Properties of the ladder polymer cis-syndiotactic poly(phenylsilsesquioxane) in solution
| Autor: | T. E. Helminiak, Guy C. Berry |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Polymer Science: Polymer Symposia. 65:107-123 |
| ISSN: | 1936-0959 0360-8905 |
| DOI: | 10.1002/polc.5070650113 |
| Popis: | Studies on the properties of the double-chain ladder polymer of cis-syndiotactic poly(phenylsilsesquioxane) (PPSQ) in dilute and concentrated solutions are reported. Data on the intrinsic viscosity [η], the second virial coefficient A2, and the mean-square radius of gyration 〈s2〉 as functions of molecular weight M, temperature, and solvent lead to the conclusion that the conformation of PPSQ can be modeled with a wormlike chain model with a persistence length ρ of 74 A. These data cannot be used to assess the extent of intramolecular inflexibility, e.g., resistance to rotational isomerization, of PPSQ. For concentrated solutions (0.05 ⩽ c ⩽ 0.20 g/ml) the limiting viscosity ⩾0 at zero shear rate is proportional to cM for cM < ⩾2Mc and to (cM)3,4 for cM ⩾ ρ2Mc, where Mc = 9120. The product Xc (〈s20/M) × ρ2Mc/ma is equal to 356 × 10−17 for PPSQ, close to the value 400 × 10−17 typical of single-chain polymers. The reduced flow curve ηK/ϵ0 versus ηCK for the viscosity ϵK as a function of shear rate K is not far different from that for single-chain polymers—here, the time constant ηC is equal to η0R0 with R0 the limits of the recovery function RK, at small K(R0 is often denoted Je0). The values of ηc are intermediate to ηc for a flexible single-chain polymer and the relaxation time ηR for rotatory diffusion of a rigid coil. Plots of RK versus K superpose with plots of the transient recovery R0(ϑ) with ϑ = K−1 over the limited range ηCK < 1 where ϑ is the recovery time (R0(ϑ) goes to R0 for large ϑ), similar to behavior found with solutions of single-chain polymers. |
| Databáze: | OpenAIRE |
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