Amphiphilic polymer conetworks (APCNs) are polymer networks composed of hydrophilic and hydrophobic chain segments. Their applications range from soft contact lenses to membranes and biomaterials. APCNs based on polydimethylsiloxane (PDMS) and poly(2‐hydroxyethyl acrylate) are flexible and elastic in the dry and swollen state. However, they are not good at resisting deformation under load, i.e., their toughness is low. A bio‐inspired approach to reinforce APCNs is presented based on the incorporation of poly(β‐benzyl‐L‐aspartate) (PBLA) blocks between cross‐linking points and PDMS chain segments. The mechanical properties of the resulting peptide‐reinforced APCNs can be tailored by the secondary structure of the peptide chains (β‐sheets or a mixture of α‐helices and β‐sheets). Compared to non‐reinforced APCNs, the peptide‐reinforced networks have higher extensibility (53 vs. up to 341%), strength (0.71 ± 0.16 vs. 22.28 ± 2.81 MPa), and toughness (0.10 ± 0.04 vs. up to 4.85 ± 1.32 MJ m−3), as measured in their dry state. The PBLA peptides reversibly toughen and reinforce the APCNs, while other key material properties of APCNs are retained, such as optical transparency and swellability in water and organic solvents. This paves the way for applications of APCNs that benefit from significantly increased mechanical properties.
When a water drop is placed onto a soft polymer network, a wetting ridge develops at the drop periphery. The height of this wetting ridge is typically governed by the drop surface tension balanced by elastic restoring forces of the polymer network. However, the situation is more complex when the network is swollen with fluid, because the fluid may separate from the network at the contact line. Here we study the fluid separation and network deformation at the contact line of a soft polydimethylsiloxane (PDMS) network, swollen with silicone oil. By controlling both the degrees of crosslinking and swelling, we find that more fluid separates from the network with increasing swelling. Above a certain swelling, network deformation decreases while fluid separation increases, demonstrating synergy between network deformation and fluid separation. When the PDMS network is swollen with a fluid having a negative spreading parameter, such as hexadecane, no fluid separation is observed. A simple balance of interfacial, elastic, and mixing energies can describe this fluid separation behavior. Our results reveal that a swelling fluid, commonly found in soft networks, plays a critical role in a wetting ridge.
more » « less- Award ID(s):
- 1849213
- NSF-PAR ID:
- 10215058
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Communications Materials
- Volume:
- 2
- Issue:
- 1
- ISSN:
- 2662-4443
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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