Ryan Baumgartner

Functional polyesters derived from alternating copolymerization of norbornene anhydride and epoxides

Herein, we report the synthesis of polyesters via the alternating copolymerization of epoxides and cis-5-norbornene-endo-2,3-dicarboxylic anhydride (NB). The polymers are demonstrated to be of perfectly alternating structure with monomodal peak distributions and low polydispersity indexes. We demonstrate that these polyesters can be functionalized using thiol–ene and tetrazine click chemistry to form polymers with alternating functionality. Furthermore, we show that these polymers can be made thermally responsive, and can even be crosslinked when mixed with Grubbs’ catalyst.

Cooperative polymerization of α-helices induced by macromolecular architecture

Catalysis observed in enzymatic processes and protein polymerizations often relies on the use of supramolecular interactions and the organization of functional elements in order to gain control over the spatial and temporal elements of fundamental cellular processes. Harnessing these cooperative interactions to catalyse reactions in synthetic systems, however, remains challenging due to the difficulty in creating structurally controlled macromolecules. Here, we report a polypeptide-based macromolecule with spatially organized α-helices that can catalyse its own formation. The system consists of a linear polymeric scaffold containing a high density of initiating groups from which polypeptides are grown, forming a brush polymer. The folding of polypeptide side chains into α-helices dramatically enhances the polymerization rate due to cooperative interactions of macrodipoles between neighbouring α-helices. The parameters that affect the rate are elucidated by a two-stage kinetic model using principles from nucleation-controlled protein polymerizations; the key difference being the irreversible nature of this polymerization.

Modulation of polypeptide conformation through donor-acceptor transformation of side-chain hydrogen bonding ligands

Synthetic polypeptides have received increasing attention due to their ability to form higher ordered structures similar to proteins. The control over their secondary structures, which enables dynamic conformational changes, is primarily accomplished by tuning the side-chain hydrophobic or ionic interactions. Herein we report a strategy to modulate the conformation of polypeptides utilizing donor–acceptor interactions emanating from side-chain H-bonding ligands. Specifically, 1,2,3-triazole groups, when incorporated onto polypeptide side-chains, serve as both H-bond donors and acceptors at neutral pH and disrupt the α-helical conformation. When protonated, the resulting 1,2,3-triazolium ions lose the ability to act as H-bond acceptors, and the polypeptides regain their α-helical structure. The conformational change of triazole polypeptides in response to the donor-acceptor pattern was conclusively demonstrated using both experimental-based and simulation-based methods. We further showed the utility of this transition by designing smart, cell-penetrating polymers that undergo acid-activated endosomal escape in living cells.Hydrogen bonding plays a major role in determining the tridimensional structure of biopolymers. Here, the authors show that control over a polypeptide conformation can be achieved by altering the donor-acceptor properties of side-chain triazole units via protonation-deprotonation.

A delayed curing ROMP based thermosetting resin

Here, we develop a heat curing thermosetting resin using ring-opening metathesis polymerization. The resin has a prolonged working time at room temperature and cures rapidly at elevated temperatures. We detail the delayed cure activity and investigate the resulting thermal and mechanical properties of the cured materials.