Large aggregate species in conjugated polymer solutions characterized by dynamic light scattering and in situ rheological/flow turbidity measurements Chih J. Lin 1, Chan Y. Kuo 1, Chi C. Hua 1, * Show A. Chen 2 1 Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621,Taiwan, R.O.C. 2 Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu 300, Taiwan, R.O.C. Date: 2008/07/01 Complex Fluids & Molecular Rheology Laboratory, Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621, Taiwan, R.O.C. Speaker: Chi C. Hua （華繼中）

Imagining PLED display Spin- coating Casting Ink-jet printing Films Electro-luminescent conjugated polymer film

Aggregation Properties in MEH-PPV Solutions Thermal irreversibility in the solution Viscosity — Existence of unstable aggregation properties Hua et al, J Rheol 49, 641 (2005) Poly[2-methoxy-5-(2’-ethyl- hexyloxy)- 1,4-phenylene vinylene] (MEH-PPV) M w : 70,000-10,000 g/mol PDI: 2.5 5mg/ml

Parameter-Free Coarse-Grained Simulations Which yields the exact (generally poor) solvent qualities for MEH-PPV solutions: Toluene: 0.32 Chloroform: 0.38 cf. Theta condition: MEH-PPV monomers per Kuhn length highly collapsed chain conformation

Dynamic Light Scattering (DLS)/Photoluminescence (PL): Effects of solvent quality and concentration M/T: 1 mg/mlM/T: 3 mg/ml, no filtrationM/C: 3 mg/ml, no filtration M/T M/C

In situ rheological/flow turbidity measuring apparatus Derived specific turbidity representation equation

Specific turbidity measuring theory Kerker, M., 1969, THE SCATTERIG OF LIGHT AND OTHER ELECTROMAGNETIC RADIATION, Academic Press, Inc., San Diego. Heller, W., and W. J. Pangonis, “Theoretical Investigations on the Light Scattering of Colloidal Spheres. I. The Specific Turbidity,” J. Chem. Phys. 26, (1956) Liberatore, M. W., and A. J. McHugh, “Dynamics of shear-induced structure formation in high molecular weight aqueous solutions,” J. Non- Newton. Fluid 132, (2005) Plot figure of specific turbidity vs. Mie radius So, quantity of Mie radius can get from equation of fitting curve.

Experimental design and procedure: DLS In-situ rheological/flow turbidity measurement Use DLS to measure hydrodynamic radius before shearing. Compared Mie radius with R h by two so different theory. Under shear flow 10 min Shear rate ： 60 [s -1 ] Flow rested 15 min Under shear flow 10 min Shear rate ： 151~2,800 [s -1 ] Flow rested 15 min Altered shear rate Under shear flow 10 min Shear rate ： 60 [s -1 ] Flow rested 15 min Under shear flow 10 min Shear rate ： 151~2,800 [s -1 ] Flow rested 15 min Run2 Run1 Altered shear rate MEH-PPV/DOP Sample Main ideal is changed experiment factors of conc. and aging time, to observe the influence of two factors on aggregated properties. Conc. [mg/ml] Aging time W/o aging2 days aging Experiment factors setting The run1 is observed the behaviors while samples under various shear flow field The run2 is observed the behaviors while samples experienced high shear flow field

Specific turbidity signal at various shear rate (w/o aging) 0.02 mg/ml0.3 mg/ml1.0 mg/ml3.0 mg/ml

Summary of specific turbidity (w/o aging) At the lowest concentration, i.e., 0.02 mg/ml, the fluctuation in specific turbidity was noticed to be very large, suggesting that the aggregation state is unstable. The specific turbidity decreased with increased sample concentration. In both shearing and relaxation region, the specific turbidity of 0.3 mg/ml and 1.0 mg/ml sample solutions were lower than those before the shearing treatment.

Specific turbidity signal at various shear rate (2 days aging) 0.02 mg/ml0.3 mg/ml1.0 mg/ml3.0 mg/ml

Summary of specific turbidity (2 days aging) Under sample with 2 days aging, the qualitative trends are the same as sample w/o aging. Signal fluctuation of the 0.3 mg/ml sample solution is very large in the relaxation region. Suggesting that the aggregation state become unstable after shearing treatment.

The effect of concentration on aggregation properties W/o aging2 days ageing

Summary of the effect of concentration With or without 2 days aging, Mie radius and increased with decreased sample concentration.

The influence of aging on aggregated properties 0.02 mg/ml0.3 mg/ml 1.0 mg/ml3.0 mg/ml Shear thinning Max.

Summary of aging influence All concentration samples have the same trend, the Mie radius and increased while sample with aging. The 3.0 mg/ml sample solution shows shear-thinning behavior whether sample w/o aging or with 2 days aging.

Comparison of results from flow turbidity and DLS measurements Aging effectConc. Mie radius from specific turbidity R h from dynamic light scattering Before shearing W/o aging 0.02 mg/ml mg/ml mg/ml mg/ml Aged 2 days 0.02 mg/ml mg/ml mg/ml mg/ml Good agreement was founded between the results from both measurements. The Mie radius was differed from R h in low concentration, 0.02 mg/ml.

Conclusion The aggregation properties of MEH-PPV solution precursor solution, as they highly depend on sample concentration and sample with or w/o aging. The results obtained from in-situ rheological/flow turbidity measurements and dynamic light scattering have great consistence.