高取向立构复合化聚乳酸超细纳米纤维膜的制备及长效驻极与滤除PM_(0.3)性能

Preparation of Aligned Stereocomplexed Poly(lactic acid)Nanofibrous Membranes for Long-term Electret and Efficient PM_(0.3)Filtration

利用聚L-乳酸(PLLA)和聚D-乳酸(PDLA)链之间建立的立构复合产生强的分子间相互作用,并通过高压电场极化和高倍取向拉伸赋予聚乳酸(PLA)纳米纤维高的取向和细化,同时促进电活性相(β相、立构复合晶)的形成.得益于高取向的纤维形貌和优异的电活性,高取向立构复合化PLA(AS-PLA)纳米纤维膜的介电常数和表面电位分别高达1.68和5.4 kV.同时,AS-PLA纳米纤维膜表现出卓越的过滤性能和摩擦电性能,特别是PDLA添加量为40%时制备的PLLA/PDLA40纳米纤维膜,即使在85 L/min的高气流量下对超细空气颗粒物(PM_(0.3))的滤除效率仍达到90.51%,且空气阻力仅为240.6 Pa,明显优于纯PLA纤维膜(滤除效率80.34%,空气阻力251.4 Pa).此外,在高湿度(RH=70%)和高强度呼吸气流(85 L/min)条件下,由AS-PLA纳米纤维膜作为摩擦电活性层组装的摩擦纳米发电机(TENG)过滤器仍显示出优异的PM_(0.3)去除效率,达到95.02%,远远超过普通PLA过滤器(去除效率仅为89.50%),表现出强的电荷再生能力.电活性的提高显著改善了纳米纤维膜的初始极化能力和摩擦电性能,在保证纤维膜初始电荷充足的同时可依赖摩擦电效应实现电荷再生,在不牺牲空气阻力的前提下实现长效过滤.

The stereocomplexation between poly(L-lactide)(PLLA)and poly(D-lactide)(PDLA)chains was used to generate strong intermolecular interactions,which could be further enhanced by using high-voltage electric field and intensive mechanical stretching to prompt extreme alignment and refinement of poly(lactic acid)(PLA)nanofibers and the formation of electroactive phase(i.e.,βphase,stereoscopic complexation crystal).Due to the aligned nanofiber morphology and excellent electroactivity,the dielectric constant and surface potential of aligned stereocomplexed PLA(AS-PLA)nanofibrous membranes were increased to 1.68 and 5.4 kV,respectively.Moreover,AS-PLA nanofibrous membranes showed excellent filtration performance and triboelectric performance.In particular,the PLLA/PDLA40 prepared with 40%PDLA addition achieved an ultrafine air particle(PM_(0.3))removal efficiency of 90.51%and an air resistance of only 240.6 Pa at airflow capacity of 85 L/min,which was significantly superior to pure PLLA fibrous membrane(80.34%,251.4 Pa).In addition,even at high humidity(RH=70%)and high respiratory airflow capacity(85 L/min),the triboelectric nanogenerator(TENG)based filter assembled with AS-PLA nanofibrous membrane as the triboelectric layer showed excellent PM_(0.3)removal efficiency of 95.02%,far exceeding that of normal PLA filters(only 89.50%).The increase of electroactivity significantly improved the initial polarization ability and triboelectric performance of the nanofibrous membranes,which could rely on the triboelectric effect to achieve charge regeneration while ensuring the sufficient of the initial charge.It ensures long-term filtration without sacrificing air resistance.