14 Questions
What is the result of incorporating a solvent into the structure of polymers?
Formation of a gel
What is the purpose of polymers as film coatings in pharmaceutical applications?
To mask the unpleasant taste of a drug
Which of the following is NOT a characteristic of an ideal polymer system?
Toxic
What is an example of a polymer-based technology in drug delivery?
Controlled release
What type of polymers are rarely 100% crystalline?
Crystalline polymers
What is the role of polymers in pharmaceutical applications?
To control viscosity and flow
What is the meaning of the word 'polymer'?
Many parts
What is the main difference between homopolymers and copolymers?
Homopolymers have identical monomer units
What is the effect of cross-linking on the solubility of a polymer?
It decreases the solubility
What is the characteristic of a highly cross-linked polymer?
It is highly rigid
What is the reason why highly cross-linked polymers do not melt?
They degrade at high temperatures before their chains start to move
What is the characteristic of linear polymers?
They have a high melting temperature
What is the characteristic of branched polymers?
They have a low melting temperature
What is formed when cross-linked polymers are added to solvents?
A gel
Study Notes
Polymers
- Polymers are substances of high molecular weight made up of repeating monomer units.
- Examples of polymers include proteins (monomer is amino acid) and polysaccharide (monomer is saccharide).
- The word "polymer" means "many parts".
Polymer Categories
- Polymers can be classified based on composition, with homopolymers having identical monomeric units and copolymers having more than one monomer type.
- Polymers can also be classified based on linkage and structure, with characteristics such as:
- Linear or Branched
- Crosslinking or not
- Crystalline or amorphous
- Entangled polymers with secondary bonding
Branched or Linear Polymers
- Polymers can be branched or linear, with branched polymers forming networks and having a low melting temperature.
- Linear chains have a higher chance of approaching each other in their solid state, increasing their crystallinity and melting temperature.
Polymer Crosslinking
- Linear or branched chains may be joined by crosslinks, restricting their movement and increasing their rigidity.
- Highly cross-linked polymers are very rigid (three-dimensional) structures that degrade at high temperatures before their chains start to move.
- Crosslinking sacrifices solubility for swellability.
Gels
- Gels are formed when crosslinked polymers are added to solvents (such as water), causing the polymers to swell but not dissolve.
- The incorporation of the solvent into the polymer structure leads to the formation of the gel.
- Polymers used to prepare gels are called gelling agents (e.g., carbapol).
Crystalline and Amorphous Polymers
- Polymers are rarely 100% crystalline, as it is difficult for all regions of all chains to become aligned.
- Crystalline regions are typically found alongside amorphous regions.
Pharmaceutical Applications of Polymers
- Polymers have a range of pharmaceutical applications, including:
- Binders in tablets
- Viscosity and flow controlling agents in liquids, suspensions, and emulsions
- Film coatings to mask unpleasant tastes
- Enhancing drug stability
- Modifying drug release characteristics (e.g., controlled release, targeted release, and improved bioavailability)
Characteristics of Ideal Polymer System
- Inert and compatible with the environment
- Nontoxic
- Easily administrable
- Easy and inexpensive to fabricate the dosage form
- Good mechanical strength
Learn about polymers, their composition, and classification. Discover the differences between homopolymers and copolymers and explore their structures.
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