RUI: Laser-Zone Drawing and Annealing of High Strength Polymer Nanofibers

这项工作产生了与激光加热聚合物以设计和制造高强度纳米纤维相关的新知识。在高分子材料科学、工程和制造领域产生的科学知识和技术进步促进了经济增长，造福社会。聚合物纳米纤维在包括能源、运输、航空航天、医疗保健、电子和传感在内的各种关键行业中具有广泛的应用。理论上，纳米纤维预期比较大的常规纤维更强，但实际上纳米纤维通常弱得多。之所以出现这种差异，是因为设计有序内部结构所需的制造工艺很难应用于微小、精致的纳米纤维。该资助支持研究与聚合物拉伸过程中激光加热相关的基础科学关系，以实现对内部结构的特殊控制并提高强度。此外，该研究使用了一种独特的自动化轨道连续拉丝系统，确保了规模扩大和商业化的清晰路径。该项目为众多本科生和研究生提供了材料科学、先进制造和纳米技术方面的高级培训，并建立了通往工程学士学位研究培训计划的途径，为寻求工程学士学位的代表性不足、经济困难的学生提供支持。激光区域拉伸已证明了生产具有高拉伸强度的聚合物纤维的潜力，这些纤维的拉伸强度超过了使用传统纤维制造方法的可能性。然而，在严格控制的条件下，特别是对于聚合物纳米纤维，还没有研究控制激光区域纤维拉伸的基本热力学和材料加工关系。这项工作填补了知识空白，通过使用计算模型和实验研究的聚合物纤维受到激光加热，同时连续监测机械性能。为了加工整个光纤，激光束被顺序扫描以快速加热光纤的每个小部分或区域，使其柔韧，从而可以拉伸。在已知纤维张力和时间区温度的情况下，研究了激光区域拉伸过程中大分子结构的发展。这种方法有望促进对加工纤维的最终内部结构的显著控制，并产生优异的机械强度。自动化轨道的利用允许精细纳米纤维的受控激光区域拉伸。待测试的假设是纳米纤维的快速加热和冷却，由于它们的高表面积与体积比，促进了聚合物链在升高的温度下的排列，所述聚合物链在链松弛可能发生之前在快速冷却期间锁定在适当位置，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，更广泛的影响审查标准。

This work generates new knowledge associated with laser heating of polymers to engineer and manufacture high strength nanofibers. The scientific knowledge and technological advances generated in the areas of polymer materials science, engineering and manufacturing promote economic growth and benefit society. Polymer nanofibers have widespread applications in a variety of critical industries including energy, transportation, aerospace, healthcare, electronics and sensing. Theoretically, nanofibers are expected to be stronger than larger conventional fibers, but in practice nanofibers are usually much weaker. This discrepancy arises because the manufacturing processes required to engineer ordered internal structures are difficult to apply to tiny, delicate nanofibers. This grant supports the investigation of fundamental scientific relationships associated with laser heating during polymer nanofiber stretching for exceptional control over the internal structure and resulting enhanced strength. Furthermore, the research uses a unique automated track continuous fiber-drawing system that ensures scale up and a clear path to commercialization. The project provides advanced training in materials science, advanced manufacturing and nanotechnology to numerous undergraduate and graduate students and establishes the Path to BS Research Training Program that supports underrepresented, economically disadvantaged students seeking BS degrees in Engineering.Laser zone drawing has demonstrated the potential to produce polymer fibers with high tensile strengths that exceed what is possible using conventional fiber manufacturing methods. However, the fundamental thermodynamic and material processing relationships governing laser zone fiber drawing have not been studied under tightly controlled conditions, especially for polymer nanofibers. This work fills that knowledge gap by using computational models and experimental investigation of polymer fibers subject to laser heating while the mechanical properties are continuously monitored. To process entire fibers, the laser beam is sequentially scanned to rapidly heat each small portion or zone of a fiber to make it pliable so it can be stretched. Macromolecular structure development during laser zone drawing is investigated with known fiber tension and temporal zone temperature. This approach is expected to facilitate remarkable control over the final internal structure of the processed fiber and result in exceptional mechanical strength. The utilization of automated tracks allows for controlled laser zone drawing of the delicate nanofibers. The hypothesis to be tested is that the rapid heating and cooling of nanofibers, due to their high surface area-to-volume ratio, facilitates alignment of polymer chains at elevated temperatures that are locked in place during rapid cooling before chain relaxation can occur, thereby enhancing mechanical behavior.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.