Properties of the ladder polymer cis‐syndiotactic poly(phenylsilsesquioxane) in solution

Abstract

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 Å. 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.

Properties of some rodlike polymers in solution

“…The discussion of experimental procedures is abbreviated here, since detailed discussion of most of these appear elsewhere in this symposium [ 1,2]. Polymers were obtained from three sources: (1) PBO polymers were provided by Dr. F.…”

Transport Properties of Rodlike Particles

“…Recent work on the characterization of carbon nanotubes and other similar structures has generated renewed interest in the transport properties of rodlike particles. [1][2][3][4][5][6][7][8][9][10][11][12] Many of these studies have simply assumed that these structures are rodlike, ignoring observational evidence for finite persistence lengths, or other sources of flexibility. This paper is not concerned with the validity of the rodlike picture for any particular type of particle but instead with the validity of theoretical expressions of the transport properties of rods that are currently in use for the characterization of various nanoparticle structures.…”

Characterization and Some Insights into the Reaction Chemistry of Polymethylsilsesquioxane or Methyl Silicone Resins

“…Among these characterization techniques, the a value in the Mark-Houwink equation is repeatedly reported to give values around 1 [13][14][15], implying that PPSQ has random coil to rod-like shapes. In their dilute solution study, Helminiak and Berry concluded that the conformation of PPSQ can be represented with a wormlike chain model with a persistence length of 75Å [16]. Frye and Klosowski strongly opposed the ladder structure and suggested a more or less randomly linked array of polycyclic cages [17].…”

“…, and H T 3 16 cage molecules using gas chromatography, 1 H and 29 Si NMR, elemental analysis, and mass spectrometry. Synthesis and identification of compounds with the structures of…”