Introduction of Periodic Ketone Units on Vinyl Polymers via a Radical Alternating Copolymerization and Postpolymerization Modification: Sequence-Oriented Photodegradation in the Bulk State

The synthesis and the sequence-oriented bulk-state photodegradation of sequence-controlled polymers with a periodic structure bearing acrylamide, ketone, and vinyl ether units is reported. The alternating terpolymers can be synthesized via a radical copolymerization of a silyl-protected 1,3-butadiene bearing a methyl ether group (SBD) with a pentafluorophenyl acrylate (PFA) monomer in an alternating and 1,4-regioselective fashion. This process is followed by the addition of an amine to trigger a cascade aminolysis-desilylation reaction. The pendant alkyl group on the acrylamide unit, which is derived from the added amine, is crucial for determining the physical properties of a series of polymers, particularly the glass-transition temperature (T_g). Relatively flexible and sufficiently thermally stable polymers with T_g values below room temperature could be degraded under UV irradiation in the bulk state. Control experiments revealed that synergistic interactions between the periodically arranged ketone, vinyl ether, and acrylamide units were essential for promoting the photodegradation.