Dispersion copolymerization of acrylamide with quaternary ammonium cationic monomer in aqueous salts solution

Dispersion copolymerization of acrylamide (AM) with 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) has been carried out in aqueous salts solution containing ammonium sulfate and sodium chloride with poly(acryloylxyethyl trimethyl ammonium chloride) (PDAC) as the stabilizer and 2,2'-azobis[2-(2-inidazolin-2-yl)propane]-dihydro chloride (VA-044) as the initiator. A new particle formation mechanism of the dispersion polymerization for the present system has been proposed. The effects of inorganic salts and stabilizer concentration on dispersion polymerization have been investigated. The results show that varying the salt concentration could affect the morphology and molecular weight of the resultant copolymer particles significantly. With increasing the stabilizer concentration, the particle size decreased at first and then increased, meanwhile the effect on the copolymer molecular weight was the contrary. These results had been rationalized based on the proposed mechanism.

Preparation of Polyacrylamide Aqueous Dispersions Using Poly(sodium acrylic acid) as Stabilizer

High-solids, low-viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using Poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2'-Azobis (N,N'-dimethyleneisobutyramidine) dihydrochloride (VA-044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain-transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences, of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain-transfer agent concentration and temperature Oil the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated.

Preparation of poly(acrylamide-co-acrylic acid) aqueous latex dispersions using anionic polyelectrolyte as stabilizer

High-solids, low-viscosity, stable poly(acrylamide-co-acrylic acid) aqueous latex dispersions were prepared by the dispersion polymerization of acrylamide (AM) and acrylic acid (AA) in an aqueous solution of ammonium sulfate (AS) medium using anionic polyelectrolytes as stabilizers. The anionic polyelectrolytes employed include poly(2-acrylamido-2-methylpropanesulfonic acid sodium) (PAMPSNa) homopolymer and random copolymers of 2-acrylamido-2-methylpropanesulfonic acid sodium (AMPSNa) with methacrylic acid sodium (MAANa), acrylic acid sodium (AANa) or acrylamide (AM). The influences of stabilizer's structure, composition, molecular weight and concentration, AA/AM molar feed ratio, total monomer, initiator and aqueous solution of AS concentration, and stirring speed on the monomer conversion, the particle size and distribution, the bulk viscosity and stability of the dispersions, and the intrinsic viscosity of the resulting copolymer were systematically investigated. Polydisperse spherical as well as ellipsoidal particles were formed in the system. The broad particle size distributions indicated that coalescence of the particles takes place to a greater extent.

A composite polymer film with both superhydrophobicity and superoleophilicity

A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual-scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an 'intelligent' wettability property can be utilized to separate oil and water systems efficiently.

Double propagation based on diepoxide, a facile route to high molecular weight poly(propylene carbonate)

Poly(propylene carbonate) (PPC) with number average molecular weight (M-n) higher than 200 kg/mol was prepared via the terpolymerization of carbon dioxide, propylene oxide and diepoxide using Y(CCl3OO)(3)-ZnEt2-glycerine coordination catalyst. When equimolar ZnEt2 and diepoxide were used, double propagation active species were generated in situ by nucleophilic attack of metal alkoxide on diepoxide, leading to PPC of doubled M-n value. The molecular weight of PPC has dramatic influence on its thermal and mechanical performances. PPC with M of 227 kg/mol showed modulus of 6900 MPa, while the modulus of PPC with M-n of 109 kg/mol was only 4300 MPa. Moreover, when M-n increased from 109 to 227 kg/mol, a 37 degrees C increase of the onset degradation temperature was observed.

