Polymethylene-b-poly (acrylic acid) diblock copolymers: Aggregation and crystallization in the presence of CaCl2

Crystalline block copolymers tend to display a peculiar and intriguing behavior upon the external additives. In this work, we systematically investigated the self-assembly and crystallization behavior of polymethylene- b -poly (acrylic acid) crystalline diblock copolymer (PM- b -PAA, M 93 A 94 ) in the presence of calcium chloride (CaCl 2 ). When molar ratio between CaCl 2 and constituent deprotonated carboxyl group (COO − ) of M 93 A 94 (n, n   =   n CaCl2 /n COO − ) increased from 1:2 to 5:1, M 93 A 94 micelle gradually formed hexagonal and reticular aggregation. Further investigation of PM- b -PAA crystalline feature indicated that the crystallization of PM block was initially restrained by coordination interaction between calcium ion (Ca 2+ ) and carboxylate anion (COO − ), and then the crystallization of PM block was promoted when more Ca 2+ was added (n CaCl2 /n COO - reach to 5:1 and 13.5:1). Moreover, the conductivity measurement indicated that, when n (n CaCl2 /n COO − )   =   4, the coordination interaction between Ca 2+ and COO − was saturated, namely CaCl 2 /PAA formed tetradentate complex, and this information concerning the coordination geometry was highly consistent with the simulative calculation.