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Self-Assembly > 1st Quiz > Flashcards

1st Quiz Flashcards

1
Q

5 Classes of Self-assembly

A

Atomic, molecular, colloidal, biological, interfacial.

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2
Q

1) Building units for Atomic class
2) Self-assembly system from Atomic class

A

1) metal atom 2) Quantum dot, epitaxial film

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3
Q

1) Building units for Molecular class
2) Self-assembly system from Molecular class

A

1) Surfactant, polymers
2) Micelle, bilayer micro-emulsion, emulsion

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4
Q

1) Building units for Colloidal class
2) Self-assembly system from colloidal class

A

1) nano-particles, nanotubes, fullerene colloidal object. Fullerene (a molecule of carbon in the form of a hollow sphere).
2) Suspension, dispersion, sol, colloidal crystals

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5
Q

1) Building units for Biological class
2) Self-assembly system from Biological class

A

1) Amino-Acid, lipid biopolymer
2) DNA, RNA, protein enzyme, membrane

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6
Q

1) Building units for Interfacial class
2) Self-assembly system from Interfacial class

A

1) Surfactant, polymer, lipid
2) Surface micelle, Langmuir monolayer ( a monomolecular film formed at the air-water interface, usually composed of amphiphilic molecules.), Langmuir-Blodgett (LB) Films

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7
Q

What are the 2 kind of structures that can be formed by LBL self-assembly?

A

Flat and round

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8
Q

Static self-assembly definition:

A
  • It is a sub-class of self-assembly processes that leads to structures in either local or global equilibrium.
  • Examples: molecular crystals, folded, globular proteins.
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9
Q

Define Dynamic self Assembly

A
  • Sub-class of self-assembly processes that leads to stable non-equilibrium structures. That is, these structures exist only as long as the system is dissipating energy.
  • Examples: Perfusion of beads on a tube.
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10
Q

Define programmable or programmed self-assembly.

A
  • Sub-class of self-assembly where particles of the system carry importan information about the final desired structure or its function.
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11
Q

Draw a dentritic molecula.

A
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12
Q

Draw thiols

A

R–SH

R—S–S—R

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13
Q

Draw Silanes

A

(R-Si—-X3)

SO2 Silicon Oxide

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14
Q

Draw a fatty acid

A

R–COOH

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15
Q

Draw a Surfactant

A
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16
Q

2 Classification of Self-assembly by the system where it occurs.

A
  1. Biological
  2. Interfacial
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17
Q

The components of dendrimers (3):

A
  1. A central core,
  2. an Interior dendritic structure (the branches)
  3. an Exterior surface with functional surface groups
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18
Q

List 4 examples of self-assembly in biological systems:

A
  1. DNA double-helix
  2. Protein, enzymes
  3. Lipid by-layer
  4. Cell membrane.
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19
Q

List some Reagents for LbL deposition

A
  1. Polymers: linear, branched, copolymers –> depend on tacticity, degree of polymerization, composition, monomer sequence.
  2. Colloids: polymeric, metallic, oxidic –> depend on size, polydispersity, composition, surface functionality
  3. Biomacromolecules: Proteins, polynucleotides, bio-aggreagates
  4. Small molecules
  5. Smal & complex ions
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20
Q

What does Yasa-sheet suppress on vegetables and fruits?

A

Yasa-Sheets suppress the food’s emission of Ethylene Gas – a natural produce ripening agent that eventually makes fruits and vegetables rot

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21
Q

What is a micelle and how are they form and sizes:

A
  • Micelles are formed by a process of thermodynamic random self-assembly with the length scale of molecules. It is a spontaneous association of surfactant (or amphilic polymer) molecules.
  • They range rom 2-20 nm in diameter
  • Typically The ionic (or hydrophilic) head groups are exposed to the bulk aqueous solution, while the hydrophobic hydrocarbon tail groups form the interior of the micelle.
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22
Q

Why are micelles/self-assembly structures of interest?

A
  1. Living organisms: cell membrane, vesicles.
  2. Applications of surfactants: in cleaning/detergents (40%), textiles, cosmetics, paint, food.
23
Q

Describe Bottom-up Fabrication:

A

atoms and molecules are manipulated and combined to form larger nanoscale structures

  • <!--StartFragment-->

( Examples: DNA-assisted assembly . Assembly of polymer nano-structures Or alkanethiols can form self-assembled monolayers (SAMs) on gold colloid. galvanostatic electrodeposition of metal into porous membrane templates to include multiple segments with arbitrary sequences and thicknesses of different materials.1 ).