Spherical particles of phenolic resin treated with iron oxide

This paper describes the preparation and characterization of phenolic resins' thermospheres covered by a magnetic phase of iron oxide. The thermospheres were prepared by allowing phenol and formaldehyde to react under dispersion polymerization conditions and the iron oxide phase was incorporated in situ onto the phenolic resin particles by adding concentrated NH3 to FeCl2 in DMSO. This reaction was conducted at 70 degrees C under nitrogen atmosphere in a controlled temperature vessel, and the modified resin was isolated and dried in vacuo. Both pure and modified resins were characterized by DRX, TG- DTA, and MEV/ EDX. The modified particles were attracted by a magnetic field, indicating the fixation of magnetic iron oxide. No diffraction peaks were observed in DRX analysis; thermal analysis ( DTA) of both pure and modified resins presented exothermic events between 300 and 680 degrees C, and 300 and 570 degrees C, respectively, indicating the microstructure of the resin was modified after the treatment. Thermogravimetric analysis ( TGA) of the pure resin registered a 2.0% residue, compared to 8.0% for the modified resin. These residues correspond to about 7.0% of fixed iron oxide. MEV/ EDX analyses confirm the modification of the resins by the process of fixing iron oxide.

Neue Methoden zur Darstellung von Blockcopolymeren unter Beteiligung radikalischer Polymerisationsmechanismen

Im Rahmen dieser Dissertation wurden die Synthese und die Charakterisierung verschiedener, zum Teil neuartiger Blockcopolymere beschrieben, wobei die Einbeziehung radikalischer Polymeri-sationsmechanismen den konzeptionellen Kern ausmachte. Mit einer auf die jeweilige Kombination von Monomeren zugeschnittenen Syntheseroute gelang die Verknüpfung von Segmenten, die allein mittels der herkömmlich zur Synthese von Blockcopolymeren genutzten, ionischen Mechanismen nur mit hohem Aufwand oder gar nicht zu verbinden sind. Auf materieller Seite stand die Herstellung amphiphiler Strukturen im Vordergrund. Diese wurden entweder direkt beim Aufbau der Blockcopo-lymere oder nach anschließender polymeranaloger Umsetzung eines ihrer Segmente erhalten. Solche amphiphilen Substanzen besitzen aufgrund ihrer Grenzflächenaktivität Anwendungspotential z. B. als Stabilisatoren in der Dispersionspolymerisation oder als Flokkulantien. Es wurden drei Verfahren zum Aufbau von Blockcopolymeren untersucht:1. Die Transformation von anionischer zu freier radikalischer Polymerisation für die Synthese von Polystyrol-b-poly(N-vinylformamid) (PS-b-P(VFA)).2. Die Transformation von anionischer zu kontrollierter radikalischer Polymerisation (ATRP) für den Aufbau von Blockcopolymeren aus Poly(dimethylsiloxan) PDMS und Segmenten von t-Butylacrylat (t-BuA) bzw. (2-(Trimethylsiloxy)ethyl)methacrylat (TMS-HEMA).3. Die kontrollierte radikalische Polymerisation unter Einsatz von Triazolinyl als Gegenradikal zur Synthese von Poly[(2-(trimethylsiloxy)ethyl)methacrylat]-b-polystyrol (P(TMS-HEMA)-b-PS) als alternative Route zur anionischen Polymerisation.

Untersuchung des Aggregationsverhaltens amphiphiler Diblockcopolymere in überkritischem Kohlendioxid mittels dynamischer Lichtstreuung

