1. Liquid crystal elastomers Normal isotropic elastomer Liquid Crystal elastomer

2. Monodomain and polydomain samples Unaligned Polydomain Aligned few microns

3. Mechanical anisotropy 35º 50º 70º 80º tan  D V (like isotropic rubber) (soft elasticity) Frequency (s -1 ) Anisotropy in monodomain (All samples synthesised by Dr Ali Tajbakhsh)

4. Mechanical anisotropy 10 10 0 1 2 0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 1.0 tan  Master curve constructed using time-Temperature superposition. (Scaled to 35º) Frequency (s -1 )

5. Mechanical anisotropy 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 10 10 0 1 2 Frequency (s -1 ) tan  v monodomain d monodomain polydomain Polydomain compared with monodomain

6. l Stretching a polydomain material and clamping it during dynamic mechanical analysis – shows same behaviour as monodomain. Stretched Polydomain

7. Mechanical anisotropy 10 10 0 1 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 35 degrees 0 50 degrees 0 v monodomain d monodomain d stretched polydomain v stretched polydomain polydomain Stretched Polydomain tan 

8. Time-resolved experiments:WAXS X-rays 2-D intensified CCD detector Oscillatory shear Stretch…..and then shear COMPUTER Optical chopper

9. Fit to: I = a + b * exp(-c * (cos(  -d))^2). “d” shows azimuthal tilt  Azimuthal integration

10. Variation in tilt angle 050100150200250300350 79 79.5 80 80.5 81 81.5 82 82.5 83 83.5 84 Time (degrees of shear cycle) 80s 10s 40s Strain: movement of arm +0.5 mm 0 -0.5 mm We can successfully obtain WAXS data at 1s time-resolution without loss of image quality by binning over many cycles. Tilt angle / degrees

11. Time-resolved Optical experiments Red diode laser Amplified photodiode Oscillatory stretch COMPUTER Optical chopper Phase shift amplitude Sinusoidal strain 0.3 0.35 Strain light

12. Amplitude and phase shift 70º60º55º50º Phase shift (cycles) Amplitude / Arbitrary units Frequency / s -1 10.10.01 10.10.01 10.10.01 0.10.01 High temperatures: amplitude independent of frequency; phase shift increases Medium temperatures: amplitude decreases with frequency; phase shift shows “hump”Medium temperatures: amplitude decreases with frequency; phase shift shows “hump” Low temperatures: amplitude independent of frequency; phase shift decreases 0 0 0.1 0.2 0.3 0.4 BUCKLING 40º BUCKLING

13. Model: (assume linear) l Two processes causing changes in transparency on stretching. l One fast (affine deformation? Thinning?) l One slow (disappearance of domain boundaries?) l Both equilibrium transparency linear with strain (for small amplitude)

14. strain Transmission of light First-order rate constant Equilibrium transmission for slow process (small) sinusoidal imposed strain… …gives sinusoidal light transmission: amplitude phase shift Derivation of model

15. Amplitude data: qualitative fit BUCKLING Amplitude / Arbitrary units 0 0.1 0.2 0.3 0.4 70º60º High temperatures: amplitude independent of frequency; Medium temperatures: amplitude decreases with frequency;Medium temperatures: amplitude decreases with frequency; Low temperatures: amplitude independent of frequency; 55º50º40º 10.10.01 f / s -1 1e-4 10 k = 1e-3 k = 0.1 k = 0.01 k = 10 k = 1

16.  / s -1 0.01 0.1 10 0.00 0.01 0.02 0.03 0.01 0.02 0.03 0.01 0.02 0.03 0.01 0.02 0.03 0.01 0.02 0.03 Phase shift data: quantitative fit Phase shift (cycles) =  70º k = 6.55 s -1 60º k = 2.62 s -1 55º k = 0.75 s -1 50º k = 0.26 s -1 40º k = 0.022 s -1 c 1 = 2.16 ln (k / s -1 ) 1 / T (K -1 ) Data give good fit to model, with temperature- dependent rate constant Data consistent with Activation energy E A = 200 kJ mol-1 (assume Arrhenius equation)

17. Phase shift: t-T superposition?  / s -1 Scaled to 50º

18. Fitting our data l Assume t-T superposition, scaled for 50 degrees:  / s -1 + offset At 50º C k = 0.26 s -1 c 1 = 17.4

19. Step-strain 100s200s 10s 5s 1s 2s 3s 40º C k = 0.034 s -1 50º C k = 0.17 s -1 60º C k = 4.9 s -1 Fits first-order mono-exponential I = I 0 - A exp(-k t) k increases with temperature

20. The sinusoidal and step data agree (within error) Activation energy 200 kJ mol -1. (What does this mean?) ln (k / s -1 ) 1 / T (K -1 ) Comparison of first-order rate constants