Dilute-Solution Properties of Polystyrene Polymacromonomer Having Side Chains of over 100 Monomeric Units

Abstract

Static and dynamic light scattering and viscosity measurements were made on 12 samples of polymacromonomer F110 consisting of polystyrene with 113 styrene units in each side chain to determine the z-average mean-square radius of gyration, the hydrodynamic radius, and the intrinsic viscosity in cyclohexane at 34.5 C (the theta temperature) and toluene at 15.0 C as functions of weight-average molecular weight M w . Small-angle X-ray scattering experiment was also performed for one sample in the two solvents. The dependence of the three measured properties on M w in the range 1:9 Â 10 5 -1:3 Â 10 7 studied were consistently explained by available theories for the wormlike chain with M L (the molar mass per unit contour length) = 45500 nm À1 , À1 (the stiffness parameter) = 80 nm (in cyclohexane) or 155 nm (in toluene), and d (the chain diameter) = 16-26 nm (depending on the kind of solvent and measured property) when the end effect arising from side chains near the main-chain ends was taken into account. The side-chain length dependence of À1 , examined with the aid of previous data for three polystyrene polymacromonomers with shorter side chains of 15, 33, and 65 styrene units, was found to be almost quantitatively explained by the theory of Nakamura and Norisuye [Polym. J., 33, 874 (2001)]. That of d was also discussed in relation to the end-to-end distance of a wormlike side chain.KEY WORDS: Polymacromonomer / Radius of Gyration / Hydrodynamic Radius / Intrinsic Viscosity / Chain Stiffness / Chain Thickness /We have studied polymacromonomers consisting of polystyrene (PS) having side chains of 15, 33, and 65 monomeric units (F15, F33, and F65, respectively) in cyclohexane (a theta solvent) and toluene (a good solvent) by static 1-3 and dynamic 4,5 light scattering, small-angle X-ray scattering (SAXS), 6,7 and viscosity measurements. 3,8 The z-average mean-square radius of gyration hS 2 i z , the hydrodynamic radius R H , and the intrinsic viscosity [] obtained as functions of weight-average molecular weight M w were explained in a consistent manner by the Kratky-Porod (KP) wormlike chain model, 9 and the estimated backbone stiffness parameter (or Kuhn segment length) À1 and chain diameter d were found to depend on the side chain length and the solvent quality, being consistent with observations on different polymacromonomers by other groups. [10][11][12][13][14] To establish the relations between these molecular parameters and the side chain length, however, further work was highly desirable for polymacromonomers with longer side chains.The present paper reports an experimental study thus undertaken as an extension of our previous light scattering, SAXS, and viscosity studies to a series of PS polymacromonomer samples (designated F110) with 113 side chain units. The data obtained from these methods are comprehensively analyzed, and the side chain length dependence of À1 and d is discussed. With regard to the sample preparation, which was actually crucial to the present study, a brief remark may be in order.For v...

Effects of side-chain ends on the stiffness and excluded-volume parameters of polymacromonomers

“…The A 2 values slightly increase with temperature but are always positive in the temperature range studied. This differs from the known behavior of linear PS and benzyl-PS PM in the same solvent in that A 2 decreases with decreasing T and becomes zero at 34.5 1C, [13][14][15][16] but the results are similar to those observed for PS-MA PM. 17,19 The molecular weight dependence of A 2 for butyl-PS PM is illustrated in Figure 4, in which the filled and unfilled circles represent the data points for the toluene and cyclohexane solutions, respectively.…”

“…Therefore, we calculated M L to be 7900 nm À1 from the macromonomer molecular weight and the contour length for the unit macromonomer residue, h s ¼0.27 nm, which is known for benzyl-PS PMs. [13][14][15][16] The dashed lines in Figure 1 represent the calculated values from the above equations with l À1 ¼17 nm and B¼10 nm for cyclohexane solutions (lower line) and l À1 ¼ 20 nm and B¼13 nm for toluene solutions (upper line). Excluding the data for the lowest molecular weight sample, these lines satisfactorily fit the data points.…”

“…[10][11][12] We have studied PM consisting of a PS main chain and PS side chains with a benzyl group at each end (benzyl-PS PM) and showed that its A 2 in cyclohexane vanishes at 34.5 1C, which is identical to the Y temperature of linear PS in cyclohexane. [13][14][15][16] In contrast, the values of A 2 for PM consisting of a polymethacrylate main chain and PS side chains with a butyl group at each end (PS-MA PM) in d 12 -cyclohexane were shown to be positive at 20 1C, 17 far below the Y temperature (40 1C) of linear PS in d 12 -cyclohexane. Although the butyl end in PS-MA PM may be a primary cause of the positive A 2 , there may be a possible effect on the A 2 of the polymethacrylate main chain.…”

“…The molecular parameters for butyl-PS PM with n¼19 along with the interpolated values of B and l À1 for benzyl-PS PM with the same n estimated from the previous results [13][14][15][16]23 are summarized in Table 2. The uncertainty of these parameters is approximately ± 5%.…”

“…[10][11][12] We have studied PM consisting of a PS main chain and PS side chains with a benzyl group at each end (benzyl-PS PM) and showed that its A 2 in cyclohexane vanishes at 34.5 1C, which is identical to the Y temperature of linear PS in cyclohexane. [13][14][15][16] In contrast, the values of A 2 for PM consisting of a polymethacrylate main chain and PS side chains …”