Influence of Electric Fields on the Miscibility of Polystyrene / Poly (vinyl methyl ether) Blends Open Access

Kriisa, Annika (2015)

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Techniques which externally control and manipulate the phase behavior of miscible polymer blend systems, without altering chemistry on a molecular level, have great practical benefits. One possible mechanism is the use of electric fields, which can cause shifts in the phase separation temperature Ts for various mixtures. However, at present, there is extensive debate and limited understanding of how uniform electric fields influence the miscibility of polymeric mixtures, or even small molecules. One of the main limitations stems from the lack of experimental data with unambiguously large shifts in Ts outside of experimental error.

In this dissertation, we have characterized the fluorescence emission spectra of pyrene and anthracene dyes covalently bonded to polystyrene (PS) upon phase separation from poly(vinyl methyl ether) (PVME). It is demonstrate that slight differences in the phase separation temperature, TS, are related to proximity of the fluorophore to the PS backbone in its covalent attachment. The sharp increase in fluorescence intensity upon phase separation that occurs for all fluorophores, with little change in spectral shape, is consistent with a mechanism of static fluorescence quenching resulting from the specific interaction with a nearby quenching molecular unit.

This fluorescence technique is used to investigate the change in Ts due to the presence of electric fields. Results are presented that demonstrate that the presence of uniform electric fields strongly enhance the miscibility of PS/ PVME blends. Reliable shifts in Ts of up to 13.5 ± 1.4 K were measured for electric field strengths of E = 1.7 x 107 V/m in a 50/50 PS/PVME mixture. The finding that electric fields enhance miscibility agrees with the vast majority of existing experimental data on various mixtures.

Experimental results also show that electric fields do not have an effect on the temperature dependence of the remixing time scale in the one-phase region

Table of Contents

Chapter 1 Introduction ...1
Chapter 2 Background ...7
2.1 Polystyrene / Poly (vinyl methyl ether) Blends ...7
2.2 Thermodynamics and Kinetics of Polymer-Polymer Miscibility ...14
2.3 Understanding How Electric Fields Affect the Phase Separation Temperature Ts of Mixtures ...24
2.3.1 Experimental Literature ...24
2.3.2 Theoretical Expectations ...27
Chapter 3 Synthesis and Characterization of Fluorescently Labeled Polystyrene ...34
3.1 Free Radical Polymerization of Unlabeled and Labeled Polystyrene ...36
3.2 Synthesis of Pyrene Labeled Monomer: 1-Pyrenylbutyl Methacrylate ...46
3.3 Determination of Label Content of Fluorescently Labeled Polystyrene ...53
Chapter 4 Developing a Fluorescence Method for Detection of Phase Separation in Polystyrene / Poly (vinyl methyl ether) Blends ...59
4.1 Experimental ...63
4.2 Results and Discussion ...67
4.3 Conclusions ...76
Chapter 5 Developing Experimental Protocols for Reliably Measuring Shifts in Phase Separation Temperature Ts Under Electric Fields ...79
5.1 Protocol to Repeatedly Measure Phase Separation Temperature Ts on a Single Sample ...80
5.2 Sample Preparation Protocol and Experimental Setup for Measuring Phase Separation Temperature Ts in the Presence of Electric Fields ...91
Chapter 6 Electric Field Effect on the Miscibility of Polystyrene / Poly(vinyl methyl ether) ...100
6.1 Experimental ...105
6.2 Results and Discussion ...108
6.2.1 Measuring the Shift in Ts with Electric Fields ...108
6.2.3 Comparison with Reich and Gordon's work ...116
6.3 Conclusions ...120
Chapter 7 Electric Field Effects on the Time Scale of Remixing Dynamics of Polystyrene / Poly(vinyl methyl ether) Blends ...122
7.1 Experimental ...127
7.2 Results and discussion ...136
Chapter 8 Summary ...143
Appendix 1 ...149
Appendix 2 ...151
References ...152

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