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Macromolecules

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https://www.readbyqxmd.com/read/29657338/size-dependent-submerging-of-nanoparticles-in-polymer-melts-effect-of-line-tension
#1
Shanqiu Liu, Anupam Pandey, Joost Duvigneau, Julius Vancso, Jacco H Snoeijer
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 CO2 , closely matching the conditions of nanoparticle-nucleated polymer foaming. It is found that the degree by which the particles sink into the viscoelastic substrate is strongly size dependent and can even lead to complete engulfment for particles of diameter below 12 nm...
April 10, 2018: Macromolecules
https://www.readbyqxmd.com/read/29599567/evaluation-of-blob-theory-for-the-diffusion-of-dna-in-nanochannels
#2
Damini Gupta, Aditya Bikram Bhandari, Kevin D Dorfman
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.
March 13, 2018: Macromolecules
https://www.readbyqxmd.com/read/29479117/odijk-excluded-volume-interactions-during-the-unfolding-of-dna-confined-in-a-nanochannel
#3
Jeffrey G Reifenberger, Han Cao, Kevin D Dorfman
We report experimental data on the unfolding of human and E. coli 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...
February 13, 2018: Macromolecules
https://www.readbyqxmd.com/read/29472729/behavior-of-weak-polyelectrolyte-brushes-in-mixed-salt-solutions
#4
Joshua D Willott, Timothy J Murdoch, Frans A M Leermakers, Wiebe M de Vos
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. It is found that the collapse transition of hydrophobic, weak polyelectrolyte brushes features an intermediate two-phase state wherein a subset of chains are collapsed in a dense layer at the substrate, while the remainder of chains are well-solvated and strongly stretched away from the it...
February 13, 2018: Macromolecules
https://www.readbyqxmd.com/read/29339838/force-and-scale-dependence-of-the-elasticity-of-self-assembled-dna-bottle-brushes
#5
Márcio Santos Rocha, Ingeborg M Storm, Raniella Falchetto Bazoni, Ésio Bessa Ramos, Armando Hernandez-Garcia, Martien A Cohen Stuart, Frans Leermakers, Renko de Vries
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...
January 9, 2018: Macromolecules
https://www.readbyqxmd.com/read/29296030/self-consistent-field-lattice-model-for-polymer-networks
#6
Nicholas B Tito, Cornelis Storm, Wouter G Ellenbroek
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. Numerical results from the model for a test network exhibit close agreement with molecular dynamics simulations, including when the network is strongly sheared...
December 26, 2017: Macromolecules
https://www.readbyqxmd.com/read/29296029/-50th-anniversary-perspective-a-perspective-on-polyelectrolyte-solutions
#7
REVIEW
M Muthukumar
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...
December 26, 2017: Macromolecules
https://www.readbyqxmd.com/read/29296028/supernucleation-and-orientation-of-poly-butylene-terephthalate-crystals-in-nanocomposites-containing-highly-reduced-graphene-oxide
#8
Samuele Colonna, Ricardo A Pérez-Camargo, Haiming Chen, Guoming Liu, Dujin Wang, Alejandro J Müller, Guido Saracco, Alberto Fina
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...
December 12, 2017: Macromolecules
https://www.readbyqxmd.com/read/29213150/strategies-to-increase-the-thermal-stability-of-truly-biomimetic-hydrogels-combining-hydrophobicity-and-directed-hydrogen-bonding
#9
Hongbo Yuan, Jialiang Xu, Eliane P van Dam, Giulia Giubertoni, Yves L A Rezus, Roel Hammink, Huib J Bakker, Yong Zhan, Alan E Rowan, Chengfen Xing, Paul H J Kouwer
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...
November 28, 2017: Macromolecules
https://www.readbyqxmd.com/read/29213149/effect-of-rubber-polarity-on-cluster-formation-in-rubbers-cross-linked-with-diels-alder-chemistry
#10
L M Polgar, E Hagting, P Raffa, M Mauri, R Simonutti, F Picchioni, M van Duin
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- g -furan precursor contains phase-separated polar clusters and that cross-linking with polar bismaleimide occurs in these clusters. The heterogeneously cross-linked network of EPM- g -furan contrasts with the homogeneous network in the polar EVM- g -furan...
November 28, 2017: Macromolecules
https://www.readbyqxmd.com/read/29503464/buckling-instabilities-in-polymer-brush-surfaces-via-postpolymerization-modification
#11
Wei Guo, Cassandra M Reese, Li Xiong, Phillip K Logan, Brittany J Thompson, Christopher M Stafford, Anton V Ievlev, Bradley S Lokitz, Olga S Ovchinnikova, Derek L Patton
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...
November 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/29151620/-in-silico-synthesis-of-microgel-particles
#12
Nicoletta Gnan, Lorenzo Rovigatti, Maxime Bergman, Emanuela Zaccarelli
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 in silico . We exploit the self-assembly of a binary mixture composed of tetravalent (cross-linkers) and bivalent (monomer beads) patchy particles under spherical confinement in order to produce fully bonded networks...
November 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/29151619/improving-the-folding-of-supramolecular-copolymers-by-controlling-the-assembly-pathway-complexity
#13
Gijs M Ter Huurne, Lafayette N J de Windt, Yiliu Liu, E W Meijer, Ilja K Voets, Anja R A Palmans
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...
