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Macromolecules

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https://www.readbyqxmd.com/read/30449902/effect-of-intra-versus-intermolecular-cross-linking-on-the-supramolecular-folding-of-a-polymer-chain
#1
Gijs M Ter Huurne, Ilja K Voets, Anja R A Palmans, E W Meijer
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 n -butyl methacrylate in various ratios via reversible addition-fragmentation chain-transfer (RAFT) polymerization...
November 13, 2018: Macromolecules
https://www.readbyqxmd.com/read/30449901/critical-dependence-of-molecular-weight-on-thermoresponsive-behavior-of-diblock-copolymer-worm-gels-in-aqueous-solution
#2
Nicholas J Warren, Matthew J Derry, Oleksandr O Mykhaylyk, Joseph R Lovett, Liam P D Ratcliffe, Vincent Ladmiral, Adam Blanazs, Lee A Fielding, Steven P Armes
Reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate was used to prepare three poly(glycerol monomethacrylate) x -poly(2-hydroxypropyl methacrylate) y (denoted G x -H y  or PGMA-PHPMA) diblock copolymers, namely G37 -H80 , G54 -H140 , and G71 -H200 . 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...
November 13, 2018: Macromolecules
https://www.readbyqxmd.com/read/30416210/hydration-and-temperature-response-of-water-mobility-in-poly-diallyldimethylammonium-poly-sodium-4-styrenesulfonate-complexes
#3
Piotr Batys, Yanpu Zhang, Jodie L Lutkenhaus, Maria Sammalkorpi
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...
October 23, 2018: Macromolecules
https://www.readbyqxmd.com/read/30405273/rapid-and-quantitative-de-tert-butylation-for-poly-acrylic-acid-block-copolymers-and-influence-on-relaxation-of-thermoassociated-transient-networks
#4
Alexei D Filippov, Ilse A van Hees, Remco Fokkink, Ilja K Voets, Marleen Kamperman
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 tert -butyl groups from poly( tert -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. We compare deprotection in HFIP with the common TFA/DCM method and show that the latter does not yield clean pAA...
October 23, 2018: Macromolecules
https://www.readbyqxmd.com/read/30333669/synthesis-of-well-defined-pyrrolidone-based-homopolymers-and-stimulus-responsive-diblock-copolymers-via-raft-aqueous-solution-polymerization-of-2-n-acryloyloxy-ethylpyrrolidone
#5
O J Deane, J R Lovett, O M Musa, A Fernyhough, S P Armes
Poly( N -vinylpyrrolidone) (PNVP) is a well-known, highly polar, nonionic water-soluble polymer. However, N -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. For these reasons, alternative pyrrolidone-based monomers have been investigated. For example, the reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-( N -methacryloyloxy)ethylpyrrolidone (NMEP) has been recently investigated using various polymerization formulations...
October 9, 2018: Macromolecules
https://www.readbyqxmd.com/read/30270941/aqueous-phase-separation-behavior-of-highly-syndiotactic-high-molecular-weight-polymers-with-densely-packed-hydroxy-containing-side-groups
#6
Dorette S Tromp, Marianne Lankelma, Hannah de Valk, Emile de Josselin de Jong, Bas de Bruin
Herein we describe the Rh-catalyzed C1 polymerization of silyl-protected diazoacetates of the general formula HC(=N2 )C(=O)O(CH2 ) x OSiR3 , where x = 2-5. After polymerization and subsequent desilylation, syndiotactic polymers bearing a hydroxy-containing side group on every backbone carbon are obtained. The molecular weight of the desired polymers can be controlled via chain transfer with methanol during the polymerization. The produced polymers are compared to atactic analogues formed by [(η3 -C3 H5 )PdCl]-catalyzed polymerization of silyl-protected diazoacetates with the same general formula...
