Rigidification of Poly(p-phenylene)s through ortho-Phenyl Substitution

A sterically π-congested ortho-phenylated poly(p-phenylene) (PPP) has been synthesized with unprecedentedly high molecular weights up to 29 kDa after fractionation, as confirmed by gel permeation chromatography coupled with a multiangle laser light scattering detector. The chain translation diffusion coefficient obtained from dynamic light scattering experiments displayed strong scaling (∼Lw–0.8) to the chain contour length, indicating a rodlike shape with remarkably high rigidity of this novel PPP. These results provide an interesting insight into the relationship between the structure and the chain stiffness of PPP-based polymers and challenge the validity of the existing diffusion models in polymer physics.


3
The samples were diluted to concentrations of 0.844 g/L, 0.984 g/L and 0.584 g/L for PPP 2-3, PPP 2-2 and PPP 2-1, respectively. The solutions were then filtered through Millex LS filters with a pore size of 5 µm (Merck Millipore, Billerica, USA) into dust-free quartz light scattering cuvettes (inner diameter 18 mm, Hellma, Müllheim), which were cleaned before with acetone in a Thurmont-apparatus.

Dynamic light scattering light (DLS)
The in the solvent that can be obtained experimentally.

Synthetic procedures
Synthetic route towards tetra-ortho-bromo-biphenyl 3 The NMR data of S2, S3, and 3 were consistent with the literature, 1, 2 and thus not listed below.
The diol was dissolved in 5 mL of dry dichloromethane in a 50-mL Schlenk flask under argon.   After cooling, the reaction mixture was added to a stirred 1:1 mixture of methanol and concentrated 11 hydrochloric acid, in order to remove the nickel salts. The resulting precipitate was collected by filtration and washed with methanol, yielding PPP 2 as a colorless solid (73.0 mg, 72 % yield).
The PPP 2 was fractionated by preparative recycling GPC (eluent: chloroform) and provide PPP 2-1, PPP 2-2, and PPP 2-3. Analytical SEC profiles of the isolated polymer fractions are shown in Figure S7. The absence of residual triflate end groups was determined via MALDI-TOF MS. 1         Semi-rigid chain model:  ) and semi-rigid chain (blue lines) using three different diameters dRR (eq. (S3)) and dH (eq. (S1)). For thin rods (dRR = 1 nm), the rate of decrease of the translational diffusion, D, becomes stronger than for the semi-rigid chains (dH = 1 nm) in the rigid rod limit.
The structural of PPP 2 trimer was optimized by Universal Force Field (UFF) calculations using the Gaussian 09 software package. [2] Figure S14. Optimized PPP 2 trimer calculated by UFF. The monomer diameter was by analyzing the conformation of middle repeating unit.
The Cartesian coordinates of the optimized PPP 2 trimer are listed as follows: