Polytetrafluoroethylene repeat unit structure

Figure 5.1. Molecular structures of the chemical repeat units for common polymers. Shown are (a) polyethylene (PE), (b) poly(vinyl chloride) (PVC), (c) polytetrafluoroethylene (PTFE), (d) polypropylene (PP), (e) polyisobutylene (PIB), (f) polybutadiene (PBD), (g) c/5-polyisoprene (natural rubber), (h) traw5-polychloroprene (Neoprene rubber), (i) polystyrene (PS), (j) poly(vinyl acetate) (PVAc), (k) poly(methyl methacrylate) (PMMA), ( ) polycaprolactam (polyamide - nylon 6), (m) nylon 6,6, (n) poly(ethylene teraphthalate), (o) poly(dimethyl siloxane) (PDMS).

The chemistry of polyimides has previously been reported but the repeat unit of polytetrafluoroethylene is based upon the structure... 

The size bf the dynamical matrix, hence the order of the secular equation, to be solved for each k, is tractable for simple polsrmers (Polyethylene). But the size becomes soon untractabie for just slightly more complicates systems. For instance, the crystallographic repeat unit of isotactic polypropylene contains three monomer units and the resulting secular determinant has dimension 81. For polytetrafluoroethylene in the most stable 15/7 structure the dispersion relation contains 135 branches 144 are the branches for isotactic polystyrene. Each of the secular equation... 

Figure 14.2 Repeat unit and chain structures for (a) polytetrafluoroethylene,...

Polytetrafluoroethylene is a completely fluorinated polymer manufactured by free-radical polymerization of tetrafluoroethylene. With a linear molecular structure of repeating -CF2—CF2- units, PTFE is a crystalline polymer with a melting point of 326.7°C. Its specific gravity is 2.13—2.19. Polytetrafluoroethylene has exceptional resistance to chemicals. Its dielectric constant (2.1) and loss factor are low and stable across a wide range of temperature. It has useful mechanical properties from myogenic temperatures to 260°C. In the United States, PTFE is sold as Halon, Algoflon, Teflon, Fluon, Hostaflon, and Polyflon. ... 

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