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Final Exam Flashcards

1
Q

What are then most common shapes for micelles to take?

A

Spherical
Worm Like
Vesicles
Planar Bilayers
Inverted

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2
Q

What is the key packing parameter value for spherical micelles?

A

<1/3

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3
Q

What is the key packing parameter value for worm like micelles?

A

1/3-1/2

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4
Q

What is the key packing parameter value for vesicle micelles?

A

1/2-1

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5
Q

What is the key packing parameter value for planar micelles?

A

1

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6
Q

What is the key packing parameter value for inverted micelles?

A

> 1

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7
Q

Which type of micelle head group is more bulky?

A

Ionic

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8
Q

What is the cloud point?

A

The temperature at which an oily mixture beings to separate when chilled

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9
Q

What is the Krafft temperature?

A

The temperature at which the CMC and solubility of a surfactant are the same

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10
Q

What are the 3 extremes of polymer configuration in a solvent?

A

Rod, Random coil and Spherical Globule

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11
Q

What are the mechanisms of steric repulsion?

A

Osmotic Pressure and Elastic recoil

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12
Q

What is the mechanism of depletion flocculation? Can it be reversed?

A

Osmotic Pressure, yes

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13
Q

What are the mechanisms of bridging flocculation?

A

Favourable particle polymer binding interactions, low surface concentration of polymer, high polymer MW

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14
Q

What polymer attributes are required for steric stabilisation?

A

Sufficiently thick coating
MW approx. 3000 Da
Bulk concentration to ensure high surface concentration

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15
Q

What polymer attributes are required for depletion flocculation?

A

Non adsorbent polymer

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16
Q

What are the 4 modes of emulsion failure?

A

Creaming/Sedimentation
Phase inversion
Coalescence
Ostwald ripening

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17
Q

What is the mechanism of creaming/sedimentation?

A

Gravity driven separation depending on buoyancy

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18
Q

What is the mechanism of phase inversion?

A

Inversion of continuous and dispersed phase in near 50/50 emulsion when exposed to heat or mechanical shock

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19
Q

Ostwald ripening mechanism

A

In a polydisperse emulsion the higher Laplace pressure in small droplets drives molecules into solution, which then precipitate into larger drops

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19
Q

What is the mechanism of coalescence?

A

Surface forces fail to keep droplets apart. Upon collision drops combine

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20
Q

Provide a list of typical rheological features?

A

Yield stress
First Newtonian Plateau
Transition
Second Newtonian Plateau
Recovery rate

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21
Q

What are the basic drug release kinetics?

A

first order
t^1/2
zero order

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22
Q

What structures can give zero order kinetics?

A

Saturated solution with solid crystals inside permeable membrane capsule
Open hole in hemisphere
Initial concentration profile

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23
Q

Provide the meaning of G’ and G’’

A

G’=Elastic (storage) modulus
G’‘=Viscous (loss) modulus

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24
Q

Give the quantity and formula for the measure of material damping in yield stress materials

A

tan(delta)=G’‘/G’

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25
Q

What are the two main types of hydrogels and value of the defining quantity?

A

Honey like, tan(delta)>1
Jelly like, tan(delta)<1

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26
Q

Accelerating voltage range for TEM?

A

80-300 kV

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27
Q

What are BSE and what information do they provide in SEM?

A

Electrons that penetrate deeper into the surface before reflecting. The give information on composition or crystallography

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28
Q

What is spot size/probe current in SEM?

A

The allowed spread of electrons hitting the sample

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29
Q

What are some issues with excessively small spot size in SEM?

A

Reduced beam current results in less electrons being scattered, and the signal to noise ratio becomes too low

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30
Q

What is the benefit of increased working distance in SEM?

A

Improved depth of field

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31
Q

What are the requirements for a sample to be analysed using TEM?

A

-Very clean sample
-Very thin sample
-Inert
-Dry

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32
Q

What are the requirements for a sample to be analysed using SEM?

A

-Conductive sample
-Dry Sample
-Fully adhered to stub

33
Q

What causes astigmatism in TEM?

A

-Non uniform magnetic field
-Off centre aperture

34
Q

What is the effect of astigmatism on TEM images?

A

Image distortion

35
Q

Why is a TEM beam diverged?

A

-Increase resolution without decreasing sampled area
-Avoid film damage

36
Q

What is the wobbler used for in TEM?

A

The wobbler is a focus assist that allows easy positioning of the sample in the eucentric position

37
Q

What causes gelling at low salt concentration in dispersed systems?

A

Repulsive forces between particles keeping them ordered near the average particle spacing

38
Q

What key property can reduce viscosity at a constant volume fraction in a dispersed suspension?

A

Polydispersity

39
Q

What is the stokes shift?

A

Fluorescence occurs at lower energies than incident radiation

40
Q

What is the Raman shift?