Molecules in Self-Assembly

<!--EndFragment-->

24
Q

Describe TOP DOWN Fabrication:

A

manipulation and reduction of a bulk material to make nanoscale objects.

  • <!--StartFragment-->(examples: lithography to pattern materials where the desired final structure is etched from a bulk material. Photolithography silicon technology: Radiation-based method for fabricating electronic devices )<!--EndFragment-->
25
Q

Describe 3-4 self-assembly methods.

A
  1. Dielectrophoreis assembly (DEP): a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field.
  2. DNA assited assembly
  3. Magnetic forces assited self-assembly
  4. Self-assembly by Centrifugation and Spin annealing
  5. Languir-Blodgett
  6. Electro-static self-assembly (ESA)
26
Q

What are some of the applications of surfactants?

A
  1. Petroleum industry
    • Gas/liquid systems: oil flotation process froth, distillation and fabrication tower foams.
    • Liquid/Liquid systems: emulsion drilling fluids, enhanced oil recovery in situ emulsions
    • Liquid/solid systems: reservoir wettability modifiers, drilling mud dispersant
  2. Biomedical applications
    • ​Anesthesiology
    • covering artificial implants
    • gene transfection
    • biomembranes
    • **Sugar-based surfactants are gaining increasing attention due to advantages with regard to performance, health of consumers, and environmental compatibility compared to some standard products **
27
Q

3 examples of molecules that form micelles:

A
  1. Lipids
  2. Block-copolymers
  3. amphiphilic molecules
28
Q

Parts of an ionic surfactant (3):

A
  1. Head group
  2. Tail group
  3. Counterion.
29
Q

What is an amphiphilic molecule and draw sketch?

A

It is a molecule with a Lyophilic and Lyophobic parts combine in one molecule

  • Lyophilic part is typically a large hydrocarbon chain CH3(CH2)n, with n>4. Hydrocarbon chains attract each other (short range Van der Waals forces promoting micelle formation)
  • Lyophobic parts are ionic heads that repel each other (long range electrical forces, counteracting micelle formation)
30
Q

What does surfactant stand for?

A

Surface acting agent

31
Q

What are Cationic surfactants and sketch?

Uses of Cationic surfactants.

A
  1. When the head group bears a cationic group, it is called a cationic surfactant. The rela1vely less use of ca1onic surfactants in industry is due to their rather poor detergency, lack of suspending power for carbon, and higher cost.
    • Some well known ca1onic surfactants are,​
        • long chain amines (RNH3+ X-),
        • quaternary ammonium salts [RN(CH3)3+ X-]
        • quaternary salts of polyethylene oxide-amine deriva1ves [RN(CH3){(C2H4O)xH}2+Cl-]
  2. ore flota1on, textile industries, deodorant.
    - pesticide applications,
    - adhesion,
    - corrosion inhibition
    - preparation of cosmetics -
    - lubrication
32
Q

What are Anionic Surfactants and sketch?

Uses of Anionic surfactants.

A
  1. These surfactants readily adsorb on the posi1vely charged surfaces.
  2. Uses: cleansing formulation: shampoo, hand wash, tooth gels.
  3. The anionic surfactants are the most widely used surfactants in industrial. The

linear alkyl benzene sulfonates have the highest consumption.

Ø Some of the anionic surfactants (e.g., salts of faty acids) are precipitated from the aqueous solution in presence of salts containing Ca+2 and Al+3 ions. Therefore, their use may be restricted in certain media (e.g., hard water).

Ø The calcium and magnesium salts of alkyl benzene sulfonates are soluble in water. Therefore, they are much less sensitive to hard water.

33
Q

What are zwitterionic surfactants and sketch?

Uses of zwitterionic surfactants.

A
  1. They are compatible with both anionic and cationic surfactants due to the presence of both positive and negative charges.
    * ​Most of these surfactants are sensitive to pH. At high pH they are anionic surfactants and at low pH they are cationic surfactants.
  2. ​They are less irritating to eye or skin. Therefore they are widely used in cosmetics.
    • ​They are also used as fabric softeners and bactericides.
34
Q

What are non-ionic surfactants and sketch?

Uses of non-ionic surfactants.

