Hierarchical photonic pigments via the confined self ... · The most brilliant coloursin nature are obtained from wavelength-sized transparent structures. Photonic structures in nature

Hierarchical photonic pigments via the confined self-assembly of bottlebrush block copolymers

Bio-Inspired Photonics

Richard Parker, Tianheng Zhao, Dong-Po Song, Silvia Vignolini

http://www.ch.cam.ac.uk/group/vignolini/

Colour and structure

Part of the light is absorbed, part is scattered (non-directional)

Part of the light is reflected (directional) part is transmitted.

Reflected colour is STRONG but the material is TRANSPARENT

The most brilliant colours in nature are obtained from wavelength-sized transparent structures.

Photonic structures in nature

S. Kinoshita, Structural Colors in the Realm of Nature (2008)O. Karthaus, Biomimetics in Photonics (2012)

Bottlebrush block copolymers (BBCPs)

P(PS-NB)(n = 1.59)

P(PDMS-NB)(n = 1.43)

Photonic films from BBCPs

100 μm

5 mm

BBCP2 BBCP3BBCP1

MW3.3 MDa 7.1 MDa

1.0 μm

P(PS-NB)(n = 1.59)

P(PDMS-NB)(n = 1.43)

P(PDMS-NB)(n = 1.43)

! = 2 $%& '

Photonic films from BBCPs

Hierarchical photonic pigments

iridescent non-iridescent

?

self-assembly + confinement à new functionality

Spherical confinement: microdroplets

0.0

0.2

0.4

0.6

0.8

1.0

400 500 600 700

Ref

lect

ance

Wavelength / nm

1+21+32+3

BBCP 2 BBCP 3

BBCP 13

12

1 + 2 (1:1)

1 + 3 (1:1)

2 + 3 (1:2)

25 μm

Expanding the colour palette

BBCP1 BBCP1 + CB

0.0

0.2

0.4

0.6

0.8

1.0

400 500 600 700N

orm

alis

ed re

flect

ance

Wavelength / nm

BBCP1

BBCP1 + CB

25 μm

Functional additive - enhance the contrast

ϴ = 5� 15� 30� 45�

diffuse illumination

direct illumination

ϴϴ

ϴ

ϴ = 5� 15� 30� 45�

2 wt% BBCP2

Structurally-coloured coatings

D.-P. Song, T.H. Zhao, G. Guidetti, S. Vignolini, R.M. Parker, ACS Nano, 2019, 13, 1764.

Hierarchical photonic pigments from BBCP microemulsions:• intense reflected colour – up to 100%• tuneable colour via the formulation• stimuli-responsive colour upon selective swelling

Robust interface-templated assembly process:• high tolerance to droplet size and drying rate• long-range order with minimal defects• functionality can be enhanced with additives

BBCP pigments can be embedded into coatings (e.g. paints)

Summary