 Nov 18;50(21):8637-8646. Epub 2017 Oct 18.

Institut für Chemie neuer Materialien, Universität Osnabrück, Barbarastr.7, 49076 Osnabrück, Germany.

We have investigated PLLA crystallization in lamellae-forming PS--PLLA confined to straight cylindrical nanopores under weak confinement (nanopore diameter /equilibrium PS--PLLA period ≥ 4.8). Molten PS--PLLA predominantly forms concentric lamellae along the nanopores, but intertwined helices occur even for / ≈ 7. Read More

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November 2017

Amplifying Chiroptical Properties of Conjugated Polymer Thin-Film Using an Achiral Additive.

Macromolecules 2018 Aug 26;51(15):5883-5890. Epub 2018 Jul 26.

Laboratory of Macromolecular and Organic Chemistry and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands.

Chiral conjugated polymers bearing enantiopure side chains offer the possibility to harness the effect of chirality in organic electronic devices. However, its use is hampered by the low degree of circular polarization in absorption () in most of the conjugated polymer thin-films studied. Here we demonstrate a versatile method to significantly increase the by using a few weight percentages of a commercially available achiral long-chain alcohol as an additive. Read More

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Growth Regimes of Poly(perfluorodecyl acrylate) Thin Films by Initiated Chemical Vapor Deposition.

Macromolecules 2018 Aug 20;51(15):5694-5703. Epub 2018 Jul 20.

Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.

Control over thin film growth (e.g., crystallographic orientation and morphology) is of high technological interest as it affects several physicochemical material properties, such as chemical affinity, mechanical stability, and surface morphology. Read More

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Grafting from a Hybrid DNA-Covalent Polymer by the Hybridization Chain Reaction.

Macromolecules 2018 Jul 5;51(14):5157-5164. Epub 2018 Jul 5.

Department of Supramolecular and Biomaterials Chemistry, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.

Nucleic acid-polymer conjugates are an attractive class of materials endowed with tunable and responsive character. Herein, we exploit the dynamic character of nucleic acids in the preparation of hybrid DNA-covalent polymers with extendable grafts by the hybridization chain reaction. Addition of DNA hairpins to an initiator DNA-dextran graft copolymer resulted in the growth of the DNA grafts as evidenced by various characterization techniques over several length scales. Read More

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July 2018
1 Read

Linear Viscoelasticity of Weakly Hydrogen-Bonded Polymers near and below the Sol-Gel Transition.

Macromolecules 2018 Jul 27;51(13):4910-4916. Epub 2018 Jun 27.

Macromolecular Chemistry and New Polymeric Materials, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.

Supramolecular polymers bearing weak hydrogen bonds (sticker) can express outstanding dynamic properties due to their labile association. Studying the linear viscoelasticity (LVE) of this type of polymer can provide us with sufficient knowledge to design polymeric materials for applications that need dynamic properties such as self-healing. Using different compositions of flexible weak stickers, LVE analysis showed scalings corresponding to a transition from a linear precursor to a cluster. Read More

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Effect of Self-Assembly of Oxalamide Based Organic Compounds on Melt Behavior, Nucleation, and Crystallization of Isotactic Polypropylene.

Macromolecules 2018 Jul 21;51(13):4882-4895. Epub 2018 Jun 21.

Aachen-Maastricht Institute of BioBased Materials (AMIBM), Maastricht University, P.O. Box 616, 6200MD, Maastricht, The Netherlands.

We report on the effect of an aliphatic oxalamide based nucleating agent () on the melt and crystallization behavior of isotactic polypropylene (PP) under defined shear conditions. Through polarized optical microscopy, we demonstrate that self-assembles from the PP melt into rhombic crystals whereas their size and distribution proved highly dependent on the employed cooling rates. The presence of 0. Read More

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July 2018
10 Reads

Effects of Surfactant and Urea on Dynamics and Viscoelastic Properties of Hydrophobically Assembled Supramolecular Hydrogel.