November 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/29151618/heterofunctional-poly-ethylene-glycol-peg-macroinitiator-enabling-controlled-synthesis-of-abc-triblock-copolymers
#14
Lies A L Fliervoet, Marzieh Najafi, Mathew Hembury, Tina Vermonden
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. This novel PEG macroinitiator allows the development of elegant synthesis routes for PEG midblock-containing ABC copolymers that does not require protection of initiating sites or polymer end-group postmodification...
November 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/29151617/poly-arylene-ethynylene-alt-arylene-vinylene-s-based-on-anthanthrone-and-its-derivatives-synthesis-and-photophysical-electrochemical-electroluminescent-and-photovoltaic-properties
#15
Suru Vivian John, Věra Cimrová, Christoph Ulbricht, Veronika Pokorná, Aleš Růžička, Jean-Benoit Giguère, Antoine Lafleur-Lambert, Jean-François Morin, Emmanuel Iwuoha, Daniel Ayuk Mbi Egbe
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 ( P1 - P5 ) based on poly[(arylene ethynylene)- alt -(arylene vinylene)]s backbone (-Ph-C≡C-Anth-C≡C-Ph-CH=CH-Ph-CH=CH-) n . During the synthesis of P1 - P5 , different alkyloxy side chains were incorporated in order to tune the properties of the polymers...
November 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/29093606/enhanced-electrical-conductivity-of-molecularly-p-doped-poly-3-hexylthiophene-through-understanding-the-correlation-with-solid-state-order
#16
Jonna Hynynen, David Kiefer, Liyang Yu, Renee Kroon, Rahim Munir, Aram Amassian, Martijn Kemerink, Christian Müller
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. Through this approach, we are able to establish how the electrical conductivity varies with regard to a series of predefined structural parameters...
October 24, 2017: Macromolecules
https://www.readbyqxmd.com/read/29033466/silane-acrylate-chemistry-for-regulating-network-formation-in-radical-photopolymerization
#17
Johannes Steindl, Thomas Koch, Norbert Moszner, Christian Gorsche
Photoinitiated silane-ene chemistry has the potential to pave the way toward spatially resolved organosilicon compounds, which might find application in biomedicine, microelectronics, and other advanced fields. Moreover, this approach could serve as a viable alternative to the popular photoinitiated thiol-ene chemistry, which gives access to defined and functional photopolymer networks. A difunctional bis(trimethylsilyl)silane with abstractable hydrogens (DSiH) was successfully synthesized in a simple one-pot procedure...
October 10, 2017: Macromolecules
https://www.readbyqxmd.com/read/28970637/surface-interaction-parameter-measurement-of-solvated-polymers-via-model-end-tethered-chains
#18
Richard J Sheridan, Sara V Orski, Ronald L Jones, Sushil K Satija, Kathryn L Beers
We present a method for the direct measurement of the relative energy of interaction between a solvated polymer and a solid interface. By tethering linear chains covalently to the surface, we ensured the idealized and constant configuration of polymer molecules for measurement, modeling, and parameter estimation. For the case of amine-terminated polystyrene bound to a glycidoxypropyl silane film submerged in cyclohexane-d12, we estimated the χ parameter for the temperature range 10.7 °C to 52.0 °C, and found a downward sloping trend that crosses the χ = 0...
September 2017: Macromolecules
https://www.readbyqxmd.com/read/28919648/optical-imaging-of-large-gyroid-grains-in-block-copolymer-templates-by-confined-crystallization
#19
Raphael Dehmel, James A Dolan, Yibei Gu, Ulrich Wiesner, Timothy D Wilkinson, Jeremy J Baumberg, Ullrich Steiner, Bodo D Wilts, Ilja Gunkel
Block copolymer (BCP) self-assembly is a promising route to manufacture functional nanomaterials for applications from nanolithography to optical metamaterials. Self-assembled cubic morphologies cannot, however, be conveniently optically characterized in the lab due to their structural isotropy. Here, the aligned crystallization behavior of a semicrystalline-amorphous polyisoprene-b-polystyrene-b-poly(ethylene oxide) (ISO) triblock terpolymer was utilized to visualize the grain structure of the cubic microphase-separated morphology...
August 22, 2017: Macromolecules
https://www.readbyqxmd.com/read/28867829/ph-responsive-schizophrenic-diblock-copolymers-prepared-by-polymerization-induced-self-assembly
#20
Sarah L Canning, Thomas J Neal, Steven P Armes
Polymerization-induced self-assembly (PISA) is used for the highly convenient and efficient preparation of ampholytic diblock copolymer nanoparticles directly in acidic aqueous solution. Cationic nanoparticles comprising a protonated polyamine stabilizer block and a hydrophobic polyacid core-forming block are formed at pH 2. Micelle inversion occurs at pH 10 to produce anionic nanoparticles with an ionized polyacid stabilizer block and a hydrophobic polyamine core-forming block. Macroscopic precipitation occurs at around pH 6-7, which lies close to the isoelectric point of this ampholytic diblock copolymer...
August 22, 2017: Macromolecules
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