Conformal transition of form II to form I in poly(L-proline) and the aggregation of form I. I. Acetic acid–propanol solvent system

✍ Scribed by Hyun Don Kim; Chun Hag Jang; Taikyue Ree

• Book ID: 105337501
• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 756 KB
• Volume: 28
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/pola.1990.080280526

✦ Synopsis

Abstract

The conformational transition of Form II → Form I of Poly‐L‐proline and the intermolecular aggregation of the product Form I during and after the transition in the HOAc‐propanol mixture solvent were studied, the ratio of HOAc:propanol being changed as 1:9, 1:6, and 1:4 v/v. For the study, the viscosity, light scattering, and dynamic light scattering of the system were measured. The experimental results exhibit that the concentration of Form II promotes the end‐to‐end type aggregation during and after the transition Form II → I. The extent of the aggregation is reduced in the order of the ratios of HOAc/propanol 1:9, 1:6, and 1:4 v/v. The end‐to‐end type aggregation is also reduced at higher temperatures. It was also observed that the end‐to‐end type aggregation occurs abruptly and strongly after the transition of Form II → I occurred to some extent. The point of the abrupt occurrence depends on the solvents and temperature. The light scattering and translational diffusion‐coefficient measurements showed also similar phenomena. It was also observed that the side‐by‐side type aggregation occurs when the initial concentration of Form II of poly‐L‐proline is relatively small, and the transition temperature is relatively high (35 and 45°C). All the above mentioned experimental results are explained by a simple principle described in the text.