„Untersuchung des Aggregationsverhaltens amphiphiler Diblockcopolymere in überkritischem Kohlendioxid mittels dynamischer Lichtstreuung“ In der vorliegenden Arbeit wurde die Mizellenbildung von Diblockcopolymeren des Typs PS-b-PDMS in überkritischem Kohlendioxid (CO2,SC) mittels dynamischer Lichtstreuung (DLS) charakterisiert. Zu diesem Zweck wurden Mischungen aus den Diblockcopolymeren in CO2,SC mit Styrol als Monomer druckabhängig auf diese Fähigkeit hin untersucht. Eine Mizellenbildung konnte anhand der gemessenen hydrodynamischen Radien Rh gezeigt werden. Um eine Vergleichsmöglichkeit gegenüber den mit Styrol gefüllten Kern-Hüllen-Mizellen zu bekommen, wurde das Diblockcopolymer PS-b-PDMS (9/27) zunächst ohne Styrol auf die Fähigkeit hin untersucht ungefüllte Mizellen zu bilden. Durch Druckvariation konnte ein kritischer Mizellendruck von ca. 46,7 MPa bei einer Temperatur von 338 K im Experiment bestätigt werden, der gefundene Rh liegt bei ca. 34 nm. Dagegen setzt die Aggregation bei einer PS-b-PDMS (9/27)/Styrol/CO2,SC- Mischung bei einem wesentlich niedrigeren Druck ein. Durch Druckvariation zwischen 38 MPa und 45,7 MPa wurde eine Größenänderung der Mizellen beobachtet. Durch zeitabhängige-DLS-Messungen am gleichen System bei einem bestimmten Druck wurde ein langsames Schrumpfen der Mizellen gefunden. Um den Einfluß der Blockgröße der verwendeten Amphiphile auf die Mizellenbildung zu untersuchen wurde das System PS-b-PDMS(6/37)/Styrol/CO2,SC mit Hilfe der DLS im Bereich zwischen 39,4 MPa und 43,1 MPa untersucht. Die Druckänderung zeigte für Rh ein nahezu invariantes Verhalten, daß durch eine verlängerte PDMS-Blocklänge und eine damit verbundene Kompensation der verschiedenen Wechselwirkungskräfte zwischen Mizellenkern, -hülle und CO2,SC erklärt werden kann. Im System PS-b-PDMS(6/16)/Styrol/CO2,SC konnte experimentell mit Hilfe der DLS erst nach einer ver-änderten molaren Zusammensetzung eine Mizellenbildung ab 40 MPa ermöglicht werden. Allerdings ändert sich auch in diesem System der hydrodynamische Radius ebenfalls mit dem Druck. Je nach Druck-, Temperatur- und molarer Zusammensetzung variiert die Tendenz der Systeme, Mizellen zu bilden die eine Emulsion stabilisieren können. Für die in Dispersions-Polymerisationsreaktionen eingesetzten Diblockcopolymere bedeutet dieses Ergebnis differenzierte Applikationsmöglichkeiten. Mit den ermittelten Konzentrationsverhältnissen an Amphiphil und Monomer konnte ein Bereich gefunden werden, in dem die thermodynamischen Bedingungen für die Mizellenbildung einerseits und die Vorraussetzungen für die DLS andererseits gegeben sind.

Anisotrope Kolloide aus flüssigkristallinen Polymeren

In dieser Arbeit wird die Synthese, Charakterisierung und Manipulation anisotroper Kolloide aus flüssigkristallinen Polymeren beschrieben. Um Kolloide verschiedener Größe und aus verschiedenen Polymeren zu erhalten, wurden verschiedene Techniken verwendet. Einerseits wurden Kolloide aus nematischen und smektischen Polymeren mit Durchmessern meist im Bereich von 0,5 bis 3,5 Mikrometern hergestellt. Dazu wurden 16 verschiedene Acrylat- und Methacrylatmonomere synthetisiert und mittels Dispersionspolymerisation polymerisiert. Durch Variation der Polymerisationsbedingungen wurden Kolloide verschiedener Größe und Polydispersität erhalten. Durch Saatpolymerisation konnten zudem die Kugelgrößen bei gleichbleibend geringer Polydispersität erhöht werden. Polarisationsmikroskopie zeigt, dass die meisten Kolloide mit einer Größe zwischen ca. 2 bis 4 Mikrometern eine bipolare Direktorkonfiguration haben. Einige dieser Kolloide wurden mit einer optischen Pinzette mit zirkular polarisiertem Licht eingefangen und rotiert. Zum anderen wurden verschiedene flüssigkristalline Polymere (Polysiloxane, Hauptkettenpolymere und Polyacrylate) durch den Miniemulsionsprozess in Kolloide mit Durchmessern im Bereich von ca. 50 bis 300 nm überführt. Durch Variation der Emulgator- und Polymermenge sowie der Art des Emulgators konnte die Kugelgröße beeinflusst werden. Für die Polysiloxankolloide erfolgte die Aufklärung ihrer inneren Struktur mittels TEM und Kryo-TEM, da durch das Silizium im Polymerrückgrat ohne zusätzliches Anfärben ein Kontrast vorhanden ist. Die TEM-Aufnahmen zeigen deutlich die smektische Schichtstruktur innerhalb der Kolloide aus „verdünnten“ Copolysiloxanen und sind somit der erste direkte Beweis für die Mikrophasenseparation zwischen den Mesogenen und Polysiloxanketten, die bisher basierend auf Röntgenmessungen nur indirekt vorhergesagt wurde. Für die Copolysiloxane mit 2-Ring-Mesogenen wurden zwiebelartige Strukturen und für die Copolysiloxane mit 3-Ring-Mesogenen parallele Schichtstrukturen gefunden. Im ersten Fall folgt die smektische Schichtstruktur der Kugelsymmetrie des Kolloids, im zweiten Fall dominiert die Tendenz der smektischen Schichten, sich parallel anzuordnen.

