A study of the crystallization of the n-alkane C246H494 from solution: Further manifestations of the inversion of crystallization rates with temperature

✍ Scribed by Sally J. Organ; Peter J. Barham; Mary J. Hill; Andrew Keller; Robert L. Morgan

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 310 KB
• Volume: 35
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199708)35:11<1775::aid-polb10>3.0.co;2-5

✦ Synopsis

The newly available, strictly uniform n-alkane, C 246 H 494 , has been crystallized from dilute solution. The rates of crystallization were followed by differential scanning calorimetry (DSC) as a function of temperature. Two pronounced rate inversions were registered. The dissolution temperatures of the crystals formed show a sharp discontinuity at the temperature of the rate minimum. From this it is inferred (reinforced by the precedent of previous work on C 198 H 398 ) that a transition from extended to once folded crystallization is taking place at the temperature of the minimum. The methods by which the rate curves were constructed are laid out in step by step detail, leaving no possible doubt about the reality of the rate inversion. The rate inversion is attributed to ''self-poisoning,'' and this concept is extended to embrace the wider issue of mutually interacting competition of possible phase variants (''polymorphs'') of which the extended and folded chain crystals represent one special example. In addition, some further effects are noted and discussed regarding solubility behavior.