1. How does the addition of solvents and additives, due to their abnormal effects, can affect the process of polymerization?
a) increase initiator efficiency
b) increase radical generation
c) enhance chain initiation rate
d) all of the mentioned
Explanation: The solvents, while behaving abnormally, sometimes can induce an increase in initiator efficiency or radical generation, which consequently increases the rate of chain initiation as well as polymerization.
2. What is the value of intercept of the line plotted between the terms (2kt/kp2)(Rp2/[I][M]2) and Rp/[M], when there is simultaneous occurrence of bimolecular termination and termination by degradative process?
a) 2fkd
b) fkd
c) kt’/kp
d) [I]
Explanation: For simultaneous occurrence of bimolecular termination and termination by degradative process, under steady-state condition, the equation is given by-
2kt[M∙]2 + kt’[I][M∙] = 2fkd [I].
On eliminating the radical concentration term, [M∙], we get
(2kt/kp2)(Rp2/[I][M]2) = 2fkd – (kt’/kp) Rp/[M] .
So, from the above equation, when straight line is plotted, it has a negative slope and the intercept value gives the value of 2fkd.
3. Viscosity of the polymerization medium has a great influence on the termination process. State true or false.
a) True
b) false
Explanation: Viscosity of the polymerization medium ofcourse has a influence on termination reaction, for termination being a diffusion based process. The solvent modification of termination reaction causes different kt values depending on the viscosity medium
4. With the introduction of solvents in modifying the initiator species and affecting the degradative chain transfer, the value of parameter kp2/kt , changes with the solvent concentration. State true or false.
a) true
b) false
Explanation: The kinetic parameter kp2/kt practically remains unchanged over a whole range of dilution, when the solvents play an important role in modifying the initiator species and bring into effect noticeable degradative chain transfer.
5. What is the special feature of the olefin metathesis and metathesis polymerization?
a) use of initiators
b) use of catalysts with high potential
c) use of solvents
d) none of the mentioned
Explanation: The special feature of this process is the use of catalyst with novel selectivity and high potential for effective chemical transformations for olefin metathesis.
6. What is the main driving force of the ring-opening metathesis polymerization reaction?
a) solvent concentration
b) relief of ring strain
c) catalyst activity
d) all of the mentioned
Explanation: The main driving force of the ROMP reaction is the relief of ring strain.
When the metal carbene attacks the double bond of the ring, it gives rise to highly strained intermediate. The ring then opens to give the beginning of the polymer.
7. Which of the following features are dependent on the solvent used in ring opening metathesis polymerization reaction?
a) rate of reaction
b) molecular weight
c) catalyst activity
d) all of the mentioned
Explanation: The solvent used plays an important role in the formation of carbene and thus affect the catalytic activity. Moreover by altering the solvent in the reaction, the rate of the reaction and the molecular weight of the polymer to be formed can be varied.
8. Which of the following functional group on the ring system poisoned the Grubb’s catalyst for the first time?
a) nitrile group
b) oxygenate groups
c) sulphate groups
d) hydrate groups
Explanation: Nitrile or amine groups poisoned the Grubb’s catalyst for the first time.
9. Which of the following substituent groups on the ring system can affect the Molybdenum or tungsten metathetic catalyst in ROMP?
a) oxygenate group
b) sulphate groups
c) amine groups
d) hydrate groups
Explanation: Molybdenum or Tungsten metathetic catalyst are affected by the oxygenate and nitrogenous groups attached to the ring in ROMP polymerization. The substituent groups can deleteriously react with the catalysts and affect its activity.
10. How does Norbornene epoxide affect the rate of ROMP reaction if RuCl3 and alcohol mixture is used as a catalyst?
a) increases
b) decreases
c) no change
d) cannot be determined
Explanation: This happens due to the production of metalloxacyclobutane complex, which directly gives the ruthenium trichloride carbene complex upon metathetic opening.