Macromolecules 2018 Jul 25;51(13):4813-4820. Epub 2018 Jun 25.

Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Institute for Complex Molecular Systems, and Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

Physically associated hydrogels based on strong hydrophobic interactions often have attractive mechanical properties that combine processability with elasticity. However, there is a need to study such interactions and understand their relation to the macroscopic hydrogel properties. Therefore, we use the surfactant sodium dodecyl sulfate (SDS) and urea as reagents that disrupt hydrophobic interactions. Read More

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Protection of opening lids: very high catalytic activity of lipase immobilized on core-shell nanoparticles.

Macromolecules 2018 Jan 1;51(2):289-296. Epub 2018 Jan 1.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Various hydrophobic supports have been used for lipase immobilization since the active site of lipase can be opened in a hydrophobic environment. Nevertheless, the increase of lipase activity is still limited. This study demonstrates a hyperactivation-protection strategy of lipase after immobilization on poly(-butyl acrylate)-polyaldehyde dextran (PBA-PAD) core-shell nanoparticles. Read More

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January 2018
4 Reads

Miniemulsion ARGET ATRP via Interfacial and Ion-Pair Catalysis: From ppm to ppb of Residual Copper.

Macromolecules 2017 Nov 3;50(21):8417-8425. Epub 2017 Nov 3.

Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.

It was recently reported that copper catalysts used in atom transfer radical polymerization (ATRP) can combine with anionic surfactants used in emulsion polymerization to form ion pairs. The ion pairs predominately reside at the surface of the monomer droplets, but they can also migrate inside the droplets and induce a controlled polymerization. This concept was applied to activator regenerated by electron transfer (ARGET) ATRP, with ascorbic acid as reducing agent. Read More

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November 2017
4 Reads

Electrochemically Mediated Reversible Addition-Fragmentation Chain-Transfer Polymerization.

Macromolecules 2017 Oct 13;50(20):7872-7879. Epub 2017 Oct 13.

Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213.

An electrochemically mediated reversible addition-fragmentation chain-transfer polymerization (RAFT) of (meth)acrylates was successfully carried out via electroreduction of either benzoyl peroxide (BPO) or 4-bromobenzenediazonium tetrafluoroborate (BrPhN) which formed aryl radicals, acting as initiators for RAFT polymerization. Direct electroreduction of chain transfer agents was unsuccessful since it resulted in the formation of carbanions by a two-electron transfer process. Reduction of BrPhN under a fixed potential showed acceptable control, but limited conversion due to the generation of a passivating organic layer grafted on the working electrode surface. Read More

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October 2017
3 Reads

A Vinyl Ether-Functional Polycarbonate as a Template for Multiple Postpolymerization Modifications.

Macromolecules 2018 May 16;51(9):3233-3242. Epub 2018 Apr 16.

Department of Chemistry, Department of Chemical Engineering, Department of Materials Science & Engineering, and Laboratory for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842-3012, United States.

A highly-reactive vinyl ether-functionalized aliphatic polycarbonate and its block copolymer were developed as templates for multiple post-polymerization conjugation chemistries. The vinyl ether-functional six-membered cyclic carbonate monomer was synthesized by a well-established two-step procedure starting from 2,2-bis(hydroxymethyl)propionic acid. An organobase-catalyzed ring-opening polymerization of the synthesized monomer afforded polycarbonates with pendant vinyl ether functionalities (PMVEC). Read More

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May 2018
6 Reads

Physical Networks from Multifunctional Telechelic Star Polymers: A Rheological Study by Experiments and Simulations.

Macromolecules 2018 Apr 3;51(8):2872-2886. Epub 2018 Apr 3.

Computational Chemical Physics, Faculty of Science and Technology, and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands.

