Simple Monomers for Precise Polymer Functionalization During Ring-Opening Metathesis Polymerization

Abstract

Controlling the monomer sequence of synthetic polymers is a grand challenge in polymer science. Conventional sequence control has been achieved in dispersed polymers by exploiting the kinetic tendencies of monomers and their order of addition. While the sequence of blocks in multiblock copolymers can be readily tuned using sequential addition of monomers (SAM), control over the sequence distribution is eroded as the targeted block size approaches a single monomer unit (i.e., X n ∼ 1) due to the stochastic nature of chain-growth reactions. Thus, unique monomers are needed to ensure precise single additions. Herein, we investigate common classes of cyclic olefin monomers for ring-opening metathesis polymerization (ROMP) to identify monomers for single unit addition during sequential monomer addition synthesis. Through careful analysis of polymerization kinetics, we find that easily synthesized oxanorbornene imide monomers are suitable for single-addition reactions. With the identified monomers, we demonstrate the synthesis of multiblock copolymers containing up to three precise functionalization sites and singly cross-linked four-armed star copolymers. We envision that expanded kinetic analyses of monomer reactivities in ROMP reactions will enable novel polymer synthesis capabilities such as the autonomous synthesis of sequence-defined polymers or one-shot multiblock copolymer syntheses.

Unexpected Periodicity in Cationic Group 5 Initiators for the Ring-Opening Polymerization of Lactones

“…It is similarly feasible that catalytic application of Nb and Ta complexes bearing coordinated lactones distinct from the monomer feed could enable facile modification of polymer properties through the aforementioned stoichiometric (or, where a co-initiator is used, substoichiometric) synthesis-stage installation of single differentiated monomer residues via intramolecular reaction with the alkoxide initiating group. The authors are unaware of any alternative one-pot routes to achieving precise single-unit differentiation in the ROP of lactones or lactides (ring-opening transesterification polymerization, ROTEP), and while such sequence control has been reported for other polymerization types, such as the ring-opening metathesis polymerization (ROMP) of cyclic olefins, − among others, , this has typically been reliant upon reactivities in which the addition of the desired single-monomer unit reversibly deactivates the active species. ,, One notable exception to this general requirement is Foster and co-workers’ recent report concerning the ROMP of oxanorbornene imide monomers, wherein discrepancies between different monomer stereoisomers’ binding affinity for the Hoveyda–Grubbs catalyst used and the rates at which they respectively underwent propagation were exploited to achieve single-unit addition . The current system, similarly, does not necessitate such a deactivation event.…”

“… 52 , 53 , 55 One notable exception to this general requirement is Foster and co-workers’ recent report concerning the ROMP of oxanorbornene imide monomers, wherein discrepancies between different monomer stereoisomers’ binding affinity for the Hoveyda–Grubbs catalyst used and the rates at which they respectively underwent propagation were exploited to achieve single-unit addition. 53 The current system, similarly, does not necessitate such a deactivation event. However, in this case stoichiometric introduction of the differentiated monomer residue instead arises directly as a result of the catalytic induction.…”

Controllable Wet-Brush Blending of Linear Diblock Copolymers with Phenolic/DDSQ Hybrids toward Mesoporous Structure Phase Diagram

“…Self-assembled structures such as typical lamella (LAM), hexagonal packing cylinder (HPC), sphere, double gyroid (DG), and even special Frank–Kasper phases of immiscible diblock copolymers (BCP) have been widely investigated during recent years because of their potential applications including soft lithography, photonic crystals, nanocomposites, and mesoporous materials. − The synthetic strategies of BCP with composition and structural variety are mainly from sequential addition of monomer through controlled living polymerization techniques or coupling reactions from the active chain ends with two different polymer chains. − It is well-known that the self-assembled structures are primarily dependent on the volume fraction, interaction parameter (χ), and degree of polymerization ( N ); however, mediating the volume fraction is complicated and time-consuming through the controlled living polymerization . As a result, blending homopolymer (A or B) into an A- b -B diblock copolymer is a relatively simpler method to mediate different self-assembled structures for varying volume fractions …”

Installing a Single Monomer within Acrylic Polymers Using Photoredox Catalysis

“…Previous work incorporating successive single-unit monomer insertion reactions to access oligomers, ,,, exactly 1 monomer into polymers by ring-opening metathesis polymerization (ROMP), , and statistically incorporating monomers into polymers using reversible–deactivation radical polymerization (RDRP) ,, versus the incorporation of exactly 1 vinyl ether monomer into polyacrylates using RDRP.…”

“…Monomer design can be used to place single functionalities in polynorbornenes using ring-opening metathesis polymerization (ROMP, Figure ). , However, accessing analogous structures using reversible-deactivation radical polymerization (RDRP) has not been accomplished because radical polymerizations rely entirely upon monomer addition kinetics. A chain-end deactivation approach similar to the one used for ROMP is inaccessible due to the radical nature of RDRP.…”