Synthesis and Structure-Efficiency Relations of 1,3,5-Benzenetrisamides as Nucleating Agents and Clarifiers for Isotactic Poly(propylene)

This paper presents the synthesis and properties of 1,3,5-benzenetrisamides with a particular focus on structure-efficiency relationships of nucleation and optical property enhancement of isotactic poly(propylene) (i-PP). A family of twenty 1,3,5-benzenetrisamide derivatives was synthesized, in which the direction of the amide linkage between the core and the peripheral substituents, as well as their length (C-3 to C-6) and flexibility were systematically varied. Dissolution- and recrystallization temperatures of the additives in the polymer melt, the crystallization temperature of i-PP, and the optical properties clarity and haze were determined in the additive concentration range from 200 to 2 500 ppm. Within the reported series of compounds, few exhibited very good nucleating and clarification abilities, only one with outstanding characteristics, whereas other, very closely related derivatives were found to be incapable to nucleate or clarify i-PP, although, intriguingly, most are structural isomers. We conclude that it is the particular chemical structure of the additive that determines its crystallization/self-assembly process, and, therewith, the structure of the heterogeneous nuclei, and at a higher hierarchical level the morphology of the poly(propylene) solid state and its final properties; and, hence, that a predictive understanding is still elusive.