**2. Poly(olefin sulfone)s**

Poly(olefin sulfone)s are copolymers of olefin monomers and sulfur dioxide (**Figure 1**). They possess sulfonyl groups (‐SO<sup>2</sup> ‐) in the main chain and are easily synthesized by radical polymerization of an olefin monomer in a liquefied sulfur dioxide [14]. Peroxides, such as tert‐butyl hydroperoxide, benzoyl peroxide, and diethyl ether peroxides, are used as polymerization initiators. The peroxide and sulfur dioxide act as a redox initiator and generate a radical species that reacts with an olefin monomer (**Figure 2**). While the sulfonyl radical is fairly stable, the olefin radical is unstable. The olefin radical generated in liquefied sulfur dioxide immediately reacts with a sulfur dioxide molecule to form an alkylated sulfonyl radical. The sulfonyl radicals then react with the olefin monomers to generate a polymer chain. Note that the sulfur atom of the sulfonyl radical is positively charged; therefore, it cannot react with the sulfur atom of sulfur dioxide, which is also positively charged. In addition, the olefin monomer and sulfur dioxide form a 1:1 charge‐transfer complex in the liquefied SO<sup>2</sup> solution. The olefin‐SO<sup>2</sup> complex reacts like a monomer unit in the radical polymerization process. Thus, the resulting poly(olefin sulfone) is a 1:1 alternating copolymer of olefin monomers and SO<sup>2</sup> [15].

**Figure 2.** Polymerization of olefin monomers in liquefied sulfur dioxide.

Poly(olefin sulfone)s

123

http://dx.doi.org/10.5772/intechopen.69317

**Figure 3.** Examples of poly(olefin sulfone)s.

### **2.1. Synthesis of poly(olefin sulfone)s**

At ambient pressure, sulfur dioxide gas liquefies when cooled to temperatures below –10.2**°**C. The polarity of liquefied sulfur dioxide is comparable to that of dichloromethane, so liquefied sulfur dioxide dissolves a wide range of olefins. A high‐pressure polymerization tube containing 1.0 g of an olefin monomer and 3.2 × 10−4 mol of t‐butyl hydroperoxide (a redox initiator) was connected to a vacuum line and cooled in liquefied nitrogen. The tube was evacuated, and 6.0 g of sulfur dioxide was added by transfer through a vacuum line. The mixture was stirred for 24 h at –13**°**C. The resulting polymer was reprecipitated in methanol. Examples of chemical structures of simple poly(olefin sulfone)s are shown in **Figure 3**.

**Figure 1.** Structure of poly(olefin sulfone)s.

**Figure 2.** Polymerization of olefin monomers in liquefied sulfur dioxide.

of low‐energy irradiation for the depolymerization [4–10]. The unzipping degradation of a polymer main chain containing heteroatoms by X‐ray or electron‐beam irradiation has been achieved. For a poly(1‐butene sulfone), only partial depolymerization occurs, and olefins are

Degradation of a poly(olefin sulfone) doped with a photosensitizer has been investigated [13]. The degradation of poly(1‐butene sulfone) doped with pyridine N‐oxide was induced by irradiation with 300‐nm light. In this system, however, a crosslinking reaction occurs in addition to degradation of the main chain. The number of photoinduced breaks in the main chain was 10–12. High‐efficiency depolymerization to constituent monomers was achieved for poly(olefin sulfone)s containing photobase generators using low‐energy light irradiation.

Poly(olefin sulfone)s are copolymers of olefin monomers and sulfur dioxide (**Figure 1**). They

erization of an olefin monomer in a liquefied sulfur dioxide [14]. Peroxides, such as tert‐butyl hydroperoxide, benzoyl peroxide, and diethyl ether peroxides, are used as polymerization initiators. The peroxide and sulfur dioxide act as a redox initiator and generate a radical species that reacts with an olefin monomer (**Figure 2**). While the sulfonyl radical is fairly stable, the olefin radical is unstable. The olefin radical generated in liquefied sulfur dioxide immediately reacts with a sulfur dioxide molecule to form an alkylated sulfonyl radical. The sulfonyl radicals then react with the olefin monomers to generate a polymer chain. Note that the sulfur atom of the sulfonyl radical is positively charged; therefore, it cannot react with the sulfur atom of sulfur dioxide, which is also positively charged. In addition, the olefin monomer and

complex reacts like a monomer unit in the radical polymerization process. Thus, the resulting

At ambient pressure, sulfur dioxide gas liquefies when cooled to temperatures below –10.2**°**C. The polarity of liquefied sulfur dioxide is comparable to that of dichloromethane, so liquefied sulfur dioxide dissolves a wide range of olefins. A high‐pressure polymerization tube containing 1.0 g of an olefin monomer and 3.2 × 10−4 mol of t‐butyl hydroperoxide (a redox initiator) was connected to a vacuum line and cooled in liquefied nitrogen. The tube was evacuated, and 6.0 g of sulfur dioxide was added by transfer through a vacuum line. The mixture was stirred for 24 h at –13**°**C. The resulting polymer was reprecipitated in methanol. Examples of

sulfur dioxide form a 1:1 charge‐transfer complex in the liquefied SO<sup>2</sup>

poly(olefin sulfone) is a 1:1 alternating copolymer of olefin monomers and SO<sup>2</sup>

chemical structures of simple poly(olefin sulfone)s are shown in **Figure 3**.

‐) in the main chain and are easily synthesized by radical polym-

solution. The olefin‐SO<sup>2</sup>

[15].

present in the gas produced by the irradiation [11, 12].

**2. Poly(olefin sulfone)s**

122 Alkenes

possess sulfonyl groups (‐SO<sup>2</sup>

**2.1. Synthesis of poly(olefin sulfone)s**

**Figure 1.** Structure of poly(olefin sulfone)s.

**Figure 3.** Examples of poly(olefin sulfone)s.
