The confined self-assembly of photonic pigments: from synthetic polymer brushes to sustainable cellulosic colloids

Colour is an essential medium for our communication, and the use of dyes and pigments in our society dates back to prehistoric times. While traditional dyes and pigments rely on chemical composition to produce colours by selective absorption and emission, it is also possible to create bright and vivid colours using nanostructured materials. Such structurally coloured materials are readily found in nature, from insects to plants, yet they are challenging to fabricate artificially on a large scale. In this thesis, I present a series of examples of exploiting the self-assembly process of two types of photonic building blocks to fabricate structurally coloured materials. The first system uses cellulose nanocrystals (CNCs), extracted from wood or cotton, which can self-organise as a cholesteric liquid crystal phase to form a helicoidal nano-architecture that reflects the visible light. CNCs are sustainable and biocompatible, but these large anisotropic colloids have slow kinetics and a complex self-assembly process. The second system exploits bottlebrush block copolymers (BBCPs). These rigid, giant macromolecules are well-known for microphase separation into a wide variety of nanostructures. Although more challenging to synthesise, BBCPs allow for a very rapid self-assembly process. All previous studies using both systems encountered challenges in obtaining uniform optical appearance over large areas. I demonstrate a different approach to produce photonic pigments by confining the self-assembly process into nano-litre droplets. The strong surface interaction and faster kinetics have shown to significantly enhance the structural uniformity, which leads to an improved and exotic optical response and colourimetric behaviours to environmental stimuli. Finally, as such confinement is achievable through industrial methods like printing and emulsification, the developed methodologies pave the way for the scalable production of photonic materials for pigment applications.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2020

Author dc:creator

• Zhao, Tianheng

Advisor dc:contributor.advisor

• Vignolini, Silvia

• self-assembly
• cellulose nanocrystal
• microfluidics
• nanomaterials
• photonic
• photonic material

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/08b3b8c6-afcb-46e9-8e9d-1329b5e45fa0/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

Author Identifier

0000-0002-2705-0329
0000-0003-0664-1418

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/329652