Local Chain Dynamics of Poly(oxyethylene) Studied by the Fluorescence Depolarization Method

Abstract

The local chain dynamics of poly(oxyethylene) (POE) labeled with anthryl group in the middle of the main chain was examined by the fluorescence depolarization method. The relaxation time of the local motion was evaluated and its molecular weight dependence was shown. POE had a mean relaxation time in the order of subnanoseconds. The value of the relaxation time increased with the molecular weight in the range of MW < 4000 and reached an asymptotic value at MW of about 4000. The relaxation time and the activation energy for local motion of POE were compared with those of some styrene and methacrylate polymers and the characteristics of POE chain were discussed. POE had a much higher local chain mobility than other polymers. This high local chain mobility of POE results from the molecular structure of POE chain.

Molecular Weight Effect on Local Motion of Polystyrene Studied by the Fluorescence Depolarization Method

“…In the case of POE, the result that the relaxation time in a good solvent was kept constant against molecular weight in a high molecular weight region was similarly explained by the excluded-volume effect. 20 However in this study, the relaxation time in ethyl acetate (poor solvent) was almost constant against molecular weight as in benzene (good solvent) in a wide range of high molecular weight, i.e., the values of Tm/IJ near MW = 10 5 are almost equal to that for cPS 13. Ethyl acetate is a poor solvent, and the coil expansion due to excluded-volume effect for high molecular weight PS is considered to be rather weak.…”

“…20 The second harmonic of Ti: sapphire laser (SpectraPhysics Tsunami) was used at a wavelength of 397 nm as a light source and 4 MHz pulse was picked up by a pulse selector (Spectra-Physics Model 3980). The excitation light was vertically polarized, and the fluorescence components parallel and perpendicular to the plane of the excitation light were measured by a microchannel plate-photomultiplier tube (MCP-PMT) (Hamamatsu Photonics R3809) through cutoff filters V-42 and Y-44 (Hoya).…”

“…1 -21 For the local motion, which is fairly a fundamental process in chain dynamics, many experimental methods have been utilized, e.g., NMR, 5 -7 ESR, 8 dielectric relaxation, 9 -11 dynamic light scattering, 12 • 13 neutron scattering, 14 and fluorescence depolarization. [15][16][17][18][19][20][21] The fluorescence depolarization method provides direct information about the local motion of polymer chains through a fluorescent probe that is covalently bonded to the polymer main chain. By using this method, we have examined the influence of molecular structure/ 6 · 19 stereoregularity, 17 and quality of solvent16·18 on the chain dynamics of a variety of polymers.…”

“…19 We also have reported the local chain dynamics of poly(oxyethylene) (POE) in good solvents and discussed the molecular weight effect. 20 The static and dynamic properties of polystyrene (PS), a common polymer, have been widely studied. 2 · 6 -9 • 16 · 17 We have reported the effects of the solvent quality on the local dynamics of PS 17 and discussed the difference t To whom correspondence should be addressed.…”

“…16 From the standpoint of the molecular structure, it is interesting to compare the molecular weight effect of PS with that of POE, which is dynamically more flexible than PS. 20 Monnerie et al studied the molecular weight effect of PS on the local motion by NMR, 6 and concluded that the effect of the overall rotational diffusion is negligible on the spin-spin relaxation time of the local motion in a high molecular weight region and that the correlation time remains constant in MW > 10 4 . Prior to Monnerie's work, similar findings have been reported by Allerhand and Hailstone, 7 Stockmayer and Matsuo, 9 and Bullock eta!.…”