Highly Orthogonal Functionalization of ADMET Polymers via Photo-Induced Diels-Alder Reactions

Within the current contribution, we introduce two strategies for the catalyst-free, modular, ambient temperature synthesis of ABC triblock copolymers via photoinduced Diels-Alder reactions. On the one hand, the 2-formyl-3-methylphenoxy (FMP) moiety (a second generation photoenol precursor) was employed for orthogonal polymer polymer conjugations using terminal acrylates of diblock copolymers synthesized via acyclicdiene-metathesis (ADMET) polymerizations to directly prepare triblock copolymers. On the other hand, the disparate reactivity of 2,5-dimethylbenzophenone (first generation photoenol) and the FMP moiety was exploited to selectively synthesize complex triblock copolymers (6.5 kDa <= M-n <= 11.5 kDa, 1.16 <= PDI <= 1.30) via a sequential one pot approach utilizing the extraordinary orthogonality of the photoinduced Diels-Alder reaction. Polymers functionalized with a photoenol (second generation) moiety were employed for conjugation reactions with polymers featuring an acrylate terminus, while polymers having a photoenol (first generation) end group were employed for selective conjugations of maleimide functional polymers. In this context, the selective head-to-tail ADMET polymerization was employed as a straightforward methodology for the preparation of bifunctional polymers having a terminal acrylate and a photoenol end-group.