Baker-Williams polymer fractionation column

Two advantages of HPPLC should be mentioned here its general applicability and its only moderate dependence on column activity. The first aspect refers to the fact that solubility and precipitability are common characteristics of a wide variety of polymers. In principle, HPPLC is Baker-Williams fractionation by means of modern HPLC techniques. 

In order to familiarize himself with macromolecules, he spent a postdoctoral year (1950-1951) with Professor A. Tiselius in Sweden. Together with Aim and Hagdahl they developed the method of gradient elution analysis. On his return to England, he showed how to apply temperature gradients to columns which, with solvent gradients, permit high polymer fractionation. These are called Baker-Williams columns. 

In column fractionation (157,158) the polymer is precipitated onto an inert support, which is placed at the top of a packed column (159). A solvent mixture of increasing solvent power is pumped through the column a temperature gradient is often maintained. This is known as Baker-Williams fractionation (160). This technique is applicable to all amorphous homopolymers and crystalline ho-mopol5miers above the melting point. For copol5miers and more complex compositions, the same technique may be employed, but the analysis is considerably more difficult. 

Another type of fractionation is called the Successive Solution Fractionation (SSF). In the SSF after phase separation the polymer-lean phase is removed and forms fraction 1. The polymer-rich phase is diluted by addition of solvent up to the initial volume of the feed phase and forms now the feed phase for separation step 2 etc. Continuous thermodynamics has also been applied to Baker-Williams fractionation where the polymer is fractionated in a column using a solvent and a non-solvent. The superposition of a solvent and nonsolvent gradient and a temperature gradient leads to a very high separation efficiency. 

In trying to fractionate samples of PMA by a gradient column according to Baker and Williams (3), we found small quantities (some parts per thousand) of an acetone-insoluble polymer at the top of the column. The viscosity numbers of the eluted PMA were between 4.2 (first fraction) and 4.55 (last fraction). Before fractionation, the polymer mixture showed a reproducible viscosity number of 5.3. 

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