Acceleration of the crystal growth rate of low molecular weight organic compounds in supercooled liquids in the presence of polyhydroxybutyrate

Abstract

Modification of the crystallization kinetics of amorphous systems is an important topic, in particular in the area of drug delivery. Herein, we studied the impact of polyhydroxybutyrate (PHB), a biocompatible polymer with a low glass transition temperature (Tg), on crystal growth rates from the supercooled liquid phase of a variety of organic compounds. Low levels of PHB were mixed with the supercooled liquid and growth rates were monitored using optical microscopy at several temperatures above the Tg of the mixture. Growth rates were determined from a plot of crystal size as a function of time. It was found that PHB inhibited the growth of low Tg compounds, while accelerated crystal growth was observed for compounds that had a much higher Tg (>50 °C) than the polymer. The observations were rationalized based on the extent of mobility differences between the crystallizing compound and the polymer. This is the first reported example of a polymer having compound specific inhibitory or accelerator effects on crystal growth.