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Macromolecules

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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
#1
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
#2
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
#3
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
https://www.readbyqxmd.com/read/28469284/tough-supramolecular-hydrogel-based-on-strong-hydrophobic-interactions-in-a-multiblock-segmented-copolymer
#4
Marko Mihajlovic, Mariapaola Staropoli, Marie-Sousai Appavou, Hans M Wyss, Wim Pyckhout-Hintzen, Rint P Sijbesma
We report the preparation and structural and mechanical characterization of a tough supramolecular hydrogel, based exclusively on hydrophobic association. The system consists of a multiblock, segmented copolymer of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dimer fatty acid (DFA) building blocks. A series of copolymers containing 2K, 4K, and 8K PEG were prepared. Upon swelling in water, a network is formed by self-assembly of hydrophobic DFA units in micellar domains, which act as stable physical cross-link points...
April 25, 2017: Macromolecules
https://www.readbyqxmd.com/read/28416888/tailoring-pore-size-and-chemical-interior-of-near-1-nm-sized-pores-in-a-nanoporous-polymer-based-on-a-discotic-liquid-crystal
#5
Subham Bhattacharjee, Jody A M Lugger, Rint P Sijbesma
A triazine based disc shaped molecule with two hydrolyzable units, imine and ester groups, was polymerized via acyclic diene metathesis in the columnar hexagonal (Colhex) LC phase. Fabrication of a cationic nanoporous polymer (pore diameter ∼1.3 nm) lined with ammonium groups at the pore surface was achieved by hydrolysis of the imine linkage. Size selective aldehyde uptake by the cationic porous polymer was demonstrated. The anilinium groups in the pores were converted to azide as well as phenyl groups by further chemical treatment, leading to porous polymers with neutral functional groups in the pores...
April 11, 2017: Macromolecules
https://www.readbyqxmd.com/read/28316344/mechanoluminescent-imaging-of-osmotic-stress-induced-damage-in-a-glassy-polymer-network
#6
Jess M Clough, Jasper van der Gucht, Rint P Sijbesma
A chemiluminescent mechanophore, bis(adamantyl-1,2-dioxetane), is used to investigate the covalent bond scission resulting from the sorption of chloroform by glassy poly(methyl methacrylate) (PMMA) networks. Bis(adamantyl)-1,2-dioxetane units incorporated as cross-linkers underwent mechanoluminescent scission, demonstrating that solvent ingress caused covalent bond scission. At higher cross-linking densities, the light emission took the form of hundreds of discrete bursts, widely varying in intensity, with each burst composed of 10(7)-10(9) photons...
March 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/28392603/nanoparticle-motion-in-entangled-melts-of-linear-and-nonconcatenated-ring-polymers
#7
Ting Ge, Jagannathan T Kalathi, Jonathan D Halverson, Gary S Grest, Michael Rubinstein
The motion of nanoparticles (NPs) in entangled melts of linear polymers and nonconcatenated ring polymers are compared by large-scale molecular dynamics simulations. The comparison provides a paradigm for the effects of polymer architecture on the dynamical coupling between NPs and polymers in nanocomposites. Strongly suppressed motion of NPs with diameter d larger than the entanglement spacing a is observed in a melt of linear polymers before the onset of Fickian NP diffusion. This strong suppression of NP motion occurs progressively as d exceeds a and is related to the hopping diffusion of NPs in the entanglement network...
February 28, 2017: Macromolecules
https://www.readbyqxmd.com/read/28260814/preparation-and-cross-linking-of-all-acrylamide-diblock-copolymer-nano-objects-via-polymerization-induced-self-assembly-in-aqueous-solution
#8
Sarah J Byard, Mark Williams, Beulah E McKenzie, Adam Blanazs, Steven P Armes
Various carboxylic acid-functionalized poly( N , N -dimethylacrylamide) (PDMAC) macromolecular chain transfer agents (macro-CTAs) were chain-extended with diacetone acrylamide (DAAM) by reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization at 70 °C and 20% w/w solids to produce a series of PDMAC-PDAAM diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). TEM studies indicate that a PDMAC macro-CTA with a mean degree of polymerization (DP) of 68 or higher results in the formation of well-defined spherical nanoparticles with mean diameters ranging from 40 to 150 nm...
February 28, 2017: Macromolecules
https://www.readbyqxmd.com/read/28216792/effect-of-monomer-solubility-on-the-evolution-of-copolymer-morphology-during-polymerization-induced-self-assembly-in-aqueous-solution
#9
Amy A Cockram, Thomas J Neal, Matthew J Derry, Oleksandr O Mykhaylyk, Neal S J Williams, Martin W Murray, Simon N Emmett, Steven P Armes
Polymerization-induced self-assembly (PISA) has become a widely used technique for the rational design of diblock copolymer nano-objects in concentrated aqueous solution. Depending on the specific PISA formulation, reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization typically provides straightforward access to either spheres, worms, or vesicles. In contrast, RAFT aqueous emulsion polymerization formulations often lead to just kinetically-trapped spheres. This limitation is currently not understood, and only a few empirical exceptions have been reported in the literature...
