CONFORMATION OF A CONJUGATED POLYELECTROLYTE IN AQUEOUS SOLUTION: SMALL ANGLE NEUTRON SCATTERING.
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| Title: | CONFORMATION OF A CONJUGATED POLYELECTROLYTE IN AQUEOUS SOLUTION: SMALL ANGLE NEUTRON SCATTERING. |
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| Authors: | Wang, Deli1 (AUTHOR), Moses, Daniel2 (AUTHOR), Bazan, GuillermoC.2 (AUTHOR), Heeger, AlanJ.2 (AUTHOR), Lal, Jyostana3 (AUTHOR) |
| Source: | Journal of Macromolecular Science: Pure & Applied Chemistry. Dec2001, Vol. 38 Issue 12, p1175-1189. 15p. 2 Charts. |
| Subjects: | Polyelectrolytes, Scattering (Physics), Polymers, Luminescence |
| Abstract: | Small angle neutron scattering (SANS) by a conjugated, luminescent polyelectrolyte, poly[5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene] (MBL-PPV), was investigated at semi-dilute concentrations in aqueous solution at room temperature. The polymer conformation was studied in pure deteurated water and in solutions with added salt, in solutions with added dicationic quencher and in solutions with added surfactant. A single broad peak in the scattered intensity, I(q), was observed for all concentrations in salt free solutions; the peak position and peak intensity per monomer unit scale with the MBL-PPV concentration as qm ∼ c1/2 and I(qm)/c ∼ c-1/2, respectively. The upturn of I(q) at low q (q<0.08Å--) results from aggregation of the polymer chains; the sizes of the aggregates increase with increasing concentration. The addition of excess salt completely removes the broad peak from the scattering pattern as the salt ions screen the repulsive interchain electrostatic interaction. In high salt solutions, I(q) ∼ q--, over a wide range of q, indicating a rigid-rod conformation for the conjugated chains with persistence length greater than 800Å. Cationic surfactant, DTA, was found to separate the polyelectrolyte chains from each other. Initial experiments in the presence of dicationic quencher indicate an increase in the aggregate size. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Small angle neutron scattering (SANS) by a conjugated, luminescent polyelectrolyte, poly[5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene] (MBL-PPV), was investigated at semi-dilute concentrations in aqueous solution at room temperature. The polymer conformation was studied in pure deteurated water and in solutions with added salt, in solutions with added dicationic quencher and in solutions with added surfactant. A single broad peak in the scattered intensity, I(q), was observed for all concentrations in salt free solutions; the peak position and peak intensity per monomer unit scale with the MBL-PPV concentration as qm ∼ c1/2 and I(qm)/c ∼ c-1/2, respectively. The upturn of I(q) at low q (q<0.08Å--) results from aggregation of the polymer chains; the sizes of the aggregates increase with increasing concentration. The addition of excess salt completely removes the broad peak from the scattering pattern as the salt ions screen the repulsive interchain electrostatic interaction. In high salt solutions, I(q) ∼ q--, over a wide range of q, indicating a rigid-rod conformation for the conjugated chains with persistence length greater than 800Å. Cationic surfactant, DTA, was found to separate the polyelectrolyte chains from each other. Initial experiments in the presence of dicationic quencher indicate an increase in the aggregate size. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 10601325 |
| DOI: | 10.1081/MA-100108376 |
