Search results for "Gel permeation chromatography"

Disproportionierung und kombination als abbruchmechanismen bei der radikalischen polymerisation von styrol, 1.Versuche mit 14C-markierten 2,2′-azoiso…

1975

Die Substanzpolymerisation von Styrol mit 14C-markiertem 2,2′-Azoisobutyronitril (AIBN) wurde bei 52°C experimentell untersucht. Die Polymerisation wurde dilatometrisch verfolgt, die Molekulargewichte der entstandenen Polymeren viskosimetrisch ermit-telt, der Gewichtsbruch der einkettigen Molekule gelchromatographisch bestimmt und die Anzahl der markierten Endgruppen ausgezahlt. Die eingehende kinetische Analyse erhartet die neueren Erkenntnisse uber den Abbruchmechanismus. Danach liegt bei der Polymerisation von Styrol neben der Kombination auch Disproportionierung vor. Bulk polymerisation of styrene initiated by 14C-labelled 2,2′-azoisobutyronitrile (AIBN) was studied at 52°C. The polymer…

Synthesis of polymer nanogels by electro-Fenton process: investigation of the effect of main operation parameters

2017

Recently, electro-Fenton (EF) process has been shown as a promising, facile, effective, low cost and environmentally-friendly alternative for synthesizing polymer nanogels suitable as biocompatible nanocarriers for emerging biomedical applications. Here, the electrochemically-assisted modification of poly(vinylpyrrolidone) (PVP) by EF process was studied to assess the role of key operation parameters for a precise modulation of polymer crosslinking and its functionalization with [sbnd]COOH and succinimide groups. The dimensions of the nanogels, in terms of hydrodynamic radius (Rh) and weight-average molecular weight (Mw), can be tuned up by controlling the electrolysis time, current density…

Solution behavior of 4-arm poly(tert-butyl acrylate) star polymers

2010

Abstract This paper reports the synthesis of 4-arm poly( tert -butyl acrylate) stars of different molar masses up to 10 6  g/mol by the “core-first” method using ATRP. All obtained stars have a monomodal and narrow molar-mass distribution ( The dilute-solution properties of these star polymers were investigated in good solvents (tetrahydrofuran and acetone). Gel permeation chromatography and dynamic and static light scattering were used to measure the hydrodynamic properties including intrinsic viscosity [ η ], radius of gyration R g , hydrodynamic radius R h , second virial coefficient A 2 and diffusion coefficient D 0 . These data were used to establish relationships between these paramet…

Purification, partial amino acid sequence and structure of the product of raucaffricine-O-β-d-glucosidase from plant cell cultures of Rauwolfia serpe…

1999

Plant cell suspension cultures of Rauwolfia produce within 1 week approximately 250 nkat/l of raucaffricine-O-beta-D-glucosidase. A five step procedure using anion exchange chromatography, chromatography on hydroxylapatite, gel filtration and FPLC-chromatography on Mono Q and Mono P delivered in a yield of 0.9% approximately 1200-fold enriched glucosidase. A short protocol employing DEAE sepharose, TSK 55 S gel chromatography and purification on Mono Q gave a 5% recovery of glucosidase which was 340-fold enriched. SDS-PAGE showed a Mr for the enzyme of 61 kDa. The enzyme is not glycosylated. Structural investigation of the enzyme product, vomilenine, demonstrated that the alkaloid exists in…

Macromolecules in ordered media VIII. High-performance size-exclusion chromatography as a technique for characterizing the interaction between polyan…

1997

Abstract The association of polyanions with liposomes based on dimyristoyl phosphatidyl choline and stearylamine at a ratio of 50:50 was investigated in terms of the binding model and, to a lesser extent, of the partition model. Aqueous size-exclusion chromatography has been proposed as a major technique for monitoring the interactions between liposomes and polyelectrolytes and the results were compared with those obtained by fluorescence spectroscopy. Quantitatively, the extent of the association follows the order: Sodium poly(styrene sulfonate) ( K A = 10 000 M −1 ), poly (acrylic acid) ( K A = 2000 M −1 ) and poly ( l -glutamic acid) ( K A = 700 M −1 ). Also, the effect of the ionic stre…

