Search results for "anion"

Ferrocenyl-functionalized long chain branched polydienes

2009

A convenient two-step approach for the synthesis of ferrocenyl-functionalized long chain branched polydienes, based on both butadiene and isoprene, respectively, is presented. Classical living anionic polymerization was used to synthesize different AB n type poly(diene) macromonomers with moderate molecular weights between 1700 and 3200 g/mol and narrow polydispersity. Quantitative end-capping with chlorodimethylsilane resulted in the desired AB n macromonomer structures. In the ensuing Pt-catalyzed hydrosilylation polyaddition, branched, functionalized polydienes were obtained by a concurrent AB n + AR type of copolymerization with mono-and difunctional ferrocenyl silanes (fcSiMe 2 H or fc…

1971

The anionic polymerization of β-propiolactone at 25°C in ethanol initiated by the betain was investigated. Macrozwitterions of the structure were produced, n being intentionally as low as ca. 11. The structure of the product was proven by the nitrogen content of the reprecipiated polymer, by IR and NMR spectroscopy and by titration of the carboxylate endgroups. Some carboxylic acid endgroups were formed by chain transfer with the solvent ethanol. The positive charge at the polymer chain was proven by electrophoresis of polymer after esterification of the carboxylate chain end. Furthermore the dielectric constant of dilute solutions of the polymer in CHCl3 was determined and is discussed. Th…

Synthetic approaches towards new polymer systems by the combination of living carbocationic and anionic polymerizations

1996

This study summarizes recent efforts to obtain by combination of living carbocationic and anionic polymerizations block copolymers which are potential precursors for building new well-defined polymeric architectures with microphase separated morphology. Living carbocationic polymerization (LCCP) yields telechelic polyisobutylene (PIB) chains with a variety of useful endgroups, such as tert-chlorine, isopropenyl, primary hydroxyl, tolyl etc. When tolyl-ended PIB was used as precursor for macroinitiator of living anionic polymerization of 2-(tert-butyldimethylsilyloxy)ethyl methacrylate (tBuMe2SiOEMA), mixtures of homopolymers and block copolymers were formed due to incomplete lithiation of t…

1976

A number of acryl and methacryl derivatives of different sulfanilamides (1a—I) were prepared and polymerized. The fixation of the sulfonamide to the polymerizable group was carried out directly, using the acryl- and methacrylamides, and by means of spacer groups, to favour the enzymatic or hydrolytic release of the drug moiety. Selected sulfonamide types of different pKA values were used, and the pH-dependant solubility of the corresponding polymers was studied. The monomeric acryloyl and methacryloyl sulfonamides were homopolymerized radically by AIBN. For distribution studies polysulfadiazineacrylamide, 14C-labelled in the main chain (2e'), was synthesized. Copolymerization with 2-methyls…

ChemInform Abstract: Diastereodivergent Synthesis of Fluorinated Cyclic β3-Amino Acid Derivatives.

2016

The ability of 2-p-tolylbenzyl carbanions to behave as a source of chiral benzylic nucleophiles has been shown in its reaction with fluorinated imines. The process takes place with high levels of stereocontrol, rendering the corresponding amines as single diastereoisomers. Subsequent cross-metathesis followed by intramolecular aza-Michael reaction makes the synthesis of fluorinated homoproline derivatives bearing three stereogenic centers possible. Furthermore, the selectivity of the cyclization process can easily be tuned up in a diastereodivergent manner simply by changing the reaction conditions.

Ylide als polymerisationsinitiatoren. I. Salzhaltige und salzfreie phosphoniumylide

1972

Phosphorylide, R3PCHX und R3PCH2·LiBr, konnen eine anionische Polymerisation von Vinylmonomeren starten. Dabei werden im Falle des Methacrylnitrils und des Methylmethacrylats die Ylide als Endgruppen in die Polymeren eingebaut. Bei den salzfreien Yliden hangt die Startwirksamkeit von der Basizitat des Ylidcarbanions ab, die Struktur dieser Ylide hat aber keinen mesbaren Einflus auf das Molekulargewicht und die Taktizitat der entstehenden Polymeren. Im Gegensatz dazu wird bei der Initiierung mit den salzhaltigen Yliden auch die Taktizitat der Polymeren von den Substituenten der Phosphorylide beeinflust. Phosphorous ylids, R3PCHX and R3PCH2·LiBr, are able to start an anionic polymerization of…

1981

1991

Telechelic α,ω-macrozwitterions — narrowly distributed polystyrene chains oppositely charged at each end — were synthesized via anionic polymerization using direct functionalization with the initiator and the termination agent. The resulting products were purified (zwitterion content ≥ 0,95) and characterized with gel permeation chromatography, viscometry, static and dynamic light scattering and small-angle neutron scattering. In unpolar solvents as toluene, the polymeric zwitterions form clusters with molecular weights depending on concentration. In the dilute case, the clusters are relatively small and consist of approximately 8 zwitterions. The structure of these clusters is discussed by…

ChemInform Abstract: Multifunctional Poly(ethylene glycol)s

2011

In the rapidly evolving multidisciplinary field of polymer therapeutics, tailored polymer structures represent the key constituent to explore and harvest the potential of bioactive macromolecular hybrid structures. In light of the recent developments for anticancer drug conjugates, multifunctional polymers are becoming ever more relevant as drug carriers. However, the potentially best suited polymer, poly(ethylene glycol) (PEG), is unfavorable owing to its limited functionality. Therefore, multifunctional linear copolymers (mf-PEGs) based on ethylene oxide (EO) and appropriate epoxide comonomers are attracting increased attention. Precisely engineered via living anionic polymerization and d…

Electrochemical production of initiators for polymerization processes

2007

The most important technological interest in initiator production lies, in the electrosynthesis of complex catalytic systems, i. e. coordination compounds and Ziegler-Natta catalysts, although the choice of olefins to be polymerized with these electrosynthesized complexes is still limited to ethylene and to very few other monomers.