Ch. 7 Molecules for Living Flashcards
Define polymers
Polymers formed when many smaller molecules, called monomers, are joined by covalent bonds
define monomers
a small molecule that combines with other monomers to make a polymer
what is polymerisation
chemical reaction in which many small molecules (monomers) link together by covalent bonds to form one large molecule (polymer)
what are the two types of polymerisation
o Addition polymerisation (involves an addition reaction)
o Condensation polymerisation (involves a condensation reaction)
what is thermoplastic
a polymer that can be melted + reshaped
what is thermosetting
→ a polymer that cannot be melted or reformed (more chemically resistance, durable/ stronger)
what is addition polymers
formed by adding together without the loss of any atoms, through addition polymerisation
What type of molecular bonding is required for addition polymers and why
- monomer must have double bond b/w two carbon atoms
o The breaking of double bond provides each carbon with available bond to form bonds with other monomers
What is the difference in polyethylene between Low density (LDPE) and high density (HDPE)
- L= significant branching (prevent packing // fewer dispersion forces)
- H= unbranched, stronger dispersion
What is LDPE and HDPE known as
o (a) HDPE= more ordered structure (said to be crystalline) while (b) LDPE= more random structure (amorphous)
how do you name a polymer
- Named by putting ‘poly’ in front of the polymer name
- Brackets used around the name when the monomer name
o Is more than one word; e.g. poly(vinyl chloride)
o Beings with a number; e.g. poly(1-chloroethene)
What forces are involved in PVC and what does it occur
- Chlorine=highly electronegative // attracts election towards the –C-CL- bond = creates polar bond with Cl atoms slightly negative and C atoms slightly positive
- Dipole dipole interactions add to dispersion forces b/w polymer chains to make stronger intermolecular forces = holds polymer chains more strongly together
What are plasticisers
→ small molecules inserted b/w polymer chains- sometimes added to hold polymer chains further apart and weaken intermolecular forces between chains
o Makes polymer more flexible
What are the 3 arrangements of Polypropylene
- Isotactic (same side)
- Atactic (random)
- Syndiotactic (alternate on either side)
what is stereo regular
- Isotactic + syndiotactic= forms of polypropylene called stereoregular polymers
o Semi crystalline
what is a co polymer
: a polymer produced from two or more different monomers
What are 6 important features of polymers
o Crystallinity o Branching o Chain length o Side groups o Cross linking o Stability and biodegradability
Explain the feature of crystallinity
- can be crystalline region (strainer bonding, non permeable)
- or amprhpus (random,, large gaps b/w molcules= weak intermolecular
Explain the feature of branching
- low branching= pack closely > more crystalline
Explain the feature of chain length
long chain= harder
Explain the feature of side groups
- bigger side group= reduces flexibility
Explain the feature of cross linking
increases rigitity
Explain the feature of stability and biodegradability
- increased biodegradability by copolymerised with natural polymer segments
addition polymers require double bond, condensation polymers require..
functional groups
what is a polyester
condensation polymers in which the monomers are joined by an ester link
what are polyesters formed from either:
- single monomer (hydroxyl functional group at one end and carboxylic acids on the other)
- two different monomer (one with two hydroxyls and another with two carboxyl groups)
what is a polyamide
condensation polymers in which the repeating units are held together by amide links (-CO-NH-) (Link also found in proteins= peptide link)
what are polyamides formed from either:
o Single monomer that has an amino acid (-NH2) at one end and a carboxyl (-COOH) at the other
o Two different monomers- one with amino groups at each end (a diamine) and one monomer with carboxyl groups at each end (dicarboxylic acid)
