【作者】 汪钟凯；

【导师】 王志刚；

【作者基本信息】 中国科学技术大学 ， 材料加工工程， 2014， 博士

【摘要】 仿生材料由于其独特的性能得到广泛的研究和应用。本文首先设计制备了新型纤维素接枝聚异戊二烯共聚物,研究了该共聚物的微相分离和流变行为。以纤维素接枝聚异戊二烯为基础,设计制备了皮肤结构和力学性能仿生材料(CBPs)。并利用原位小角X-射线散射(SAXS)和广角X-射线衍射(WAXD)技术研究CBPs在循环拉伸过程中微结构的演变过程。此外,纤维素接枝聚异戊二烯共聚物还被用于设计和制备高弹力弹性体,模拟节肢弹性蛋白的杰出力学性能。其具体内容包括以下几个方面：1.本文报道了一种精心设计的新型接枝共聚物,该共聚物源自于两种具备相反物理性能的天然高分子：刚性且亲水的纤维素和柔性且疏水的聚异戊二烯(天然橡胶的类似物)。因此,该共接枝聚物将集柔性和刚性,疏水性和亲水性于一个大分子。所设计的纤维素接枝聚异戊二烯共聚物(Cell-g-PI)是通过补充催化剂和还原剂原子转移自由基聚合(SARA ATRP)制备的。FT-IR,1H NMR,13C NMR和TGA实验结果证明成功制备了Cell-g-PI。TEM和DMA实验结果证明Cell-g-PI发生微相分离。水接触角实验结果证明Cell-g-PI的疏水性随着聚异戊二烯侧链的增长而增大。通过白组织沉淀法可以制备核-壳结构的Cell-g-PI纳米微球。2.人类皮肤具备高度的非线性力学性能,这对皮肤的生理功能非常重要。在小应变时皮肤非常柔顺,而在大应变时皮肤非常强韧,从而保护人体内在组织和器官。然而,目前制备皮肤力学性能仿生材料仍然是一个重大挑战。本文设计制备了基于两种天然高分子的杂化材料,刚性的纤维素和弹性的天然橡胶,模拟皮肤的力学性能。所制备的杂化高分子展现高度非线性力学性能,非常接近皮肤的力学性能。更重要的是,通过调节纤维素的含量可以精确调节该杂化材料的力学性能,从而模拟不同类型的皮肤。3.研究结果显示循环拉伸使CBPs具备类似皮肤微结构和力学性能。原位小角X-射线散射(SAXS)和广角X-射线衍射(WAXD)实验被用来进一步研究循环拉伸过程中CBPs微结构演化过程。TEM结果显示CBPs样品展现两相结构：纤维素纳米球分散在聚异戊二烯基体中。原位SAXS实验结果显示拉伸过程中纤维素纳米微球逐渐转变为纤维素纳米纤维并取向。除去外力,纤维素纳米纤维不能变回纳米球。原位WAXD实验结果显示拉伸过程中聚异戊二烯链段首先发生取向,且整个拉伸过程中并无三维有序晶体结构产生。4.节肢弹性蛋白由于具备杰出的力学性能而受到广泛的关注,最近有大量研究致力于制备节肢弹性蛋白仿生材料。然而,在合成材料领域,制备具备节肢弹性蛋白力学性能的仿生材料仍然不可实现。本文设计了基于纤维素和天然橡胶的高弹力弹性体(HREs)模拟节肢弹性蛋白的力学性能。FT-IR,1HNMR,13C NMR和TGA实验结果证明成功制备了HREs。TEM结果显示纤维素纳米微球均匀分散在弹性基体中作为交联点。力学性能分析显示HREs具备类似节肢弹性蛋白的力学性能。更多还原

【Abstract】 Biomimetic materials have been intensively studied due to their unique properties and have been wide applied. In this dissertation, we first design novel cellulose-graft-polyisoprene copolymers and studied their microphase structure and rheological properties. Then we prepared multi-phase polymers to mimic the micro structure and mechanical properties based on these cellulose-graft-polyisoprene copolymers (CBPs). In situ small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques were used to study the micro structure rearrangement during cyclic tensile deformation of CBPs. Moreover, cellulose-graft-polyisoprene copolymers were used in the design of high resilient elastomers to mimic the mechanical properties of resilin. The details and key conclusions are described as follows:1. An elegant design of novel graft copolymers based on two natural abundant biopolymers with opposite physical properties:rigid and hydrophilic cellulose, and flexible and hydrophobic synthesized polyisoprene (analogue of natural rubber), which combines the rigidity and flexibility, hydrophobicity and hydrophilicity all in one macromolecules. These cellulose-graft-polyisoprene (Cell-g-PI) copolymers were synthesized via homogenous supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP). FT-IR,1H NMR,13C NMR and TGA measurements demonstrate that Cell-g-PI copolymers are successfully prepared. TEM and DMA results illustrate that phase separation occurs in Cell-g-PI copolymers. Water contact angle measurements verify that their hydrophobicity increases with increasing polyisoprene side chain length. In addition, the core-shell Cell-g-PI nanoparticles in water can be prepared via self-organized precipitation (SORP) method.2. Human skin exhibits highly nonlinear elastic properties that are essential to its physiological functions. It is soft at low strain but stiff when strained, thereby protecting internal organs and tissues from mechanical trauma. However, to date, the development of materials to mimic the unique mechanical properties of human skin is still a great challenge. Here we report a bioinspired design of multiphase polymers combining two important plant-based biopolymers, stiff cellulose and elastic polyisoprene (natural rubber), to mimic human skin. The hybridpolymers show highly nonlinear mechanical properties closely mimicking that of human skin. Importantly, the mechanical properties of the hybrid polymers can be tuned by adjusting cellulose content, providing the opportunity to synthesize materials that mimic different types of skins. Given the simplicity, efficiency, and tunability, this design may provide a promising strategy for creating artificial skin both for general mechanical and biomedical applications.3. The CBPs samples exhibit human skin like mechanical properties and dermis-like microstructures after cyclic tensile deformation. In order to develop a more complete understanding of the deformation-induced structure rearrangements of CBPs samples, we performed in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) measurements. TEM image shows that the undeformed CBPs samples separated into two phases:cellulose nanospheres and polyisoprene matrix. Simultaneous SAXS and tensile measurements have been recorded during tensile loading/unloading cycles of the CBPs samples. The results demonstrated that the cellulose nanospheres change into nanofibers and orientate during stretching. After relaxation, the formed cellulose nanofibers do not return to nanospheres. WAXD data verified that the amorphous polyisoprene segments are increasingly oriented along the deformation direction and no crystalline structure formed during the whole tensile deformation process.4. Resilin possesses outstanding mechanical properties, which motivated recent effort in the engineering of resilin-like materials for biomedical applications. However, the preparation of synthetic materials to mimic the mechanical properties of resilin is still a challenge. In this dissertation, we designed high resilient elastomers (HREs) based on stiff cellulose and flexible polyisoprene. FT-IR,1H NMR, CP/MAS solid state13C NMR, and TGA were performed to demonstrate the successful preparation of HREs. TEM images show that cellulose nanoaprticles homogeneously embedded in polyisoprene matrix and act as cross-linkers. Mechanical analyze on HERs verified that they exhibit mechanical properties comparable to that of resilin.更多还原