Polymerization Flashcards
2 major types
step-growth
addition polymerization
step-growth
tend to have atoms other than C in backbone
what do you need for step-growth
2 different f.g.s react to form a new f.g.
small molecule is evolved (H20, HCl, CH3OH) condensation rxn
addition polymerization typically needs
each monomer has at least 1 double bond to which elements of two other monomers are added
chain rxn. or chain growth polymerization
free radical, anionic or cationic
how to name?
of C in each monomer
head to tail or head to head?
head to tail is less sterically hindered
tacticity
relative position of groups along carbon chains
influences final properties
isotactic
groups on the same side of the molecule (all wedges or all dashes)
syndiotactic
groups on alternate sides of the molecule (wedge, dash, wedge, etc.)
atactic
random mixture of wedges and dashes
if more regular arrangement of groups along C backbone….
isotactic or syndiotactic – chains pack better and are more crystalline
stronger
it is endothermic to break ___ bonds and exothermic to form ___ bonds. overall the rxns are ____
pi, sigma
exothermic
does entropy increase or decrease during polymerization?
decrease
thermodynamic analysis
as temp increases T(S) term becomes significant and may cause depolymerization
causes a temp ceiling TsubC
naming homopolymers
named after starting monomer
ex. ethylene —> polyethylene
vinyl chloride —> poly(vinyl chloride)
