Search results for "condensation"

1981

Polyamides 3 containing constant and definite numbers of oxyethylene units were prepared by condensation polymerization of suitable diamines and diesters, both of which containing oxyethylene units. The polymer structure was determined by IR and 1H NMR spectroscopy. Almost all polymers are crystals melting at ≈ 40°C and show a complexation ability towards alkalimetal cations. It was also found that diesters containing oxyethylene units show a higher condensation rate than alkylene diesters, which is explained by an inductive effect of the ether oxygene. However, no remarkable difference in the condensation rate was found between diamines containing oxyethylene units and the corresponding al…

Versatile Responsive Surfaces via Hybrid Polymers Containing Acetal Side Groups

2009

Two hybrid polymers, poly(methylsilsesquioxane)-poly(2,2-diethoxyethyl acrylate) and poly-(methylsilsesquioxane)-poly(1,3-dioxolan-2-ylmethyl acrylate), were synthesized and used for preparation of stable surface coatings. Their acetal side groups could be functionalized via solution-dipping with different primary amines and hydroxylamines after acidic deprotection and thus allowed for flexible modification of the surface hydrophilicity. Functionalization with a thermo-responsive polymer resulted in a thermo-responsive surface with temperature-dependent contact angles. Further, the two types of acetals showed different stability toward acidic treatment and could be addressed independently.

1967

Optically active polyamides with regular structural sequences have been prepared from L-lysine and adipic acid. A novel optically active symmetrical diamine, N.N'-bis(L-5-amino-5-carboxyl-amyl)adipamide, was obtained by treating L-lysine with adipyl chloride in the presence of copper(II) ions. The interfacial polycondensation of this diamine with adipyl chloride afforded a regular polymer, while the polycondensation of L-lysine with adipyl chloride gave an irregular polymer of the same analytical composition. The melting points, optical rotations and the optical rotatory dispersions of these polymers were investigated. Optisch aktive Polyamide mit regelmasiger Struktur wurden aus L-Lysin un…

Fragment condensation on solid-phase in the synthesis of an amphiphilic glycopeptide from the homophilic recognition domain of epithelial cadherin 1

1998

Abstract The lipo-glycopeptide 6 containing the homophilic recognition motif of mouse epithelial cadherin 1 was synthesised via a fragment condensation on a solid phase linked peptide using an allylic anchor and a pentafluorophenol-based coupling reagent.

A novel synthesis of polymers with anthracene and dihydroanthracene subunits in the main chain

1993

A new polycondensation method to connect redox-active and chromophoric subunits by forming a C-C bond and leading to a polyhydrocarbon is described. 1,ω-bis(9,10-Dihydro-9-anthry)alkanes with various alkylene spacers can be deprotonated by butyllithium to afford a monoanion in each dihydroanthracene moiety. Alkylation with dielectrophiles such as dibromoalkanes yields soluble polymers with dihydroanthracene units in the main chain. The reaction proceeds regioselectively in the 9,10-position. Aromatization generates a polymer with anthracene units. The molecular weights are determined by GPC up to Mn = 10 000. To prove the structure and to calibrate the GPC, suitable model compounds were syn…

Thermodynamic properties and cloud droplet activation of a series of oxo-acids

2010

Abstract. We have investigated the thermodynamic properties of four aliphatic oxo-dicarboyxlic acids identified or thought to be present in atmospheric particulate matter: oxosuccinic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, and 4-oxopimelic acid. The compounds were characterized in terms of their cloud condensation nuclei (CCN) activity, vapor pressure, density, and tendency to decarboxylate in aqueous solution. We deployed a variety of experimental techniques and instruments: a CCN counter, a Tandem Differential Mobililty Analyzer (TDMA) coupled with a laminar flow-tube, and liquid chromatography/mass spectrometry (LC/MS). The presence of the oxo functional group in the α-position ca…

Der (2-Phenyl-2-trimethylsilyl)ethyl-(PTMSE)-Ester – eine neutral spaltbare Carboxyschutzgruppe/The (2-Phenyl-2-trimethylsiylyl)ethyl (PTMSE) Ester –…

2002

(2-Phenyl-2-trimethylsilyl)ethyl (PTMSE) esters of aminoacids and peptides are stable under the conditions of hydrogenolytic cleavage of benzoxycarbonyl(Z) and benzyl ester groups, base-induced removal of Fmoc groups, palladium(0)-catalyzed removal of allyloxycarbonyl (Aloc) and even acidolytic cleavage of Boc groups. PTMSE esters are also stable under the conditions of peptide condensation reactions. The PTMSE ester is selectively cleaved by treatment with tetrabutylammonium fluoride (TBAF) trihydrate in dichloromethane, i. e. under almost neutral conditions, within a few minutes and, therefore, considered a valuable novel carboxy protecting group.

High-Performance Electron-Transporting Polymers Derived from a Heteroaryl Bis(trifluoroborate)

2011

In this communication, we report that dipotassium aryl bis(trifluoroborate)s make stable and easy-to-purify yet reactive monomers under Suzuki polycondensation reactions. A bis(trifluoroborate) of 2-alkylbenzotriazole was prepared successfully and copolymerized with dibromobenzothiadiazole in the presence of a Pd catalyst and LiOH, yielding high molecular weight conjugated polymers. This polymer (P1) composed of all electron-accepting units shows excellent electron-transport properties (μ(e) = 0.02 cm(2) V(-1) s(-1)), which proves the value of the aryl bis(trifluoroborate) monomers and suggests that many other types of semiconducting polymers that could not be accessed previously can be syn…

Rigid biobased polycarbonates with good processability based on a spirocyclic diol derived from citric acid

2020

Introducing biobased polymers from renewable sources for use as high-performance thermoplastics with high demands on mechanical rigidity, transparency, thermal stability, as well as good processability, is a significant challenge. In the present work we have designed and prepared a rigid biobased bis-spirocylic diol by di-cycloketalization of a bicyclic diketone (cis-bicyclo[3.3.0]octane-3,7-dione, obtained from citric acid) using trimethylolpropane. This spiro-diol monomer has two reactive primary hydroxyl groups and the synthesis from inexpensive biobased starting materials is straightforward and readily upscalable, involving no chromatographic purification. In order to explore the useful…

Synthesis and Characterization of a New Class of Fully Aromatic Liquid Crystal Polymers

1999

Abstract A new fully aromatic LCP, obtained by polycondensation of N-(4-carboxyphenyl) trimellitimide and tert-butyl hydroquinone (FAPT), was previously described. The polymer shows very interesting physical and mechanical properties but a very high glass transition temperature which does not allow a good processability. In order to overcome this problem, a new class of LCPs, obtained by partial substitution of the dicarboxylic moiety with isophthalic acid, is described. The new thermoplastic materials were characterized from the physicochemical and mechanical point of view. All the polymers obtained with an isophthalic acid (FA-IA) content varying from 10 to 40% of the substituted moiety s…