The effects of co-lyophilized polymeric additives on the glass transition temperature and crystallization of amorphous sucrose

The purpose of this study was to measure the effect of co-lyophilized polymers on the crystallization of amorphous sucrose, and to test for a possible relationship between the ability of an additive to raise the T-g of a sucrose-additive mixture, relative to the T-g of pure sucrose, and its ability to inhibit crystallization. Differential scanning calorimetry was used to measure the glass transition temperature, T-g, the non-isothermal crystallization temperature, T-c, and the induction time for crystallization, Q, of sucrose in the presence of co-lyophilized Ficoll or poly(vinylpyrrolidone) (PVP). The effect of these polymers on the crystallization of sucrose was significant as demonstrated by a marked increase in T-c, and in the induction time (Q) in the presence of relatively small amounts (1-10%) of additive. Surprisingly, small amounts of polymeric additive had no effect on the T-g of sucrose, although at higher concentrations, the T-g increased proportionally. Thus, it appears that the inhibition of sucrose crystallization by the addition of small amounts of a higher-T-g component cannot be attributed solely to changes in molecular mobility associated with an increase in T-g.