Controlling the gelation temperature of biomimetic polyisocyanides

Abstract

Thermosensitive polymers show an entropy-driven transition from a well-solvated to a poorly solvated polymer chain, resulting in a more compact globular conformation. The transition at the lower critical solution temperature (LCST) is often sharp, which allows for a wide range of smart material applications. At the LCST, oligo(ethylene glycol)-substituted polyisocyanides (PICs) form soft hydrogels, composed of polymer bundles similar to biological gels, such as actin, fibrin and intermediate filaments. Here, we show that the LCST of PICs strongly depends linearly on the length of the ethylene glycol (EG) tails; every EG group increases the LCST and thus the gelation temperature by nearly 30 °C. Using a copolymerisation approach, we demonstrate that we can precisely tailor the gelation temperature between 10 °C and 60 °C and, consequently, tune the mechanical properties of the PIC gels.

Influence of Network Topology on the Viscoelastic Properties of Dynamically Crosslinked Hydrogels

“…At this moment, we can only speculate about the structure of the network equilibrated at 20 • C. Considering the properties of individual polymers, the estimated distance between CCs is ∼14 nm. This is on the same length scale as the L p determined for closely related tri(ethylene glycol) functionalized PIC polymers (12-30 nm) (Jaspers et al, 2016;Kouwer et al, 2018;Schoenmakers et al, 2018a). As a result of their increased…”

“…Considering the yield of both reactions, it can be assumed that ∼80% of CC-forming peptides are coupled to the PIC polymer. This ultimately results in an average spacing of CC-forming peptides of ∼14 nm, which is similar to the L p of closely related tri(ethylene glycol) functionalized PIC polymers (12-30 nm) (Jaspers et al, 2016;Kouwer et al, 2018;Schoenmakers et al, 2018a). It can thus be assumed that the L p and the distance between crosslinks is on a similar length scale.…”

Virus-like particles as crosslinkers in fibrous biomimetic hydrogels: approaches towards capsid rupture and gel repair

“…To obtain PIC copolymers with an LCST between 10 °C and 20 °C in the physiological buffer solutions (required for the virus particles 17,41 ), we added a small amount of tetra(ethylene glycol) functionalised monomer to the polymerisation mixture ( Figure 1). 44 Random copolymerisation using nickel perchlorate as a catalyst followed standard procedures. 20 After purification by multiple precipitations, the polymer length was determined by viscometry and yielding M v = 486 kDa and 585 kDa for two independently polymerised batches.…”

Crosslinking of fibrous hydrogels

“…Provided that the crosslinking reaction is carried out in the presence of the bundles, crosslinker concentrations of 50 µm are sufficient to stabilize the architecture. For the PIC gels, presented here, bundle formation is thermally induced (and reversible), which means that crosslinking should take place above the gelation temperature, which is readily tuned between 10 and 60 °C by simply changing the ethylene glycol tails 31 . We find that the mechanical properties at the crosslinking conditions are irreversibly captured and cooling shows minor impact on the architecture or the mechanical properties of the material.…”