18 Questions
What is the primary method of conducting addition polymerization?
All of the above
How is control of molecular weight achieved in addition polymerization?
By selecting appropriate initiator and monomer concentrations and temperature
Which type of reaction involves the addition of monomer to successive radicals in chain growth polymerization?
Propagation reaction
How is each successive propagation reaction characterized in chain growth or propagation reaction?
By the rate constant of propagation
What expression represents all successive propagation steps in chain growth polymerization?
$M + M = k_p M$
In chain-growth polymerization, what is used to achieve control of molecular weight under specific conditions?
Chain transfer agent
Which type of polymerization proceeds by an equilibrium step reaction mechanism?
Step-Growth Polymerization
In which type of polymerization does the growth process involve intermolecular condensation reactions between related functional groups?
Step-Growth Polymerization
Which type of polymerization has a slower step process compared to addition or chain polymerization?
Condensation Polymerization
In which type of polymerization can any two species of any size, including monomers, react and contribute to the growth process?
Chain-Growth Polymerization
Which type of polymerization sees the monomer disappear much faster in the early stages of the process?
Step-Growth Polymerization
Which type of polymerization allows for the isolation of molecular species in the intermediate stages of growth?
Step-Growth Polymerization
What is the main characteristic of addition polymerization?
Conversion of unsaturated monomers to polymers of high molecular weight
Which type of monomers readily undergo addition polymerization?
Unsaturated monomers like vinyl compounds and conjugated diolefins
What initiates the chain polymerization process?
Heat, light, or chemical additives known as initiators or catalysts
Which step in chain-growth polymerization involves the actual growth of the polymer chain?
Propagation of the chain
How can chain polymerization be characterized?
Fast and typically involving three distinguishable steps
What term is used to describe the mechanism of addition polymerization?
Chain-growth polymerization
Study Notes
Addition Polymerization
- Addition polymerization is usually done in gas phase, liquid bulk monomer, or under melt condition, or by solution, suspension, or emulsion techniques.
- Control of molecular weight is achieved by selecting appropriate initiator and monomer concentrations and temperature of polymerization.
- Chain transfer agents can be used to control molecular weight.
Chain Growth or Propagation Reaction
- The chain growth or propagation reaction involves the addition of monomer M to RM and to the successive radicals.
- Each successive propagation reaction is characterized by the rate constant of propagation kp.
- The radical reactivity is independent of chain length as long as the end structural segment is the same.
Characteristics of Addition Polymerization
- Addition polymerization is a process by which unsaturated monomers are converted to polymers of high molecular weight.
- It exhibits the characteristics of a typical chain reaction.
- Many different classes of unsaturated monomers, such as ethylene, olefins, vinyl compounds, and conjugated diolefins, undergo this type of polymerization.
Stages of Addition Polymerization
- Initiation of the chain process is triggered by heat, light, high energy radiations, or chemical additives (initiators or catalysts).
- Propagation of the chain or the chain growth process is the second stage.
- Cessation of the chain growth, i.e. the chain termination process, is the final stage.
Comparison with Condensation Polymerization
- Chain-growth polymerization is a fast reaction, whereas step-growth polymerization is a slower process.
- Monomers bearing functional groups undergo condensation polymerization.
- The growth process in condensation polymerization is characterized by relatively slow intermolecular condensation reactions.
- Any two species of any size, including monomers, may react and contribute to the growth process in condensation polymerization.
Explore the differences between addition/chain-growth polymerization and condensation/step-growth polymerization, including the techniques used and factors affecting molecular weight control. Table 3.1 provides further insight into these processes.
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