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a) b - École Polytechnique de Montréal

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1.1 Introduction<br />

CHAPTER 1 - INTRODUCTION AND OBJECTIVES<br />

The study of the <strong>de</strong>velopment of morphology in immiscible polymer blends is a domain of great<br />

interest due to the influence of morphology on the physico-mechanical properties of the<br />

materials as well as the control of the microstructure. Although obtaining <strong>de</strong>sired properties(Paul<br />

& Newman, 1978) by blending two or several components is a key challenge in polymer blends,<br />

it is also important because novel complex microstructures for special applications can be<br />

prepared. Polymer melt-blending is even more interesting, since by controlling the <strong>de</strong>termining<br />

parameters in the liquid-state, <strong>de</strong>sirable structures with different geometries can be obtained.<br />

Therefore, providing the required thermodynamic and kinetic conditions for a multi-component<br />

blend processed via melt-blending results in the preparation of the <strong>de</strong>sired self-assembly (the<br />

notion that physical or chemical driving forces produce the necessary material microstructure<br />

without the need for any external intervention) materials. For example, a binary blend of 40/60<br />

polymer A/polymer B can show both matrix-dispersed morphology and co-continuous structure<br />

<strong>de</strong>pending on the mentioned properties. This implies that these systems, due to governing<br />

properties, self-assemble to matrix-dispersed morphology or co-continuous morphology. Ternary<br />

polymer blends in the polymer blend world is a critical case. It has been shown that due to<br />

thermodynamic properties, three polymers can either be in contact with one another and make<br />

three-phase contact, or one polymer can separate the second and third ones. These two cases are<br />

seen in all the systems where liquids are in contact with each other. The most important ones are<br />

<strong>de</strong>tected in cell structures. Some of the examples are represented in Figure 1-1. More<br />

complicated cases can be found in cell structures as phases hierarchically assembled in or<strong>de</strong>r<br />

(Figure 1-2).<br />

A key challenge in polymer blends is how to provi<strong>de</strong> the system requirements to obtain <strong>de</strong>sired<br />

morphologies. The structures shown in Figure 1-1 are very close to the thermodynamically<br />

controlled self-assembled structures ma<strong>de</strong> by polymer blends. In this case, the goal is <strong>de</strong>signing<br />

novel materials and finally replacing them with real materials or applying them in hightechnology<br />

applications. Some of the important structures produced are introduced in Figure 1-3.<br />

1

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