Macromolecular-bottlebrush polymeric gels with tissue-mimetic swelling and mechanical properties

活体组织的独特之处在于它们能够在几乎恒定的水分数下无缝地跨越一系列机械特性，从超软的大脑到超坚韧的软骨。相反，组织的合成类似物（即聚合凝胶）目前无法在不影响其力学的情况下控制水量。本文提出了一种基于瓶刷-大分子结构的新型聚合物材料，可以实现对凝胶组成和力学性能的独立可编程控制。与传统的线性聚合物相比，瓶刷结构引入了无数的侧链或“刷毛”，这些侧链或“刷毛”提供了额外的分子参数，以在不改变水分数的情况下调节柔软度。此外，定制侧链末端的化学性质将为模拟组织设备的增材制造提供新的应用，例如可编程和可注射材料。提出的新型聚合物凝胶将通过整合尖端聚合物化学、软物质物理和新兴技术，为跨学科研究提供充足的机会，这些技术可能会在生物医学设备、组织工程支架和软机器人等许多应用领域取得突破。技术概述该项目将解决三个基本挑战。首先，将平衡膨胀率和凝胶力学性能分别与侧链长度和接枝密度等刷状网络的结构参数相关联。建筑-膨胀-力学相关性的三角测量将提供对膨胀、柔软和非线性力学响应的独立控制。例如，这将创造出一系列前所未有的合成凝胶，它们具有相同的溶剂分数，但模量在几个数量级内变化很大。第二个目标是设计类似刷子的介块，使模拟组织弹性体的无溶剂注射成为可能。目前面临的挑战是如何将固化时间从几秒钟控制到几天，而不考虑完全固化聚合物网络的机械性能。最后，目标1和目标2的成功实施将使一类基于热敏水凝胶的新型生物链接材料成为可能，这种材料可以注入和3d打印具有明确溶剂组分和机械性能的物体。这里的主要挑战是将打印材料的受控温度凝胶化与目标1和目标2中追求的基于架构的设计目标相结合。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYLiving tissues are distinct in their ability to seamlessly span a range of mechanical properties from ultra-soft brain to super-tough cartilage at nearly constant water fraction. On the contrary, synthetic analogs of tissues (i.e. polymeric gels) are currently not capable to control the amount of water without affecting their mechanics. A new class of polymeric materials based on bottlebrush-macromolecular architectures is proposed here to enable independent and programmable control over gel composition and mechanical properties. In contrast to traditional linear polymers, the bottlebrush architecture introduces a myriad of side chains or “bristles” that afford additional molecular parameters to tune softness without changing the water fraction. Furthermore, tailoring the chemistry of side-chain ends will empower novel applications such as programmable and injectable materials for additive manufacturing of tissue-mimetic devices. The proposed novel class of polymeric gels will provide ample opportunities for interdisciplinary research through integration of cutting-edge polymer chemistry, soft-matter physics, and emerging technologies that may lead to breakthroughs in many applications such as biomedical devices, tissue-engineering scaffolds, and soft robotics. TECHNICAL SUMMARYThe project will address three fundamental challenges. First, the equilibrium swelling ratio and gel’s mechanical properties will be separately correlated with architectural parameters of brush-like networks such as the side chain length and grafting density. Triangulation of architecture-swelling-mechanics correlations will afford independent control over swelling, softness, and non-linear mechanical response. For example, this will create an unprecedented series of synthetic gels with the same solvent fraction, but widely different moduli varying within several orders of magnitude. The second goal is to design brush-like mesoblocks that enable solvent-free injection of tissue-mimetic elastomers. The challenge is to control curing time from seconds to days separate from mechanical properties of fully cured polymer networks. Lastly, successful implementation of goals 1 and 2 will enable a new class of bioink materials based on thermosensitive hydrogels that can inject and 3D-print objects with well-defined solvent fractions and mechanical properties. The main challenge here is to integrate controlled-temperature gelation of printed materials with the design-by-architecture objectives pursued in goals 1 and 2.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.