Excluded-Volume Effects on the Mean-Square Radius of Gyration and Intrinsic Viscosity of Isotactic Oligo- and Poly(methyl methacrylate)s

Abstract

The mean-square radius of gyration and intrinsic viscosity were determined for isotactic poljKmethyl methacrylate) (i-PMMA) with the fraction of racemic diads fT *» 0.01 in acetone at 25.0 °C and in chloroform at 25.0 °C in the range of weight-average molecular weight Mw from 6.58 x 102 to 1.93 x 106. The results for the gyration-and viscosity-radius expansion factors Os and a, for i-PMMA along with those previously obtained for atactic poly(methyl methacrylate) (a-PMMA) with fT = 0.79 in the same solvents are found to become functions only of the scaled excluded-volume parameter z defined in the Yamakawa-Stockmayer-Shimada theory on the basis of the helical wormlike chain. Here, a, for i-PMMA has been calculated as before by taking account of the dependence on solvent of the Flory-Fox factor in the unperturbed state. Thus the present results along with the previous ones for atactic polystyrene (a-PS), polyisobutylene, and a-PMMA lead to the conclusion that the quasi-two-parameter scheme is valid for Os and a, for a variety of polymer-solvent systems irrespective of the differences in chain stiffness, local chain conformation, and solvent condition. This also indicates that there is no draining effect on a, at least for these systems. It is found that the effects of chain stiffness on as and remain appreciable even for Afw > 106 for i-PMMA as well as for a-PS and a-PMMA. The effects are smaller for i-PMMA than for a-PMMA both in acetone and in chloroform, reflecting the fact that the former chain is less stiff than the latter. It is also found that the values of the binary-cluster integral ß between beads (segments) for the two PMMAs in the same solvent are almost identical with each other, indicating that ß is independent of the stereochemical structure of the polymer chain.

A New Framework of Polymer Solution Science. The Helical Wormlike Chain

“…Figure 1 shows double-logarithmic plots of (S 2 )/x (in A 2 ) against x for atactic polystyrene (a-PS) with the fraction of racemic diads fr = 0.59 in cyclohexane at 34.SOC (8) 17 • 18 and in toluene at 15.0°C/ 9 atactic poly(methyl methacrylate) (a-PMMA) with fr=0.79 in acetonitrile at 44.0°C (8) 20 and in acetone at 25.0°C, 21 isotactic (i-) PMMA with fr=O.Ol in acetonitrile at 28.0°C (8) 22 and in acetone at 25.0°C, 23 poly(n-butyl isocyanate) (PBIC) in tetrahydrofuran (THF) at 40°C, 24 and schizophyllan in O.ol N NaOH at 25°C. 25 The data have been obtained from light scattering measurements except for fractions of the flexible polymers with (S 2 ) 1 i 2 ;:S80A, for which those have been obtained from small-angle X-ray scattering (SAXS) measurements.…”

“…Figure 8 shows double-logarithmic plots of against z for a-PS in toluene at 15.0°C, 19 a-PMMA in acetone at 25.ooc and in chloroform at 25.0°C, 21 and i-PMMA in chloroform at 25.0°C. 23 The solid and dotted curves represent the QTP and TP theory values, respectively. There is good agreement between the QTP theoretical and experimental values.…”

“…For the details, the reader is referred to Chapter 8 of HWCPS. 1 Figure 10 shows double-logarithmic plots of against z for a-PS in toluene at 15.0°C, 42 in benzene at 25.0°C, 57 and in MEK at 35.0°C, 57 a-PMMA in acetone at 25.0°C, in chloroform at 25.0°C, and in nitroethane at 30.0°C, 21 i-PMMA in acetone at 25.0°C and in chloroform at 25.0°C, 23 PIB in n-heptane at 25.0°C, 42 and PDMS in toluene at 25.0oC. 58 The data points for rxH, which have not been plotted in Figure 10, coincide with those for within experimental error.…”

“…At the B temperature, which is now defined as the temperature at which A 2 vanishes for large M, and (3 must vanish, so that A 2 at the B temperature, which we denote by A 2 ,e, is given by (23) This indicates that A 2 ,e does not vanish except at large M. Thus the TP scheme is valid also for A 2 only in the limit of M--+oo. Figure II shows double-logarithmic plots of A 2 (in cm 3 molg-2 ) against M for a-PS in cyclohexane at 34.SOC (B) and in toluene at 15.oac.…”

Rheological properties of silica dispersions stabilized by stereoregular poly(methyl methacrylate)

“…Actually, the two main reasons for that are the differences in chain expansion and the number of adsorbed sequences per chain, which are both dependent on the polymer stere- oregularity. Kamijo et al [26] have pointed out differences in the expansion factor α according to the PMMA tacticity by carrying out viscometric and light-scattering experiments at a temperature of 25 • C in good solvents. Moreover, the preferential adsorption of locally stiffer isotactic segments may change the density profile across the adsorbed layer according to the relative content of isotactic sequences in the PMMA.…”