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1.When considering the mechanism of formation of such a polymer, briefly describe what the physicochemical and mechanical properties of the polymer chain, which is most different from monomers or small molecules.

 

 

 

 

 

1. When considering the mechanism of formation of such a polymer, briefly describe what the physicochemical and mechanical properties of the polymer chain, which is most different from monomers or small molecules, are.

 

 

 

 

 

 

2. Figure 1(b) shows the formation mechanism of typical thermoplastic polymer polyethylene (PE), and Figure 1(d) shows the mechanism of formation of typical thermoset polymer epoxy network. In particular, as shown in Figure 1(c), the differences in physicochemical properties can be predicted by comparing the two polymers. Because each epoxy chain is cured to one another, it exhibits very different physical and chemical properties than thermoplastic polymers such as polyethylene (PE). Describe two or more of the greatest features.

 

 

2. DSC measures differences in the amount of heat required to increase the temperature of a sample and a reference as a function of temperature. Basically, heat capacity or thermal capacity is the amount of heat required to increase the temperature of a substance by one degree. Figure 2(a) shows a thermodynamic behavior of the material showing the change in heat capacity with the temperature under isobaric conditions. Figure 2(b) shows typical thermodynamic behaviors of amorphous polymer and semi-crystalline polymer, respectively.

 

 

 

 

1. Figure 2(a) describes a change of the heat capacity according to temperature. Please express and discuss in detail through a change of the enthalpy (DH) behavior according to temperature.

 

 

2. In the case of the amorphous polymer, explain the reason why the glass transition temperature appears in the thermal behavior (Figure 2(b)) according to temperature. (Explain using microbrownian motion in detail.)

 

3. Describe in a logical way the crystallinity can be extracted through the thermal phase transition of the semi-crystalline polymer. Also, illustrate and briefly describe the thermal behavior of the crystallization behavior with temperature reduction in Figure 2(b).

 

 

 

 

 

 

3.Figure 3 below shows a thermodynamic behavior of various types of polymers. Generally, the polymer exhibits a 1st order phase transition (T_m) and a 2nd order phase transition (T_g). However, as in the case below, the polymer of (1) shows only the 2nd order transition, and the polymer of (3) shows only the 1st order transition. Polymer (2), which is the most polymeric characteristic, shows 1st and 2nd transitions at the same time.

 

 

 

 

1. Predict which film structure will be seen before each polymer (1 to 3) shows thermal transitions. (Please express it in the lamellar and amorphous chain.)

 

 

 

2. Figure 3 shows the thermodynamic behavior of the free volume with temperature. If so, describe and briefly explain the thermodynamic behavior of the temperature-dependent thermal capacity (C_p) for all polymers (1 to 3). (Please describe an endothermic or exothermic behavior clearly.)

 

 

 

 

 

 

 

 

4.A polydispersed sample of polystyrene (PS) is prepared by mixing three monodisperse samples in the following proportions:

 

A : 3 g, 10,000 molecular weight PS

B : 2 g, 30,000 molecular weight PS

C : 1 g, 300,000 molecular weight PS

 

Using this information, describe a final correlation equation to calculate the number-average MW and weight-average MW of the mixture, respectively. (Not necessary to derive a final value.)

 

 

5.There are two main ways to define the size of a polymer chain. The mean square end-to-end distance (R_rms, <r²>^0.5) and radius of gyration (R_g, <s²>^0.5) Figure 4(a) below shows the difference between R_rms and R_g in the random polymer coil, which is a typical polymer chain.

   

 

Figure 4.

 

1. Explain precisely the reasons why these differences are caused by each concept.

 

2. The stiffness of the polymer chain affects the chain size of the polymer as shown in Fig. 4(b). However, other factors that affect the size of the polymer chain can be considered in various ways. Suggest two or more representative arguments and explain briefly. (However, consider the polymer chain in solution.)

 

 

 

6.Figure 5 below shows examples of the first order phase transition among thermodynamic behaviors of various crystalline polymers depending on the kind of polymer.

 

 

Figure 5.

1. Use the Gibbs free energy (DG_f) to describe the thermodynamic meaning of the melting temperature (T_m) indicating the 1st order phase transition and briefly describe it. (Please explain using Figure 5(a)).

