Viscosity measurements have been made on two series of polymacromonomer samples consisting only of polystyrene (PS) and having fixed side chain lengths of 15 and 33 styrene residues (designated F15 and F33) in cyclohexane at 34.5 °C (the ϑ temperature) and in toluene at 15 °C (a good solvent). The intrinsic viscosities [η] obtained as functions of (total) weight-average molecular weight M w (in the ranges from 5.1 × 103 to 6.5 × 106 for the F15 polymer and from 5.4 × 104 to 1.1 × 107 for the F33 polymer) are analyzed on the basis of the wormlike chain with or without excluded volume. They are described quantitatively by the current theories over the almost entire range of M w studied, when the contribution of side chains near the main-chain ends to the polymacromonomer contour is incorporated into the analysis. The estimated parameters are consistent with those derived previously from gyration radius data, confirming that while the contour length per main-chain residue in the ϑ or good solvent is close to the value expected for the all-trans conformation, the chain stiffness is much higher in the good solvent than in the ϑ solvent due to enhanced monomer−monomer repulsions. The hydrodynamic diameter for each polymacromonomer in cyclohexane, slightly smaller than that in toluene, is about twice as large as the unperturbed end-to-end distance expected for the linear PS molecule having the same degree of polymerization as the side chain.

ABSTRACT:Light scattering and viscosity measurements were made on cyclohexane and toluene solutions of a series ofpolymacromonomer samples consisting of polystyrene with 65 monomer units in each side chain to determine the z-average mean-square radius of gyration< s 2 >,and the intrinsic viscosity [I]] as functions of the weight average molecular weight in a range from 2.9 X 10 5 to 8.6 X 10 6 • The theta temperature for the polymacromonomer in cyclohexane was determined to be 34.5°C. The ,data in this solvent at 34.5°C and toluene at 15°C (a good solvent) were quantitatively described by the wormlike chain with II. 1 (the Kuhn segment length)=36 nm and ML (the molecular weight per unit contour length)=25000nm-1 in the former and with ll.-1 =75nm and ML=25000nm-1 in the latter. The molecular weight dependence of [I]] in each solvent was also explained by this model chain when the end effect arising from side chains near the main-chain ends was taken into account. The above II. -l values in the two solvents and the previous estimates for polystyrene polymacromonomers with shorter side chains were used to examine the dependence of the backbone stiffness on side chain length. It was found that II. -l increases almost linearly with the side-chain molecular weight for both solvents but with a larger slope in toluene than in cyclohexane.KEY WORDS Light Scattering I Intrinsic Viscosity I Polystyrene Polymacromonomer I Wormlike Chain I Chain Stiffness IIn previous studies of this series, 1 -4 we found from light scattering and viscosity measurements that two polymacromonomers consisting of polystyrene with 15 and 33 styrene units in each side chain (polymacromonomers F15 and F33) behave like wormlike chains in cyclohexane at the theta temperature and in toluene, a good solvent, at 15'C. The backbone stiffness expressed in terms of the Kuhn segment length A -1 was higher for the F33 polymer, being consistent with the earlier finding5-7 that for polymacromonomers consisting of the poly(methyl methacrylate) backbone and polystyrene side chains in toluene (a good solvent), A -1 increases with side chain length. We also found that A -1 is larger in the good solvent than in the theta solvent for both F15 and F33. These findings ought to be theoretically explained in terms of side chain-side chain and side chainmain chain interactions, but at present, we deem it necessary to extend the experimental work to a polystyrene polymacromonomer with a larger side chain length in order to establish the experimental relations between the backbone stiffness and the side chain length in both theta and good solvents.Thus we prepared polystyrene polymacromonomer samples with 65 side chain units and different mainchain lengths, and determined z-average mean-square radii of gyration < s 2 >z and intrinsic viscosities [7]] for them by static light scattering and viscometry in cyclohexane at the theta temperature and in toluene at 15°C. In the work reported below, we analyze the results on the basis of the wormlike chain and compare the e...

ABSTRACT:Dynamic light scattering measurements have been made on two series of polymacromonomer samples consisting of polystyrene with 33 styrene side-chain residues (F33) in cyclohexane at 34.5 C (a theta solvent) and with 65 styrene side-chain residues (F65) in cyclohexane at 34.5 C and toluene at 15 C (a good solvent) to determine the translational diffusion coefficient D as functions of the weight-average degree of polymerization of the main chain, N w , ranging from 15 to 3030 for F33 and from 42 to 1250 for F65. The D data are compared with those previously obtained for a polystyrene polymacromonomer with a shorter side chain length of 15 styrene residues. The hydrodynamic radius R H at fixed N w is larger for a longer side-chain polymer and in toluene than in cyclohexane (for F65), reflecting the higher backbone stiffness for the longer side chain and in the good solvent. The N w -dependence of R H and that of the reduced hydrodynamic radius (the ratio of R H to the radius of gyration hS 2 i 1=2 ) for the respective polymacromonomers are fitted by the theoretical curves for the wormlike chain with the model parameters leading to fits of previous data for the intrinsic viscosity ([]) and hS 2 i, provided that the chain diameters d are taken to be 1.29-1.35 times those from []. This discrepancy in d is similar to what was found for thin stiff chains, revealing certain shortcomings of the current hydrodynamic theories. It is pointed out that polystyrene polymacromonomers with large diameters relative to Kuhn's segment length are hydrodynamically similar to flexible chains for which the available theories for D contain an error of about 15% in the Gaussian-chain limit. [DOI 10.1295/polymj.37.529] KEY WORDS Polymacromonomer / Dynamic Light Scattering / Translational Diffusion Coefficient / Hydrodynamic Radius / Wormlike Chain / Chain Stiffness / Theta Solvent / It has been shown in the last one decade that polymacromonomers, regular comb polymers with dense side chains, behave like stiff chains in dilute solution despite being composed of flexible chain units. [1][2][3][4][5][6] This stiffening effect of side chains ought to be explained in terms of intramolecular interactions between or among monomeric units. To this end, unequivocal determination of the relationships between the backbone stiffness and the side chain length and between the backbone stiffness and the excluded-volume strength is essential, but even systematic data for statistical and hydrodynamic properties are yet insufficient. Notably, Wintermantel et al.1 remarked that measured radii of gyration hS 2 i and intrinsic viscosities [] for a polymacromonomer consisting of the poly(methyl methacrylate) (PMMA) main chain and polystyrene (PS) side chains in toluene, a good solvent, were not consistently explained by the unperturbed wormlike chain, 7 a typical model for stiff polymers. Recently, we investigated polymacromonomers F15, F33, and F65 consisting only of PS with 15, 33, and 65 side chain residues, respectively, in cyclohexane at 34.5 C (...

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