Mass polymer

The wide variety of ketomethylene and amino ketone monomers that could be synthesized, and the abiUty of the quinoline-forming reaction to generate high molar mass polymers under relatively mild conditions, allow the synthesis of a series of polyquinolines with a wide stmctural variety. Thus polyquinolines with a range of chain stiffness from a semirigid chain to rod-like macromolecules have been synthesized. Polyquinolines are most often prepared by solution polymerization of bis(i9-amino aryl ketone) and bis (ketomethylene) monomers, where R = H or C H, in y -cresol with di-y -cresyl phosphate at 135—140°C for a period of 24—48 h (92). 

Unsaturated polyesters are low-molar-mass polymers (1500-2500) obtained by the polyesterification of stoichiometric mixtures of diols and mixtures of saturated and unsaturated diacids or anhydrides (see Section 2.4.2.1). 

This polymer, which has the structure [—CH2CH(CH3)—] arose as a commercial material following the work of Natta on catalysts for the preparation of high relative molar mass polymers from alkenes. Following his work on the polymerisation of ethylene, Natta showed in 1954 that it was possible to prepare analogous polymers of propylene. Commercial exploitation followed rapidly, and poly (propylene) was first marketed in 1957. 

Chain polymerisation Monomer concentration decreases steadily with time. High molar mass polymer is formed at once and the molar mass of such early molecules hardly changes at all as reaction proceeds. Long reaction times give higher yields but do not affect molar mass. The reaction mixture contains only monomer, high molar mass polymer, and a low concentration of growing chains. 

Chain reactions are used to prepare a variety of high molar mass polymers of commericial importance and in practice may take one of four forms, namely bulk, solution, suspension, and emulsion methods. These four methods are described in the sections that follow, together with the loop modification which has become of commercial importance recently in producing latexes by emulsion polymerisation for the paint industry. 

From Table 6.5 quantitative determination of end groups can be seen to be increasingly uncertain particularly above a value of of 10 000. Nonetheless, end group analysis may be useful in certain circumstances, particularly for lower molar mass polymers and oligomers, where it may be a fairly straightforward approach to obtaining useful data. 

The effect is that the polymer molecules are separated into fractions. These are measured by an appropriate detector located at the end of the column, and the detector records the response as a peak on a chart. The chromatogram thus consists of a series of peaks corresponding to different elution volumes, the shortest elution volume being due to the largest molar mass polymer molecules within the sample. Details of the molar mass distribution can be determined from the size and number of the individual peaks in the chromatogram. An example of a gel permeation chromatogram is shown as Figure 6.4. 

Vander Heyden, Y., Hartmann, C., Massart, D.L., Hollands, A.M.J., Nuyten, P. and Schoenmakers, R, Ruggedness testing of a size-exclusion chromatographic assay for low molecular-mass polymers, /. Chromatogr. A, 756,89,1996. 

Experimentally, the adsorbed amount is usually expressed as T i.e. mass polymer/area of surface. This is usually obtained from a mass balance technique, after analysing the equilibrium solution, r a 0ex> but an exact correlation is difficult to establish. 

Fig. 1. Capsule permeability as measured by the inverse GPC method. Capsules were made from 1.25% A-carrageenan (Fluka) and 0.02% carboxymethylcellulose (Aqualon) in 0.9% sodium chloride (core polymers) and 2% polydimethylamine-co-epichlorohydrin modified, quater-nized (Scientific Polymer Products) and a quaternary amine (Agefloc B50, CPS) in PBS (receiving bath) using a 3 min reaction time. The capsules were subsequently washed with PBS, coated for 15 min with 0.1% LV alginate (Kelco) and again washed in PBS. Two molecular size dex-trans were used to probe the capsule permeability. 170 kD dextran is almost totally excluded while the lower molar mass polymers permeated the membrane to varying extents...

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