Facile Synthesis of Functional Periodic Copolymers: A Step toward Polymer-Based Molecular Arrays

A step-growth strategy was investigated for preparing functional periodic copolymers. Functional heterotelechelic alpha-alkyne, omega-azido poly(styrene-co-N-substituted maleimide) precursors (M-n approximate to 2500 g.mol(-1)) have been prepared and subsequently polymerized by copper-catalyzed azide-alkyne cycloaddition (CuAAC). These precursors have been first synthesized by sequential atom transfer radical copolymerization of styrene and a N-substituted maleimide (i.e., benzyl maleimide, N-(2-(amino-tBOC)-ethylen)-maleimide, or benzyl N,N-maleoylglycinate) initiated by 3-(1,1,1-trimethylsilyl)-2-propynyl 2-bromo-2-methylpropanoate. In this approach, styrene homopolymerization was First started, and a discrete amount oft lie maleimide comonomer (e.g., 1 equiv as compared to initiator) was added when styrene half-conversion was reached. This controlled maleimide addition resulted in the Formation of well-defined polystyrene segments containing a functional maleimide in the middle of their chains (i.e., in average I unit per chain). Subsequently, the sequence-controlled copolymers poly(styrene-omega-N-substituted maleimide) have been transformed into reactive heterotelechelic polymers. Various synthetic pathways have been compared for preparing these reactive intermediates. Ultimately, these heterotelechelic precursors were polymerized by CuAAC. H-1 NMR and SEC evidenced the formation of high-molecular-weight Periodic copolymers.