Search results for "polymerization"

Radikalpolymerisation von methylmethacrylat im gesamten umsatzbereich. Stationäre und instationäre experimente zur bestimmung von wachstums- und abbr…

1989

Free-radical polymerization of methyl methacrylate in bulk at 0°C over the full range of conversion is reported. Details for stationary and non-stationary experiments are described allowing to measure both kinetically relevant ratios fk/ka and kw/ka, f representing radical efficiency, kw rate constants of propagation and ka rate constant of termination. From these ratios the absolute rate constants kw and ka are available. The photochemical decay of the initiator 1,1′-azodicyclohexanenitrile in connection with the rotating-sector technique and observation of the post-effect after stopping the initiator decay were used. The rate of polymerization and the number- and weight-average molar mass…

1987

Die radikalinduzierte polymerisation von acrolein und α-methylacrolein in dimethylformamid. Polymere acroleine. 22. Mitt.1

1962

Die Polymerisation von Acrolein in Dimethylformamid (DMF) bei 40 und 50°C mit wechselnden Mengen Azodiisobuttersaurenitril wird beschrieben. Bei Umsatzen uber 16% tritt unter diesen Bedingungen Gelbildung ein. Methacrolein wurde mit verschiedenen Katalysatoren in DMF polymerisiert. Die Polymerisate bleiben bis zu hohen Umsatzen in Losung. Die Bruttoaktivierungsenergie ergibt sich zu 21 kcal/Mol. Die Bruttogeschwindigkeit als Funktion der Monomeren-Konzentration und der Konzentration von Azodiisobuttersaurenitril last sich bei 50°C durch folgende Gleichung beschreiben: The polymerization of acrolein in DMF at 40 and 50°C. in presence of varying amounts of azodiisobutyronitrile was investigat…

1987

Enantioresolution in electrokinetic chromatography-complete filling technique using sulfated gamma-cyclodextrin. Software-free topological anticipati…

2016

Few papers have tried to predict the resolution ability of chiral selectors in capillary electrophoresis for the separation of the enantiomers of chiral compounds. In a previous work, we have used molecular information available on-line to establish enantioresolution levels of basic compounds using highly sulfated β-CD (HS-β-CD) as chiral selector in electrokinetic chromatography-complete filling technique (EKC-CFT). The present study is a continuation of this previous work, introducing some novelties. In this work, the ability of sulfated γ-cyclodextrin (S-γ-CD) as chiral selector in EKC-CFT is modelled for the first time. Thirty-three structurally unrelated cationic and neutral compounds …

Crystallization and Preliminary X-Ray Analysis of Rotavirus Protein VP6

1998

ABSTRACT As a first step to gain insight into the structure of the rotavirus virion at atomic resolution, we report here the expression, purification, and crystallization of recombinant rotavirus protein VP6. This protein has the property of polymerizing in the form of tubular structures in solution which have hindered crystallization thus far. Using a combination of electron microscopy and small-angle X-ray scattering, we found that addition of Ca 2+ at concentrations higher than 100 mM results in depolymerization of the tubes, leading to an essentially monodisperse solution of trimeric VP6 even at high protein concentrations (higher than 10 mg/ml), thereby enabling us to search for crysta…

Infinite coordination polymer networks metallogelation of aminopyridine conjugates and in situ silver nanoparticle formation

2018

Herein we report silver(i) directed infinite coordination polymer network (ICPN) induced self-assembly of low molecular weight organic ligands leading to metallogelation. Structurally simple ligands are derived from 3-aminopyridine and 4-aminopyridine conjugates which are composed of either pyridine or 2,2'-bipyridine cores. The cation specific gelation was found to be independent of the counter anion, leading to highly entangled fibrillar networks facilitating the immobilization of solvent molecules. Rheological studies revealed that the elastic storage modulus (G') of a given gelator molecule is counter anion dependent. The metallogels derived from ligands containing a bipyridine core dis…

Phenoxyamidine Zn and Al Complexes: Synthesis, Characterization, and Use in the Ring-Opening Polymerization of Lactide

2019

International audience; Herein we report the synthesis of new ditopic ligands, which consist of a phenoxy group and N,N,N'trisubstituted amidines linked by a methylene spacer (L1-L4). Their coordination chemistry has been studied/investigated with Zn(II) and Al(III). Alkane elimination route between the phenol-amidine proligands (L1H-L4H) and Et2Zn led to dinuclear complexes [(L1-L4)ZnEt]2 (1a-4a) in which the Zn centers are chelated by phenoxyamidine ligands and bridged through the oxygen atom of the phenoxy groups. Salt metathesis reaction between two equivalents of the sodium amidine phenate L1Na and ZnCl2 led to a bis-chelate chiral spiro-complex (L12Zn) 1a'. Analogous alkane eliminatio…

A head-to-head comparison of poly(sarcosine) and poly(ethylene glycol) in peptidic, amphiphilic block copolymers

2015

Abstract In this work we compare chemical and solution properties, like critical aggregate concentrations (CAC) and hydrodynamic radii of aggregates based on either poly(ethylene glycol) or poly(sarcosine) block copolymers in aqueous solution. The amine functionalized, hydrophilic polymers poly(sarcosine) (degree of polymerization, X n  = 100 and 200) and PEG (X n  = 121 and 242) of comparable hydrodynamic volume were used to initiate the ring opening polymerization of α-amino acid- N -carboxyanhydrides based on ɣ-benzyl- l -glutamate (Glu(OBn)) or e-carboxybenzyl- l -lysine (Lys(Z)). The second, hydrophobic block was kept at a degree of polymerization of 25 and 50 to enable a direct compar…

Morphology of Sponge Spicules: Silicatein a Structural Protein for Bio-Silica Formation

2010

Most forms of multicellular life have developed a calcium-based skeleton, while only a few specialized organisms complement their body plan with silica, such as sponges (phylum Porifera). However, the way in which sponges synthesize their silica is exceptional. They use an enzyme, silicatein, for the polymerization/polycondensation of silica, and thereby form their highly resistant and stabile massive siliceous skeletal elements (spicules). During this biomineralization process (i.e., biosilicification), hydrated amorphous silica is deposited within highly specialized sponge cells, ultimately resulting in structures that range in size from micrometers to meters. This peculiar phenomenon has…