The Structure of Amorphous Solids and Polymers

MSE 2001 HW 9

Which of these statements is NOT true about glasses?

Adding chemical modifiers to SiO₂ glass strengthens the bonding in the glass network and usually raises the glass transition temperature.

Compared to a completely amorphous polymer of the same composition, a semi-crystalline polymer is expected to:

 

(I)   have greater optical transparency.

(II)  show improved stability to higher operating temperatures.

(III) appear more uniformly colored after dying.

(IV) exhibit a higher elastic modulus.

(V)  be a better vapor barrier when used in food packaging.

(II), (IV), and (V)

How would you best describe the structure of this polymer?  (Assume the different colored spheres represent different monomer chemistries.)

Grafted copolymer

What kind of tacticity does this polypropylene chain have? 

Syndiotactic

Which of these monomers, when used in a step-growth reaction, would definitely form a thermoset polymer?

 

Monomer C

In window glass, silicon is

tetrahedrally coordinated to 4 oxygens.

Semicrystalline polymers are opaque because

the crystallites scatter light.

Adding cross-links to a polymer will...

will make the polymer more rigid.

If two solid glasses have identical compositions, they will also have identical properties.

False

Which of these polymers is LEAST likely to crystallize.

Polysytrene [C₂H₃(C₆H₅)]_n

"Super balls" that bounce really high are an example of...

a thermoset polymer with its Tg below room temperature.

The glass transition temperature is always below the melting temperature of a material.

True

 Which of these monomers could be used for a free radical, chain growth polymerization? (Choose ALL that could be used)

Both B and D

Amorphous solids have short range order.

True

Hydrogels dissolve in water.

False

Ceramic glasses A and B have the same composition but glass A has a higher fictive temperature than glass B.  Which of these statements could be accurate about these two glasses?

Glass A was quenched from a higher temperature than glass B, leading to glass A being less dense than glass B.

Adding a PbO modifier to SiO₂ glass will result in a new glass that has...

...a higher refractive index and a lower glass transition temperature than pure SiO₂ glass_.

Which of these techniques could be used to probe the short range order in window glass?

B. Using x-ray scattering to collect a radial distribution function.