Polymerization and Polymer Structure

The unique cataljdic oxidative coupling polymerization to high-molecular-weight, linear aromatic ethers is typically carried out at room temperature by bubbling oxygen through a solution of 2,6-xylenol monomer in the presence of a copper-based catalyst [1, 2, 4]. 

The commercial synthesis of PPE is carried out at 77 to 122°F (25 to 50°C) [4,6]. However, these polymerizations are exothermic and generally require cooling to attain high-molecular-weight products and selectivity. Atypical catalyst is composed of a cuprous halide salt and one or more amines such as pyridine, dibutyl amine, or certain hindered diamines [5—8]. 

The principal repeat unit in high-molecular-weight polymer, 6, is the 2,6-dimethyl-l,4-phenylene unit [13, 14]. In general, a 2,6-dimethylphenoxy tail end group and a 3,5-dimethyl-4-hydroxyphenyl head end group are present at opposite ends of the poljnner chain [15]. 

The miscible blends of PPE and styrenic resins are often referred to as modified PPE resins. The styrenic resins can vary from crystal polystyrene to high-impact polystyrene (HIPS). 

In theory, properties of miscible blends should be additive (linear behavior) based on the linear contribution from each polymer fraction [16]. Some properties such as glass transition temperatures and heat distortion temperatures exhibit near-linear behavior in PPE/PS blends, as shown in Fig. 9.2 [17, 18]. 

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