Alternating ring-opening metathesis polymerization

A method for producing a polymer comprising the repeating unit Ia or Ib:

• which comprises contacting an olefin of structure IIa or IIb with a cyclobutene of structure III
• in the presence of an olefin metathesis catalyst, wherein
• R is selected form the group consisting of H, C1-C20 alkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, heterocyclyl, aryl, aralkyl, C1-C20 alkoxy, C1-C20 alkylthio, C2-C20 alkenyloxy, C2-C20 alkenylthio, C3-C6 cycloalkyloxy, C3-C6 cycloalkylthio, aryloxy, arylthio, heterocyclyloxy, or heterocyclylthio;
• R1 through R6 are independently selected from the group consisting of H, C1-C20 alkyl, C2-C20 alkenyl, C3-C6 cycloalkyl, C1-C20 hetero-substituted alkyl, aryl, heterocyclyl, aralkyl, C1-C20 alkoxy, C2-C20 alkenyloxy, C3-C6 cycloalkyloxy, aryloxy, heterocyclyloxy, and halogen;
• or one or more pairs of substituents selected from the group consisting of R1-R2, R2-R3, R3-R4, and R5-R6, together with the carbons to which they are attached, form a carbocyclic or heterocyclic ring;
• additionally or alternatively, any of R1-R6 may represent two substituents bonded to the same carbon atom, which are independently selected from the above group;
• R7 and R8 are independently selected from the group consisting of H, C1-C20 alkyl, C1-C20 hetero-substituted alkyl, C3-C6 cycloalkyl, aryl, heterocyclyl, C1-C20 alkoxy, C1-C20 acyloxy, C1-C20 substituted-amino, C1-C20 protected-amino, C3-C6 cycloalkyloxy, aryloxy, heterocyclyloxy, and halogen;
• with the proviso that any carbon-carbon double bonds in R or in R1 through R6 are essentially unreactive toward metathesis reactions with the catalyst.