Stiff Chain Behavior of Poly(phthaloyl-trans-2,5-dimethyIpiperazine) in Dilute Solution

Abstract

ABSTRACT:Fractionated samples of poly(phthaloyl-trans-2,5-dimethylpiperazine) in various organic solvents at 25"C were studied by light scattering, viscosity, and sedimentation velocity. The data obtained for z-average mean-square radii of gyration (S2)z, intrinsic viscosities [7)], and sedimentation coefficients so exhibited features predictable for stiff or semiflexible chains. Thus an attempt was made to analyze the data by combination of the Yamakawa-Fujii theory for intrinsic viscosity and the Benoit-Doty expression for mean-square radius of gyration of unperturbed wormlike chains with a reasonable assumption for the partial specific volume. In this way, three parameters q, ML, and d characterizing the wormlike cylinder were estimated for each solvent; for example, q=33 A, ML=33 daltons/A, and d=7.4 A in N-methyl-2-pyrrolidone. Here q is the persistence length, ML is the molecular weight per unit length of the wormlike cylinder, and d is the its diameter. The estimated parameter values were found to reproduce quite closely the observed molecular weight dependence of (S 2 ),, [ri], and so.KEY WORDS Poly(phthaloyl-trans-2,5-dimethylpiperazine) / Wormlike Chain / Persistence Length / Dilute Solution / RefractiveIndex Increment / Light Scattering / Intrinsic Viscosity / Sedimentation Coefficient / Yamakawa-Fujii Theory / Benoit-Doty Theory / Poly (phthaloyl-trans-2, 5 -dimethylpiperazine) (abbreviated PPDP in the following presentation) is one of a series of polyamides synthesized by Morgan, et al.

Stiff Chain Behavior of Poly(terephthaloyl-trans-2,5-dimethylpiperazine) in Dilute Solution

“…778 cm 3 jg), together with (/)==2.05 x 10 23 assumed on the basis of our previous finding. 1 In Table IV, theML values (31 and 35 daltonsjA) for PTDP in two different solvents may be compared to . 30.3 daltons;A, the molecular weight per unit length in the N-N direction of the piperazine ring of the PTDP molecule (see Figure 1).…”

“…These values obeyed the Gradstone-Dale relationship, which had been established for PPDP in our previous paper. 1…”

“…3, 1978 Poly(terephthaloyl-trans-2,5-dimethylpiperazine) Figure 3. Concentration dependence of (KcfR0) 1 12 for PTDP fractions in trifluoroethanol at 25°C: (l), upper c-scale; Q, lower c-scale.…”

“…In a previous paper 1 we reported that the dimensional and hydrodynamic behavior of poly-(phthaloy 1-trans-2, 5-dimethy !piperazine) (PPDP) in dilute solution can be described quantitatively by the theory for unperturbed wormlike chains. 2 • 3 This finding was consistent with the prediction that the internal rotation about C-rp bonds in PPDP should be considerably hindered, so that the PPDP chain ought to be fairly stiff (see Figure 1).…”

“…Concentration dependence of (Kc/R9o)1 1 2 for PTDP fractions f-13, f-14, and f-15 in trifiuoroethanol at 25°C: Q, Uu; CD, Uv; •• values corrected for optical anisotropy. Table II.…”