Solutions to quizes 1-3

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Solutions to quizes 1-3
Quiz 1 Physics and Chemistry of Hybrid Organic Materials
Write your name, and student ID number at top of page. Then write the
question and your answer down on your paper in English for 1-10 below.
1) What are hybrid organic-inorganic materials? Materials with both organic and
inorganic components, generally at least one of which is nanoscale in dimensions
2) What instrumentation can you use to determine if a material is amorphous or
crystalline? Best ascertained with XRD
3) Name three applications for hybrids. Dental composite fillings, tough hybrid
plastic for truck beds, air barrier membranes for tennis balls, photovoltaics or
organic light emitting diodes, antiscratch coatings for eye glasses, protective
coatings for buildings, wind shield coatings that shed water, optical fibers,
photoresists, adhesives, paint, photochromic coatings, and more
4) What are three benefits of using hybrid materials? Improved thermal stability,
strength, modulus, fire resistance, hardness, abrasion or scratch resistance, higher
refractive index, lower gas permeability than an organic material. More flexible,
tougher, elastic, and easier to process than inorganic materials.
5) How would you characterize the solubility of a hybrid in organic solvents? Try
dissolving small amounts of the hybrid in organic solvents with heating
6) How can you tell if you have a hybrid material or if it is just an organic
polymer or inorganic material? Burn it. If it burns and there is a residue that
doesn’t burn, its a hybrid.
7) Why are some hybrids white in appearance (like clouds)? Mie scattering
8) How can you tell if a hybrid has one or two phases? With SEM, TEM, AFM and
optical microscopes
9) What determines the experimentally measured strength of any material
(including hybrids)? Bond strengths.
10) Name a naturally occurring hybrid organic inorganic material? Enamel and
dentin in teeth, bone, chitin in lobsters, sea urchin spins, sponges, spider and
octopus beaks, pearl and shell nacre, egg shells.
Quiz 2 Physics and Chemistry of Hybrid Organic Materials
Write your name, and student ID number at top of page. Then write the
question and your answer down on your paper in English for 1-10 below.
1) Name three Naturally occurring hybrid organic-inorganic materials?
Any three of the following:
a) nacre
b) bone
c) dentin
d) enamel
e) chitin exoskeletons of lobsters
f) spider fangs
2) What are the inorganic and organic components in nacre (Mother of pearl)?
Inorganic: Argonite and organic: protein
3) What does hierarchical mean (in regards to materials)? Give an example of a
hierarchical material. Different structures at different length scales (sizes). An
example would be Nacre or bone or chitin exoskeletons.
4) Briefly describe how you could physically mix silica particles with an organic
polymer like polystyrene? Melt the polystyrene and physically mix in the dry silica
particles as a powder
or
Dissolve the polystyrene in solvent and mix in the particles also dispersed in solvent.
Cast mixture and evaporate solvent.
5) What is the difference between intercalation and exfoliation when making claypolymer hybrids? Intercalation is the polymers replacing surfactant in the clay but
leaving the stacked structure intact. Exfoliation is when the polymers unstack the 2-D
sheets and disrupt the structure.
6) Give three examples of inorganic components physically mixed into hybrids:
Any three of the below:
a) Silica particles
f) metal nanoparticles
b) Titanium dioxide
g) metal sulfide nanoparticles
c) fullerenes
h) graphene
d) carbon nanotubes
e) POSS
7) What is a nanocomposite hybrid organic inorganic material? Give an example of
a nanocomposite.
A hybrid with one or more of its phases is nanometer scale in size.
An example would be nacre
or
POSS in polypropylene
8) What are three ways to make inorganic particles?
Sol-gel polymerization, flame (aerosol) synthesis, emulsion polymerization,
precipitation, electrochemistry, electroless reductions or oxidations
9) Describe the two main reactions that occur when metal alkoxide monomers, like
organotrialkoxysilanes, polymerize?
Hydrolysis: replacing alkoxide groups with OH groups
Condensation: reaction of OH groups to form Si-O-Si groups
10) Why do gels form from hybrid monomers?
Gels form because the hybrid monomer polymerizes into macromolecules with high
enough molecular weight that they phase separate from solution as solid particles.
This is called a sol. The solid particles gel when they are concentrated enough to
percolate through the liquid.
Quiz 3 (June 10): Write your name, and ID number at top of page. Then write
the question and your answer down on your paper in English for 1-10 below.
1) What is a polysilsesquioxane? A hybrid material with the following chemical
formula: (RSiO1.5)n, generally made by sol-gel polymerization of
organotrialkoxysilanes.
2) What is POSS? Polyhedraloligosilsesquioxane
3) Why do POSS form (instead of polymer)? At low monomer concentration and/or
with bulky organic groups cyclization to polyhedral structures is favored.
4) What happens to the physical properties (glass transition temperature, strength,
modulus, melt viscosity) of an organic polymer when POSS is dispersed in it. They all
increase.
5) What are bridged polysilsesquioxanes? Bridged polysilsesquioxanes have an
organic bridging group attached to two or more silsesquioxane groups through Si-C
bonds. : (O1.5Si-R-SiO1.5)n,
6) What is the most common commercial application for organotrialkoxysilanes?
Coupling agent for polymer composites.
7) Compare the mechanical properties (strength, modulus) of bridged
polysilsesquioxanes with silica. Bridged polysilsesquioxanes generally have moduli
and strength equal to or greater than of silica.
8) How can you determine if you have made POSS in the laboratory? What
techniques would you employ? Si-NMR, XRD, melting point.
9) Describe the sol-gel process: Hydrolysis and condensation of a monomer to afford
polymers that phase separate as solid particles. The solid particles gel when they
achieve percolation.
10) Why do bridged polysilsesquioxanes generally form as gels and regular
polysilsesquioxanes form as soluble polymers or POSS? Regular polysilsesquioxanes
have greater difficulty reaching molecular weights high enough for solid particle to
phase separate due to the steric bulk of the organic group and only three alkoxide
groups. Having two or more trialkoxysilyl groups allows very rapid molecular growth
and facilitates phase separation as solid particles.

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