**3. Catalysts used in redox polymerization systems**

Various compounds such as ceric, manganese, copper, iron, vanadium ion salts, and hydrogen peroxide were used as catalysts for the synthesis of block copolymers through redox polymerization. The ceric-based catalysts are the most widely used in these catalyst systems. The redox systems containing other catalysts were also examined. Ce(IV) or permanganate initiators, which combine with reducing agent containing a hydroxyl or carboxyl group, are the more commonly used initiators.

Ceric salts have shapes such as ceric(IV) ammonium nitrate (CAN), ceric(IV) ammonium sulfate (CAS), ceric(IV) sulfate (CS), and ceric perchlorate. As oxidation strength, ceric perchlorate > ceric nitrate > ceric sulfate were observed (1.7, 1.6, and 1.4 V), respectively, in the studies carried out with vinyl monomers [26]. A wide range of usages in the free radical production has been found by taking advantage of its amplifying properties in redox polymerization. The reduction reaction is given below.

The Ce(IV) salts and the Ce(IV) salt-reducing substance system are used as initiators for vinyl polymerizations in aqueous acidic solutions [27]. Organic reductant substances most commonly used with the Ce(IV) salts are alcohols, glycols, aldehydes, ketones, and carboxylic acids [27, 28]. Ce(IV) salts are used only in acidic solutions and most preferably in 0.5 or higher acid concentrations [29]. The solution's color is yellow. The turning point can be determined even without an indicator in hot and non-dilute solutions.

It has been proven by research that Ce(IV) ion cannot initiate acrylamide polymerization alone and water is not oxidized by Ce(IV) ions [27]. So the radicals that start polymerization occur as a result of the reaction between the Ce(IV) ion and the reducing substance. A general mechanism is proposed for this.

When keeping the concentration of methyl methacrylate and Azo I constant and increasing the concentration of Ce(IV) up to 6 × 10<sup>−</sup><sup>4</sup> mol L<sup>−</sup><sup>1</sup> , the polymerization rate also increased proportionally with [Ce(IV)]½ in the methyl methacrylate polymerization initiated by the hydroxyl functional group with a redox pair Ce(IV)-Azo I. This adherence explains the bimolecular termination. The rapid degradation of polymerization in high Ce(IV) concentrations indicates that active chains are terminated by Ce(IV) [30].

Arslan and Hazer [31] reported the polymerization of methyl methacrylate initiated by ceric ammonium nitrate (MMA) in the form of combination with polytetrafuran diol (PTHF-diol) and polycaprolactone diol (PCL-diol) in aqueous nitric acid. PMMA-*b*-PTHF and PMMA-*b*-PCL block copolymers were obtained. The polymerization reactions are presented in **Figure 1**.

Hazer et al. [32] searched the polymerization of methyl methacrylate initiated by ceric ammonium nitrate and poly(glycidyl azide)-diol in the aqueous nitric acid. Poly(methyl methacrylate)-*b*-poly(glycidyl acrylate) copolymer was obtained. The reaction mechanism is shown in **Figure 2**.

**41**

**Figure 3.**

**Figure 1.**

**Figure 2.**

*azide)-diol (PGA-diol).*

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

The synthesis pathway of the copolymers is shown in **Figure 3**.

*Synthesis of PMMA-*b*-PCL-*b*-PMMA block copolymer with PCL-diol/Ce(IV) redox systems.*

*Polymerization of methyl methacrylate initiated by ceric ammonium nitrate in combination with poly(glycidyl* 

*Polymerization of acrylamide with poly(ethylene glycol)azoester/Ce+4 redox system.*

Çakmak et al. [33] used redox reactions in the preparation of acrylamide-ethylene glycol block copolymers (PAAm-PEG) containing azo groups in the main chain.

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

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

Çakmak et al. [33] used redox reactions in the preparation of acrylamide-ethylene glycol block copolymers (PAAm-PEG) containing azo groups in the main chain. The synthesis pathway of the copolymers is shown in **Figure 3**.

