A series of polyethylene terephthalate resins were characterized for molecular weight by light scattering measurements in trifluoracetic acid (TFA) solution and for intrinsic viscosity in TFA and in a mixture of tetrachloroethane (TCE)/phenol. The following viscositymolecular weight relations were established : [?ITFA = 4.33*10-4 M F , [?]T'E;phenol = 2.29.10-4 MY3 The unperturbed dimensions (
SynopsisAromatic poly(amic acids) derived from pyromellitic dianhydride and 4,4',-diaminodiphenyl ether were characterized by dilute solution techniques. Number-average molecular weights a,, of 13 samples ranged from 13,000 to 55,000 (DP 31-131). Weight-average molecular weights aw of 21 samples ranged from 9,900 to 266,000. The ratio &fw/&f,, was between 2.2 and 4.8. Heterogeneous polymerization yielded higher molecular weight polymer than homogeneous polymerization. The molecular weight could be varied systematically by control of stoichiometric imbalance. Use of very pure monomers and solvent gave polymers of relatively high number-average molecular weight (-50, 000) and the most probable molecular weight distribution aw/a,, = 2. Impure monomers and/or solvent resulted in lower number-average molecular weight (an E 20,000-30,000) and wider distributions (hTW/a,, = 3-5). The Mark-Houwink relation obtained was [ q ] = 1.85 X 10-*AiwO.*o The exponent is characteristic of moderately extended solvated coils. The unperturbed chain dimensions (T?/M)~'* were 0.848 A., and the steric factor u was 1.24 which is close to the limiting value of unity for an equivalent chain with free internal rotations. The sedimentation constant-molecular weight relation was SO = 2.70 X 10-21i?,~,39. This exponent is consistent with the Mark-Houwink exponent.
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