Homopolymer molecular weights, determination

The GPC analysis of block copolymers is handicapped by the difficulty in obtaining a calibration curve. A method has recently been suggested to circumvent this difficulty by using the calibration curves of homopolymers. This method has been extended so that the calibration curves of block copolymers of various compositions can be constructed from the calibration curve of one-component homopolymers and Mark-Houwink parameters. The intrinsic viscosity data on styrene-butadiene and styrene-methyl methacrylate block polymers were used for verification. The average molecular weight determined by this method is in excellent agreement with osmometry data while the molecular weight distribution is considerably narrower than what is implied by the polydispersity index calculated from the GPC curve in the customary manner. 

For radiolysis studies of the grafting solutions without cellulose, i.e. homopolymer runs, tubes were either lightly stoppered or sealed off at 10-J Torr after three freeze-thaw cycles. For the molecular weight determinations on the homopolymers, oligomer solution was poured into excess methanol, the precipitated polystyrene collected, dried and analysed by g.p.c. on a Waters Associates Model ALG/GPS201 instrument. 

Determination of Homopolymer Molecular Weights Understanding the structure and physicochemical properties of polymeric materials is essential... 

The first objective of this contribution will be to elucidate the problem of true molecular weight determination of an homopolymer the poly(methylphenyl)silane by the combined use of LS and GPC techniques. 

Below T polymers are stiff, hard, britde, and glass-like above if the molecular weight is high enough, they are relatively soft, limp, stretchable, and can be somewhat elastic. At even higher temperatures they flow and are tacky. Methods used to determine glass-transition temperatures and the reported values for a large number of polymers may be found in References 7—9. Values for the T of common acrylate homopolymers are found in Table 1. 

The number average molecular weights, Mq, of the polymers obtained in Table II ranged from 1300 to 3900 as determined by vapor nressure osmometry (VPO), and they were further characterized by - -H- and C-NMR spectrometry at ambient temperature and at 90°C, as well as by IR spectroscopy. The homopolymers of isopropenylferro-cene were found to have the expected structure, P, shown below, obtained by polymerization through the isopropenyl units, as indicated by spectroscopic characterization ... 

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