1. Where is the copolymer equation of binary copolymerization not applicable?
a) free radical systems
b) cationic systems
c) anionic systems
d) none of the mentioned
Explanation: The copolymer equation is relevant and applicable to radical, cationic and anionic systems, despite variations in values of reactivity ratios depending on the mode of chain propagation.
2. When is the copolymerization said to be an ideal copolymerization?
a) Copolymer composition F1 not equal to monomer feed composition f1
b) r1r2=1
c) r1=r2
d) r1=1
Explanation: A copolymerization is said to be an ideal copolymerization when the chain radicals have equal preference to add one of the monomers over the other.
3. Which of the following is true if the two monomers involved in copolymerization, are equally reactive with each radical?
a) r1=r2=1
b) F1=f1
c) random arrangement of monomer units
d) all of the mentioned
Explanation: When r1=r2=1, then under such condition, the monomers are equally reactive with chain radicals and the radicals cannot distinguish between the two monomers. Moreover, the composition of copolymer is the same as that in the feed and the monomer units are arranged in a random manner.
4. Which of the following is correct regarding the alternate copolymerization?
a) r1r2=1
b) r1=r2=1
c) r1r2=0
d) r1r2>1
Explanation: For perfect alternation in the copolymer structure the values of r1 and r2 are nearly equal to zero, as the chain growth strictly takes place by cross-propagation.
5. What is the value of copolymer composition (mole fraction), F1 for alternate copolymerization?
a) 0.5
b) 1
c) r1
d) 2
Explanation: For alternation, r1=r2=0
And F1 = (r1f12+f1f2)/(r1f12+2f1f2+r2f22)
Substituting the values, we obtain F1= 0.
6. Which of the following combinations undergoing polymerization give polysulphones
a) olefins and sulphur dioxide
b) cycloolefins and metal sulphate
c) olefins and sulphur trioxide
d) vinyl monomer and sulphur ring
Explanation: Polysuplhones are obtained by the radical polymerization of monomers like olefins, cyclo-olefins, vinyl compounds in liquid sulphur dioxide.
7. Calculate the feed composition for azeotropic copolymerization of methy methacrylate and styrene at 60ᵒC.(Given that r1=0.46 and r2=0.52)
a) 0.47
b) 0.56
c) 0.235
d) 0.94
Explanation: For azeotropic copolymerization,
(f1)c = (1-r2)/(2-r1-r2)
Substituting the values, we get (f1)c = 0.47.
8. What is the composition of copolymer formed by the copolymerization of 60% vinyl acetate and 40% vinyl chloride at 60ᵒC, given that r1=0.23 and r2=1.68?
a) 0.39
b) 0.78
c) 0.63
d) cannot be determined
Explanation: The copolymer composition is calculated by the following equation-
F1 = (r1f12+f1f2)/(r1f12+2f1f2+r2f22)
Substituting the values, we obtain F1= 0.39.
9. What is the copolymer composition for azeotropic copolymerization of Acrylonitrile and 1,3-butadiene at 50ᵒC, given that r1=0.02 and r2=0.30?
a) 0.21
b) 0.417
c) 0.84
d) 0.62
Explanation: For azeotropic copolymerization,
Critical feed monomer composition is given by-(f1)c=(1-r2)/(2-r1-r2)
Substituting the values, we get (f1)c=0.42
And copolymer composition is given by-
F1 = (r1f12+f1f2)/(r1f12+2f1f2+r2f22).
Thus, F1= 0.417.
10. Methacrylic acid and 2-vinyl pyridine are copolymerized together at 70ᵒC, where r1 and r2 have values 0.58 and 1.55, respectively. Which of the following component is present in more quantity in the copolymer formed in earlier stage?
a) methacrylic acid
b) 2-vinyl pyridine
c) equimolar composition
d) none of the mentioned
Explanation: For the reaction of copolymerization, k1,1=0.58k1,2 and k2,2=1.55k2,1. In both the cases, 2-vinyl pyridine is consumed at a faster rate than methacrylate by each of the radicals. So 2-vinyl pyridine is present in more quantity in the copolymer formed at an earlier stage.