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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 acyclic-diene-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.
Winkler et al. (2012) studied this question.