Design and Synthesis of Quick Setting Nonswelling Hydrogels via Brush Polymers

Abstract

Brush polymers have emerged as components of novel materials that show huge potential in multiple disciplines and applications, including self‐assembling photonic crystals, drug delivery vectors, biomimetic lubricants, and ultrasoft elastomers. However, an understanding of how this unique topology can affect the properties of highly solvated materials like hydrogels remain under investigated. Here, it is investigated how the high functionality and large overall size of brush polymers enhances the gelation kinetics of low polymer weight percent gels, enabling 100‐fold faster gelation rates and 15‐fold higher stiffness values than gels crosslinked by traditional star polymers of the same composition and polymer chain length. This work demonstrates that brush polymer topology provides a useful means to control gelation kinetics without the need to manipulate polymer composition or crosslinking chemistry. The unique architecture of brush polymers also results in restrained or even nonswelling behavior at different temperatures, regardless of the polymer concentration. Brush polymers therefore are an interesting tool for examining how high‐functionality polymer building blocks can affect structure–property relationships and chemical kinetics in hydrogel materials, and also provide a useful rapidly‐setting hydrogel platform with tunable properties and great potential for multiple material applications.

Bottlebrush Polymer-Conjugated Melittin Exhibits Enhanced Antitumor Activity and Better Safety Profile

“…Transmission electron microscopy (TEM) shows that pacMEL Clv exhibits a globular structure with a dry-state diameter of 23 ± 3 nm, which is in line with dynamic light scattering (DLS) analysis (a D h of 34.1 ± 0.4 nm, Figure C,D). The observed globular morphology of pacMEL is the result of the collapse of the hydrophobic polynorbornene backbone in aqueous solution, which has been reported in other studies and simulations. , Considering the number of the side chains (DP n ∼ 30) in our design, the polymer used in pacMEL has entered the bottlebrush regime and should offer stronger steric inhibition of external macromolecules than the slightly branched star polymers. , Y PEG-MEL exhibits an expected smaller cumulant D h of 21.0 ± 0.5 nm. ζ-potential measurements indicate that PEGylation reduces the overall positive charge of MEL, especially by the bottlebrush PEG; both the pacMELs exhibit a near-neutral ζ-potential (0.3 mV) compared with natural MEL (∼8 mV, Figure E).…”

“…The observed globular morphology of pacMEL is the result of the collapse of the hydrophobic polynorbornene backbone in aqueous solution, which has been reported in other studies and simulations. 32,33 Considering the number of the side chains (DP n ∼ 30) in our design, the polymer used in pacMEL has entered the bottlebrush regime and should offer stronger steric inhibition of external macromolecules than the slightly branched star polymers. 21,34 Y PEG-MEL exhibits an expected smaller cumulant D h of 21.0 ± 0.5 nm.…”

Brush Polymers as Nanoscale Building Blocks for Hydrogel Synthesis

“…In other words, the degree of valency or f for each brush polymer can be specified as a function of the brush polymer synthesis, thereby providing a good model to study the influence of f on the hydrogel behavior. A preliminary study has now demonstrated that cross-linking the arms of water-soluble brush polymers can indeed induce interesting properties in the resulting gels. , For example, these hydrogels exhibited rapid gelation (100-fold increase in gelation rate compared with 4-arm star polymers of an identical arm length) and nearly entirely nonswelling behavior at body temperature (∼37 °C). Because these properties make brush polymer gels potentially beneficial in different biomedical applications, it is important to further investigate the relationship between the brush polymer design and the properties of resulting hydrogels to understand how the brush topology affects the gel behavior in a more systematic manner.…”

Linking microscopic structural changes and macroscopic mechanical responses in a near-ideal bottlebrush elastomer under uniaxial deformation

“…Such features of BB polymers have stimulated researchers to develop various functional materials, including ultrasoft elastomers 2,3 exhibiting mechanochromism 4 or reprocessability, 5 nanoporous materials, 6 polymer ink with tunable structural color, 7 and quick-setting hydrogels. 8 In particular, elastomers and gels formed by cross-linking of BB polymers have been studied extensively because the unique chain architecture directly influences mechanical properties. The seminal work by Vatankhah-Varnosfaderani 3 showed that the use of BB polymers as components of network polymers enabled soft and strain-stiffening mechanical responses similar to biological tissues, which were inaccessible for conventional gels and elastomers.…”