Search results for "End-group"

Nanoparticles Built of Cross-Linked Heterotelechelic, Amphiphilic Poly(dimethylsiloxane)-b-poly(ethylene oxide) Diblock Copolymers

2000

Novel short chain α,ω-heterotelechelic amphiphilic poly(dimethylsiloxane)-b-poly(ethylene oxide) diblock copolymers (PDMS−PEO) with total molecular weights below 10 000 g/mol are synthesized, characterized, and used as basic constituent parts for functionalized nanoparticles. The self-assembly of the amphiphilic diblock copolymer in water as a solvent selective for the PEO block leads to the formation of spherical and cylindrical micellar structures with diameters between 10 and 25 nm. The core of the micelles is built of the hydrophobic PDMS chains, whereas the corona is set up by the hydrophilic PEO blocks. By using α,ω-heterotelechelic diblock copolymers, it is possible to fix the core o…

High molecular arborescent polyoxyethylene with hydroxyl containing shell

2004

Abstract Arborescent polyoxyethylene of high molar mass (2×10 5  g/mol) and narrow molar mass distribution was synthesized in a three-stage process. In the first stage a triblock copolymer of ethylene oxide (central block, DP ca. 90) and 2,3-epoxypropanol-1 (short flanking blocks, DP ca. 5) was synthesized. The potassium alcoholate derived from this copolymer was used to initiate the polymerization of ethylene oxide and the subsequent addition of protected glycidol (1-etoxyethyl glycidyl ether). After deprotection the short polyglycidol blocks were used as branching units for the next generation. Repeated step by step process leads to the ‘pom-pom like’ branched polyoxyethylene macromolecul…

Cylindrical Polypeptide Brushes

2005

Cylindrical brushes with poly(L-lysine) and poly(L-glutamate) side chains were prepared by grafting through and grafting from techniques. Grafting from is shown to be more successful for the synthesis of cylindrical brushes with high molar mass main and side chains.

Hyperbranched poly(glycolide) copolymers with glycerol branching points via ring-opening copolymerization

2015

Abstract Sn(Oct) 2 -catalyzed synthesis of hyperbranched poly(glycolide) copolymers with glycerol branching points in the backbone is possible via ring-opening multi-branching copolymerization (ROMBP) of glycolide and 5HDON (5-hydroxymethyl-1,4-dioxan-2-one). Using this strategy, well-defined and soluble branched polyesters with apparent molecular weights (M n ) in the range of 1300–2000 g mol −1 and varying comonomer content (5HDON/glycolide = 30:70–70:30) were obtained. 2D NMR spectroscopy, thermal analysis and MALDI-TOF mass spectrometry confirmed the successful incorporation of both monomers and the resulting branched structure. Multiple end group functionality offers the possibility fo…

The glass transition of mixtures of polystyrene with alkyl-terminated oligostyrene — experimental evidence for microphase separation in a polymer ble…

1995

Mixtures of high molecular weight polystyrene (P n = 961.5 ; T g = 373 K) and sec-butyl-terminated oligostyrene (P n = 10.6 ; T g = 302 K) show a dependence of the glass transition on the composition (i.e., number-average molecular weight) which cannot be described by the classic equations of Fox & Flory or Kanig & Ueberreiter. Addition of small amounts of the oligostyrene strongly decreases the glass transition, and above an oligomer content of 40 wt.-% the glass transition remains constant within experimental error. This behavior can be attributed to the unfavorable interactions between the alkyl-terminated oligomer and the high molecular weight PS. As a result the oligomer is a bad solve…

An All-ROMP Route to Graft Copolymers

2007

A new versatile synthesis strategy for macromonomers has been developed that uses the living ring-opening metathesis polymerization (ROMP) with commercial Grubbs first generation ruthenium initiators. Homopolymers as well as diblock copolymers were end-functionalized with norbornene derivatives to serve as macromonomers. The graft copolymerization of the macromonomers was also carried out employing ROMP. Well-defined and highly functional graft copolymers are accessible by this new synthetic route.

Characterization of blends with polyamide 6 and ethylene acrylic acid copolymers at different acrylic acid content

2002

In this work the morphological, calorimetric, rheological and mechanical behaviour and fourier transmission infrared analysis of blends made with polyamide 6 (PA6) and ethylene acrylic acid copolymers (EAA) containing different amount of acrylic acid were investigated. The results observed from the sample characterizations evidenced as acrylic acid cause a compatibilizing effect between polyethylene and polyamide components with modifications of blends morphology and mechanical behaviour. These effects are enhanced with increase of the acrylic acid content in the copolymer and they were attributed generally to hydrogen bond interactions among the acrylic acid group and the functional groups…

Cyclodextrins in Polymer Synthesis:  Free-Radical Polymerization of Methylated β-Cyclodextrin Complexes of Methyl Methacrylate and Styrene Controlled…

2000

Vergleich der zahl aktiver zentren und einiger kinetischer konstanten bei der polymerisation von äthylen, propylen und buten-1 mit ZIEGLER-NATTA-kata…

1972

Fur die drei Olefine, Athylen, Propylen und Buten-1, werden mit dem Katalysatorsystem TiCl3/Al(C2H5)2Cl in Abhangigkeit von der Polymerisationszeit gemessen: der Polymerisationsverlauf, die Zahl der Metall-Polymer-Bindungen (uber Endgruppenbestimmung nach Abbruch mit tritiiertem Alkohol) und die Viskositat der gebildeten Polymeren. Aus diesen Daten lassen sich die Polymerisationsgeschwindigkeit, die Konzentration an aktiven Zentren, die Uneinheitlichkeit sowie weitere Reaktionskonstanten bestimmen. Die Ergebnisse werden diskutiert; sie lassen den Schlus zu, das sich ein im Ausgangszustand gleiches Katalysatorsystem monomerspezifisch verhalt und verandert. With the catalytic system TiCl3/Al(…

Can Hyperbranched Polymers Entangle? Effect of Hydrogen Bonding on Entanglement Transition and Thermorheological Properties of Hyperbranched Polyglyc…

2016

Melt rheology and thermal phase transition of a series of hyperbranched polyglycerol samples (hbPG) (DB ≈ 60%) in a broad molecular weight range (Mn = 600–440 000 g/mol) were investigated and correlated to both molecular weight and nature of the end group (hydroxyl vs permethylated and trimethylsilylated). The well-characterized and defined flexible polyethers are particularly suitable to shed light on the linear viscoelastic behavior with respect to (i) hyperbranched topology and (ii) hydrogen bond interactions, particularly in comparison to the perfectly linear polyglycerol counterparts studied recently [Osterwinter, C.; Macromolecules 2015, 48, 119−130]. We present a detailed examination…