Side chain behavior couples to main chain conformation: Thermochromism, solvatochromism, ionochromism,… 

This is the basis for sensor technologies

In the ordered state

diffraction

X-ray powder

10

20

30

2q (deg.)

Intensity (arb units.)

25 C (ordered)

45 C (disordered)

Free Energy

A

B

is the path on cooling

Thermotropic

columnar

mesophase

Ordered state

Order-Disorder

Transition Temperature

A

B

A Simple Free Energy  Diagram

250

300

350

400

Absorbance (Arb. Units)

On warming

-35 C

-20 C

30 C

35 C

40 C

45 C

50 C

0 C

5 C

15 C

20 C

Wavelength (nm)

isosbestic

point

UV absorption

Photoluminescence is also strongly impacted!