Habit modification of 5,6-dimethyl-1H-benzotriazole in the presence of nonionic triblock copolymers

The effects of different nonionic surfactants on the habit modification of 5,6-dimethyl-1H-benzotriazole (5,6-DMBTA) were evaluated. Three different triblock copolymers, Pluronic® F-127, Pluronic® L44NF, and Pluronic® P-123 were selected as nonionic surfactants. Crystallization was achieved by pH adjustment in an aqueous solution with or without the presence of surfactants. Pluronic® P-123 was found to have the most dramatic effect in changing the crystal habit of 5,6-DMBTA from needles to platelets. The surfactant with a smaller hydrophobic block, Pluronic® L44NF, or the one with a larger hydrophilic block, Pluronic® F-127, yield only shorter needles for the crystal habit. This indicates that both blocks of a surfactant backbone have an impact on habit modification. Analytical data confirmed that none of the three surfactants were incorporated into the crystal lattice of 5,6-DMBTA after crystallization. All the habit modified crystals have the same crystal form as the original 5,6-DMBTA crystal sample, indicating that solely a habit modifying process took place. ► Same crystal form was observed for habit modified and control 5,6-dimethyl-1H-benzotriazole. ► Both blocks of the copolymer impact the crystal habit. ► Pluronic® P-123 had the most dramatic effect by changing the habit from needles to platelets. ► No incorporation of surfactant into the crystal lattice was observed by XRD, DSC, and TGA.