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Thin films of polydopamine, a melanin-like material formed by the oxidative polymerization of dopamine in aqueous solution, have attracted much recent interest as functional coatings. Here we demonstrate the use of modified polydopamine as an initiator layer for surface-initiated polymerization, synthesized by reacting dopamine with 2-bromoisobutyryl bromide (BIBB) before deposition. Modified polydopamine...
Within a polymer thin film, free volume elements have a wide range of size and topology. This broad range of free volume element sizes determines the ability for a polymer to perform molecular separations. Herein, six permeable thermally rearranged (TR) polymers and their precursors were studied. Using atomistic models, cavity size (free volume) distributions determined by a combination of molecular...
Multi-walled carbon nanotubes (MWNTs) are modified to possess the hydroxyl groups and are used as coinitiators to polymerize poly(ε-caprolactone) (PCL) or poly(α-chloro-ε-caprolactone) (PαClCL) by surface-initiated ring-opening polymerization. Pendent chlorides were converted into azides by the reaction with sodium azides. Finally, various types of terminal alkynes were reacted with pendent azides...
The synergistic effect of using polystyrene-grafted multi-walled carbon nanotubes (PSgMWCNT) and a surfactant in the dispersion of MWCNT in a self-assembled poly(styrene-b-isoprene-b-styrene) (SIS) block copolymer is reported. The functionalization of MWCNT with polystyrene achieved by the grafting-from approach is not enough to disperse them in the SIS block copolymer. However, a high dispersion...
Effects of electric poling, mechanical stretching, and dipolar interaction on the formation of ferroelectric (β and/or γ) phases in poly(vinylidene fluoride) (PVDF) have been studied in electrospun fibers of PVDF/polyacrylonitrile (PAN) and PVDF/polysulfone (PSF) blends with PVDF as the minor component, using wide-angle X-ray diffraction and Fourier transform infrared techniques. Experimental results...
Electrically conductive polymer composites (CPCs) based on carbon nanotubes (CNTs) and polycarbonate were investigated regarding their electrical resistance change in different solvents like tetrahydrofuran, acetone, and ethyl acetate. CPCs containing 0.086 to 2.778 vol.% CNT were melt mixed using a twin-screw extruder under optimised conditions and subsequently compression-moulded.All sensing experiments...
We report a systematic study of the crystallization and rheological behavior of poly(ethylene oxide) (PEO)–clay nanocomposites. To that end a series of nanocomposites based on PEOs of different molecular weight (10 3 < MW < 10 5 g/mol) and clay surface modifier was synthesized and characterized. Incorporation of organoclays with polar (MMT-OH) or aromatic groups (MMT-Ar) suppresses...
The thixotropic clay suspensions composed of laponite particles and Mg–Fe layered double hydroxide nanosheets were examined. By adding a very small amount of the layered double hydroxide nanosheets overall rheological properties of the host laponite suspension have been changed. Though the particle concentration of the mixture suspension is only about 1 wt%, the mixture quickly becomes a gel in a...
A-type single crystals were prepared in dilute water/acetone solutions by crystallizing narrow fractions of short amylose chains biosynthesized in vitro. The 5 μm-long spindle-shaped crystals were observed by scanning and transmission electron microscopy. Electron diffraction patterns were recorded from frozen-hydrated crystals at different tilt angles around selected crystallographic axes. In particular,...
Large amount of work has been reported on the annealing of polypropylene (PP) and the related changes in mechanical properties. However, the structure–property correlations and the physical origin of annealing induced microstructural evolution are still not very clear. In this work, taking β-form PP (β-PP) as example, the microstructural changes induced by annealing were investigated from macromolecular...
An additional centrifugal field applied to an electrostatic field in a novel electrospinning technique was proposed in this study. An additional centrifugal field can not only remove bending instability of electrically charged liquid jets during the electrospinning process but can also fabricate aligned and molecularly oriented nanofibers. The results indicated that combining a strong stretching force...
The reinforcement mechanism of nano inclusions on the mechanical properties of nanocomposites is still a controversial issue. In this work, the polyethylene (PE) polymer nanocomposites were simulated by infusing different kinds of nano inclusions (bucky-ball, graphene, single-walled-carbon-nanotube (SWNT), X-shaped SWNT junction and Y-shaped SWNT junction) into PE matrices. The effects of these nano...
Curing of LCTs in an AC electric field was studied to understand the interplay between crosslink reaction and formation of a liquid crystalline (LC) phase and its effect on mechanical thermal properties on resulting thermosetting films. We show that dicyanate thermosetting monomers with ester functionality exhibit the ability to realign even after long curing times and allow poling of the LC director...
A series of soluble poly(amic acid) precursors were prepared from a new carbzole-containing monomer, 3,3′-bis[9-carbazole(ethyloxy)biphenyl]-4,4′-diamine (HAB-CBZ) by polycondensation with four different aromatic dianhydrides: pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-diphenylethertetracarboxylic dianhydride (ODPA), and 3,3′,4,4′-diphenylsulfonyltetracarboxylic...
Photoredox pairs consisting of selenocarbocyanine dye cations and phenyltrialkylborate anions were employed as the novel, effective visible-wavelength initiators of the radical polymerization of acrylic monomer. The influence of the sensitizers and electron donor structure on the photopolymerization kinetics of multiacrylate monomer was investigated by photo-DSC. It was found that the polymerization...
Here we report the results of a three dimensional hybrid self-consistent field theoretic (HSCFT) model describing the equilibrium particle distribution of spherical nanoparticles within symmetric AB diblock copolymer melts. Holding the polymer composition and morphology fixed, we consider a comprehensive parameter space comprised of the Flory interaction parameter describing interactions between B...
In spite of the continued interest in the yield, flow and fracture behavior of glassy homopolymers and the important role that crazing plays in their ultimate mechanical response, the basic understanding of the molecular level processes that govern craze initiation still remains murky. Here we revisit some early experiments of Argon and Hannoosh of the 1970s on craze initiation in homo polystyrene...
Poly(N-isopropylacrylamide)-block-poly(N-vinylpyrrolidone) diblock copolymer (PNIPAAm-b-PVPy) was successfully synthesized via sequential reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process, in which the chain transfer agent of xanthate was in situ afforded via the reaction of isopropylxanthic disulfide (DIP) with 2,2-azobisisobutylnitrile...
The polyphosphazenes {[NP(O 2 C 12 H 8 )] 0.75 [NP(O–C 6 H 4 –CH 2 –CH 2 –CH 2 –OH)(O–C 6 H 5 )] 0.25 } n and {[NP(O 2 C 12 H 8 )] 0.75 [NP(O–C 6 H 4 –(CH 2 –CH 2 –CH 2 –OH)) 2 ] 0.25 } n , having pendant...
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