The equilibrium mechanical properties of a cross-linked gel of telechelic star polymers are studied by rheology and Brownian dynamics simulations. The Brownian dynamics model consists of cores to which Rouse arms are attached. Forces between the cores are obtained from a potential of mean force model developed by Likos and co-workers. Read More

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April 2018
1 Read

The Multifaceted Role of Methylaluminoxane in Metallocene-Based Olefin Polymerization Catalysis.

Macromolecules 2018 Jan 2;51(2):343-355. Epub 2018 Jan 2.

Inorganic Chemistry and Catalysis Group, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.

In single-site olefin polymerization catalysis, a large excess of cocatalyst is often required for the generation of highly active catalysts, but the reason for this is unclear. In this work, fundamental insight into the multifaceted role of cocatalyst methylaluminoxane (MAO) in the activation, deactivation, and stabilization of group 4 metallocenes in the immobilized single-site olefin polymerization catalyst was gained. Employing probe molecule FT-IR spectroscopy, it was found that weak Lewis acid sites, inherent to the silica-supported MAO cocatalyst, are the main responsible species for the genesis of active metallocenes for olefin polymerization. Read More

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January 2018
16 Reads

Synthesis of High Molecular Weight Poly(glycerol monomethacrylate) via RAFT Emulsion Polymerization of Isopropylideneglycerol Methacrylate.

Macromolecules 2018 May 16;51(9):3221-3232. Epub 2018 Apr 16.

Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, U.K.

High molecular weight water-soluble polymers are widely used as flocculants or thickeners. However, synthesis of such polymers via solution polymerization invariably results in highly viscous fluids, which makes subsequent processing somewhat problematic. Alternatively, such polymers can be prepared as colloidal dispersions; in principle, this is advantageous because the particulate nature of the polymer chains ensures a much lower fluid viscosity. Read More

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Thermomechanical Properties and Glass Dynamics of Polymer-Tethered Colloidal Particles and Films.

Macromolecules 2017 Nov 30;50(21):8658-8669. Epub 2017 Oct 30.

Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.

Polymer-tethered colloidal particles (aka "particle brush materials") have attracted interest as a platform for innovative material technologies and as a model system to elucidate glass formation in complex structured media. In this contribution, Brillouin light scattering is used to sequentially evaluate the role of brush architecture on the dynamical properties of brush particles in both the individual and assembled (film) state. In the former state, the analysis reveals that brush-brush interactions as well as global chain relaxation sensitively depend on grafting density; i. Read More

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November 2017
1 Read

Modulation of Surface-Initiated ATRP by Confinement: Mechanism and Applications.

Macromolecules 2017 Aug 19;50(15):5711-5718. Epub 2017 Jul 19.

Laboratory of Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zürich, Switzerland.

The mechanism of surface-initiated atom transfer polymerization (SI-ATRP) of methacrylates in confined volumes is systematically investigated by finely tuning the distance between a grafting surface and an inert plane by means of nanosized patterns and micrometer thick foils. The polymers were synthesized from monolayers of photocleavable initiators, which allow the analysis of detached brushes by size-exclusion chromatography (SEC). Compared to brushes synthesized under "open" polymerization mixtures, nearly a 4-fold increase in brush molar mass was recorded when SI-ATRP was performed within highly confined reaction volumes. Read More

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August 2017
1 Read

Characterizing the Interface Scaling of High Block Copolymers near the Order-Disorder Transition.

Macromolecules 2018 Jan 15;51(1):173-180. Epub 2017 Dec 15.

Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070, United States.

Advancements in the directed self-assembly of block copolymers (BCPs) have prompted the development of new materials with larger effective interaction parameters (). This enables BCP systems with phase separation at increasingly small degrees of polymerization (). Very often these systems reside near the order-disorder transition and fit between the weak and strong segregation limits where the behavior of BCP systems is not as thoroughly understood. Read More

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January 2018

Photonic Resins: Designing Optical Appearance via Block Copolymer Self-Assembly.

