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Questions and Answers
What type of polymerization involves the linear growth of molecules and the shifting of free radicals?
What type of polymerization involves the linear growth of molecules and the shifting of free radicals?
- Chain-growth polymerization (correct)
- Step-growth polymerization
- Ring-opening polymerization
- Cross-linking polymerization
Which factor is NOT typically associated with polymerization reactions?
Which factor is NOT typically associated with polymerization reactions?
- Evolution of heat
- Monomer immobilization (correct)
- Residual monomer
- Shrinkage
What is the primary characteristic of the ring opening mechanism in polymerization?
What is the primary characteristic of the ring opening mechanism in polymerization?
- Results in high thermal expansion
- Involves only linear monomers
- Utilizes cyclic monomers with terminal reactive groups (correct)
- Leads to a frozen spatial configuration
Which method of termination in radical polymerization involves the direct coupling of two radicals?
Which method of termination in radical polymerization involves the direct coupling of two radicals?
What type of material is an example of a polymer formed via ring-opening polymerization?
What type of material is an example of a polymer formed via ring-opening polymerization?
What key aspect is affected by the thermal behavior of polymers during polymerization?
What key aspect is affected by the thermal behavior of polymers during polymerization?
What major disadvantage is associated with residual monomer in polymerization processes?
What major disadvantage is associated with residual monomer in polymerization processes?
During which stage of polymerization would shrinkage primarily occur?
During which stage of polymerization would shrinkage primarily occur?
What is the term for a polymer composed of a single type of monomer?
What is the term for a polymer composed of a single type of monomer?
Which of the following best describes an oligomer?
Which of the following best describes an oligomer?
In terms of spatial configuration, what does a branched polymer refer to?
In terms of spatial configuration, what does a branched polymer refer to?
What type of polymer consists of more than one type of monomer?
What type of polymer consists of more than one type of monomer?
Which of the following is a natural polymer?
Which of the following is a natural polymer?
What is the primary bond type in intermolecular forces within polymers?
What is the primary bond type in intermolecular forces within polymers?
Which of the following is not a characteristic of the polymerization reaction?
Which of the following is not a characteristic of the polymerization reaction?
What is the result of a polymer that is classified based on its origin?
What is the result of a polymer that is classified based on its origin?
Which characteristic is true for thermoplasts?
Which characteristic is true for thermoplasts?
What differentiates addition polymerization from condensation polymerization?
What differentiates addition polymerization from condensation polymerization?
Which type of polymerization is typically slower and produces shorter polymer chains?
Which type of polymerization is typically slower and produces shorter polymer chains?
Which of the following polymers is associated with condensation polymerization in clinical applications?
Which of the following polymers is associated with condensation polymerization in clinical applications?
What is the main reason condensation polymerization results in small molecular weight products?
What is the main reason condensation polymerization results in small molecular weight products?
Which statement is true regarding thermosets?
Which statement is true regarding thermosets?
What initiates the activation and initiation in addition polymerization?
What initiates the activation and initiation in addition polymerization?
Which of the following properties is NOT typically associated with thermoplasts?
Which of the following properties is NOT typically associated with thermoplasts?
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Study Notes
Free Radical Polymerization
- Involves radical compounds with an unpaired electron, initiated using light or chemical means.
- Initiation requires a radical generator like benzoyl peroxide to form free radicals.
Propagation
- Characterized by linear growth of molecules through the addition of free radicals to the end of the growing chain.
Termination Mechanisms
- Direct Coupling: Two free radicals combine to terminate the reaction.
- Hydrogen Atom Transfer: Involves the transfer of hydrogen atoms between radicals, leading to new bond formation.
Factors Influencing Polymerization
- Heat generation occurs during polymerization.
- Shrinkage and the presence of residual monomer can affect the final product.
Ring Opening Mechanism
- Utilizes terminal reactive groups within cyclic monomers.
- Examples: Polyether rubber impression material and low shrinkage composites (Siloranes).
Types of Polymers
- Thermoplasts: Physical reactions, soft, can be remelted and reformed. Sensitive to heat. Example: Acrylic resin.
- Thermosets: Chemical reactions, cannot be remelted, degrades upon heating, high mechanical properties.
Polymer Preparation Reactions
-
Condensation Polymerization:
- Involves stepwise reactions with multiple monomer species.
- Produces low molecular weight due to by-product elimination.
- Slower with shorter polymer chains. Relevant in polysulfide rubber impression materials.
-
Addition Polymerization:
- Faster reaction without by-products.
- Results in high molecular weight polymers.
Polymer Structure
- Polymers are long-chain organic molecules made of repeated units called monomers.
- Monomer: Smallest repeating unit (single).
- Oligomer: Short polymer composed of 10 monomers.
Bonding Types in Polymers
- Intramolecular bonds (primary bonds) are covalent.
- Intermolecular bonds (secondary bonds) connect individual polymer chains.
Polymerization Reaction
- Process by which monomer units chemically link to form high molecular weight polymers.
- Homopolymers: Comprised of one type of monomer.
- Copolymer: Made from more than one type of monomer.
Classification of Polymers
-
By origin:
- Natural: Proteins, polysaccharides, DNA, RNA.
- Synthetic: Bakelite, nylon, PMMA, polyvinyl chloride.
-
By spatial configuration:
- Linear, branched, and cross-linked structures.
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