Polymer 3: Polymers in solution Flashcards
Explain the stages of dissolution that occur in a polymer?
- Diffusion of solvent molecules into polymer to form a gel
Macromolecules of polymer get surrounded (solvated) - Dissolution of gel
Water molecules start dissolving it
What happens to a cross linked polymer?
- The macromolecule has strong covalent bonds so it’ll only absorb the water slightly but cannot dissolve in water
- Expands and swells a little to form a gel
- Leads to no dissolution though
- Strong crystallinity
What does solubility occur?
When the Delta G in the free energy equation is negative
What are the factors in the gibbs free energy equation that affect solubility?
Delta H= Enthalpy of mixing
Delta S= entropy of mixing
T= temperature
What is gibbs free energy equation?
Delta G = Delta H - T Delta S
What are the four factors that affect solubility?1
- Polymer to solvent interactions (chemical nature of both solvent and polymer)
- Cross linking or strong intramolecular interactions
- Temperature
- Molecular weight of the molecules
Describe how polymer and solvent interactions work?
- Polar polymers are soluble in polar solvents
2. Non polar polymers are soluble in non polar solvents
How does molecular weight play a role in solubility?
Smaller molecular weight means that polymer can dissolve more easily since solvate molecules can pick them up more easily
How does temperature play a role in solubility?
- As you increase the temperature, each polymer reaches a single phase
- As it hits this phase, it becomes more soluble
- Can go from single to double phase
- Or double to single phase
What is temperature induced phased separation?
- When the molecule is completely soluble at a temperature such as 15 degrees in water
- As temperature increases, the macromolecule forms hydrogen bonds
- Macromolecule collapses to form nanoparticles to create precipitate
Give an example of pharmaceutical appliances of temperate sensitive polymers?
- Thrombolytic enzyme in the blood stream can dissolve thrombus
- If you heat the enzyme in the leg region, you can cause it to work better on thrombus
- Due to at 38 degrees it precipitates to work better
If a molecule is more charged, what does that mean in terms of water? Give examples?
- More soluble
- Example:
- COO- , NH3+ or OH- are very hydrophilic
What functional group makes hydrophobic molecules so hydrophobic?
CH3 group makes molecule quite hydrophobic
How do you turn a hydrophobic molecule into more soluble hydrophilic molecules?
- Changing the CH3 group into an OH group
2. Changing CH3 group on the repeating unit into a H group
If a molecule has low critical solution temperature, what does that mean?
Soluble in cold water, when you heat it, causes it to precipitate