Macromolecules 2018 Mar 15;51(6):2395-2400. Epub 2018 Mar 15.

Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, Massachusetts 01003, United States.

Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. Read More

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March 2018
1 Read

Size-Dependent Submerging of Nanoparticles in Polymer Melts: Effect of Line Tension.

Macromolecules 2018 Apr 16;51(7):2411-2417. Epub 2018 Mar 16.

Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, and Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands.

Adhesion of nanoparticles to polymer films plays a key role in various polymer technologies. Here we report experiments that reveal how silica nanoparticles adhere to a viscoelastic PMMA film above the glass transition temperature. The polymer was swollen with CO, closely matching the conditions of nanoparticle-nucleated polymer foaming. Read More

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April 2018
1 Read

Evaluation of Blob Theory for the Diffusion of DNA in Nanochannels.

Macromolecules 2018 Mar 20;51(5):1748-1755. Epub 2018 Feb 20.

Department of Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, 421 Washington Ave SE, Minneapolis, Minnesota 55455, USA.

We have measured the diffusivity of λ-DNA molecules in approximately square nanochannels with effective sizes ranging from 117 nm to 260 nm at moderate ionic strength. The experimental results do not agree with the non-draining scaling predicted by blob theory. Rather, the data are consistent with the predictions of previous simulations of the Kirkwood diffusivity of a discrete wormlike chain model, without the need for any fitting parameters. Read More

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March 2018
2 Reads

Buckling Instabilities in Polymer Brush Surfaces via Postpolymerization Modification.

Macromolecules 2017 Nov 30;50(21):8670-8677. Epub 2017 Oct 30.

School of Polymer Science and Engineering, University of Southern Mississippi, Hattiesburg, MS 39406.

We report a simple route to engineer ultrathin polymer brush surfaces with wrinkled morphologies using post-polymerization modification (PPM), where the length scale of the buckled features can be tuned from hundreds of nanometers to one micrometer using PPM reaction time. We show that partial crosslinking of the outer layer of the polymer brush under poor solvent conditions is critical to obtain wrinkled morphologies upon swelling. Characterization of the PPM kinetics and swelling behavior via ellipsometry and the through-thickness composition profile via time-of-flight secondary ion mass spectroscopy (ToF-SIMS) provided keys insight into parameters influencing the buckling behavior. Read More

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November 2017
4 Reads

Odijk excluded volume interactions during the unfolding of DNA confined in a nanochannel.

Macromolecules 2018 Feb 24;51(3):1172-1180. Epub 2018 Jan 24.

Department of Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, 421 Washington Ave SE, Minneapolis, Minnesota 55455, USA.

We report experimental data on the unfolding of human and genomic DNA molecules shortly after injection into a 45 nm nanochannel. The unfolding dynamics are deterministic, consistent with previous experiments and modeling in larger channels, and do not depend on the biological origin of the DNA. The measured entropic unfolding force per friction per unit contour length agrees with that predicted by combining the Odijk excluded volume with numerical calculations of the Kirkwood diffusivity of confined DNA. Read More

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February 2018
5 Reads

Behavior of Weak Polyelectrolyte Brushes in Mixed Salt Solutions.

Macromolecules 2018 Feb 17;51(3):1198-1206. Epub 2018 Jan 17.

Membrane Science and Technology, Mesa+ Institute for Nanotechnology, University of Twente, Enschede 7500 AE, The Netherlands.

Hydrophilic and hydrophobic weak polybasic brushes immersed in aqueous solutions of mixed salt counterions are considered using a mean-field numerical self-consistent field approach. On top of the solvent quality of the polymer, the counterion-solvent interactions are accounted for by implementing Flory-Huggins interaction parameters. We show that ion specificity within the brush can bring about large changes in conformation. Read More

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February 2018
2 Reads

Self-healing hydrogels formed by complexation between calcium ions and bisphosphonate-functionalized star-shaped polymers.

