Temperature Coefficients of Unperturbed Chain Dimensions for Polystyrene and Poly(α-methylstyrene)

Abstract

The temperature coefficient d lnhR 2 i 0 =dT of the unperturbed mean-square end-to-end distance hR 2 i 0 with T the absolute temperature was determined from light scattering measurements for atactic polystyrene (a-PS) with the fraction of racemic diads f r ¼ 0:59 and atactic poly(-methylstyrene) (a-PMS) with f r ¼ 0:72, both in toluene (good solvent) and in the range of temperature 15.0-55.0 C, on the assumption that the binary-cluster integral and hence the gyration-radius expansion factor do not depend on T. It is then found that d lnhR 2 i 0 =dT is definitely negative for a-PS with a weak helical nature but almost vanishes for a-PMS with a strong helical nature. The results are consistent with the helical wormlike chain theory prediction. [

Solution SAXS measurements over a wide temperature range to determine the unperturbed chain dimensions of polystyrene and a cyclic amylose derivative

“…The data points in toluene monotonically decrease with increasing temperature, and the obtained slope of d lnC  /dT = −1.0  10 −3 K −1 is slightly larger than that estimated by Osa et al 6 (dashed line in Figure 4c, d lnC  /dT = −1.7  10 −3 K −1 ) in the same solvent system, and substantially the same as those determined in multiple  solvents by Mays et al 5 In the framework of the wormlike chain model,  −1 can be defined as the ratio of the bending force constant of the wormlike chain to k B T, where k B is the Boltzmann constant.…”

“…In terms of the helical wormlike chain model, a similar value was obtained at 300 K, that is, d lnC  /dT = −3.21  10 −3 K −1 . 6 In contrast, C  in MEK exhibits a minimum around 10 C, suggesting that (helical) wormlike or RIS parameters should depend on the temperature, at least in MEK. According to Munk et al, 43 specific interactions between the phenyl ring of PS and the carbonyl group of ethyl acetate reduces the chain dimensions of PS.…”

“…[2][3][4] Both models predict that the unperturbed dimensions depend on temperature. The chain dimensions were observed to depend on temperature for some flexible polymers, e.g., polystyrene (PS), 5,6 poly(-methylstyrene), 6,7 1,4-polybutadiene 7 and syndiotactic poly(methylmethacrylate) 8 from near room temperature to ~60 C. Other than this temperature range, Hong et al 9 measured light scattering for PS up to 140 C to investigate excluded volume effects.…”