September 25, 2018: Macromolecules
https://www.readbyqxmd.com/read/30270940/time-dependent-atr-ftir-spectroscopic-studies-on-solvent-diffusion-and-film-swelling-in-oil-paint-model-systems
#7
Lambert Baij, Joen J Hermans, Katrien Keune, Piet D Iedema
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. Using dynamic mechanical analysis (DMA), the glass transition temperature of our model systems was found to be close to room temperature...
September 25, 2018: Macromolecules
https://www.readbyqxmd.com/read/30174342/blob-size-controls-diffusion-of-free-polymer-in-a-chemically-identical-brush-in-semidilute-solution
#8
Zhenyu J Zhang, Steve Edmondson, Matthew Mears, Jeppe Madsen, Steven P Armes, Graham J Leggett, Mark Geoghegan
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-1.42±0.09 . It is proposed that a characteristic blob size associated with the grafted (brush) layer defines the region through which the r-PEG diffusion occurs. The diffusion coefficients for r-PEG in semidilute solution were found to be similar to those in the brushes...
August 28, 2018: Macromolecules
https://www.readbyqxmd.com/read/30258253/two-robust-strategies-toward-hydrogels-from-quenched-block-copolymer-nanofibrillar-micelles
#9
Kai Zhang, Aaditya Suratkar, Sitara Vedaraman, Vasudevan Lakshminarayanan, Laurence Jennings, Piotr J Glazer, Jan H van Esch, Eduardo Mendes
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- b -poly(ethylene oxide) (PS- b -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...
August 14, 2018: Macromolecules
https://www.readbyqxmd.com/read/30135611/amplifying-chiroptical-properties-of-conjugated-polymer-thin-film-using-an-achiral-additive
#10
Chidambar Kulkarni, Stefan C J Meskers, Anja R A Palmans, E W Meijer
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 ( g abs ) in most of the conjugated polymer thin-films studied. Here we demonstrate a versatile method to significantly increase the g abs by using a few weight percentages of a commercially available achiral long-chain alcohol as an additive. This additive enhances the chiroptical properties in both absorption and emission by ca...
August 14, 2018: Macromolecules
https://www.readbyqxmd.com/read/30135610/growth-regimes-of-poly-perfluorodecyl-acrylate-thin-films-by-initiated-chemical-vapor-deposition
#11
Alberto Perrotta, Paul Christian, Andrew O F Jones, Fabian Muralter, Anna Maria Coclite
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. The effect of process parameters on the molecular organization of perfluorinated polymers deposited via initiated chemical vapor deposition (iCVD) has been previously reported. We showed that the tendency of poly(1 H ,1 H ,2 H ,2 H -perfluorodecyl acrylate) (pPFDA) to organize in an ordered lamellar structure is a function of the filament and substrate temperatures adopted during the iCVD process...
August 14, 2018: Macromolecules
https://www.readbyqxmd.com/read/30057430/grafting-from-a-hybrid-dna-covalent-polymer-by-the-hybridization-chain-reaction
#12
Willem E M Noteborn, Joeri A J Wondergem, Anastasiia Iurchenko, Farhad Chariyev-Prinz, Dominique Donato, Ilja K Voets, Doris Heinrich, Roxanne E Kieltyka
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. Additionally, aggregation of the initiator DNA-graft copolymer before the hybridization chain reaction was observed resulting in the formation of kinetically trapped aggregates several hundreds of nanometers in diameter that could be disrupted by a preheating step at 60 °C prior to extension at room temperature...
July 24, 2018: Macromolecules
https://www.readbyqxmd.com/read/30258252/crystal-growth-in-polyethylene-by-molecular-dynamics-the-crystal-edge-and-lamellar-thickness
#13
Tuukka Verho, Antti Paajanen, Jukka Vaari, Anssi Laukkanen
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. Away from the edge, the lengthening of the stems is limited by a lack of available slack length in the chains...
