Search results for "polymers"
showing 10 items of 3567 documents
Structural variations in amphiphiles: Discoidal multivalent cations
1986
Fourteen cationic multipolar amphiphiles have been synthesized with pyridinium or trimethylammonium head groups. The hydrophobic cores are planar ring systems (benzene or triphenylene) to which two, three, four, or six decylene or undecylene alkyl chains are attached by ester linkages. The hydrophilic head groups are bound to the outer ends of the alkyl chains.
Electrically conductive TCNQ complexes of aromatic ionenes
1995
New types of complex salts of 7,7',8,8'-tetracyanoquinodimethane with aromatic ionenes and their model compounds were prepared. The electrical conductivity and the activation energy were measured and discussed in relation to their structure. The effects of the nature of the aromatic unit, and the flexibility and rigidity of the polymer backbone were compared with the corresponding model compounds. The effects of frequency and temperature are discussed in terms of the molecular structure of the complex. The electroconductivity at room temperature of the 1 :1 polymer complex salts was found to be between 2 x 10 -4 and 7 x 10 -5 S/cm, while that of the model complex salts was between 1.3 x 10 …
Oxidation-responsive polyether block copolymers lead to non-ionic polymer surfactants with multiple amine N-oxides
2019
Block copolymers consisting of a nonpolar poly(propylene oxide) block and a poly(glycidyl amine) block were prepared by anionic ring-opening polymerization (AROP). The tertiary amine groups of the block copolymers were quantitively transformed into the corresponding zwitterionic amine N-oxides, as confirmed by 1H NMR and 15N NMR spectroscopy. This leads to strongly amphiphilic polyether block copolymers with multiple N-oxides. Full oxidation of the amine groups was also possible in situ in an emulsion, demonstrating the oxidation-responsive character of this new class of non-ionic polymeric surfactants.
The anionic copolymerization of 5-(N,N-diisopropylamino)isoprene with styrene
1995
The anionic copolymerization of 5-(N,N-diisopropylamino)isoprene (N,N-diisopropyl-2-vinylallylamine) and styrene initiated with alkyllithium compounds is studied. Copolymers obtained from different compositions are characterized by size-exclusion chromatography (SEC), differential scanning calorimetry and by 1 H NMR and 13 C NMR spectroscopy. Under these conditions the dialkylaminoisoprene, similar to butadiene and isoprene, is more reactive than styrene and is incorporated faster into the polymer backbone. The incomplete conversion of the monomers has been attributed to the formation of intra-or intermolecular complexes between the Li + counterion at the chain end and amino groups. Because…
ABA Triblock Copolymers Based on Linear Poly(oxymethylene) and Hyperbranched Poly(glycerol): Combining Polyacetals and Polyethers
2013
The synthesis of hyperbranched-linear-hyperbranched ABA triblock copolymers based on a linear poly(oxymethylene) (POM) block and hyperbranched poly(glycerol) (hbPG) blocks is described. The polymers containing a polyacetal polyether structure were prepared from linear bishydroxy-functional POM macroinitiators, obtained by cationic ring-opening polymerization of trioxane and 1,3-dioxolane as a comonomer with formic acid as a transfer agent and subsequent hydrolysis of the formate group. Partial deprotonation of the resulting hydroxyl groups permitted “hypergrafting” of glycidol by anionic ring-opening multibranching polymerization (ROMBP). With respect to the hyperbranched blocks, the obtain…
Oxidative oligomerization of cyclodextrin-complexed bifunctional phenols catalyzed by horseradish peroxidase in water
2000
The HRP-catalyzed oligomerization of hydrophobic bifunctional phenols in water was realized by the use of 2,6-di-O-methylated β-cyclodextrin. The molecular weights of the resulting oligomers were in the same region as they were reached by conventional HRP-catalyzed oligomerizations in water/dioxane-mixtures. The polymerizable moieties, maleimide and methacrylamide, were not affected during the oligomerization process, as proofed by NMR, MALDI-TOF and FT-IR measurements. It was therefore possible to get soluble functionalized oligomers, which were crosslinked via radical copolymerization with suitable components (styrene, MMA) or heating.
Evaluation of mucoadhesive properties of α,β-poly(N-hydroxyethyl)-dl-aspartamide and α,β-poly(aspartylhydrazide) using ATR–FTIR spectroscopy
2002
Abstract The mucoadhesive properties of α,β poly( N -hydroxyethyl)- dl -aspartamide (PHEA) and α,β-polyaspartylhydrazide (PAHy) have been investigated using attenuated total reflection infrared (ATR–FTIR) spectroscopy. In particular, films based on these polymers have been contacted with a mucin solution at pH 7 and, the interfacial interaction and interpenetration between the glycoprotein and PHEA or PAHy have been studied by analysing the ATR–FTIR spectra. A diffusion model using a solution of Ficks' second law has been employed to determine the diffusion coefficient of water into polymeric films as a consequence of interdiffusion which occurs at the polymer film/mucin solution interface.
Epifluorescence microscopy studies of fatty acid monolayers: Domain formation induced by polymeric gegenions
1991
The monolayer behavior of long-chain fatty acids at the air/water interface on a poly(ethyleneimine) containing subphase was investigated. The interaction of the polymeric gegenions in the subphase leads to expanded states and permits the visualization of the aggregation behavior of different long-chain fatty acids via fluorescence microscopy. The monolayer morphologies and their variability were intensively studied by fluorescence microscopy. In addition, the transfer of the complexed fatty acid monolayers to solid substrates has been investigated.