Anisotrope Kolloide aus flüssigkristallinen Polymeren

In dieser Arbeit wurden Kolloide aus flüssigkristallinen Polymeren dargestellt und untersucht.rnrnDie Methode der Dispersionspolymerisation zur Darstellung von Kolloiden aus flüssigkristallinen Polyacrylaten wurde in unpolare Lösungsmittel adaptiert, umrneine Manipulierbarkeit anisotroper Kolloide durch elektrische Felder zu erreichen.rnDazu wurden ein Gemisch aus THF und Siliconöl als Reaktionsmischung gewähltrnund polysiloxanbasierte Polymere und Copolymere als Stabilisatoren eingesetzt.rnDabei auftretende unerwartete Auswirkungen auf die Mesogenkonfiguration führtenrnzu einer Untersuchung der Abhängigkeit der Mesogenkonfigurationen von der Oberflächenverankerung der Mesogene. Schließlich wurde eine Kontrolle derrnOberfl¨achenverankerung der Mesogene und somit eine Kontrolle der Mesogenkonfigurationen unter Ausnutzung der Eigenschaften flüssigkristallin/nicht flüssigkristalliner Blockcopolymere erreicht. Zu diesem Zweck wurde auch ein neuer Makroinitiator entwickelt. Kleine Kolloide konnten mittels eines elektrischen Feldes gedreht bzw. zu Linien angeordnet werden.rnrnEinige neue Polysiloxane wurden zum Einbau in flüssigkristalline Kolloide viarnMiniemulsion synthetisiert. Sie wurden charakterisiert und in Kolloide überführt. Aufgrund zu hoher Übergangstemperaturen konnten bei den meisten jedoch keine Strukturen aus phasenseparierten Polysiloxane gefunden werden. Die Ausbildung der Strukturen in solchen Kolloiden konnte aber trotzdem verstanden werden.rnrnAus vernetzten Hauptkettenpolymeren sollten aktuierende Kolloide hergestelltrnwerden. Dazu wurde das entsprechende Hauptkettenpolymer hergestellt, charakterisiert und per Miniemulsion in Kolloide überführt. Die dargestellten Kolloide wurden unter dem TEM geheizt und zeigten Formänderungen, die jedoch nicht kontrolliert und noch irreversibel waren.

Uptake mechanism, intracellular trafficking and endo-lysosomal pH monitoring of polystyrene nanoparticles

