Radical Addition/Polyethylene/PP

Question 1

in radical addition what end of double bond is attacked?

Answer 1

tail end so you get a head-to-tail conformation

Question 2

tacticities

Answer 2

iso (same)

syndio (alternating)

atactic (random)

Question 3

special about polyethylene radical rxn

Answer 3

growing chain radical reacts with a H from a terminated chain to form 2º radical and make branches

or back-biting (H from same chain)

or H from solvent

Question 4

HDPE

Answer 4

long linear chains

strong, harder, better packing

van der waals forces made pseudo x-links

Question 5

LDPE

Answer 5

long chain with many branches prohibiting packing

softer, pliable material

Question 6

PE polymerization rxn conditions

Answer 6

free radical under high P/T (favors branching)

Question 7

how get HDPE if branching during radical rxn?

Answer 7

Zieglar-Natta coordination catalyst

ethylene at low P/Rm T

not free radical!!!!

get less branching, more dense, crystalline, linear HDPE

Question 8

Zieglar-Natta Catalysts reagents

Answer 8

triethyl aluminum

titanium tetrachloride

transition metal catalyst

organometallic co-catalyst

Question 9

what happens in Zieglar Natta PE

Answer 9

get straight chain HDPE

Question 10

propylene with Zieglar Natta

Answer 10

get isotactic PP

stereospecific, regiospecific head-to-tail

Question 11

atactic PP

Answer 11

soft, amorphous polymer, not crystalline

no order in chains

poor physical/thermal properties

Question 12

isotactic PP

Answer 12

crystalline/pack well; useful

high MP 183ºC; excellent physical properties (tough)

crystalline and amorphous areas b/c chains are so long they cant all line up straight “semicrystalline”