Soft underwater adhesives that can function in physiological environments are in high demand for biomedical applications. This study establishes a clear link between the composition and mechanical properties of complex coacervates from poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and poly(N,N-[(dimethylamino) propyl]methacrylamide) (PMADAP) with degrees of polymerization (DP) close to 100. Choosing such low DP offers several advantages including low water contents corresponding to strong mechanical properties while remaining in the unentangled regime to allow injectability at high salt concentrations. Most importantly, this strategy favors the occurrence of the salt-induced sol–gel transition near physiological concentrations, where these materials form sticky hydrogels because of their viscoelastic dissipative nature. The fluidlike coacervate prepared at 0.75 M NaCl behaves as a soft adhesive when injected in physiological conditions. This adhesive satisfies a nontrivial trade-off between injectability and final mechanical properties. Alternatively, the gel-like coacervate prepared at 0.1 M NaCl offers an instant-stick solution in physiological conditions with a remarkable underwater adhesion energy reaching 65 J m^–2 at 2 s⁻¹ without the need for a trigger or any form of postreinforcement. These coacervates mimic the behavior of soft adhesives in air and may be useful as biomedical adhesives.

中文翻译：

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生理条件下基于凝聚层的水下胶粘剂

在生物医学应用中对可以在生理环境中起作用的水下软粘合剂有很高的要求。这项研究建立了聚（2-丙烯酰胺基-2-甲基丙烷磺酸）（PAMPS）和聚（N，N-[（（二甲氨基）丙基]甲基丙烯酰胺）（PMADAP）复合凝聚层的组成与力学性能之间的明确联系聚合度（DP）接近100。选择这样的低DP提供了几个优点，包括低水含量对应于强机械性能，同时保持在无缠结状态以允许在高盐浓度下可注射。最重要的是，该策略有利于在生理浓度附近发生盐诱导的溶胶-凝胶转变，由于它们的粘弹性耗散性质，这些物质形成粘性的水凝胶。在生理条件下注射时，以0.75 M NaCl制备的液状凝聚层表现为柔软的粘合剂。这种粘合剂满足了可注射性和最终机械性能之间的重要平衡。另外，在0.1 M NaCl溶液中制备的凝胶状凝聚层可在生理条件下提供速溶溶液，水下粘附力达到65 J m在2 s ^-1时为^–2，无需扳机或任何形式的后期加固。这些凝聚层模拟了空气中软粘合剂的行为，可用作生物医学粘合剂。