What is the intracellular fate of nanoparticles (NPs) taken up by the cells? This question has been investigated for polystyrene NPs of different sizes with a set of molecular biological and biophysical techniques.rnTwo sets of fluorescent NPs, cationic and non-ionic, were synthesized with three different polymerization techniques. Non-ionic particles (132 – 846 nm) were synthesized with dispersion polymerization in an ethanol/water solution. Cationic NPs with 120 nm were synthesized by miniemulsion polymerization Particles with 208, 267 and 603 nm were produced by seeding the 120 nm particle obtained by miniemulsion polymerization with drop-wise added monomer and polymerization of such. The colloidal characterization of all particles showed a comparable amount of the surface groups. In addition, particles were characterized with regard to their size, morphology, solid content, amount of incorporated fluorescent dye and zeta potential. The fluorescent intensities of all particles were measured by fluorescence spectroscopy for calibration in further cellular experiments. rnThe uptake of the NPs to HeLa cells after 1 – 24 h revealed a much higher uptake of cationic NPs in comparison to non-ionic NPs. If the same amount of NPs with different sizes is introduced to the cell, a different amount of particles is present in the cell medium, which complicates a comparison of the uptake. The same conclusion is valid for the particles’ overall surface area. Therefore, HeLa cells were incubated with the same concentration, amount and surface area of NPs. It was found that with the same concentration always the same polymer amount is taking up by cells. However, the amount of particles taken up decreases for the biggest. A correlation to the surface area could not be found. We conclude that particles are endocytosed by an excavator-shovel like mechanism, which does not distinguish between different sizes, but is only dependent on the volume that is taken up. For the decreased amount of large particles, an overload of this mechanism was assumed, which leads to a decrease in the uptake. rnThe participation of specific endocytotic processes has been determined by the use of pharmacological inhibitors, immunocytological staining and immunofluorescence. The uptake of NPs into the endo-lysosomal machinery is dominated by a caveolin-mediated endocytosis. Other pathways, which include macropinocytosis and a dynamin-dependent mechanism but exclude clathrin mediated endocytosis, also occur as competing processes. All particles can be found to some extent in early endosomes, but only bigger particles were proven to localize in late endosomes. No particles were found in lysosomes; at least not in lysosomes that are labeled with Lamp1 and cathepsin D. However, based on the character of the performed experiment, a localization of particles in lysosomes cannot be excluded.rnDuring their ripening process, vesicles undergo a gradual acidification from early over late endosomes to lysosomes. It is hypothesized that NPs in endo-lysosomal compartments experience the same change in pH value. To probe the environmental pH of NPs after endocytosis, the pH-sensitive dye SNARF-4F was grafted onto amino functionalized polystyrene NPs. The pH value is a ratio function of the two emission wavelengths of the protonated and deprotonated form of the dye and is hence independent of concentration changes. The particles were synthesized by the aforementioned miniemulsion polymerization with the addition of the amino functionalized copolymer AEMH. The immobilization of SNARF-4F was performed by an EDC-coupling reaction. The amount of physically adsorbed dye in comparison to covalently bonded dye was 15% as determined by precipitation of the NPs in methanol, which is a very good solvent for SNARF-4F. To determine influences of cellular proteins on the fluorescence properties, a intracellular calibration fit was established with platereader measurements and cLSM imaging by the cell-penetrable SNARF-4F AM ester. Ionophores equilibrated the extracellular and intracellular pH.rnSNARF-4F NPs were taken up well by HeLa cells and showed no toxic effects. The pH environment of SNARF-4F NPs has been qualitatively imaged as a movie over a time period up to 1 h in pseudo-colors by a self-written automated batch program. Quantification revealed an acidification process until pH value of 4.5 over 24 h, which is much slower than the transport of nutrients to lysosomes. NPs are present in early endosomes after min. 1 h, in late endosomes at approx. 8 h and end up in vesicles with a pH value typical for lysosomes after > 24 h. We therefore assume that NPs bear a unique endocytotic mechanism, at least with regards to the kinetic involvedrn

Synthesis and characterization of dual-functionalized core-shell fluorescent microspheres for bioconjugation and cellular delivery

The efficient transport of micron-sized beads into cells, via a non-endocytosis mediated mechanism, has only recently been described. As such there is considerable scope for optimization and exploitation of this procedure to enable imaging and sensing applications to be realized. Herein, we report the design, synthesis and characterization of fluorescent microsphere-based cellular delivery agents that can also carry biological cargoes. These core-shell polymer microspheres possess two distinct chemical environments; the core is hydrophobic and can be labeled with fluorescent dye, to permit visual tracking of the microsphere during and after cellular delivery, whilst the outer shell renders the external surfaces of the microspheres hydrophilic, thus facilitating both bioconjugation and cellular compatibility. Cross-linked core particles were prepared in a dispersion polymerization reaction employing styrene, divinylbenzene and a thiol-functionalized co-monomer. These core particles were then shelled in a seeded emulsion polymerization reaction, employing styrene, divinylbenzene and methacrylic acid, to generate orthogonally functionalized core-shell microspheres which were internally labeled via the core thiol moieties through reaction with a thiol reactive dye (DY630-maleimide). Following internal labeling, bioconjugation of green fluorescent protein (GFP) to their carboxyl-functionalized surfaces was successfully accomplished using standard coupling protocols. The resultant dual-labeled microspheres were visualized by both of the fully resolvable fluorescence emissions of their cores (DY630) and shells (GFP). In vitro cellular uptake of these microspheres by HeLa cells was demonstrated conventionally by fluorescence-based flow cytometry, whilst MTT assays demonstrated that 92% of HeLa cells remained viable after uptake. Due to their size and surface functionalities, these far-red-labeled microspheres are ideal candidates for in vitro, cellular delivery of proteins, as described in the accompanying paper.

