**2. Redox polymerization**

Redox initiator polymerization was first discovered in Germany (1937); then it attempted to remove the induction period in aqueous or emulsion polymerization by adding a reducing agent to the oxidant initiator in the USA (1945) and in England (1946). Only the increase of rate of polymerization (RP) along with the expected decrease in the induction period was observed at that rate. The main characteristic of the compounds which form a redox pair for aqueous polymerization is their solubility in water, producing active, stable, and relatively fast radicals [1, 18].

The polymerizations activated by a reaction between an oxidant and a reducing agent are called redox polymerizations. The essence of redox activation is a reduction-oxidation process. In this process, an oxidant, i.e., Ce (IV) or Mn (III), forms a complex by simply reacting organic molecules at the beginning, which then decomposes unimolecularly to produce free radicals that initiate polymerization. There are peroxides, persulfates, peroxide phosphate, and salts of transition metals among the oxidants commonly used. These oxidants form effective redox systems with various reducing agents such as alcohols, aldehydes, amines, and thiols for the aqueous polymerization of vinyl monomers. The basic properties of the components forming a redox pair for aqueous polymerization are their water solubility and the quite rapid and stable release of active radicals [19, 20]. It is easy to control the

**39**

*Copolymer Synthesis with Redox Polymerization and Free Radical Polymerization Systems*

hydroxyl or carboxyl group, are more commonly used initiators [25].

and kd is the rate constant for initiator cleavage in the redox reaction.

reaction rate by changing the concentration of metal ion or peroxide, except for the use of low temperatures in redox systems [21]. There are many studies about block copolymer synthesis in the literature. Starting with a redox operation is only one

The synthesis of block copolymers with redox systems provides a number of technical and theoretical advantages as compared with the other methods. Redox polymerization minimizes side reactions under favor of its applicability at low temperatures [24]. In radical polymerization, redox systems are widely used as initiators, and a result is accomplished in a very short time. When compared with the other methods, it is the main advantage of processing at a very moderate temperature (low; 30 kcal/mole for thermal start and 10–20 kcal/mole for activation energy). This shows that it can minimize possible side reactions. The Ce(IV) or permanganate initiators, which combine with a reducing agent that includes a

The mechanism and the speed of redox polymerization can be shown with the

where R·is the form of one or two CH2OH functional groups converted to CH2O

where M in the equation shows the polymerizable monomer by the redox

There could be three types of endings: linear, bimolecular, and oxidative termi-

*DOI: http://dx.doi.org/10.5772/intechopen.88088*

method to obtain such polymers [22, 23].

following equations:

For initiation,

For growing,

nation of the first radical: For linear termination,

For bimolecular termination,

For the first radical formation,

method and ki shows the starting rate constant.

where *kt*1 is the linear termination rate constant.

where *kt*2 is the bimolecular termination rate constant.

For oxidative termination of the first radical,

*Copolymer Synthesis with Redox Polymerization and Free Radical Polymerization Systems DOI: http://dx.doi.org/10.5772/intechopen.88088*

reaction rate by changing the concentration of metal ion or peroxide, except for the use of low temperatures in redox systems [21]. There are many studies about block copolymer synthesis in the literature. Starting with a redox operation is only one method to obtain such polymers [22, 23].

The synthesis of block copolymers with redox systems provides a number of technical and theoretical advantages as compared with the other methods. Redox polymerization minimizes side reactions under favor of its applicability at low temperatures [24]. In radical polymerization, redox systems are widely used as initiators, and a result is accomplished in a very short time. When compared with the other methods, it is the main advantage of processing at a very moderate temperature (low; 30 kcal/mole for thermal start and 10–20 kcal/mole for activation energy). This shows that it can minimize possible side reactions. The Ce(IV) or permanganate initiators, which combine with a reducing agent that includes a hydroxyl or carboxyl group, are more commonly used initiators [25].

The mechanism and the speed of redox polymerization can be shown with the following equations:

For the first radical formation,

$$\text{Ce(IV)} \text{ + } \text{R} \xrightarrow{\text{k}\_{\text{it}}} \text{R} \text{ + } \text{Ce(III)} + \text{II}^{\dagger}$$

where R·is the form of one or two CH2OH functional groups converted to CH2O and kd is the rate constant for initiator cleavage in the redox reaction.

For initiation,

*Redox*

quickly [17].

science.

radicals [1, 18].

