Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, BC, V8W 3V6 Canada.
Langmuir. 2010 Apr 20;26(8):5998-6008. doi: 10.1021/la904561b.
We demonstrate a new strategy for producing hierarchical polymer nanostructures, which combines nanoscale self-assembly of amphiphilic block copolymers at the air-water interface with microscale templated assembly of the resulting aggregates on chemically patterned substrates. Aggregates are formed via interfacial self-assembly of 141k polystyrene-b-poly(ethylene oxide) (PS-b-PEO, MW = 141k, 11.4 wt % PEO) or a blend of 185k PS-b-PEO (MW = 185k, 18.9 wt % PEO) and PS-coated CdS nanoparticles to form strandlike copolymer or copolymer-nanoparticle aggregates. Using Langmuir-Blodgett (LB) techniques, the aggregates are then transferred to patterned substrates possessing alternating hydrophilic/hydrophobic stripes, obtained by microcontact printing octadecyltrichlorosilane (OTS) on glass. The aggregates are transferred under various conditions of surface pressure, orientation of the patterned substrate, and withdrawal speed. Templated assembly of aggregates into the hydrophilic substrate domains is achieved when the hydrophilic/hydrophobic stripes are oriented perpendicular to the water surface during LB transfer; this is explained by surface energy heterogeneities along the subphase-substrate contact line, which induce selective dewetting and concomitant monolayer rearrangement at the drying front. In contrast, parallel orientation of stripes results in nonselective transfer of the monolayer without registration to the underlying surface pattern. By studying the effect of surface pressure, we show that packing constraints imposed by compression of aggregates to high surface densities prevent the formation of patterned LB films that match the established periodicity of the OTS-patterned glass. As well, it is shown that efficient transfer of aggregates to the patterned glass requires slower substrate withdrawal speeds compared to transfer to unpatterned hydrophilic glass.
我们展示了一种生产分级聚合物纳米结构的新策略，该策略结合了两亲性嵌段共聚物在气-水界面的纳米尺度自组装以及所得聚集体在化学图案化基底上的微尺度模板组装。通过界面自组装 141k 聚苯乙烯-b-聚（环氧乙烷）（PS-b-PEO，MW=141k，11.4wt%PEO）或 185k PS-b-PEO（MW=185k，18.9wt%PEO）和 PS 包覆的 CdS 纳米粒子的混合物形成链状共聚物或共聚物-纳米粒子聚集体。然后使用 Langmuir-Blodgett（LB）技术将聚集体转移到具有交替亲水性/疏水性条纹的图案化基底上，该基底通过微接触印刷十八烷基三氯硅烷（OTS）在玻璃上获得。在各种表面压力、图案化基底取向和退出速度条件下进行聚集体的模板组装。当 LB 转移过程中亲水性/疏水性条纹垂直于水面取向时，聚集体在亲水基底域中进行模板组装；这可以通过亚相-基底接触线沿线的表面能各向异性来解释，该各向异性诱导在干燥前沿处选择性去湿和伴随的单层重排。相比之下，条纹的平行取向导致单层无选择地转移而不与底层表面图案对准。通过研究表面压力的影响，我们表明聚集体压缩到高表面密度所施加的堆积限制阻止了与 OTS 图案化玻璃的既定周期性匹配的图案 LB 膜的形成。此外，还表明与转移到无图案的亲水玻璃相比，聚集体有效转移到图案化玻璃需要较慢的基底退出速度。
