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As a result, the estimated number density of tie chains (ρx) decreases by orders of magnitude till the percolation threshold of about 4% RR P3HT, below which the reported charge mobility of the blends abruptly drops off to that of pure RRa P3HT.
Finally, some preliminary results are also included as a part of the future work to better understand the nature of nematic ordering and the universal correlation between chain dimensions and entanglements in conjugated polymers.
Entanglement molecular weight (Me) for RR P3HT (~16 kg/mol) is also determined to be about a factor of 3 larger than that for RRa P3HT (5 kg/mol) by modeling the linear viscoelastic data and analyzing the molecular weight dependence of zero-shear viscosity.
Because the persistence lengths for RR and RRa P3HT are nearly the same based on static light scattering and intrinsic viscosity measurements in dilute solutions, the difference in Me could be due to the possible nematic phase in only RR P3HT (not RRa P3HT).
A general correlation between Tgs and chemical structures of 32 conjugated polymers with drastically different backbone and alkyl side chain structures is found through a newly defined effective atomic mobility, m.
This effective atomic mobility is directly calculated from the assigned mobility values for atoms belonging to different groups in the repeat unit.
Future experiments that probe the nematic ordering in RR P3HT are warranted.
The density of tie chains (ρx) in RR P3HT is estimated by examining the linear shear semicrystalline rheology for different molecular weights of RR P3HT and multiple blends ratios of RR and RRa P3HTs.
This is a reasonable hypothesis, because of the apparent increase in Me via the nematic ordering as observed for PFTBT and PCDTBT.
But unlike PFTBT and PCDTBT, no clear signatures of nematic-isotropic transition is observed currently for RR P3HT, except for some suggestive evidence from wide-angle X-ray scattering, validity check of Cox-Merz rule, and polarized Raman spectroscopy.