July 10, 2018: Macromolecules
https://www.readbyqxmd.com/read/30018463/linear-viscoelasticity-of-weakly-hydrogen-bonded-polymers-near-and-below-the-sol-gel-transition
#14
Milad Golkaram, Csaba Fodor, Evelyne van Ruymbeke, Katja Loos
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. By introducing one sticker per repeating unit of the precursor polymer, the effect of sticker distribution along the chain as well as phase separation is excluded...
July 10, 2018: Macromolecules
https://www.readbyqxmd.com/read/30018462/effect-of-self-assembly-of-oxalamide-based-organic-compounds-on-melt-behavior-nucleation-and-crystallization-of-isotactic-polypropylene
#15
Carolus H R M Wilsens, Laurence G D Hawke, Enrico M Troisi, Daniel Hermida-Merino, Gijs de Kort, Nils Leoné, Ketie Saralidze, Gerrit W M Peters, Sanjay Rastogi
We report on the effect of an aliphatic oxalamide based nucleating agent ( OXA3,6 ) on the melt and crystallization behavior of isotactic polypropylene ( i PP) under defined shear conditions. Through polarized optical microscopy, we demonstrate that OXA3,6 self-assembles from the i PP melt into rhombic crystals whereas their size and distribution proved highly dependent on the employed cooling rates. The presence of 0.5 wt % of OXA3,6 in i PP results in a significant suppression in i PP melt viscosity, which could not be explained via molecular modeling...
July 10, 2018: Macromolecules
https://www.readbyqxmd.com/read/30018461/effects-of-surfactant-and-urea-on-dynamics-and-viscoelastic-properties-of-hydrophobically-assembled-supramolecular-hydrogel
#16
Marko Mihajlovic, Hans M Wyss, Rint P Sijbesma
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. The model hydrogel is based on a segmented copolymer between poly(ethylene glycol) (PEG) and hydrophobic dimer fatty acid (DFA)...
July 10, 2018: Macromolecules
https://www.readbyqxmd.com/read/29915431/a-vinyl-ether-functional-polycarbonate-as-a-template-for-multiple-postpolymerization-modifications
#17
Sangho Cho, Gyu Seong Heo, Sarosh Khan, Jessica Huang, David A Hunstad, Mahmoud Elsabahy, Karen L Wooley
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). The vinyl ether moieties on the resulting polymers were readily conjugated with hydroxyl- or thiol-containing compounds via three different post-polymerization modification chemistries - acetalization, thio-acetalization, and thiol-ene reaction...
May 8, 2018: Macromolecules
https://www.readbyqxmd.com/read/29805184/synthesis-of-high-molecular-weight-poly-glycerol-monomethacrylate-via-raft-emulsion-polymerization-of-isopropylideneglycerol-methacrylate
#18
Craig P Jesson, Victoria J Cunningham, Mark J Smallridge, Steven P Armes
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. Herein we exemplify the latter approach by reporting the convenient one-pot synthesis of high molecular weight poly(glycerol monomethacrylate) (PGMA) via the reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization of a water-immiscible protected monomer precursor, isopropylideneglycerol methacrylate (IPGMA) at 70 °C, using a water-soluble poly(glycerol monomethacrylate) (PGMA) chain transfer agent as a steric stabilizer...
May 8, 2018: Macromolecules
https://www.readbyqxmd.com/read/29910512/physical-networks-from-multifunctional-telechelic-star-polymers-a-rheological-study-by-experiments-and-simulations
#19
Vishal Metri, Ameur Louhichi, Jiajun Yan, Guilhem P Baeza, Krzysztof Matyjaszewski, Dimitris Vlassopoulos, Wim J Briels
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. Both experimentally and in the simulations, networks were created by attaching sticker groups to the ends of the arms of the polymers, which were next allowed to form bonds among them in a one to one fashion...
April 24, 2018: Macromolecules
https://www.readbyqxmd.com/read/29657338/size-dependent-submerging-of-nanoparticles-in-polymer-melts-effect-of-line-tension
#20
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
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