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

这项工作产生了与聚合物激光加热相关的新知识，以设计和制造高强度纳米纤维。在聚合物材料科学、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和造福社会。聚合物纳米纤维在能源、交通、航空航天、医疗保健、电子和传感等重要行业有着广泛的应用。理论上，纳米纤维应该比更大的传统纤维更强，但实际上纳米纤维通常要弱得多。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。这笔赠款支持研究与聚合物纳米纤维拉伸过程中的激光加热相关的基本科学关系，以实现对内部结构的特殊控制并由此提高强度。此外，这项研究使用了独特的自动轨道连续拉丝系统，确保了规模扩大和明确的商业化道路。该项目为众多本科生和研究生提供材料科学、先进制造和纳米技术方面的高级培训，并建立了通向BS研究培训计划的途径，该计划支持未被充分代表、经济困难的学生寻求工程学学士学位。激光分区绘制展示了生产具有高拉伸强度的聚合物纤维的潜力，这种潜力超过了使用传统纤维制造方法的可能。然而，在严格控制的条件下，还没有研究控制激光区域光纤拉伸的基本热力学和材料加工关系，特别是对于聚合物纳米纤维。这项工作填补了这一知识空白，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，同时连续监测力学性能。为了加工整个纤维，激光束被顺序扫描，以快速加热纤维的每一小部分或区域，使其柔韧，从而可以拉伸。在已知纤维张力和瞬时区域温度的情况下，研究了激光拉拔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，并产生卓越的机械强度。自动化轨道的使用允许对精细的纳米纤维进行受控的激光区域拉伸。要测试的假设是，纳米纤维的快速加热和冷却，由于其高表面积与体积比，有助于在快速冷却期间锁定的高分子链在高温下对齐，然后发生链松弛，从而增强机械性能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.