Martensitic Phase Transition of Petroselinic Acid:  Influence of Polytypic Structure

Abstract

Polytypism and solid-state phase transitions of petroselinic acid (cis-6-octadecenoic acid) have been investigated with microscopic observation and micro-FT-IR spectroscopy. Polytypism was confirmed for the low-melting (LM) phase. In solution crystallization of the LM phase, polytypic transformation from a single-layered polytype to a double-layered one was observed. The LM phase performs a solid-state phase transition to the high-melting phase through two mechanisms. One mechanism involves the thermally induced nucleation and growth of the product phase, which is dominant upon a slow heating process. The other mechanism can be regarded as a martensitic transition, where rapid cooperative molecular displacements are initiated by a local stress. The martensitic transition occurs when a single crystal of the single-layered polytype suffers rapid heating or mechanical stress. However, no martensitic transition was observed for the double-layered polytype. The difference in transition behavior between the two polytypes was interpreted on the basis of crystal structures.

Shape-memory effect in an organosuperelastic crystal

“…We have discovered that organic crystals potentially show superelasticity (organosuperelasticity), 9 , 10 which allows the recovery of their shapes from mechanical deformation with a martensitic transformation while some organic and organoionic crystals are known to exhibit a shear-induced martensitic transformation without spontaneous shape-recovery properties. 11 – 14 However, we could not find the shape-memory effect in the organosuperelastic crystals of terephthalamide 9 or 3,5-difluorobenzoic acid, 10 probably due to the poor thermal connection of their mechanical phase. SMAs are known to have a specific thermal phase connection between their superelastic region and twinning region.…”

Supercolossal Uniaxial Negative Thermal Expansion in Chloranilic Acid Pyrazine, CA-Pyz

“…For example, there has been a number of reports over the years of “bending crystals”, which undergo dramatic shape changes either on heating or on the application of mechanical stress, some of which have been recently reviewed. , This behavior is usually linked to the evolution of twin structures associated with phase transitions and, as such, closely related to the phenomena that lead to effects such as shape memory and superelasticity in metal alloys like nitinol. There has, therefore, been significant interest in martensite-like transitions in organic crystals; − recent examples of materials exploiting these include the superelastic terephthalamide and the organic shape memory material (P n Bu 4 ) + (BPh 4 ) − . Mechanical twinning leads to effects such as ferroelasticity and superelasticity, and a number of molecular systems have been reported with this property. − Finally, N , N -dimethyl-4-nitroaniline crystals have recently been shown to display superplasticity .…”

Infrared spectroscopy and differential scanning calorimetry studies of binary combinations of cis-6-octadecenoic acid and octadecanoic acid

“…PSA is a positional isomer of oleic acid and has been reported to have some moderate penetration enhancement properties (Morimoto et al, 1996;Takeuchi et al, 1998). Furthermore, PSA exhibits unusual phase behavior for a fatty acid having been shown to undergo a martensitic (displacive) phase transition at room temperature (Kaneko et al, 1997).…”