February 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/28216791/molecular-processes-leading-to-necking-in-extensional-flow-of-polymer-solutions-using-microfluidics-and-single-dna-imaging
#10
Shaurya Sachdev, Aswin Muralidharan, Pouyan E Boukany
We study the necking and pinch-off dynamics of liquid droplets that contain a semidilute polymer solution of polyacrylamide close to overlap concentration by combining microfluidics and single DNA observation. Polymeric droplets are stretched by passing them through the stagnation point of a T-shaped microfluidic junction. In contrast with the sudden breakup of Newtonian droplets, a stable neck is formed between the separating ends of the droplet which delays the breakup process. Initially, polymeric filaments experience exponential thinning by forming a stable neck with extensional flow within the filament...
December 27, 2016: Macromolecules
https://www.readbyqxmd.com/read/27795581/abc-triblock-copolymer-worms-synthesis-characterization-and-evaluation-as-pickering-emulsifiers-for-millimeter-sized-droplets
#11
C J Mable, K L Thompson, M J Derry, O O Mykhaylyk, B P Binks, S P Armes
Polymerization-induced self-assembly (PISA) is used to prepare linear poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) [PGMA-PHPMA-PBzMA] triblock copolymer nano-objects in the form of a concentrated aqueous dispersion via a three-step synthesis based on reversible addition-fragmentation chain transfer (RAFT) polymerization. First, GMA is polymerized via RAFT solution polymerization in ethanol, then HPMA is polymerized via RAFT aqueous solution polymerization, and finally BzMA is polymerized via "seeded" RAFT aqueous emulsion polymerization...
October 25, 2016: Macromolecules
https://www.readbyqxmd.com/read/27708458/raft-dispersion-alternating-copolymerization-of-styrene-with-n-phenylmaleimide-morphology-control-and-application-as-an-aqueous-foam-stabilizer
#12
Pengcheng Yang, Oleksandr O Mykhaylyk, Elizabeth R Jones, Steven P Armes
We report a new nonaqueous polymerization-induced self-assembly (PISA) formulation based on the reversible addition-fragmentation chain transfer (RAFT) dispersion alternating copolymerization of styrene with N-phenylmaleimide using a nonionic poly(N,N-dimethylacrylamide) stabilizer in a 50/50 w/w ethanol/methyl ethyl ketone (MEK) mixture. The MEK cosolvent is significantly less toxic than the 1,4-dioxane cosolvent reported previously [Yang P.; Macromolecules2013, 46, 8545-8556]. The core-forming alternating copolymer block has a relatively high glass transition temperature (Tg), which leads to vesicular morphologies being observed during PISA, as well as the more typical sphere and worm phases...
September 27, 2016: Macromolecules
https://www.readbyqxmd.com/read/27660374/surface-anchored-poly-n-isopropylacrylamide-orthogonal-gradient-networks
#13
C K Pandiyarajan, Michael Rubinstein, Jan Genzer
We present a versatile synthetic route leading toward generating surface-attached polyacrylamide gels, in which the cross-link density varies continuously and gradually across the substrate in two orthogonal directions. We employ free radical polymerization to synthesize random copolymers comprising ~5% of photoactive methacrylyloxybenzophenone (MABP), ~5% of thermally active styrene sulfonyl azide (SSAz), and ~90% of N-isopropylacrylamide (NIPAAm) units. The presence of MABP and SSAz in the copolymer facilitates control over the cross-link density of the gel in an orthogonal manner using photoactivated and thermally activated cross-linking chemistries, respectively...
July 26, 2016: Macromolecules
https://www.readbyqxmd.com/read/27478250/determining-the-effective-density-and-stabilizer-layer-thickness-of-sterically-stabilized-nanoparticles
#14
Bernice Akpinar, Lee A Fielding, Victoria J Cunningham, Yin Ning, Oleksandr O Mykhaylyk, Patrick W Fowler, Steven P Armes
A series of model sterically stabilized diblock copolymer nanoparticles has been designed to aid the development of analytical protocols in order to determine two key parameters: the effective particle density and the steric stabilizer layer thickness. The former parameter is essential for high resolution particle size analysis based on analytical (ultra)centrifugation techniques (e.g., disk centrifuge photosedimentometry, DCP), whereas the latter parameter is of fundamental importance in determining the effectiveness of steric stabilization as a colloid stability mechanism...