Characterization of Chemical Composition along the Molar Mass Distribution in Polyolefin Copolymers by GPC Using a Modern Filter-Based IR Detector

2013

Summary Gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC), is the technique routinely used at high temperature to analyze the molar mass distribution in polyolefins. The distribution of comonomer along the molar mass distribution in a copolymer is a key microstructural feature that determines the macroscopic properties of the material, and thus, its range of possible applications and performance. The direct coupling of a modern filter-based infrared (IR) detector to a high temperature GPC instrument, by means of a heated flow-through cell, is here described. The analyses are carried out by recording the continuous IR absorbance chromatograms at selected …

Organometallic Oligomers Based on Bis(arylacetylide)bis(P-chirogenic phosphine)platinum(II) Complexes: Synthesis and Photonic Properties

2013

A series of P-chirogenic oligomers of the type (-C≡C-aryl-C≡C-PtL2-)n [L = (R)- and (S)-P(Ph)(iPr)(C17H35); aryl = 1,4-benzene, 2,1,3-benzothiadiazole] along the corresponding achiral analogues (L = PBu3) and model complexes PhC≡CPtL2C≡CPh were prepared from the ephedrine strategy and were fully characterized [(1)H, (31)P NMR; IR; small-angle X-ray scattering (SAXS); gel permeation chromatography (GPC); thermal gravimetric analysis (TGA); circular dichroism, UV-vis, and luminescence spectroscopy; photophysics, and degree of anisotropy measurements]. From the CD measurements, the chiral environment of the phosphine ligands is modestly felt by the aryl moieties. Concurrently, the TGA shows th…

Molecular characterization of α,β-poly[( N -hydroxyethyl)- dl –aspartamide] by light scattering and viscometry studies

2000

Abstract α,β-poly[(N-hydroxyethyl)- dl -aspartamide] (PHEA) is a new synthetic polymer which is of interest in biomedical applications. In this paper, the molecular characterization of PHEA by multi-angle laser light scattering and viscometry off-line and on-line to a size exclusion chromatography system is reported. These techniques furnish an exhaustive and consistent characterization of the PHEA polymer. The fractionation of the PHEA macromolecules was relatively simple. Using an aqueous mobile phase of medium ionic strength, the elution was substantially regular and the macromolecules were not aggregate. The molar mass M of four PHEA samples approximately ranges from 46 to 53 K g/mol, t…

Main Chain Conformation and Anomalous Elution Behavior of Cylindrical Brushes As Revealed by GPC/MALLS, Light Scattering, and SFM

1999

High molar mass polymacromonomers based on methacryloyl end-functionalized oligo methacrylates (Mn = 2410 g/mol) adopt the conformation of wormlike cylindrical brushes. Comparison of the absolute molar mass, Mw, determined by static light scattering and the contour length, Lw, of the molecules measured by SFM in the dry state revealed the length per vinylic main chain monomer of the cylindrical structure to be less than 0.1 nm, thus being much shorter than the maximum value of 0.25 nm. In solution this shrinkage could be quantified to 0.071 nm per monomer by Holtzer analysis of the scattering curves which in addition yielded the Kuhn statistical segment length lk = 120 nm. GPC MALLS investi…

1995

About 340 g of a cycloaliphatic ionene (see formula given in the introduction) were fractionated by a continuous countercurrent extraction method (CPF). The efficiency of the separation was checked by viscometry and gel permeation chromatography (GPC). Ten different fractions with number average molecular masses between 16 000 and 29 000 D were obtained and their glass transition temperatures T g determined by differential scanning calorimetry (DSC) for their bromide and tetrafluoroborate salts. No molecular weight dependence of T g was found, in contrast to recently reported results with aliphatic ionenes, where - in case of the bromide - T g increases with rising molecular weight.