 

2. In Figure 5(b), explain why the melting points of the two polymers differ from each other in terms of enthalpy (DH_f) and entropy (DS_f), respectively.

 

 

3. The difference in melting points of the two polymers (polyethylene and polyamide) in Fig. 5(c) is due to the difference in the enthalpies of the hydrogen bonds between the polymer chains. (O, X)

 

4. In Figure 5(d), compare the melting temperatures of the three polymers and briefly explain why.

 

5. As shown in Fig. 5 (e), although the polymer is formed in the same chain, the melting temperature may vary depending on the molecular weight. Briefly explain why.

7.Figure 6(a) shows a typical step-growth polymerization. Figure 6(b) shows the polymerization formation process that shows the difference between the two step-growth & chain-growth methods.

 

 

 

Figure 6.

 

1. The step-growth polymerization shown in Fig. 6(a) is divided into a process in which byproducts (H₂O or HCl) are not generated and a process in which byproducts are generated. Express each representative reaction procedure using the formula.

 

2. Describe briefly the reason why there is a big difference in the formation process of two polymerization methods as shown in Fig. 6(b).

 

 

 

 

 

 

 

 

8.Figure 7(a) shows the typical chain-growth polymerization. Also, Figure 7(b) shows the molecular weight distribution over time, which shows the difference between the two polymerization methods (step-growth & chain-growth).

 

 

 

Figure 7.

1. The most representative of the chain-growth polymerization shown in Fig. 7(a) is radical polymerization. Depending on the initiator used, it can be divided into various types of polymerization methods, of which radical is most commonly used. If so, describe the process of radical polymerization in three broad ways and briefly explain it.

 

2. As shown in Figure 7(b), a more suitable method for obtaining high molecular weight is step-growth polymerization. (O, X)

 

3. Figure 7(c) shows representative initiators. The process in which each initiator ultimately forms a radical participating in polymer polymerization is shown in the formulas. Simplify the process of polymerizing polystyrene using one of the radicals

   1.When considering the mechanism of formation of such a polymer, briefly describe what the physicochemical and mechanical properties of the polymer chain, which is most different from monomers or small molecules.

    

    

   

    

    

    

4. When considering the mechanism of formation of such a polymer, briefly describe what the physicochemical and mechanical properties of the polymer chain, which is most different from monomers or small molecules, are.

5.  

    

    

    

    

    

6. Figure 1(b) shows the formation mechanism of typical thermoplastic polymer polyethylene (PE), and Figure 1(d) shows the mechanism of formation of typical thermoset polymer epoxy network. In particular, as shown in Figure 1(c), the differences in physicochemical properties can be predicted by comparing the two polymers. Because each epoxy chain is cured to one another, it exhibits very different physical and chemical properties than thermoplastic polymers such as polyethylene (PE). Describe two or more of the greatest features.
7.  

    

   2. DSC measures differences in the amount of heat required to increase the temperature of a sample and a reference as a function of temperature. Basically, heat capacity or thermal capacity is the amount of heat required to increase the temperature of a substance by one degree. Figure 2(a) shows a thermodynamic behavior of the material showing the change in heat capacity with the temperature under isobaric conditions. Figure 2(b) shows typical thermodynamic behaviors of amorphous polymer and semi-crystalline polymer, respectively.

    

   

    

    

    

8. Figure 2(a) describes a change of the heat capacity according to temperature. Please express and discuss in detail through a change of the enthalpy (DH) behavior according to temperature.

9.  

    

10. In the case of the amorphous polymer, explain the reason why the glass transition temperature appears in the thermal behavior (Figure 2(b)) according to temperature. (Explain using microbrownian motion in detail.)

11.  

12. Describe in a logical way the crystallinity can be extracted through the thermal phase transition of the semi-crystalline polymer. Also, illustrate and briefly describe the thermal behavior of the crystallization behavior with temperature reduction in Figure 2(b).

13.  

     

     

     

     

     

    3.Figure 3 below shows a thermodynamic behavior of various types of polymers. Generally, the polymer exhibits a 1st order phase transition (T_m) and a 2nd order phase transition (T_g). However, as in the case below, the polymer of (1) shows only the 2nd order transition, and the polymer of (3) shows only the 1st order transition. Polymer (2), which is the most polymeric characteristic, shows 1st and 2nd transitions at the same time.