July 26, 2016: Macromolecules
https://www.readbyqxmd.com/read/27375300/raft-aqueous-dispersion-polymerization-of-n-2-methacryloyloxy-ethyl-pyrrolidone-a-convenient-low-viscosity-route-to-high-molecular-weight-water-soluble-copolymers
#15
Victoria J Cunningham, Matthew J Derry, Lee A Fielding, Osama M Musa, Steven P Armes
RAFT solution polymerization of N-(2-(methacryoyloxy)ethyl)pyrrolidone (NMEP) in ethanol at 70 °C was conducted to produce a series of PNMEP homopolymers with mean degrees of polymerization (DP) varying from 31 to 467. Turbidimetry was used to assess their inverse temperature solubility behavior in dilute aqueous solution, with an LCST of approximately 55 °C being observed in the high molecular weight limit. Then a poly(glycerol monomethacylate) (PGMA) macro-CTA with a mean DP of 63 was chain-extended with NMEP using a RAFT aqueous dispersion polymerization formulation at 70 °C...
June 28, 2016: Macromolecules
https://www.readbyqxmd.com/read/27375299/biosynthetic-polymers-as-functional-materials
#16
REVIEW
Andrea S Carlini, Lisa Adamiak, Nathan C Gianneschi
The synthesis of functional polymers encoded with biomolecules has been an extensive area of research for decades. As such, a diverse toolbox of polymerization techniques and bioconjugation methods has been developed. The greatest impact of this work has been in biomedicine and biotechnology, where fully synthetic and naturally derived biomolecules are used cooperatively. Despite significant improvements in biocompatible and functionally diverse polymers, our success in the field is constrained by recognized limitations in polymer architecture control, structural dynamics, and biostabilization...
June 28, 2016: Macromolecules
https://www.readbyqxmd.com/read/27134312/morphology-and-proton-transport-in-humidified-phosphonated-peptoid-block-copolymers
#17
Jing Sun, Xi Jiang, Aaron Siegmund, Michael D Connolly, Kenneth H Downing, Nitash P Balsara, Ronald N Zuckermann
Polymers that conduct protons in the hydrated state are of crucial importance in a wide variety of clean energy applications such as hydrogen fuel cells and artificial photosynthesis. Phosphonated and sulfonated polymers are known to conduct protons at low water content. In this paper, we report on the synthesis phosphonated peptoid diblock copolymers, poly-N-(2-ethyl)hexylglycine-block-poly-N-phosphonomethylglycine (pNeh-b-pNpm), with volume fractions of pNpm (ϕNpm) values ranging from 0.13 to 0.44 and dispersity (Đ) ≤ 1...
April 26, 2016: Macromolecules
https://www.readbyqxmd.com/read/27134311/a-robust-cross-linking-strategy-for-block-copolymer-worms-prepared-via-polymerization-induced-self-assembly
#18
J R Lovett, L P D Ratcliffe, N J Warren, S P Armes, M J Smallridge, R B Cracknell, B R Saunders
A poly(glycerol monomethacrylate) (PGMA) chain transfer agent is chain-extended by reversible addition-fragmentation chain transfer (RAFT) statistical copolymerization of 2-hydroxypropyl methacrylate (HPMA) with glycidyl methacrylate (GlyMA) in concentrated aqueous solution via polymerization-induced self-assembly (PISA). A series of five free-standing worm gels is prepared by fixing the overall degree of polymerization of the core-forming block at 144 while varying its GlyMA content from 0 to 20 mol %. (1)H NMR kinetics indicated that GlyMA is consumed much faster than HPMA, producing a GlyMA-rich sequence close to the PGMA stabilizer block...
April 26, 2016: Macromolecules
https://www.readbyqxmd.com/read/27175037/cyclic-graft-copolymer-unimolecular-micelles-effects-of-cyclization-on-particle-morphology-and-thermoresponsive-behavior
#19
Rebecca J Williams, Anaïs Pitto-Barry, Nigel Kirby, Andrew P Dove, Rachel K O'Reilly
The synthesis of cyclic amphiphilic graft copolymers with a hydrophobic polycarbonate backbone and hydrophilic poly(N-acryloylmorpholine) (PNAM) side arms via a combination of ring-opening polymerization (ROP), cyclization via copper-catalyzed azide-alkyne cycloaddition (CuAAC), and reversible addition-fragmentation chain transfer (RAFT) polymerization is reported. The ability of these cyclic graft copolymers to form unimolecular micelles in water is explored using a combination of light scattering, small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryoTEM) analyses, where particle size was found to increase with increasing PNAM arm length...
April 12, 2016: Macromolecules
https://www.readbyqxmd.com/read/27019522/a-critical-appraisal-of-raft-mediated-polymerization-induced-self-assembly
#20
Sarah L Canning, Gregory N Smith, Steven P Armes
Recently, polymerization-induced self-assembly (PISA) has become widely recognized as a robust and efficient route to produce block copolymer nanoparticles of controlled size, morphology, and surface chemistry. Several reviews of this field have been published since 2012, but a substantial number of new papers have been published in the last three years. In this Perspective, we provide a critical appraisal of the various advantages offered by this approach, while also pointing out some of its current drawbacks...
March 22, 2016: Macromolecules
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