12 Questions
What is needed to begin chain-growth polymerization?
An initiator (a radical, cation, or anion)
How is the mechanism of radical polymerization similar to the radical addition of HBr to an alkene?
A carbon radical is added to the double bond
Describe the initiation step in the mechanism of chain-growth addition polymers.
Homolysis of the weak O-O bond of the peroxide forms RO, which then adds to a molecule of monomer to form a carbon radical
What happens during the propagation step in chain-growth addition polymers?
The carbon radical formed during initiation adds to another alkene molecule to form a new C – C bond and another carbon radical
What effect does branching have on the intermolecular interactions of LDPE?
Weaker intermolecular interactions
How is branching initiated in the formation of branched polyethylene during radical polymerization?
Abstraction of a hydrogen atom from an existing polymer chain
What is the temperature and pressure used in the first commercial polyethylene process?
500°C and 1000 atmospheres
What is the primary use of LDPE in today's context?
Blow-molding of films for packaging and trash bags
What type of interactions hold together the ordered regions of polyethylene chains?
Van der Waals interactions
How do crystalline regions affect the toughness of a polymer?
They impart toughness to a polymer.
What characterizes a polymer's behavior on heating, and how are they defined?
Tg and Tm, glass transition temperature and melt transition temperature.
What effect does branching have on the amorphous nature and softness of polymers?
Branching makes polymers more amorphous and softer.
This quiz covers the key concepts of chain-growth polymerization in chemistry, including the role of initiators, the formation of radicals, cations, or anions as intermediates, and the mechanism involving initiation, propagation, and termination.
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