AFPM-EXAM-2-Ordered-mesoporous-materiasl

Who discovered M41S

Mobil Research and Corporation

What are the three members of the MCM family

Hexagonal
Cubic
Lamellar

What does MCM-41 look like

hexagonal

What does MCM-48 look like

cubic (interconnected pores)

What does MCM-50 look like

Lamellar (layers of organic-inorganic phases)

What is the general self-assembly mechanism of mesoporous metal oxides

Surfactant micelle->micellar rod->hexagonal surfactant array->hybrid array-> ordered mesoporous mixed metal oxide

what are the general structure directing agents

Alkyl trimethylammonium bromides, Primary alkyl
amines, monododecyl phosphates, sulphonates, triblock copolymers

what are the general Inorganic sources

alkoxides, chlorides, nitrates, sulfates

what are the two main interactions for mesoporous material formation

Electrostatic and hydrogen bonding interactions

what are the major two components of mesoporous materials

surfactant and inorganic species

What are the five pathways for mesoporous phases

cationic+anionic->S(+)I(-)
anionic+cationic->S(-)I(+)
neutral+neutral->S(o)I(o)
cationic+cationic->S(+)X(-)I(+)
anionic+anionc->S(-)X(+)I(-)

Co-self-assembly mechanism at alkaline conditions

Single chain surfactant molecules react with anionic polysiloxane species
Micelles rearrange according to charge matching and shape.
Condensation of the polysiloxane species occur with increasing time and temperature.

what is electrokinetic behavior

Advantages of mesoporous phases

Periodic ordered porous materials at different length scales
Pore architectures (hexagonal, cubic,.)
Pore sizes ( suitable to avoid mass transfer issues )
Wall compositions (oxides, metals, polymers)
Wall nature (amorphous, crystalline)
Chemical environment (interfacial chemistry)

Critical Micelle Concentration

the concentration of surfactants above which micelles are spontaneously formed

how do you find Critical Micelle Concentration

What is a surfactant

an amphiphilic molecule that possesses both a hydrophobic group and a hydrophilic group in the molecule itself

What factors for CTAC control phase

temperature and weight %CTAC

Surfactant packing parameter

g=V/a*i
V= volume of the surfactant + cosolvent molecules
a = surfactant headgroup area
i= surfactant chain length

what surfactant packing parameter results in a cubic phase

g=1/2 (Pm3n)
1/2<g2/3 (Ia3d)

what surfactant packing parameter results in a hexagonal phase

1/3<g<1/2 (p6m)

what surfactant packing parameter results in a lamellar phase

g=1

Surfactant head group effect on surfactant packing parameter

surfactant headgroup area increase with hydrogen chain length leading to smaller g