Precise Placement of Single Monomer Units in Living Ring-Opening Metathesis Polymerization

Abstract

The locations and sequence of discrete monomers along a polymer chain can affect polymer properties and behaviors but are challenging to control even in living polymerizations. Xia and co-workers report selective single additions of a type of cyclopropene to precisely place various functional moieties at desired locations in a narrow-disperse homopolymer or block copolymer chain, opening the door to precise synthesis of polymer structures and architectures and thus control of polymer properties and self-assembly.

Oxanorbornenes: promising new single addition monomers for the metathesis polymerization

“…Exhibiting little or no ring strain, small cycloalkenes such as cyclohexene (Chex), cyclopentene (Cpen), or cycloheptene (Chep) are popular comonomers in alternating ROMP polymer synthesis. 31,32,40,41 We hypothesized that, aer fast initiation of G3 with a bulky strained monomer (such as 2-4, see above), the formed alkylidene might still react with a less bulky cycloalkene monomer. This would lead to a sterically less hindered alkylidene which could react once more with a new strained but bulky monomer leading, eventually, to an alternating sequence.…”

“…Later, Xia and co-workers introduced a creative approach for AROMP using the single molecular addition of sterically hindered cyclopropene derivatives. [40][41][42][43][44] However, the preparation of cyclopropenes for AROMP is synthetically challenging.…”

‘Sacrificial’ supramolecular assembly and pressure-induced polymerization: toward sequence-defined functionalized nanothreads

“…Inspired by precision sequencing and supramolecular self-assembly in Nature, programming primary structure in synthetic polymers remains a holy grail for organic chemists. 1 Methods that utilize differential kinetics of monomer reactivity, 2,3 exploit enthalpic or entropic driving forces, [4][5][6] or allow for preorganized monomer sequences to directly transfer to synthetic polymers garner much interest. [7][8][9] Despite the prominence of supramolecular organization and self-correction in natural biopolymer synthesis, noncovalent methods to transfer precise sequences directly to products remain underexplored, likely because the need to juxtapose reactants in an eclipsed manner necessitates tactically-precise supramolecular interactions that propagate parallel to the polymerization axis.…”

Transition-Metal-Catalyzed Polymerization of Cyclopropenes

“…In order to further control the polymer structures, the precise placement of single monomer units in living ROMP was explored by the same group [39] using CPE (Scheme 16). First, the efficiency of reinitiating the ROMP of NBE from a CPE end-capped poly-NBE was inspected.…”