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Macromolecules

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https://www.readbyqxmd.com/read/29339838/force-and-scale-dependence-of-the-elasticity-of-self-assembled-dna-bottle-brushes
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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/29151620/in-silico-synthesis-of-microgel-particles
#7
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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
https://www.readbyqxmd.com/read/29056760/dynamic-surface-enrichment-in-drying-thin-film-binary-polymer-solutions
#16
C Schaefer, J J Michels, P van der Schoot
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. It is often presumed that the experimentally observed surface enrichment required for this is caused by specific interactions of the active ingredients with each surface. By applying a generalized diffusion model, we find the dynamics to also play an important role in determining which component accumulates at which surface...
August 8, 2017: Macromolecules
https://www.readbyqxmd.com/read/29046593/wavelength-selective-sequential-polymer-network-formation-controlled-with-a-two-color-responsive-initiation-system
#17
Xinpeng Zhang, Weixian Xi, Sijia Huang, Katelyn Long, Christopher N Bowman
We report a wavelength-selective polymerization process controlled by visible/UV light, whereby a base is generated for anion-mediated thiol-Michael polymerization reaction upon exposure at one wavelength (400-500 nm), while radicals are subsequently generated for a second stage radical polymerization at a second, independent wavelength (365 nm). Dual wavelength, light controlled sequential polymerization not only provides a relatively soft intermediate polymer that facilitates optimum processing and modification under visible light exposure but also enables a highly cross-linked, rigid final material after the UV-induced second stage radical polymerization...
August 8, 2017: Macromolecules
https://www.readbyqxmd.com/read/28626247/time-resolved-saxs-studies-of-the-kinetics-of-thermally-triggered-release-of-encapsulated-silica-nanoparticles-from-block-copolymer-vesicles
#18
Charlotte J Mable, Matthew J Derry, Kate L Thompson, Lee A Fielding, Oleksandr O Mykhaylyk, Steven P Armes
Silica-loaded poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles are prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). As the concentration of silica nanoparticles present during the PISA synthesis is increased up to 35% w/w, higher degrees of encapsulation of this component within the vesicles can be achieved. After centrifugal purification to remove excess non-encapsulated silica nanoparticles, SAXS, DCP, and TGA analysis indicates encapsulation of up to hundreds of silica nanoparticles per vesicle...
June 13, 2017: Macromolecules
https://www.readbyqxmd.com/read/28553002/full-characterization-of-multiphase-multimorphological-kinetics-in-flow-induced-crystallization-of-ipp-at-elevated-pressure
#19
E M Troisi, H J M Caelers, G W M Peters
Understanding the complex crystallization behavior of isotactic polypropylene (iPP) in conditions comparable to those found in polymer processing, where the polymer melt experiences a combination of high shear rates and elevated pressures, is key for modeling and therefore predicting the final structure and properties of iPP products. Coupling a unique experimental setup, capable to apply wall shear rates similar to those experienced during processing and carefully control the pressure before and after flow is imposed, with in situ X-ray scattering and diffraction techniques (SAXS and WAXD) at fast acquisition rates (up to 30 Hz), a well-defined series of short-term flow experiments are carried out using 16 different combinations of wall shear rates (ranging from 110 to 440 s(-1)) and pressures (100-400 bar)...
May 23, 2017: Macromolecules
https://www.readbyqxmd.com/read/28529382/reversibly-manipulating-the-surface-chemistry-of-polymeric-nanostructures-via-a-grafting-to-approach-mediated-by-nucleobase-interactions
#20
Zan Hua, Robert Keogh, Zhen Li, Thomas R Wilks, Guosong Chen, Rachel K O'Reilly
"Grafting to" polymeric nanostructures or surfaces is a simple and versatile approach to achieve functionalization. Herein, we describe the formation of mixed polymer-grafted nanoparticles through a supramolecular "grafting to" method that exploits multiple hydrogen-bonding interactions between the thymine (T)-containing cores of preformed micelles and the complementary nucleobase adenine (A) of added diblock copolymers. To demonstrate this new "grafting to" approach, mixed-corona polymeric nanoparticles with different sizes were prepared by the addition of a series of complementary diblock copolymers containing thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) to a preformed micelle with a different coronal forming block, poly(4-acryloylmorpholine) (PNAM)...
May 9, 2017: Macromolecules
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