Submicron Polyethylene Particles from Catalytic Emulsion Polymerization (original) (raw)
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Aqueous Dispersions of Extraordinarily Small Polyethylene Nanoparticles
Angewandte Chemie International Edition, 2005
General methods and materials. Ethylene of 3.5 grade was supplied by Praxair. Demineralised water was distilled under argon. 2-propanol (p.a.) was degassed by four repeated freeze-thaw cycles. Chloranil (Aldrich) und sodium dodecyl sulfate (Fluka) were used without further purification. Potassium 4-(diphenylphosphino)benzenesulfonate (TPPMS) was synthesized as described in [1]. bis(1,5-cyclooctadiene) nickel was synthesized according to [2] (the compound is also available commercially, e.g. at Aldrich or Strem). TEM investigations were carried out on a LEO 912 Omega apparatus using an acceleration voltage of 120 kV. Samples were stained with RuO 4. For microtome cutting, the latex particles were embedded in nanoplast ® (a hydrophilic melamine resin). Microtome cuts of ca. 50 nm thickness were prepared with a Reichert & Jung Ultracut E microtome equipped with a 45° diamond knife supplied by Diatome. AFM experiments were performed with a Nanoscope III scanning probe microscope. The height and phase images were obtained simultaneously while operating the instrument in the tapping mode under ambient conditions. Images were taken at the fundamental resonance frequency of the Si cantilevers which was typically around 180 kHz. Typical scan speeds during recording were 0.3-1 line/s using scan heads with a maximum range of 16 × 16 µm. The phase images represent the variations of relative phase shifts (i. e. the phase angle of the interacting cantilever relative to the phase angle of the freely oscillating cantilever at the resonance frequency) and are thus able to distinguish materials by their material properties (e.g. amorphous and crystalline polymers). DSC was performed on a Perkin Elmer DSC 7 instrument or on a Pyris 1 DSC at a heating and cooling rate of 10 K min-1. T m data reported are local maxima of the second heats. DSC traces of polymer dispersions were obtained on 20 to 30 mg of dispersion with ca. 5 % by weight polymer content. NMR spectra were recorded on a Bruker ARX 300 instrument (1 H: 300 MHz; 13 C: 75 MHz). 1 H and 13 C NMR spectra were performed in 1,1,2,2-tetrachloroethane-d 2 at 122 °C. GPC analyses were carried out by Basell GmbH, Ludwigshafen on a Waters150 or GPC2000 instrument equipped with Shodex columns at 140 °C in 1,2,4-trichlorobenzene. Data is referenced to linear polyethylene standards. Dynamic light scattering on dispersions was performed on a Malvern particle sizer. Catalyst Preparation. The preparation of catalyst was performed by standard Schlenk techniques under argon. Equal molar amounts of chloranil and TPPMS were dissolved in a given amount of 2-propanol (2 to 10 mL). The obtained yellow solution was transferred to a 1.1-fold molar excess of bis(1,5-cyclooctadiene)nickel.
Probing Polymer Material Properties on the Nanometer Scale
Microscopy Today, 2010
Polymers play an essential role in modern materials science. Because of the wide variety of mechanical and chemical properties of polymers, they are used in nearly every industry. Knowledge about their physical and chemical properties on the nanometer scale is often required. However, some details about the phase-separation process in polymers are difficult to study with conventional characterization techniques because these methods cannot chemically differentiate phases with good spatial resolution without damage, staining, or preferential solvent washing.
Polymer, 2019
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Spectroscopy measurements for determination of polymer particle size distribution
2008
Polymer and copolymer emulsion lattices based on styrene and butyl-metacrylate monomers are commercially important for many paints, adhesives, and coatings applications. The latex properties depend strongly on the copolymer composition, and particle size distribution, which in turn is function of the preparation of the latex and on the formulation of the emulsion designed for the particular application. This paper describes the implementation of multiwavelength spectroscopy measurements for size and distribution of the latex emulsions. The quantitative interpretation of the transmission spectrum is performed in the portion where no absorption is present (300-820 nm) leading to reliable estimated of particle size populations in the range of 0.02-20 m. Particle size and particle size distribution of polymers and copolymers as function of reaction time and emulsion formulation are found in agreement with Smith Ewart (case 2 kinetics). The possibility of obtaining information from a single multiwavelength measurement makes UV-Vis spectroscopy a powerful tool for characterization of dispersed systems.
The response of microstructure to processing in a series of poly(siloxaneimide) copolymers
Journal of Polymer Science Part B: Polymer Physics, 1993
Poly ( siloxaneimide ) ( PSI ) segmented copolymers exhibit organized microdomains if the blocks are sufficiently incompatible. As with neat diblock and triblock copolymers, the processing route employed to prepare films of PSI materials is expected to influence the dimensions and/or morphology of the resultant microstructure. In this work, small-angle neutron scattering (SANS ) is utilized to characterize the disordered microstructure found in films of a series of PSI copolymers which are subjected to solvent casting and various thermal treatments. Microstructural dimensions such as the periodicity and correlation length are deduced from the Teubner-Strey (TS) model for disordered microemulsions.
