Question

Isotactic Polypropylene (C3H6 MW=42g/mol), a thermo plastic is synthesized using bulk polymerization. For a monodisperse sample (PDI=1) the bigger molecule(higher degree of polymerization) contain the same total mass of the polymer sample than the smaller molecules(lower degree of polymerization). For a polydisperse sample the MW fractions do not contain the same mass.

Flexlife is the capability of polymeric material to withstand repeated bending without fracture. The Z average MW (Mz) is a measure of flexlofe as well as the predominance of high MW fractions.

Question: For the composition of the melt below:

(a) What are the number average MW (Mn), weight average MW (Mw), the Z average MW (Mz) and polydispersity index? Is the sample monodisperse?

-CH3—CH—СН2—СH—СH2—CH—CH2—СH-CH2—CH- I CH3 Снз снз CНз CНз isotactic polyproрylene Moles dp 5000 55 2000 25 1000 20 ΣΝΜ Μ ΣΜ η1 ΣΜΜ ΣΝΜ 2 W ΣΜΜ Σ ΝΜ? 3 2 Ζ PDI = M, / M η Σ838

Answer 1

N2 - 2000 N,23 N3=100o N3=20 ENiMi N,+N2+N3 NA 5s XJ000+ 25X 2o0ot 20 X 1o00 SS25 2o 34s000 34 So M2 =3450 ENiMi 11 NIM, +N2N +N3N3 20 xfooo) S5X50002 +15 x (2000) +20 X1O0o 55 x S00o+25 x 2ooo 137 X10 100X10 20 X1o 345000 (137s100 +20) X10 4.3 X 103 3 uS000 MW 4300 Mw 4300 P PI 1.24 3450 Mn monodinterse sample 94 PDI = I then P DI> but hese puty disganse Mo it as sample

3 ENiMi M2 ENiM 55 x5000)+ 25 x (2000)+ 20 x000) oo o)2 200 x10 20 x 10 495 X106 4.745 XID