#### **Figure 1.**

*Redox*

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

Various compounds such as ceric, manganese, copper, iron, vanadium ion salts, and hydrogen peroxide were used as catalysts for the synthesis of block copolymers through redox polymerization. The ceric-based catalysts are the most widely used in these catalyst systems. The redox systems containing other catalysts were also examined. Ce(IV) or permanganate initiators, which combine with reducing agent containing a hydroxyl or carboxyl group, are the more commonly used initiators. Ceric salts have shapes such as ceric(IV) ammonium nitrate (CAN), ceric(IV) ammonium sulfate (CAS), ceric(IV) sulfate (CS), and ceric perchlorate. As oxidation strength, ceric perchlorate > ceric nitrate > ceric sulfate were observed (1.7, 1.6, and 1.4 V), respectively, in the studies carried out with vinyl monomers [26]. A wide range of usages in the free radical production has been found by taking advantage of its amplifying properties in redox polymerization. The reduction reaction is given below.

The Ce(IV) salts and the Ce(IV) salt-reducing substance system are used as initiators for vinyl polymerizations in aqueous acidic solutions [27]. Organic reductant substances most commonly used with the Ce(IV) salts are alcohols, glycols, aldehydes, ketones, and carboxylic acids [27, 28]. Ce(IV) salts are used only in acidic solutions and most preferably in 0.5 or higher acid concentrations [29]. The solution's color is yellow. The turning point can be determined even without an

It has been proven by research that Ce(IV) ion cannot initiate acrylamide polymerization alone and water is not oxidized by Ce(IV) ions [27]. So the radicals that start polymerization occur as a result of the reaction between the Ce(IV) ion

When keeping the concentration of methyl methacrylate and Azo I constant

tion rate also increased proportionally with [Ce(IV)]½ in the methyl methacrylate polymerization initiated by the hydroxyl functional group with a redox pair Ce(IV)-Azo I. This adherence explains the bimolecular termination. The rapid degradation of polymerization in high Ce(IV) concentrations indicates that active

Arslan and Hazer [31] reported the polymerization of methyl methacrylate initiated by ceric ammonium nitrate (MMA) in the form of combination with polytetrafuran diol (PTHF-diol) and polycaprolactone diol (PCL-diol) in aqueous nitric acid. PMMA-*b*-PTHF and PMMA-*b*-PCL block copolymers were obtained.

Hazer et al. [32] searched the polymerization of methyl methacrylate initiated by ceric ammonium nitrate and poly(glycidyl azide)-diol in the aqueous nitric acid. Poly(methyl methacrylate)-*b*-poly(glycidyl acrylate) copolymer was obtained. The

mol L<sup>−</sup><sup>1</sup>

, the polymeriza-

and the reducing substance. A general mechanism is proposed for this.

and increasing the concentration of Ce(IV) up to 6 × 10<sup>−</sup><sup>4</sup>

The polymerization reactions are presented in **Figure 1**.

**3. Catalysts used in redox polymerization systems**

indicator in hot and non-dilute solutions.

chains are terminated by Ce(IV) [30].

reaction mechanism is shown in **Figure 2**.

**40**

*Synthesis of PMMA-*b*-PCL-*b*-PMMA block copolymer with PCL-diol/Ce(IV) redox systems.*

**Figure 2.**

*Polymerization of methyl methacrylate initiated by ceric ammonium nitrate in combination with poly(glycidyl azide)-diol (PGA-diol).*

**Figure 3.** *Polymerization of acrylamide with poly(ethylene glycol)azoester/Ce+4 redox system.*

Shimizu et al. [34] synthesized redox reaction with the poly(*N*-isopropylacrylamide-*b*-ethylene glycol) [(PNIPAM)-*b*-(PEG)] thermo-responsive block copolymers in ceric ammonium nitrate catalyzer using the PEG macroinitiator. The synthesis mechanism of block copolymers is shown in **Figure 4**.

