3 years ago

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

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, M93A94) in the presence of calcium chloride (CaCl2). When molar ratio between CaCl2 and constituent deprotonated carboxyl group (COO) of M93A94 (n, n=nCaCl2/nCOO ) increased from 1:2 to 5:1, M93A94 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 (Ca2+) and carboxylate anion (COO), and then the crystallization of PM block was promoted when more Ca2+ was added (nCaCl2/nCOO - reach to 5:1 and 13.5:1). Moreover, the conductivity measurement indicated that, when n (nCaCl2/nCOO )=4, the coordination interaction between Ca2+ and COO was saturated, namely CaCl2/PAA formed tetradentate complex, and this information concerning the coordination geometry was highly consistent with the simulative calculation.

Publisher URL: www.sciencedirect.com/science

DOI: S0014305717310042

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