**2. Redox polymerization**

polymerization techniques [3–7].

desired molecular weight and desired molecular way in a controlled and repeatable manner. Synthesis of polymers, which have the star, comb, brush, worm, or graft architecture, is provided by molecular structure and size-controlled radical

Until today, the synthesis of block copolymers has usually been made through ionic polymerization. But ionic polymerization requires strict conditions, and the number of monomers is relatively limited. To overcome these disadvantages, simpler and easier techniques have been used recently for block copolymer synthesis [8, 9]. It has been possible to be successful in block copolymer synthesis in recent years with RAFT-ROP [10], ATRP-ROP [11], and redox polymerization-ATRP methods which have many advantages compared to other popular methods and have been implemented by using different techniques together [12]. Due to the practicability of two transformations at the same time or through separate steps, it minimizes homopolymerization which causes side reactions. Combining different polymerization techniques should be an interesting method for block and graft copolymers because the presence of more than one monomer in a polymer chain has been by combining such different techniques [10, 13–15]. The new polymers may have amazing features with their various compositions and architectures. The synthesis of block and graft copolymers was successfully performed by combining controlled radical polymerization techniques and redox polymerization [16]. The synthesis of block copolymers ends with traditional radical polymerization based on the connection of functional groups of the chain and polymers. Though this strategy was effective and successful, it was difficult to test the molecular weight and architecture of the polymer which was obtained. To be able to solve this problem, controlled free radical polymerization techniques were developed

In this present study, the synthesis of block copolymers over separate steps or on the same step was examined with different free radical polymerization techniques and redox polymerization methods. Copolymer synthesis by combining such different techniques has recently attracted considerable attention in polymer synthesis

Redox initiator polymerization was first discovered in Germany (1937); then it attempted to remove the induction period in aqueous or emulsion polymerization by adding a reducing agent to the oxidant initiator in the USA (1945) and in England (1946). Only the increase of rate of polymerization (RP) along with the expected decrease in the induction period was observed at that rate. The main characteristic of the compounds which form a redox pair for aqueous polymerization is their solubility in water, producing active, stable, and relatively fast

The polymerizations activated by a reaction between an oxidant and a reducing agent are called redox polymerizations. The essence of redox activation is a reduction-oxidation process. In this process, an oxidant, i.e., Ce (IV) or Mn (III), forms a complex by simply reacting organic molecules at the beginning, which then decomposes unimolecularly to produce free radicals that initiate polymerization. There are peroxides, persulfates, peroxide phosphate, and salts of transition metals among the oxidants commonly used. These oxidants form effective redox systems with various reducing agents such as alcohols, aldehydes, amines, and thiols for the aqueous polymerization of vinyl monomers. The basic properties of the components forming a redox pair for aqueous polymerization are their water solubility and the quite rapid and stable release of active radicals [19, 20]. It is easy to control the

**38**

$$\mathbb{K} \text{-- } \mathbb{M} \xrightarrow{\mathbb{k}\_{\text{i}}} \mathbb{K} \mathbb{M}\_{\text{i}} \text{--}$$

where M in the equation shows the polymerizable monomer by the redox method and ki shows the starting rate constant.

For growing,

$$\begin{array}{ccccc} \cdot & \cdot & \cdot & \cdot \\ \cdot & \cdot & \cdot & \cdot \\ \cdot & \cdot & \cdot & \cdot \\ \cdot & \cdot & \cdot & \cdot \\ \cdot & \cdot & \cdot & \cdot \\ \cdot & \cdot & \cdot & \cdot \\ \cdot & \cdot & \cdot & \cdot \\ \end{array}$$

$$\mathbf{R}\mathbf{M}\_{\alpha\_1}^{\alpha\_1} \rightarrow \mathbf{M}\_{\alpha\_2} \xrightarrow{\mathbf{R}^{\alpha\_1} \rightarrow \mathbf{R}^{\alpha\_2}} \mathbf{R}\mathbf{M}\_{\alpha\_2}^{\alpha\_2}$$

There could be three types of endings: linear, bimolecular, and oxidative termination of the first radical:

For linear termination,

where *kt*1 is the linear termination rate constant. For bimolecular termination,

$$\text{RM}\_{\text{n}}^{\*} + \text{RM}\_{\text{n}}^{\*} \xrightarrow{\text{k}\_{\text{f}\_{2}}} \text{RM}, + \text{mK} \cdot$$

where *kt*2 is the bimolecular termination rate constant. For oxidative termination of the first radical,

*Redox*

where *ko* is the rate constant of the termination of the first radical.