Macromolecules 2017;50(21):8698-8706. Epub 2017 Oct 19.

Biomedical Engineering Department, Materials Science and Engineering Department, Chemical and Biological Engineering Department, Chemistry of Life Processes Institute, Institute for Bionanotechnology in Medicine, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Evanston, IL, USA.

Star-shaped poly(ethylene glycol) (PEG) chain termini were functionalized with alendronate to create transient networks with reversible crosslinks upon addition of calcium ions. The gelation ability of alendronate-functionalized PEG was greatly dependent on the number of arms and arm molecular weight. After mixing polymer and calcium solutions, the formed hydrogels could be cut and then brought back together without any visible interface. Read More

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October 2017
3 Reads

Synthesis and Solution-Phase Characterization of Sulfonated Oligothioetheramides.

Macromolecules 2017 Jan 1;50(21):8731-8738. Epub 2017 Nov 1.

Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.

Nature has long demonstrated the importance of chemical sequence to induce structure and tune physical interactions. Investigating macromolecular structure and dynamics is paramount to understand macromolecular binding and target recognition. To that end, we have synthesized and characterized flexible sulfonated oligothioetheramides (oligo-TEAs) by variable temperature pulse field gradient (PFG) NMR, double electron-electron resonance (DEER), and molecular dynamics (MD) simulations to capture their room temperature structure and dynamics in water. Read More

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January 2017
2 Reads

Force and Scale Dependence of the Elasticity of Self-Assembled DNA Bottle Brushes.

Macromolecules 2018 Jan 28;51(1):204-212. Epub 2017 Dec 28.

Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands.

As a model system to study the elasticity of bottle-brush polymers, we here introduce self-assembled DNA bottle brushes, consisting of a DNA main chain that can be very long and still of precisely defined length, and precisely monodisperse polypeptide side chains that are physically bound to the DNA main chains. Polypeptide side chains have a diblock architecture, where one block is a small archaeal nucleoid protein Sso7d that strongly binds to DNA. The other block is a net neutral, hydrophilic random coil polypeptide with a length of exactly 798 amino acids. Read More

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January 2018
18 Reads

Self-Consistent Field Lattice Model for Polymer Networks.

Macromolecules 2017 Dec 5;50(24):9788-9795. Epub 2017 Dec 5.

Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB, Eindhoven, The Netherlands.

A lattice model based on polymer self-consistent field theory is developed to predict the equilibrium statistics of arbitrary polymer networks. For a given network topology, our approach uses moment propagators on a lattice to self-consistently construct the ensemble of polymer conformations and cross-link spatial probability distributions. Remarkably, the calculation can be performed "in the dark", without any prior knowledge on preferred chain conformations or cross-link positions. Read More

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December 2017
1 Read

: A Perspective on Polyelectrolyte Solutions.

Authors:
M Muthukumar

Macromolecules 2017 Dec 14;50(24):9528-9560. Epub 2017 Dec 14.

Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States.

From the beginning of life with the information-containing polymers until the present era of a plethora of water-based materials in health care industry and biotechnology, polyelectrolytes are ubiquitous with a broad range of structural and functional properties. The main attribute of polyelectrolyte solutions is that all molecules are strongly correlated both topologically and electrostatically in their neutralizing background of charged ions in highly polarizable solvent. These strong correlations and the necessary use of numerous variables in experiments on polyelectrolytes have presented immense challenges toward fundamental understanding of the various behaviors of charged polymeric systems. Read More

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December 2017
2 Reads

Supernucleation and Orientation of Poly(butylene terephthalate) Crystals in Nanocomposites Containing Highly Reduced Graphene Oxide.

Macromolecules 2017 Dec 21;50(23):9380-9393. Epub 2017 Nov 21.

Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Alessandria 15121, Italy.

