Search results for "polymerization"

Effect of bulkiness and lewis acidity of aluminium compounds on the anionic polymerization of methyl methacrylate in toluene

1996

The bulkiness and the Lewis acidity of added aluminium compounds strongly affect the polymerization of methyl methacrylate in toluene at −78°C. The polymerization strongly deviates from ‘ideal’ first-order kinetics, i.e. the first-order time-conversion plots are kinked at low monomer conversions. Additionally, for the more bulky and more Lewis-acid aluminium alkyls, the time-conversion plots show a further downward curvature. This curvature is not the result of a termination reaction because the polymers are free of side products like β-ketoesters or vinyl ketone units. The molecular weight distributions and tacticities of the resulting polymers are also affected. Dependent on the aluminium…

Polydimethylsiloxanes with amylose side chains by enzymatic polymerization

1996

Maltoheptaonamide modified polydimethylsiloxane was prepared applying a simplified synthetic pathway in the derivatization sequence of the carbohydrate. The products were characterized by 13C NMR and FT-IR spectroscopy. The glucan side chains of these “sweet siloxanes” were elongated by enzymatic catalysis with potato phosphorylase.

Aliphatic Polyethers: Classical Polymers for the 21st Century.

2015

Polyethers-polymers with the structural element (R'-O-R)n in their backbone--are an old class of polymers which were already used at the time of the ancient Egyptians. However, still today these materials are highly important with applications in all areas of our life, reaching from the automotive and paper industry to cosmetics and biomedical applications. In this Review, different aliphatic polyethers like poly(epoxide)s, poly(oxetane)s, and poly(tetrahydrofuran) are discussed. Special emphasis is placed on the history, the polymerization techniques (industrially and in academia), the properties, the applications as well as recent developments of these materials.

Oligo(glycerol) Methacrylate Macromonomers

2011

Linear, protected ω-methoxy oligo(glycerol) methacrylate (OGly(P)MA) macromonomers are synthesized via anionic ring-opening polymerization of ethoxyethyl glycidyl ether (EEGE) followed by termination with methacrylic acid anhydride (DP(n) = 3-11, PDI < 1.30). The covalently bound methacrylate moiety allows the homopolymerization of OGly(P)MA as well as copolymerization with low molecular weight comonomers. In homopolymerizations, macromonomers are polymerized by atom transfer radical polymerization (ATRP) yielding well-defined graft polymers (M(n) = 20,000-30,000 g mol(-1)). Acidic hydrolysis of the protecting groups releases water-soluble polyhydroxy-functional structures. First results on…

Well-defined carbohydrate-based polymers in calcium carbonate crystallization: Influence of stereochemistry in the polymer side chain on polymorphism…

2015

Abstract In this work we demonstrate the remarkable phase control on the crystallization of calcium carbonate by the stereochemistry of carbohydrate-based polymers. The polymers (poly(2-(2,3,4,6-tetra-O-acetyl-β- d -glucosyloxy)ethyl methacrylate) and poly(2-(2,3,4,6-tetra-O-acetyl-β- d -galactosyloxy)ethyl methacrylate)) have been synthesized from the respective glucose or galactose containing monomers (3 step synthesis) by RAFT polymerization leading to well-defined carbohydrate-based polymers with number averages of the molecular weights (Mw) of 10,000–18,000 g/mol and a dispersities (Đ) from 1.1 to 1.2. For the deprotected polymers we found differences in the phase selection of calcium …

Block and graft copolymers of 2-oxazolines

1994

The cationic ring-opening polymerization of 2-oxazolines is known to be initiated by alkyl halides, Lewis acids and esters of strong acids. The polymerization proceeds by a living mechanism. Numerous block and graft copolymers have already been described. Recently it was found that chloroformates (R-O-CO-CI) are also useful initiators. The mechanism of the initiation and propagation is discussed. This type of initiators allows the synthesis of different novel two-block and three-block copolymers, star-shape polymers, and a graft copolymer with a polyvinylacetate backbone.

Isobornyl Methacrylate as a Reactive Solvent of Polyethylene

2004

Solutions containing 15 wt, -% of a low-molar-mass polyethylene (PE) in isobornyl methacrylate (IBoMA), containing 0, 5 or 10 wt.-% of 1,4 butanediol dimethacrylate (BDDMA) as crosslinker, were polymerized using either benzoyl peroxide (BPO), at 80°C, or dicumyl peroxide (DCPO), with a thermal cycle attaining 150°C, as initiators. Phase separation of an amorphous PE-rich phase took place when carrying out the reaction at temperatures higher than the PE melting temperature. Partial crystallization of PE was observed when cooling to room temperature. Depending on the initial amount of BDDMA, the fraction of PE that was phase separated varied between 57 and 66% of the initial amount, with crys…

Preparation of Soft Microactuators in a Continuous Flow Synthesis Using a Liquid-Crystalline Polymer Crosslinker

2012

We present the synthesis of a polymeric liquid crystalline (LC) crosslinker and its usage in the preparation of soft microactuators. The microactuators, composed of thermoresponsive liquid crystalline elastomers (LCE), are fabricated in a microfl uidic device in a continuous “on the fl y” process. The LC polymer crosslinker is miscible with the LC monomer and provides for a rapid polymerization and crosslinking. Most importantly, it promotes an enantiotropic mesophase of the mobile monomer phase, which is not provided by conventional nonmesogenic crosslinkers. This allows an isothermal handling inside the microfl uidic setup. Temperature-driven shape changes up to 65% could be achieved by j…

Derivatization of Plasma Polymerized Thin Films and Attachment of Biomolecules to Influence HUVEC-Cell Adhesion

2011

Synthesis and Characterization of Syndiotactic Polystyrene-Polyethylene Block Copolymer

2019

The direct synthesis of syndiotactic polystyrene-block-polyethylene copolymer (sPS-b-PE) with a diblock structure has been achieved. The synthetic strategy consists of the sequential stereocontrolled polymerization of styrene and ethylene in the presence of a single catalytic system: cyclopentadienyltitanium(IV) trichloride activated by modified methylaluminoxane (CpTiCl3/MMAO). The reaction conditions suitable for affording the partially living polymerization of these monomers were identified, and the resulting copolymer, purified from contaminant homopolymers, was fully characterized. Gel permeation chromatography coupled with two-dimensional NMR spectroscopy COSY, HSQC, and DOSY confirme…