Generating in-Plane Orientational Order in Multilayer Films Prepared by Spray-Assisted Layer-by-Layer Assembly

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Layer-by-layer assembly is a common technique for creating thin films.
• Controlling the orientation of nanoscale components within these films is crucial for tailoring their properties.
• Existing methods for orienting cellulose nanofibrils (CNFs) can be complex or limited in scalability.

Purpose of the Study:

• To develop a simple and efficient method for orienting cellulose nanofibrils (CNFs) in thin films.
• To investigate the effect of spray angle on the in-plane orientation and anisotropy of CNF films.
• To produce optically birefringent films with controlled CNF alignment over large areas.

Main Methods:

• Utilizing spray-assisted alignment with varying spray angles relative to the receiving surface.
• Employing cellulose nanofibrils as anisotropic nanoscale components.
• Analyzing film orientation and anisotropy using atomic force microscopy (AFM), polarized optical microscopy, and ellipsometry.

Main Results:

• Spraying at grazing incidence angles induces a directional surface flow, aligning CNFs parallel to the spraying direction.
• This method yields films with substantial in-plane anisotropy and optical birefringence.
• The degree of orientational order is influenced by factors such as the distance between the spray nozzle and the receiving surface.

Conclusions:

• Grazing incidence spray-assisted alignment is an effective technique for orienting cellulose nanofibrils.
• This method allows for the large-area production of optically birefringent films with tunable in-plane anisotropy.
• The developed technique offers a simple and scalable approach for fabricating advanced cellulosic materials.