Göktaş et al. [12] evaluated poly(methyl methacrylate)-*b*-poly(*N*-isopropylacrylamide) [PMMA-*b*-PNIPAM] block copolymers in two steps under the catalyzer of ceric ammonium (IV) nitrate (CAN) [Ce(NH4)2(NO3)6] by using 3-bromo-1-propanol initiator, suitable for both redox polymerization and atom transfer radical polymerization which is one of the controlled radical polymerization techniques. The synthesis mechanisms of the polymerization are shown in **Figures 5** and **6**.

Zhuang et al. [16] evaluated poly(hydroxylethyl methacrylate)-branched-poly (acrylamide) (PHEMA-*branched*-PAM) polymer by combining atom transfer radical and redox polymerization methods. The synthesis mechanism of the polymer is shown in **Figure 7**.

Göktaş et al. [35] evaluated poly(methyl methacrylate-b-styrene) and poly(methyl methacrylate-b-acrylamide) which were synthesized in two steps using a combination of the redox polymerization method and the atom transfer radical polymerization (ATRP) method. The synthesis mechanisms of the polymerization are shown in **Figures 8** and **9**.

Çakmak et al. [24] evaluated poly(acrylonitrile)-*block*-poly(ethylene glycol) block copolymer via redox polymerization using Mn(III) as catalyzer. The synthesis pathway of the copolymers is shown in **Figure 10**.

**Figure 4.**

*Synthesis of poly(*N*-isopropylacrylamide)-*block*-poly(ethylene glycol) block copolymer via poly(ethylene glycol)/Ce(IV) redox pair.*

**43**

**Figure 8.**

**Figure 6.**

**Figure 7.**

*substrates.*

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

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

*Reaction pathways in the synthesis of PMMA-*b*-PNIPAM block copolymers.*

*The synthesis route of PHEMA-*branched*-PAM layers via ATRP and redox polymerization on silicon* 

*Figure 1 Chemical synthesis of PMMA-Br macroinitiator via redox polymerization.*

**Figure 5.** *Reaction pathways in the synthesis of ATRP macroinitiator.* *Copolymer Synthesis with Redox Polymerization and Free Radical Polymerization Systems DOI: http://dx.doi.org/10.5772/intechopen.88088*

**Figure 6.** *Reaction pathways in the synthesis of PMMA-*b*-PNIPAM block copolymers.*

#### **Figure 7.**

*Redox*

shown in **Figure 7**.

ization are shown in **Figures 8** and **9**.

pathway of the copolymers is shown in **Figure 10**.

Shimizu et al. [34] synthesized redox reaction with the poly(*N*-isopropylacrylamide-*b*-ethylene glycol) [(PNIPAM)-*b*-(PEG)] thermo-responsive block copolymers in ceric ammonium nitrate catalyzer using the PEG macroinitiator. The

Göktaş et al. [12] evaluated poly(methyl methacrylate)-*b*-poly(*N*-isopropylacryl-

Zhuang et al. [16] evaluated poly(hydroxylethyl methacrylate)-branched-poly (acrylamide) (PHEMA-*branched*-PAM) polymer by combining atom transfer radical and redox polymerization methods. The synthesis mechanism of the polymer is

amide) [PMMA-*b*-PNIPAM] block copolymers in two steps under the catalyzer of ceric ammonium (IV) nitrate (CAN) [Ce(NH4)2(NO3)6] by using 3-bromo-1-propanol initiator, suitable for both redox polymerization and atom transfer radical polymerization which is one of the controlled radical polymerization techniques. The

synthesis mechanisms of the polymerization are shown in **Figures 5** and **6**.

Göktaş et al. [35] evaluated poly(methyl methacrylate-b-styrene) and poly(methyl methacrylate-b-acrylamide) which were synthesized in two steps using a combination of the redox polymerization method and the atom transfer radical polymerization (ATRP) method. The synthesis mechanisms of the polymer-

Çakmak et al. [24] evaluated poly(acrylonitrile)-*block*-poly(ethylene glycol) block copolymer via redox polymerization using Mn(III) as catalyzer. The synthesis

*Synthesis of poly(*N*-isopropylacrylamide)-*block*-poly(ethylene glycol) block copolymer via poly(ethylene* 

synthesis mechanism of block copolymers is shown in **Figure 4**.