A

A shift in the wavelength of emitted light from excited samples due to excitation of short lived virtual states

41
Q

What is required for a molecule to be Raman active?

A

Symmetrical molecules with a vibration resulting in a change in polarizability.

42
Q

What is required for a molecule to be IR spectroscopy active?

A

Asymmetrical molecules with a vibration resulting in a change in dipole moment

43
Q

What is the mutual exclusion rule?

A

Molecules with a centre of symmetry have no
coincident IR and Raman bands

44
Q

How should fluorescent samples be prepared for Raman spectroscopy?

A

Photobleaching

45
Q

What are the advantages of confocal microscopy?

A

Reduced Blur
Can examine internal structures
Allows for imaging of optical sections via alteration of focal plain

46
Q

What are the key components of a confocal microscope?

A

Pinhole
Dichroic mirror
Objective
Laser

47
Q

What is the operating principle of confocal microscopy?

A

The pinhole and focal point of the objective form a conjugate pair of points, and any light originating from other points will be excluded by the pinhole

48
Q

What are the key components of an AFM?

A

-Cantilever
-Tip
-Feedback Loop
-Piezoelectric scanner
-Laser
-Photodiode

49
Q

What AFM mode should be used to study hard samples?

A

Contact mode

50
Q

What AFM mode should be used to study soft samples?

A

Tapping mode

51
Q

What AFM mode should be used to study material phase?

A

Tapping mode

52
Q

What is the key property to control in tapping mode AFM measurements?

A

Cantilever spring constant

53
Q

Which type of surfactant has a lower CMC? Why?

A

Non ionic surfactants, decreased head group repulsion favours micelle formation

54
Q

What is the ideal range of absorbance in UV-vis spectroscopy and why?

A

0.4<A<0.9. minimise relative error

55
Q

What properties can be used to increase the viscosity of a coagulated suspension?

A

Polydispersity
Decrease particle size

56
Q

What property can be used to increase the yield stress of a coagulated suspension?

A

Decrease particle size

57
Q

What is the working principle of DLS?

A

Rate of chance of noise in scattered light can be used to measure Brownian velocity

57
Q

What are some advantages of DLS?

A

Fast
Non invasive
Requires a small amount of sample

58
Q

What are some disadvantages of DLS?

A

Mean particle size is volume weighted
measures hydrodynamic diameter
does not provide information on particle shape

59
Q

What is the appropriate size range for DLS?

A

1nm - 1 micron

60
Q

What is the appropriate size range for Laser diffraction?

A

1 micron to mm

61
Q

What are some advantages of laser diffaction?

A

Well established with regulatory approval
High throughput

62
Q

What is the formula for D.O.F in a molecule

A

Linear: 3n-5
Non-liner: 3n-6

63
Q

What key factors must be accounted for when calculating collisions per second?

A

Both particles are moving
distance travelled is 2r less than centre to centre distance

64
Q

Give some methods of particle formation and size cuts

A

Grinding (1 micron-1mm)
Precipitation (10s of nanometres)
Atomisation/Spray Drying (10-200 micron)
Sol Gel

65
Q

If sodium chloride is added to sodium dodecyl sulphate (SDS) what
happens to the CMC of the solution?

A

The sodium ions bind to the anionic surfactant headgroup and decrease the head
group interactions (spacing) decreasing the CMC. In other words, adding a salt decreases
the CMC by decreasing repulsions between the charged heads of the surfactant molecule

66
Q

What value does the length scale of depletion flocculation vary with?

A

Polymer Rg

67
Q

What parameter does the force magnitude of depletion flocculation vary with?

A

Polymer concentration

68
Q

What change in CMC is expected for a longer hydrophobic group?

A

Decreased CMC. Increased hydrophobic interactions favours micelle formation

69
Q

What is the relationship between particle size and scattering angle?

A

Larger particle size reduces scattering angle

70
Q

What is the baseline in fluorescence techniques?

A

The emission of light from the sample without incident light

71
Q

What does the signal refer to in analytical techniques?

A

The radiation of interest, noise is not included

72
Q

What formulation change can reduce Ostwald ripening?

A

Addition of a small amount of insoluble oil

73
Q

What is the most significant effect of increased particle diameter at constant weight fraction?

A

Increased particle spacing/reduced number concentration

74
Q

What measurement can be used to measure the strength of intermolecular forces? What is the direction of the correlation?

A

Refractive index, increased refractive index->increased intermolecular forces

75
Q

What is the formula for CPP?

A

Vhc/ae.Lc

76
Q

What forces are competing in rayleigh-taylor breakup?

A

Shear force and surface tension

77
Q

What size distribution is produced via homogeniser emulsion formation?

A

Polydisperse

78
Q

Why does reduced particle size increase shear thinning behaviour in dispersed suspensions?

A

At a smaller particle size the distance between particles is smaller, and hence double layer effects are more pronounced.

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