Polymer Macrocycles: A novel topology to control dynamics of rubbery materials
We have successfully made synthetic polymer rings that are larger than previously reported having entanglement numbers as high as $$Z_w$$≈300 if the rings entangled as do linear chains. The synthesis was carried out using reversible radical recombination polymerization (R3P) of dithiols which produces a polymer with a very small persistence length. The reported results show surprising dilute solution behaviors due to the fact that polymeric rings expand more than their linear counterparts for polymer chains having a large number of persistence lengths, as developed in this study. The results strongly argue for a systematic investigation of the dilute solution properties of rings having different persistence lengths in different quality solvents, where the theta-condition should lead to results that are independent of the persistence length. For the rheological investigations related to chain entanglements, the polyDODT rings could be diluted so that the rheological data covered from less than one entanglement spacing relative to the linear counterpart to a value of $$Z_w$$=300. Importantly, because we were able to dilute extremely high entanglement number polyDODT rings to a similar entanglement number as those reported for polystyrene rings that were highly purified using LCCC, we demonstrated that the dynamics of the polyDODT rings virtually overlaps with the dynamics of the polystyrene rings which is very strong evidence that these high molecular weight polyDODT rings are of high purity. Our results demonstrate that the onset of entanglement in rings, as evidenced by the appearance of a rubbery plateau $$G_N^0$$ and by the onset of a strong power-law dependence of the viscosity on molecular weight (η~$$M_w^{5.8}$$) or entanglement number (η~$$Z_w^{5.8}$$), occurs at much higher molecular weights or polymer concentrations than is the case for linear chains. These results should serve as a benchmark for future investigations of the behavior of entangled, circular macromolecules.
- Research Organization:
- California Institute of Technology (CalTech), Pasadena, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0018655
- OSTI ID:
- 1971136
- Report Number(s):
- DE-SC0018655
- Country of Publication:
- United States
- Language:
- English
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