     

     

    

     

     

14. Predict which film structure will be seen before each polymer (1 to 3) shows thermal transitions. (Please express it in the lamellar and amorphous chain.)

15.  

     

     

16. Figure 3 shows the thermodynamic behavior of the free volume with temperature. If so, describe and briefly explain the thermodynamic behavior of the temperature-dependent thermal capacity (C_p) for all polymers (1 to 3). (Please describe an endothermic or exothermic behavior clearly.)

17.  

     

     

     

     

     

     

     

    4.A polydispersed sample of polystyrene (PS) is prepared by mixing three monodisperse samples in the following proportions:

     

    A : 3 g, 10,000 molecular weight PS

    B : 2 g, 30,000 molecular weight PS

    C : 1 g, 300,000 molecular weight PS

     

    Using this information, describe a final correlation equation to calculate the number-average MW and weight-average MW of the mixture, respectively. (Not necessary to derive a final value.)

     

     

    5.There are two main ways to define the size of a polymer chain. The mean square end-to-end distance (R_rms, <r²>^0.5) and radius of gyration (R_g, <s²>^0.5) Figure 4(a) below shows the difference between R_rms and R_g in the random polymer coil, which is a typical polymer chain.

       

    

     

    Figure 4.

     

18. Explain precisely the reasons why these differences are caused by each concept.

19.  

20. The stiffness of the polymer chain affects the chain size of the polymer as shown in Fig. 4(b). However, other factors that affect the size of the polymer chain can be considered in various ways. Suggest two or more representative arguments and explain briefly. (However, consider the polymer chain in solution.)

21.  

     

     

    6.Figure 5 below shows examples of the first order phase transition among thermodynamic behaviors of various crystalline polymers depending on the kind of polymer.

     

    

     

    Figure 5.

22. Use the Gibbs free energy (DG_f) to describe the thermodynamic meaning of the melting temperature (T_m) indicating the 1st order phase transition and briefly describe it. (Please explain using Figure 5(a)).

23.  

24. In Figure 5(b), explain why the melting points of the two polymers differ from each other in terms of enthalpy (DH_f) and entropy (DS_f), respectively.

25.  

     

26. The difference in melting points of the two polymers (polyethylene and polyamide) in Fig. 5(c) is due to the difference in the enthalpies of the hydrogen bonds between the polymer chains. (O, X)

27.  

28. In Figure 5(d), compare the melting temperatures of the three polymers and briefly explain why.

29.  

30. As shown in Fig. 5 (e), although the polymer is formed in the same chain, the melting temperature may vary depending on the molecular weight. Briefly explain why.

31. 7.Figure 6(a) shows a typical step-growth polymerization. Figure 6(b) shows the polymerization formation process that shows the difference between the two step-growth & chain-growth methods.

     

     

    

     

    Figure 6.

     

32. The step-growth polymerization shown in Fig. 6(a) is divided into a process in which byproducts (H₂O or HCl) are not generated and a process in which byproducts are generated. Express each representative reaction procedure using the formula.

33.  

34. Describe briefly the reason why there is a big difference in the formation process of two polymerization methods as shown in Fig. 6(b).

35.  

     

     

     

     

     

     

     

    8.Figure 7(a) shows the typical chain-growth polymerization. Also, Figure 7(b) shows the molecular weight distribution over time, which shows the difference between the two polymerization methods (step-growth & chain-growth).

     

     

    

     

    Figure 7.

36. The most representative of the chain-growth polymerization shown in Fig. 7(a) is radical polymerization. Depending on the initiator used, it can be divided into various types of polymerization methods, of which radical is most commonly used. If so, describe the process of radical polymerization in three broad ways and briefly explain it.

37.  

38. As shown in Figure 7(b), a more suitable method for obtaining high molecular weight is step-growth polymerization. (O, X)

39.  

40. Figure 7(c) shows representative initiators. The process in which each initiator ultimately forms a radical participating in polymer polymerization is shown in the formulas. Simplify the process of polymerizing polystyrene using one of the radicals