**42**

**Figure 5.**

**Figure 4.**

*glycol)/Ce(IV) redox pair.*

*Reaction pathways in the synthesis of ATRP macroinitiator.*

*The synthesis route of PHEMA-*branched*-PAM layers via ATRP and redox polymerization on silicon substrates.*

**Figure 8.** *Figure 1 Chemical synthesis of PMMA-Br macroinitiator via redox polymerization.*

**Figure 9.**

*Synthetic route poly(MMA-*b*-S) and poly(MMA-*b*-AAm) for block copolymers.*

**Figure 10.**

*Synthesis of poly(acrylonitrile)-*block*-poly(ethylene glycol) block copolymer via poly(ethylene glycol)/Mn(III) redox couple.*

Liu et al. [36] evaluated methyl acrylate (MA) and poly(ethylene glycol) (PEG) block copolymers using a novel redox system-potassium diperiodatocuprate(III)

**45**

**Author details**

Melahat Göktaş

Department of Science Education, Yüzüncü Yil University, Van, Turkey

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: melahat\_36@hotmail.com

provided the original work is properly cited.

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

[DPC]/PEG system in alkaline aqueous medium. The synthesis mechanism of the

*Block copolymerization of methyl acrylate (MA) and poly(ethylene glycol) (PEG) using potassium* 

Today, polymer materials science dominates the synthesis and design of polymers with complex architecture and advanced properties. The functional copolymers with block, graft, star, and brush structures can be prepared by controlled radical polymerization techniques. Copolymer synthesis has been important recently, especially by using controlled radical polymerizations in combination with traditional polymerization methods such as cationic polymerization and redox polymerization. This is because the homopolymer formation is minimized in block

copolymer synthesis with the combination of such different techniques.

synthesis methods contributes positively to polymer material science.

In this study, it was emphasized that block copolymer synthesis has superior properties compared to traditional polymerization methods using the redox polymerization method and different polymerization techniques, because combining different monomers in the same polymer chain in copolymer synthesis with multi-

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

polymer is shown in **Figure 11**.

*diperiodatocuprate(III)[DPC]/PEG redox system.*

**4. Conclusion**

**Figure 11.**

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

**Figure 11.**

*Redox*

**Figure 9.**

*Synthetic route poly(MMA-*b*-S) and poly(MMA-*b*-AAm) for block copolymers.*

**44**

**Figure 10.**

*redox couple.*

Liu et al. [36] evaluated methyl acrylate (MA) and poly(ethylene glycol) (PEG) block copolymers using a novel redox system-potassium diperiodatocuprate(III)

*Synthesis of poly(acrylonitrile)-*block*-poly(ethylene glycol) block copolymer via poly(ethylene glycol)/Mn(III)* 

*Block copolymerization of methyl acrylate (MA) and poly(ethylene glycol) (PEG) using potassium diperiodatocuprate(III)[DPC]/PEG redox system.*

[DPC]/PEG system in alkaline aqueous medium. The synthesis mechanism of the polymer is shown in **Figure 11**.

## **4. Conclusion**

Today, polymer materials science dominates the synthesis and design of polymers with complex architecture and advanced properties. The functional copolymers with block, graft, star, and brush structures can be prepared by controlled radical polymerization techniques. Copolymer synthesis has been important recently, especially by using controlled radical polymerizations in combination with traditional polymerization methods such as cationic polymerization and redox polymerization. This is because the homopolymer formation is minimized in block copolymer synthesis with the combination of such different techniques.

In this study, it was emphasized that block copolymer synthesis has superior properties compared to traditional polymerization methods using the redox polymerization method and different polymerization techniques, because combining different monomers in the same polymer chain in copolymer synthesis with multisynthesis methods contributes positively to polymer material science.
