000080890 001__ 80890
000080890 005__ 20181203020258.0
000080890 037__ $$aARTICLE
000080890 245__ $$aConformational and orientational order and disorder in solid polytetrafluoroethylene
000080890 269__ $$a1999
000080890 260__ $$c1999
000080890 336__ $$aJournal Articles
000080890 520__ $$aThe low-pressure phase diagram of solid poly(tetrafluoroethylene) (PTFE/Teflon) has been investigated using const.-temp./const.-pressure mol.-dynamics techniques and a new all-atom potential model for fluorocarbons. The simulation was started in an ordered low-temp. phase in which the mols. are parallel and have a helical conformation with a pitch of uniform magnitude and sign (chirality). In accordance with expt., a transition to an orientationally disordered state is obsd. upon heating. The coherent helical winding of CF2 groups also disappears abruptly at the transition but short helical segments remain and become equally distributed between left and right chirality with increasing temp. The orientational and conformational disorder is accompanied by translational diffusion along the chain direction. At a still higher temp., melting sets in. On cooling, the disordered solid phase is recovered and its structure is shown to be identical to that generated on heating. On further cooling, a spontaneous ordering transition is obsd. but the system fails to recover a uniform helical ground state. Instead, the high-pressure ordered monoclinic all-trans (alkane-like) structure is obtained: an observation that indicates a deficiency in the potential model. [on SciFinder (R)]
000080890 700__ $$aSprik, Michiel
000080890 700__ $$0241350$$aRothlisberger, Ursula$$g150117
000080890 700__ $$aKlein, Michael L.
000080890 773__ $$j97$$k3$$q355-373$$tMolecular Physics
000080890 909C0 $$0252093$$pLCBC$$xU2
000080890 909CO $$ooai:infoscience.tind.io:80890$$pSB$$particle
000080890 937__ $$aLCBC-ARTICLE-1999-001
000080890 970__ $$a34/LCBC
000080890 973__ $$aEPFL$$rREVIEWED$$sPUBLISHED
000080890 980__ $$aARTICLE