“集成天然橡胶”原理研究

Because yield of NR from biosynthesis is restricted by geographical environment, a self-providing ratio for NR in Chain is far below security cordon. It has been realized that an artificially synthesized polyisoprene rubber (IR) is optimal substitute for NR, however, after rubber hydrocarbon in NR is copied completely by IR, the diversity of both rubber in properties still is prominent, which is attributed to non-rubber components in NR. The latest investigations suggest that the non-rubber components mainly consist of proteins, phospholipids and a small quantity of fatty acids, yet it is still unclear what structures and functions of the non-rubber components endow NR with excellent performances..In the project, we plan to construct series of model systems which are derived from either NR or IR for elaborate comparision. The first systems from NR comprise the models containing only phospholipids（fatty acid）, containing both phospholipids (fatty acid)and proteins，and containing neither. The second system is prepared from the synthesized IR with modification of the end groups. The strain-induced crystallization behaviors under uniaxial tension will be studied by in situ synchrotron wide-angle X-ray diffraction and in situ dielectric relaxation spectroscopy. By employing small-angle neutron scattering and dielectric spectroscopy with the aid of 2D correlation analysis created by our group, the contribution of each non-rubber component to forming the nature networks is going to be revealed, and then the effect of nonuniformity of network chains on strain-induced crystallization behaviors as well as the relationship between the later and mechanical and tired properties of rubber will be investigated. Finally a preparation principle of “composite NR” from IR will be probed for providing basis for improving performance of IR by processing.

受地理环境限制，我国天然橡胶（NR）的自给率已低于安全警戒线。合成聚异戊二烯（IR）是NR的最佳替代物，但是当NR橡胶烃分子结构完全被IR仿制后，二者仍然显著的性能差异被归因于NR的非胶成分。按照最新认识，NR非胶成分主要包含蛋白质，磷脂及少量脂肪酸等，但是其赋予橡胶烃优异性能的结构功能还不清楚。.拟采用NR为基体设计制备包含磷脂（脂肪酸），包含磷脂（脂肪酸）和蛋白质，和两者皆不包含的模型物；通过对IR进行端基修饰，制备对应IR模型物；由此建立精细的对比体系。采用原位同步辐射宽角X衍射和原位介电松弛谱，研究模型物在单轴拉伸条件下的应变结晶行为；采用小角中子散射，一维介电松弛谱和本组发展的二维介电松弛谱揭示各非胶成分对网络的贡献，网络链非均匀性结构变化对应变诱导结晶行为的影响,以及后者与橡胶力学性能疲劳性能的关系，探讨由IR制备“集成天然橡胶”的原理，为从加工改进IR性能提供依据。

橡胶是国家安全和国民经济发展不可或缺的重要材料之一。以聚异戊二烯为橡胶烃的天然橡胶(NR)，具有合成橡胶无可比拟的优异综合性能。为了深刻理解和揭示其中奥秘，本项目从对比NR的模型物，分子水平模仿以及原理模仿等三个方面，着重对天然网络进行了研究。.首先，制备和表征了三种含有不同非胶成分的模型物NR，DPNR以及TEDPNR，通过对比研究它们对橡胶烃分子量及其分布、流体力学体积和粘度的影响以及介电松弛转变行为的变化，初步诠释了NR形成宽分子量分布和非键网络的原因；通过先进的随机光学重构显微技术第一次成功地将蛋白质和磷脂区分开来，观察到蛋白质和磷脂在胶乳和NR本体中的聚集状态及其自组装行为规律；采用同步辐射和固体核磁等深入分析非胶成分对分子运动和应变诱导结晶的影响规律，从多个角度揭示了天然网络的非均匀性，进一步离析出分子链的瞬态缠结和永久缠结，进而提出了由橡胶烃端基络合对分子链缠结的锚定而形成天然网络的机制；发现天然网络具有牺牲键的作用，证明正是其能量耗散功能，显著提高了天然橡胶的力学性能和耐疲劳性能。.同时，通过稀土催化聚合和接枝改性对NR的端基和天然网络进行仿制，制备了序列结构可控的多肽和磷脂修饰的合成异戊橡胶（IR），揭示了多肽和磷脂的组装形貌及其对分子运动、微相分离、粘弹特性、应变诱导结晶等的影响。进一步制备了多种高强高韧的IR生胶。第一次从分子水平上直接验证了NR中端基通过非键络合组装形成天然网络和支化结构的原理和功能。 .在深刻剖析NR结构与性能的基础上，发展了多种化学和填料改性IR的方法。在IR基体中引入不同类型的牺牲键和填料网络，实现了IR的高效增强增韧，揭示了牺牲键结构（种类，键能及含量）、填料网络和界面作用对橡胶能量耗散、粘弹行为、应变诱导结晶和力学性能的影响，阐明牺牲键和填料网络增强增韧橡胶的机制，实现了从原理上对NR中通过非键相互作用形成的网络的创新性模仿。.本项目取得的研究成果为理解生物合成NR具有优异性能的原理机制提供了迄今为止最深入的科学解释，也为制备性能优异的合成橡胶提供了理论依据和创新思路。