Characterisation of polydisperse branched polymers by means of gel permeation chromatography
Abstract
Theoretical gel permeation chromatography curves have been derived for model polydisperse polymers having chosen molecular weight averages and a given degree of random trifunctional branching. Gel permeation chromatography traces had been treated on a computer using the method proposed by Drott, and the molecular weight averages and a branching characteristic obtained were compared with those following directly from the model used (the Stockmayer type of distribution). The basic assumption of Drott (the ratio of the number of branch points to the molecular weight being constant) is discussed.
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Polymer molecular weights
1980, Methods in Experimental PhysicsThis chapter presents an overview of polymer molecular weights. The formation of a polymer, be it synthetic or natural, is the result of a series of random events, whereby the repeating monomeric units are joined together to form molecules, not all necessarily of the same size. The consequent collection of molecules ordinarily reflects a distribution of sizes. The distribution may be rather narrow for polymers formed through linear growth under homogeneous conditions; or quite broad, especially so if branched or formed in heterogeneous environments. Although biopolymers exhibit an amazing uniformity of size, the polymers employed in commercial plastics, especially thermoplastics, are rather long—hundreds to tens of thousands of monomer units—and may vary over this entire range of size in a single sample. In this chapter, the definitions associated with molecular weights are provided. Idealized molecular weight distribution and concepts related to number-average molecular weight are described. Intensive properties of polymers are described, and nomenclature for solution viscosity is explained. An overview of the colligative properties of polymer solutions is presented, along with the theoretical comparison of colligative properties of solutes in benzene. A discussion on polydispersity and fractionation is also presented in the chapter.
Chapter 12 Practice of gel chromatography
1975, Journal of Chromatography LibraryThis chapter discusses the technique of gel chromatography. The choice of the gel packing, together with an adequate design of the apparatus, plays a decisive role in gel chromatographic separations. In addition to fulfilling basic requirements toward the gel through its chemical inertness, the minimal adsorption of separated compounds, the swelling capacity or wettability with an eluent, etc., the gel packing must also have an adequate resolution as required by the given problem. When choosing the solvent, it must be borne in mind that the preparation of a high quality gel chromatographic column is time consuming and requires experimental dexterity. It is, therefore, desirable that the lifetime and application range of columns should be as high as possible. The solvent should be of a universal character, dissolve the great possible number of compounds, and be readily available and easy to be free from impurities. The eluent must also meet some other requirements as to its physico-chemical and physical properties.
Branching in bisphenol a polycarbonate: Gel permeation chromatography, viscometry and light scattering
1974, European Polymer JournalBranching in bisphenol A polycarbonate has been investigated by fractionation, gel permeation chromatography, viscometry and light scattering. The samples studied (Makrolon 3000 and 3000L) are branched, Makrolon 3000 more so than Makrolon 3000L. The variation of the branching parameters with molecular weight is suggestive of random branching. Comparison of the molecular weight distribution with that expected for random trifunctional branching suggests an average of about half a branch point per weight-average molecule in Makrolon 3000.
On étudie le degré de ramification dans le bisphénol A polycarbonate à l'aide de techniques comme le fractionnement, la chromatographie sur gel perméable, la viscosimétrie et la diffusion de la lumière. Les échantillons étudiés (Makrolon 3000 et 3000L) sont ramifiés, le Makrolon 3000 étant plus ramifié que le Makrolon 3000L. La variation des paramètres de ramification avec la masse moléculaire semble indiquer que la ramification est statistique. La comparaison de la distribution de la masse moléculaire observée avec celle correspondant à une ramification statistique trifonctionnelle semble montrer qu'on a en moyenne un demi point de branchement par molécule (moyenne en poids) dans le Makrolon 3000.
Mediante frazionamento, cromatografia a permeazione di gel, viscometria e diffusione luminosa, si è investigato l'innesto in policarbonato di bisfenolo A. I campioni studiati (Makrolon 3000 e 3000L) sono ad innesto, più il Makrolon 3000 che il Makrolon 3000L. La variazione dei parametri di innesto a seconda del peso molecolare spiega l'innesto a caso. Il confronto della distribuzione di peso molecolare con quella che ci si attende per l'innesto trifunzionale a caso, suggerisce, per il Makrolon 3000, una media di circa un punto e mezzo di innesto per ogni molecola di peso medio.
