Pressure-induced amorphization and disordering on cooling in a crystalline polymer

Sanjay Rastogi, Mark Newman, Andrew Keller

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


IN the course of exploring the phase diagram of the polymer poly(4-methyl-pentene-l) as a function of temperature and pressure by in situ X-ray diffraction, we have discovered some unusual phase behaviour. The polymer, crystalline under ambient conditions, becomes amorphous reversibly on increasing pressure in two widely separated temperature regimes (∼20°C and ∼200°C), the transformation occurring via a liquid-crystalline state. This suggests the possibility of 're-entrant' liquid-crystal and amorphous phases as pressure or temperature are varied. In the higher-temperature regime, the melting point shows a maximum as a function of pressure. The lower-temperature amorphous phase becomes crystalline on heating, and reverts to the glassy, disordered phase on cooling. Whereas pressure-induced amorphization has been observed previously in other systems, such as ice, silica and A1PO4, we know of no precedent for the disordering on cooling that we observe. © 1991 Nature Publishing Group.
Original languageEnglish (US)
Pages (from-to)55-57
Number of pages3
Issue number6339
StatePublished - Jan 1 1991

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