ACS Applied Materials & Interfaces, 2011
Polymeric bicontinuous microemulsions (BμE), found in well-designed ternary blends of two homopolymers and a diblock copolymer, have been extensively studied in the bulk, for example, as versatile templates for the synthesis of nanoporous materials. However, there have been few reports regarding BμE-forming blends as films and the potential impact of confinement on the morphology of such blends. We have investigated the morphology of ternary blends of polyethylene (PE), poly(ethylene-alt-propylene) (PEP), and poly(ethylene-b-ethylenealt-propylene) (PEÀPEP) on a variety of substrates. The films were rendered nanoporous by selective extraction of the PEP component, which also created contrast for scanning electron microscopy (SEM). Blends that form BμEs in the bulk were found to undergo an evolution of morphology from a BμE to a macro-phase separated state, induced by the segregation of blend components to the film interfaces. The dynamics of the transformation are accelerated by decreasing film thickness. The results presented indicate that BμEs can be kinetically trapped on arbitrary substrates, which has important implications for the production of bicontinuous, nanoporous films.
Polyelectrolyte nanocages via crystallized miniemulsion droplets
Chemical Communications, 2011
Experimental Section Measurements. 1 H NMR (500 MHz) spectra were acquired in CDCl 3 using a Varian INOVA-500 spectrometer at 25 °C. Tetramethylsilane (TMS) was used as an internal reference for 1 H NMR spectroscopy. FT-IR spectra were obtained on a Bruker Tensor 27 system using attenuated total reflectance (ATR) sampling accessories. High resolution mass spectra were obtained on a ThermoFinnigan MAT XL spectrometer. Atomic force microscopy (AFM) measurements were performed on an Asylum Research MFP-3D AFM instrument operating in tapping mode. The AFM samples were prepared from dilute sample solutions (0.1 mg/mL in water) by solvent casting on fresh cleaved mica. The measurements were conducted in air at ambient conditions by using Si cantilevers with a spring constant of ca. 20-95 N/m and a resonance frequency of about 145-230 kHz, with image resolution of 512 × 512 points and a scan rate of 1 Hz. The AFM tip was purchased from Nanoscience Instruments with a tip radius smaller than 10 nm. Transmission electron microscopy (TEM) images were obtained by using a JEOL 2010 microscope. TEM samples were prepared by solvent casting on 300 mesh carboncoated copper grids from dilute sample solutions (0.1 mg/mL in water). The TEM samples were stained with saturated uranyl acetate aqueous solution for 10 minute prior to TEM measurements. Differential scanning calorimetry (DSC) measurements were performed using a TA Instruments Q200 system with a RCS-90 cooling device under nitrogen in the temperature range of 10-60 °C, with a heating rate of 5 °C/min.
Scalable Synthesis of a New Class of Polymer Microrods by a Liquid–Liquid Dispersion Technique
Advanced Materials, 2004
Fabrication of PPy Nanoparticles: For the synthesis of the PPy nanoparticles with an average diameter of 2 nm, octyltrimethylammonium bromide (OTAB; 6.0 g) was magnetically stirred in 40 mL of distilled water at 3 C. Pyrrole (1.0 g) was then added dropwise to the surfactant solution, and iron(III) chloride (5.561 g) dissolved in a small amount of distilled water was added to the reaction mixture. Chemical polymerization proceeded for 3 h at 3 C. The reaction product was then transferred to a separating funnel and excess methanol was added to remove the surfactant and residual iron(III) chloride. A small amount of isooctane was added to promote the precipitation of the PPy nanoparticles. The upper solution containing surfactant and unreacted iron(III) chloride was discarded and the nanoparticle precipitate was dried in a vacuum oven at room temperature. PPy nanoparticles with a diameter of about 6 nm were prepared using decyltrimethylammonium bromide (DeTAB; 2.3 g), following the same procedure. Carbonization Process: In a typical carbonization procedure, the PPy nanoparticles (about 2 g) collected from two runs of the microemulsion polymerization were precarbonized at 800 C for 3 h under Ar gas flow (0.2 L min ±1). Carbon felt was put at the inlet of Ar flow to reduce the oxidation of the polymer precursor. After the pretreatment at 800 C, the weight of the carbonized product was reduced to 30±35 % of the initial loading weight. The ªmissingº components, formed as a result of carbonization reactions such as denitrogenation, dehydrogenation, and dehalogenation, are removed by the Ar flow. The products of two runs of the pretreatment were collected and transferred to a quartz tube 4 cm in diameter. The quartz tube was evacuated and refilled with argon repeatedly. The argon-filled quartz tube was then placed in an electrical furnace equipped with a larger diameter alumina tube (6 cm in diameter). The valve of the quartz tube was opened and the alumina tube containing the quartz tube was evacuated and refilled with argon repeatedly. The second carbonization proceeded with streaming argon at a heating rate of 3 C min ±1. After 6 h of carbonization, the residual soot was collected and toluene was added to the quartz tube containing the sublimed fullerene film. The quartz tube was sonicated with gentle heating. The crude soot was refluxed with toluene in a standard Soxhlet extractor at 100 C for 12 h. Instrumental Analysis: TEM images were taken with a JEOL 2010 F microscope and EDX analysis was performed using a Philips CM 20 microscope. MALDI-TOF mass spectra were obtained with a Voyager-DE STR Biospectrometry Workstation (Applied Biosystems) operating in positive mode at an accelerating voltage of 20 kV using dithranol as the matrix. HPLC analysis was performed with a HP1100 liquid chromatograph. A 250 mm 4.6 mm i.d. monomeric octadecylsilica (ODS) column was used as the stationary phase. A mixture of toluene and methanol (55:45) was used as the mobile phase at a flow rate of 0.6 mL min ±1. Detection was performed with a diode-array detector at a detection wavelength of 330 nm.