Polymer Chain Dynamics. II. Intermittent Process of Orientational Relaxation of Polystyrene Main Chain

Abstract

ABSTRACT:Polystyrene chains having an anthryl group in the middle of its back bone (PSAPS), whose degrees of polymerization are 3200, 2500, and 730, were used to detect orientational relaxation of polymer segments. In order to explain the power law behavior of fluorescence anisotropy decay curves ofPSAPS chain, it was assumed that the orientational relaxation of segments is caused by the reaction between segments and solvent molecules. Further the distribution of interval time between relaxation phenomena was considered. According to above two assumptions, a hyperbolic function have been derived as an orientational auto-correlation function. We propose the "intermittent process" of polymer segments as one of the probable description for the oricntational relaxation process of polystyrene back bone. The hyperbolic exponent f3 is related to the characteristic activation energy E. of a polymer segment. Diffusive motion is the most important elemental process in the self-organization phenomenon. Diffusion refers to the transport process of matter in space with time. The study of the self-organization phenomenon is equivalent to that of relationship between space and time. We have been claiming the significance of a hierarchical viewpoint for the vast number of motion. 1 -3 . The polymer system has almost motion correlating the self-organization process. Thus it is necessary to establish first appropriate methods to estimate each motion for understanding the self-organization phenomenon.As considering primary process of the conformational change of a polymer chain, the orientational relaxation motion is firstly mentioned as an elemental motion in a microscopic region. In the last twenty years, many theoretical and experimental studies of orientational relaxation phenomena of a polymer chain were reported by many authors. 4 -10 Most of studies assumed that orientational relxation of polymer segments consists of a few modes. However, in reality, a polymer chain has the vast number of internal freedom about motion. It is important to make a realistic picture of orientational relaxation behavior on the basis of a model reflecting the distribution of relaxation time.The trend in experimental studies on the orientational relaxation process of a segment at the center of a polymer back bone began with the Valeur's reports. 4 • 11 • 12 They studied an orientational auto-correlation function describing fluorescence anisotropy decay curves of polystyrene chain having an anthryl group in the middle of its back bone (PSAPS) in dilute solution. The VJGM function was proposed, on the basis of a realistic description of the relaxation called by the 3-bond motion, where r 1 and r 2 are 582 relaxation times corresponding to the conformational jump and the out-of-lattice motions. They suggested that an orientational auto-correlation function is to be r(t) t-112 in the later stage of the relaxation process. That is to say, they found the fluorescence anisotropy of PSAPS obeys the power law at long times.Hall and Helfand 7 and Viovy, Mo...

Polymer Chain Dynamics III. Intermittent Orientational Relaxation of Terminal Segment on Polystyrene Chain

“…The values of reference temperature T, for PSA agrees with that of PSAPS chains 16 as shown in Table III. Reference temperature Polymer Chain Dynamics Ill. Tr is related to characteristic activation energy for orientational relaxation of a segment.…”

“…In our previous paper, 16 it was found that the origin of hyperbolic fluorescence anisotropy decay curves of PSAPS chain is the intermittent process of orientational relaxation of polymer segments composed with a few monomers. The relaxation of segments was regarded as the reaction between segments and solvent molecules.…”

“…It was found that the origin of hyperbolic anisotropy decay curves of PSAPS chain is the intermittent relaxation 16 of the segment which is made up of a few monomers. That is to say, orientational relaxation of segments rarely occurs, but the velocity of the relaxation is rapid.…”

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