The ring-opening polymerization of cyclic butylene terephthalate into poly(butylene terephthalate) (pCBT) in the presence of reduced graphene oxide (RGO) is an effective method for the preparation of polymer nanocomposites. The inclusion of RGO nanoflakes dramatically affects the crystallization of pCBT, shifting crystallization peak temperature to higher temperatures and, overall, increasing the crystallization rate. This was due to a supernucleating effect caused by RGO, which is maximized by highly reduced graphene oxide. Read More

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December 2017
4 Reads

Strategies To Increase the Thermal Stability of Truly Biomimetic Hydrogels: Combining Hydrophobicity and Directed Hydrogen Bonding.

Macromolecules 2017 Nov 15;50(22):9058-9065. Epub 2017 Nov 15.

Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525AJ Nijmegen, The Netherlands.

Enhancing the thermal stability of proteins is an important task for protein engineering. There are several ways to increase the thermal stability of proteins in biology, such as greater hydrophobic interactions, increased helical content, decreased occurrence of thermolabile residues, or stable hydrogen bonds. Here, we describe a well-defined polymer based on β-helical polyisocyanotripeptides (TriPIC) that uses biological approaches, including hydrogen bonding and hydrophobic interactions for its exceptional thermal stability in aqueous solutions. Read More

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November 2017
2 Reads

Effect of Rubber Polarity on Cluster Formation in Rubbers Cross-Linked with Diels-Alder Chemistry.

Macromolecules 2017 Nov 7;50(22):8955-8964. Epub 2017 Nov 7.

Department of Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.

Diels-Alder chemistry has been used for the thermoreversible cross-linking of furan-functionalized ethylene/propylene (EPM) and ethylene/vinyl acetate (EVM) rubbers. Both furan-functionalized elastomers were successfully cross-linked with bismaleimide to yield products with a similar cross-link density. NMR relaxometry and SAXS measurements both show that the apolar EPM--furan precursor contains phase-separated polar clusters and that cross-linking with polar bismaleimide occurs in these clusters. Read More

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November 2017
3 Reads

Synthesis of Microgel Particles.

Macromolecules 2017 Nov 18;50(21):8777-8786. Epub 2017 Oct 18.

CNR-ISC, Uos Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy.

Microgels are colloidal-scale particles individually made of cross-linked polymer networks that can swell and deswell in response to external stimuli, such as changes to temperature or pH. Despite a large amount of experimental activities on microgels, a proper theoretical description based on individual particle properties is still missing due to the complexity of the particles. To go one step further, here we propose a novel methodology to assemble realistic microgel particles . Read More

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November 2017
4 Reads

Improving the Folding of Supramolecular Copolymers by Controlling the Assembly Pathway Complexity.

Macromolecules 2017 Nov 19;50(21):8562-8569. Epub 2017 Oct 19.

Institute for Complex Molecular Systems, Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

A family of amphiphilic, heterograft copolymers containing hydrophilic, hydrophobic, and supramolecular units based on Jeffamine M-1000, dodecylamine, and benzene-1,3,5-tricarboxamide (BTA) motifs, respectively, was prepared via a postfunctionalization approach. The folding of the copolymers in water into nanometer-sized particles was analyzed by a combination of dynamic and static light scattering, circular dichroism spectroscopy, and small-angle neutron scattering. The sample preparation protocol was crucial for obtaining reproducible and consistent results, showing that only full control over the structure and pathway complexity will afford the desired folded structure, a phenomenon similar to protein folding. Read More

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November 2017
4 Reads

Heterofunctional Poly(ethylene glycol) (PEG) Macroinitiator Enabling Controlled Synthesis of ABC Triblock Copolymers.

Macromolecules 2017 Nov 30;50(21):8390-8397. Epub 2017 Oct 30.

Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Science for Life, Faculty of Science, Utrecht University, PO Box 80082, 3508 TB Utrecht, The Netherlands.

