Synthesis and Characterization of Poly (epsilon-caprol actone-b-4-vinylpyridine): Initiation, Polymerization, Solution Morphology, and Gold Metalation

Abstract

We have synthesized a difunctional initiator-the hydroxyl-4-oxo-N-alkoxyamine (HOA)-by first mixing benzoyl peroxide (BPO) and 4-hydroxyl-2,2,6,6-tetramethylpiperdinooxy (4-OH-TEMPO) in styrene at temperatures below 25 degrees C to give the 4-oxo-N-alkoxyamine (OA) and then hydrolyzing the benzoate ester on OA with NaOH. This low-temperature preparation of OA reveals that benzyloxyl radicals can be generated from the BPO through redox reaction with 4-OH-TEMPO its well as through thermal decomposition. The N-oxoammonium cation (i.e., the oxidative state of 4-OH-TEMPO), which formed as a side product, mediated the alcohol oxidation to give OA. We prepared three PCL-b-P4VP diblock copolymers (BCI-3) from HOA through two-step polymerizations: (i) diethylaluminum alkoxide-induced ring-opening polymerization of epsilon-caprolactone at 25 degrees C followed by (ii) nitroxide-mediated radical polymerization of 4-vinylpyridine Lit 125 degrees C. With the combination of biodegradable hydrophobic PCL blocks and polymeric blocks of P4VP ligands, we used the immiscible PCL-b-P4VP copolymers to transport AuCl(4) anions from aqueous phases to organic phases and to stabilize Au nanoparticles in the PCL-b-P4VP micelles Au-BC1-3 after reduction with NaBH(4).