Rotational isomeric state model for

G. D. Smith, D. Y. Yoon, and R. L. Jaffe, Macromolecules, 26, 5213 (1993). A Third-Order Rotational Isomeric State Model for Poly(oxyethylene) Based upon Ab Initio Electronic Structure Analyses of Model Molecules. 

Experimental molar cyclization equilibrium constants for cyclics in the PDA n%lt and the P1 melt at 423 K are own dotted as log gainst Ic x in Fig. 12 and 13. They are compared with theoretical values calculated by the Jacobson and Stockmayer ex esrion Eq. (6) with - 2jc- Values of < / >q required by this expression were comfHited by the exact mathematical methods of Flory and Jemi-gan 37,30) using the rotational isomeric state models for the polyesters set up by Flory and Williams 27,128). Agreement between experiment and theory is excel-... 

Eq. (6) with oji = 2x. A rotational isomeric state model for polyphosphate chains (2 76,187) was used to compute values of < rj >o required by Eq. (6). Comparison of the experimental values with the theoretical values, as well as with the values for the corresponding cyclic siloxanes (R(CH3)SiO)x [see Section III.(A)5] stronj y supports the contention that polyphos diate chains in sodium phosphate melts adopt random-coil conformations. Further evidence for the structure of sodium phosphate melts would come from precise data for macrocyclic concentrations in quenched sodium phosphate ring-chain equilibrates, if these became available. 

Figure 3 shows a plot of the fluorescence maximum for poly(n-propyl methyl silylene) in hexane vs. sin ir/2(N + 1) using a defect energy of 1650 calories/mole. Although the ag eement here seems good, the uncertainty in location of the fluorescence maximum is large as the band broadens near room temperature and may disguise a real nonlinearity. Nevertheless, this result lends credibility to the rotational isomeric state model for thermochromism in these polysilylenes. 

The rotational isomeric state model is not among the newer models used in polymer science. Its earliest application to polymers was reported half a century ago (1), using mathematical techniques invented 10 years earlier (2). Applications of the model to polymers received a strong boost from Flory s group in the 1960s, leading to the publication of his classic book on the subject at the end of that decade (3). Another book, published 25 years later, updates the techniques and applications (4). The literature now contains rotational isomeric state models for literally hundreds of polymers. A few hundred of the models that appeared in... 

San-ichiro Mizushima et al. proposed the rotational isomeric state model for internal bond rotation [9]. 

---