ABC triblock copolymers with a poly(ethylene glycol) (PEG) midblock have attractive properties for biomedical applications because of PEG's favorable properties regarding biocompatibility and hydrophilicity. However, easy strategies to synthesize polymers containing a PEG midblock are limited. In this study, the successful synthesis of a heterofunctional PEG macroinitiator containing both an azoinitiator and an atom transfer radical polymerization (ATRP) initiator is demonstrated. Read More

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November 2017
11 Reads

Poly[(arylene ethynylene)--(arylene vinylene)]s Based on Anthanthrone and Its Derivatives: Synthesis and Photophysical, Electrochemical, Electroluminescent, and Photovoltaic Properties.

Macromolecules 2017 Nov 3;50(21):8357-8371. Epub 2017 Nov 3.

Linz Institute for Organic Solar Cells, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria.

Anthanthrone and its derivatives are large polycyclic aromatic compounds (PACs) that pose a number of challenges for incorporation into the structure of soluble conjugated polymers. For the first time, this group of PACs was employed as the building blocks for the synthesis of copolymers (-) based on poly[(arylene ethynylene)--(arylene vinylene)]s backbone (-Ph-C≡C-Anth-C≡C-Ph-CH=CH-Ph-CH=CH-) . During the synthesis of -, different alkyloxy side chains were incorporated in order to tune the properties of the polymers. Read More

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November 2017
2 Reads

Polymeric Biomaterials: Diverse Functions Enabled by Advances in Macromolecular Chemistry.

Macromolecules 2017 Jan 6;50(2):483-502. Epub 2017 Jan 6.

Department of Materials Science and Engineering, University of Delaware, Newark, DE, 19716, USA.

Biomaterials have been extensively used to leverage beneficial outcomes in various therapeutic applications, such as providing spatial and temporal control over the release of therapeutic agents in drug delivery as well as engineering functional tissues and promoting the healing process in tissue engineering and regenerative medicine. This perspective presents important milestones in the development of polymeric biomaterials with defined structures and properties. Contemporary studies of biomaterial design have been reviewed with focus on constructing materials with controlled structure, dynamic functionality, and biological complexity. Read More

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January 2017
1 Read

Enhanced Electrical Conductivity of Molecularly p-Doped Poly(3-hexylthiophene) through Understanding the Correlation with Solid-State Order.

Macromolecules 2017 Oct 11;50(20):8140-8148. Epub 2017 Oct 11.

Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden.

Molecular p-doping of the conjugated polymer poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) is a widely studied model system. Underlying structure-property relationships are poorly understood because processing and doping are often carried out simultaneously. Here, we exploit doping from the vapor phase, which allows us to disentangle the influence of processing and doping. Read More

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October 2017
1 Read

Expanding the ROMP Toolbox: Synthesis of Air-Stable Benzonorbornadiene Polymers by Aryne Chemistry.

Macromolecules 2017 Jan 4;50(2):580-586. Epub 2017 Jan 4.

Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.

Benzonorbornadiene polymers synthesized by ring-opening metathesis polymerization (ROMP) are typically prone to oxidation at the benzylic/allylic position under ambient conditions. Accordingly, the use of benzonorbornadiene polymers in practical applications has remained limited. In this manuscript, we report the synthesis of poly(benzonorbornadiene) polymers using a strategic blend of benzyne chemistry and ROMP. Read More

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January 2017
5 Reads

Dynamic Surface Enrichment in Drying Thin-Film Binary Polymer Solutions.

Macromolecules 2017 Aug 18;50(15):5914-5919. Epub 2017 Jul 18.

Theory of Polymers and Soft Matter, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

Solution-cast, thin-film polymer composites find a wide range of applications, such as in the photoactive layer of organic solar cells. The performance of this layer crucially relies on its phase-separated morphology. Efficient charge-carrier extraction requires each of the components to preferentially wet one of the two electrodes. Read More

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August 2017
2 Reads