A
  • The nonionic surfactants are the second most widely used surfactants in the industry. They don’t have any significant electric charge on their surface-active part. So there is very little or no electrical interaction between the head-groups.
  • These surfactants are stable in the presence of elecrolytes.
  • Compatible with most other surfactants
  • They generate less foam than the ionic ones.
  • They disperse carbon well
  • The more ethoxylation the more water soluble (because Hydrogen bonding)
  • Insensitive to hard water.
  • Good dispersing properties.
  1. Uses:
    • Cleansing agent in detergents
    • Emulsifying agents in household formulations
    • Wetting agents in textile processing and agrochemical formulations
35
Q

Anionic examples:

A
  1. alkane carboxylic salts (soap),
  2. alkalene sulfonic salts (detergents)–> Sodium dodecylsulfate (SDS)
  3. Alkyl-aromatic sulfonic salts
36
Q

Cationic examples

A
  1. Amine salts –> cetylpyridinium bromide
  2. Quaternary ammonium salts
37
Q

Zwitterionic examples

A
  1. Long chain amino acid salts –> lecithin
  2. Betaines
38
Q

Non-ionic examples

A
  1. Long chain ethers –> tetraoxyethylene lauryl ether
  2. Fatty acid esters
  3. Amides
39
Q

Gemini surfactants $$

A

Consists of two conventional surfactant molecules chemically bonded together by a spacer.

The GS need not be symmetrically disposed about the center of the spacer.

The 2 terminal hydrocarbon tails can be short or long; the 2 polar head groups can be cationic, anionic or nonionic; the spacer can be short or long; flexible or rigid.

GS can self-assemble at much lower concentration and are superior in surface activity as compared to conventional surfactants.

40
Q

Amphiphilic block copolymer

A

chemical compound possessing both hydrophilic (water-loving, polar) and lipophilic (fat-loving) properties.

The most common hydrophilic block used to form the hydrophilic shell is the FDA approved excipient poly(ethylene glycol) (PEG) or poly(ethylene oxide) (PEO).

PEG or PEO consists of the same repea1ng monomer subunit CH2CH2O, and may have different terminal end groups, - hydroxyl group HO(CH2CH20)nH

  • methoxy group CH30(CH2CH20)nH

Block copolymers offer greater flexibility for controlling micellar structure and func1onality through choices of polymer composi1on, architec1re, molecular weight and monomer chemistry.

41
Q

Pluronic block copolymers

A

These block copolymers consist of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly (propylene oxide) (PPO) blocks arranged in A-B-A tri-block structure: PEO-PPO-PEO

42
Q

What type of surfactant is the most widely used in industry?

A

Ionic surfactants

43
Q

What type of surfactant is the second most widely used in industry?

A

The nonionic surfactants

44
Q

Explain why nonionic surfactants can be soluble in water?

A

Hydrogen bonding between oxygen atoms in ethoxyla,on units and water cause water solubility.

The more ethoxyla,on the more water soluble.

45
Q

Properties of Non-ionic surfactants. $$

A
  1. Good emulsifying properties
  2. Good compatibility with other surfactants
  3. Insensitive to hard water
46
Q

The main advantage of bio-surfactants over the petroleum-based surfactants are: $$

A
  • are their lower toxicity,
  • biodegradable nature, and
  • effectiveness at low as well as high temperatures.
47
Q

What does HLB stand for and what does it mean?

A
  • Hydrophilic Lipophilic Balance (HLB)
  • HLB is a means of numerically expressing the hydrophilic property of surfactants
48
Q

HLB equation

A

HLB = 100 x (Mn/M) / 5

Mh = the molecular mass of the hydrophilic portion of the molecule

M = the molecular mass of the whole molecule

49
Q

HLB values to predict surfactant properties of a molecule:

A value < 10

A value >10

A

A value < 10 = oil soluble (hydrophobic)

A value >10 = water soluble (hydrophilic)

50
Q

What is the difference between PEG and PEO? $$

A
  • Low molecular weight polymers, 200 to 20,000 average molecular weight, are poly(ethylene glycols) (PEG) polymerized using base catalysis
  • Poly(ethylene oxide)s (PEO) have molecular weights between 100,000 and 5,000,000, and are free-flowing white powders
51
Q

What does the 400 represents in PEG 400? $$

A

9 repeting units of PEG:

PEG MW = 44gr/mol

400/44 = 9 units of PEG

52
Q

Types of biosurfactants ($$test)

A

Particulate Biosurfactants

Glycolipids

Lipopeptides, Lipoproteins

Fatty acids

Polymeric surfactants

Phospholipids

53
Q

The main advantages of biosurfactants $$

A
  1. lower toxicity,
  2. biodegradable nature, and
  3. effectiveness at low as well as high temperatures.
54
Q

<!--StartFragment-->

what is self-assembly?

A

refers to the spontaneous formation of organized structures from many discrete components that interact with one another directly and/or indirectly **through their environment. **

Self-Assembly (4 decks)

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