Abstract
Controlling the primary sequence of synthetic polymers remains a grand challenge in
chemistry. A variety of methods that exert control over monomer sequence have been
realized wherein differential reactivity, pre-organization, and stimuli-response have
been key factors in programming sequence. Whereas much has been established in nonconjugated
systems, π-extended frameworks remain systems wherein subtle structural changes influence
bulk properties. The recent introduction of electronically biased ring-opening metathesis
polymerization (ROMP) extends the repertoire of feasible approaches to prescribe donor–acceptor
sequences in conjugated polymers, by enabling a system to achieve both low dispersity
and controlled polymer sequences. Herein, we discuss recent advances in obtaining
well-defined (i.e., low dispersity) polymers featuring donor–acceptor sequence control,
and present our design of an electronically ambiguous (4-methoxy-1-(2-ethylhexyloxy)
and benzothiadiazole-(donor–acceptor-)based [2.2]paracyclophanediene monomer that
undergoes electronically dictated ROMP. The resultant donor–acceptor polymers were
well-defined (Đ = 1.2, Mn > 20 k) and exhibited lower energy excitation and emission in comparison to ‘sequence-ill-defined’
polymers. Electronically driven ROMP expands on prior synthetic methods to attain
sequence control, while providing a promising platform for further interrogation of
polymer sequence and resultant properties.
1 Introduction to Sequence Control
2 Sequence Control in Polymers
3 Multistep-Synthesis-Driven Sequence Control
4 Catalyst-Dictated Sequence Control
5 Electronically Governed Sequence Control
6 Conclusions
Key words
ring-opening metathesis polymerization - organic synthesis - sequence controlled -
polymer chemistry - conjugated polymers - paracyclophane - donor–acceptor