Die Verzweigung in Bisphenol A-Polycarbonaten wurde untersucht durch Fraktionierung, Gelpermeationschromatographie, Viskosimetrie und Lichtstreuung. Die untersuchten Proben (Makrolon 3000 und Makrolon 3000L) sind verzweigt, Makrolon 3000 jedoch stärker als Makrolon 3000L. Die Änderung der Verzweigungsparameter mit dem Molekulargewicht zeigt das Vorliegen einer statistischen Verzweigung an. Ein Vergleich der Molekulargewichtsverteilung mit der, wie sie für eine statistische trifunktionelle Verzweigung erwartet wird, liefert durchschnittlich einen halben Verzweigungspunkt pro Gewichtsmittel in Makrolon 3000.
Characterization of low-density polyethylene by gel permeation chromatography-III. Study on the Drott method using a whole polymer
1974, European Polymer JournalTwo features of the Drott iterative procedure for the estimation of long-chain branching have been examined, viz. the proportionality between the number of long-chain branches n per molecule and its molecular weight M, and the exponent ϵ relating the ratio of intrinsic viscosities of branched and linear polymers of the same weight-average molecular weight to n. The original Drott model describing the distribution of long-chain branches (LCB) has been replaced by a more general equation: n = const. MB and an examination of the effect of the exponents B and ϵ on the molecular weight distribution (MWD) and LCB characteristics carried out. The analysis has revealed that, unless information on the LCB distribution is available, the method described by Drott for which B = 1 can hardly give meaningful information on MWD and LCB for commercial low-density polyethylenes.
On a examiné les deux caractéristiques du procédé iteratif de Drott permettant l'estimation du nombre des longues chaînes ramifiées c'est-à-dire la proportionalité entre le nombre n des longues chaînes ramifiées par molécule, et sa masse moléculaire M puis l'exposant ϵ reliant le rapport des viscosités intrinsèques des polymères ramifiés et linéaires de même masse moléculaire moyenne à n. Le modèle original de Drott décrivant la distribution des longues chaînes ramifiées (LCB) a été remplacé par une équation plus générale n = const. MB et on a examiné l'effet des exposants B et ϵ sur la distribution de la masse moléculaire (MWD) et les caractéristiques des LCB. L'analyse a montré que, à moins d'avoir des renseignements valables sur la distribution des LCB, la méthode décrite par Drott, où B = 1, donne difficilement des renseignements significatifs sur la MWD et les LCB pour un polyéthylène commercial de basse densité.
Si sono esaminate 2 caratteristiche della procedura iterativa di Drott per il calcolo degli innesti a lunga catena, a precisamente la proporzionalità tra il numero n di innesti a catena lunga per molecola e il suo peso molecolare M, e l'esponente ϵ che lega il rapporto della viscosità intrinseca di polimeri ad innesto e lineari con medesimo peso molecolare medio ponderato al numero n. Il modello originale di Drott che descrive la distribuzione di innesti a lunga catena (LCB) è stato rimpiazzato con un'equazione più generale: n = const. MB e si è eseguito un esame dell'effetto degli esponenti B e ϵ sulle caratteristiche LCB e distribuzione del peso molecolare (MWD). L'analisi ha rivelato che, a meno che non si abbiano disponibili informazioni circa la distribuzione LCB, il metodo descritto da Drott, per il quale B = 1, difficilmente fornisce informazioni significative su MWD e LCB con polietileni commerciali a bassa densità.
Zwei Charakteristika des iterativen Verfahrens von Drott für die Abschätzung von Langkettenverzweigungen wurden untersucht: Die Proportionalität zwischen der Anzahl der Langkettenverzweigungen n pro Molekül und ihrem Molekulargewicht, und der Exponent ϵ, der eine Beziehung des Verhältnisses der Viskositätszahlen von verzweigten und linearen Polymeren gleichen Gewichtsmittels zu n herstellt. Das ursprüngliche Modell von Drott, das die Verteilung der Langkettenverzweigungen (LCB) beschreibt, wurde durch eine allgemeinere Beziehung ersetzt n = const. MB und eine Abschätzung des Einflusses der Exponenten B und ϵ auf die Molekulargewichtsverteilung - MWD) und die Eigenschaften der LCB vorgenommen. Die Analyse zeigt deutlich, daβ, ohne Kenntnis der LCB Verteilung, die Methode von Drott für B = 1 kaum eine sinnvolle Information über MWD und LCB für handelsübliches Polyäthylen kleiner Dichte liefern kann.
Arabinogalactan for Hepatic Drug Delivery
1994, Bioconjugate ChemistryZur Bestimmung der Molmassenverteilung verzweigter Polyphenylchinoxaline durch Gelpermeationschromatographie und Viskosimetrie
1985, Acta Polymerica