Block 4 -- Solid State Forms Flashcards
What are the types of mixtures?
1) Physical
2) Dispersion
What is a mixture?
pure material mixed into a polymer
What are the types of solid-state forms?
1) Mixtures
2) Pure forms
What are the types of pure solid-state forms?
1) Crystalline
2) Amorphous
What are the types of crystalline solids?
1) Crystalline polymorphs
2) Solvate polymorphs
3) Co-crystal polymorphs
4) Salt polymorphs
What are characteristics of a crystalline solid?
1) long-range 3D order
2) unit cell
3) specific melting point
4) all molecules have same conformation(s)
What is polymorphism?
The ability of a substance to exist in 2 or more crystalline phases that differ in arrangement and/or conformation of the molecules in the lattice.
What initiates crystallization?
1) temperature
2) anti-solvent
3) evaporation
Describe the nucleation theories:
1) Classical:
- - monomers cluster
2) Two-step:
- - monomers cluster, then rearrange
Describe the transitions present in crystallization:
1st transition: Crystallization or supercooled liquid.
– discontinuous
2nd transition: rubber to glass
– amorphous cannot be more stable than crystal
What are the 3 temperatures represented on a crystallization transition diagram?
Tm: melting T
Tg: T at which transition from liquid to glass occurs
Tk: T at which supercooled & defective crystal intersect
How do polymorphs differ in chemical properties?
1) solubility
2) stability
3) F
4) processability
How do desolvation & dehydration affect structure of crystalline solvate?
1) New crystalline form
2) Transition to amorphous state
3) Desolvated solvate
Why would a co-crystal be used?
To increase solubility and stability
What are the pseudopolymorphs?
Solvates
Co-crystals
Salts
What are characteristics of amorphous solids?
1) lacks long-range order
2) higher solubility than crystalline
3) unstable (wants to crystallize)
4) enhanced bioavailability
How can amorphous solids be stabilized?
Via addition of polymers to create an amorphous dispersion
Describe the plot used to show solubility?
Concentration vs. Time
Describe monotropic solubility polymorphs?
Form X is more soluble than Form Y across all temperatures
How are polymorph systems of solubility termed?
Mono- and enantio-tropic
How are solids characterized?
1) Bulk
- - Thermodynamics (DSC)
- - Gravimetric (weight gain/loss–solvates)
- - Solubility (dissolution rate)
2) Molecular
- - X-ray diffraction
- - Spectroscopic
What does DSC stand for?
Differential Scanning Calorimetry
What is the output of a DSC called?
thermogram
What is the small transition in a thermogram?
glass to supercooled liquid transition
