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Cite This: J. Am. Chem. Soc. XXXX, XXX, XXX−XXX
Poly(allyl alcohol) Homo- and Block Polymers by Postpolymerization Reduction of an Activated Polyacrylamide Michael B. Larsen,† Shao-Jie Wang,‡ and Marc A. Hillmyer*,† †
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States Wanhua Chemical Group Co., Ltd., Yantai, Shandong Province 264002, People’s Republic of China
‡
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S Supporting Information *
ABSTRACT: Direct polymerization of allyl alcohol generally results in low molar mass oligomers or highly branched or cross-linked structures, and the properties and applications of linear, high molar mass poly(allyl alcohol) (PAA) are relatively unexplored. Such macromolecular materials that cannot otherwise be obtained directly can be accessed by postpolymerization modification strategies. Herein we describe the synthesis and characterization of linear, high molar mass PAA by borohydride reduction of a new activated polyacrylamide. The facile polymerization and mild reduction conditions enable the preparation of PAA of targeted molar masses and low dispersity, as well as PAA block polymers via chemoselective reduction of the activated amide moiety.
T
he growth of polymer science has been accompanied by a corresponding growth in the variety of polymerizable monomers. Among the most ubiquitous are olefinic monomers with unsaturation that enables propagation of a reactive center from the growing chain end to the next monomer; however, there still exist classes of olefins that cannot be efficiently polymerized directly. In contrast to the straightforward radical,1,2 ionic,3,4 and metal-catalyzed polymerizations5,6 of numerous vinylic species, allylic monomers generally suffer from degradative chain transfer reactions limiting their ability to propagate and achieve high molar mass, linear homopolymers (Figure 1a).7−10 Thus, the direct homopolymerization of allylic monomers is an enduring challenge. Poly(allyl alcohol) (PAA) in particular has attracted interest due to its formal equivalence to hydroxy-functionalized polypropylene.11 Previous efforts to polymerize allyl alcohol have used Brønsted or Lewis acids to inhibit chain transfer to monomer, resulting in relatively higher molar masses (Mn 5− 20 kDa).12−15 These conditions generally require either a) continuous radical generation and reinitiation by γ irradiation which results in significant branching and cross-linking; or b) extended reaction times (7 days) using thermal initiators which results in very low (