High-voltage insulation organic-inorganic nanocomposites by plasma polymerization

In organic-inorganic nanocomposites, interfacial regions are primarily influenced by the dispersion uniformity of nanoparticles and the strength of interfacial bonds between the nanoparticles and the polymer matrix. The insulating performance of organic-inorganic dielectric nanocomposites is highly influenced by the characteristics of interfacial regions. In this study, we prepare polyethylene oxide (PEO)-like functional layers on silica nanoparticles through plasma polymerization. Epoxy resin/silica nanocomposites are subsequently synthesized with these plasma-polymerized nanoparticles. It is found that plasma at a low power (i.e., 10 W) can significantly increase the concentration of C-O bonds on the surface of silica nanoparticles. This plasma polymerized thin layer can not only improve the dispersion uniformity by increasing the hydrophilicity of the nanoparticles, but also provide anchoring sites to enable the formation of covalent bonds between the organic and inorganic phases. Furthermore, electrical tests reveal improved electrical treeing resistance and decreased dielectric constant of the synthesized nanocomposites, while the dielectric loss of the nanocomposites remains unchanged as compared to the pure epoxy resin.

An investigation on the dispersion of montmorillonite (MMT) primary particles in PP matrix

A novel path of preparing PP/o-MMT nanocomposites, which pay attention to the breaking up of MMT original agglomerates and dispersing of its primary particles, rather than the intercalation or exfoliation degree of o-MMT, was reported. The method of predispersing the o-MMT particles into a polar poly(vinyl alcohol) (PVA) matrix and then melt blending the pre-treated PVA/o-MMT hybrids with PP was studied. 3-isopropenyl-alpha,alpha-dimethylbenzene-isocyanate (TMI) was used as a modifier of PVA to improve the compatibility between PVA and PP matrix. Pre-disperse o-MMT with TMI modified PVA was proved to be an effective way to get a composite with fine o-MMT particles dispersion. But the method, which is pre-dispersing o-MMT with non modified PVA and then using TMI to modify such PVA/o-MMT hybrid, would largely reduce the reaction degree between TMI and PVA because of the relatively lower reaction temperature. Although the latter method also can obtain finer dispersion composites than that with using PP-g-MAH as compatibilizer, the relatively higher degradation degree of PP matrix in this method will limit the use of this nanocomposite.

Synthesis and characterization of polyethylene/clay-silica nanocomposites: A montmorillonite/silica-hybrid-supported catalyst and in situ polymerization

A novel approach to the preparation of polyethylene (PE) nanocomposites, with montmorillonite/silica hybrid (MT-Si) supported catalyst, was developed. MT-Si was prepared by depositing silica nanoparticles between galleries of the MT. A common zirconocene catalyst [bis(cyclopentadienyl)zirconium dichloride/methylaluminoxane] was fixed on the MT-Si surface by a simple method. After ethylene polymerization, two classes of nanofillers (clay layers and silica nanoparticles) were dispersed concurrently in the PE matrix and PE/clay-silica nanocomposites were obtained. Exfoliation of the clay layers and dispersion of the silica nanoparticles were examined with transmission electron microscopy. Physical properties of the nanocomposites were characterized by tensile tests, dynamic mechanical analysis, and DSC. The nanocomposites with a low nanofiller loading (<10 wt %) exhibited good mechanical properties. The nanocomposite powder produced with the supported catalyst had a granular morphology and a high bulk density, typical of a heterogeneous catalyst system.