Natural Macromolecules: Starch, Cellulose, Proteins, Enzymes, Gelatin, Nucleic acids.

Synthetic Macromolecules: Nylon, Polystyrene, Polyethylene.

Associated Colloids (Micelles):

Definition: These are substances that behave as normal electrolytes (forming true solutions) at low concentrations, but at higher concentrations, they aggregate to form particles of colloidal size. These aggregated particles are called micelles.
Amphiphilic Nature: The molecules forming associated colloids are typically amphiphilic, meaning they have both a long hydrophobic (water-repelling) hydrocarbon tail and a hydrophilic (water-loving) polar head. Examples include soaps ($\text{RCOO}^-\text{Na}^+$) and detergents.
Critical Micelle Concentration (CMC): Micelles form only above a specific concentration known as the Critical Micelle Concentration. Below the CMC, the substance exists as individual ions or molecules in a true solution.
Kraft Temperature ($T_k$): Micelle formation also occurs only above a certain temperature, characteristic for a given surfactant, known as the Kraft temperature.
Mechanism of Formation (in aqueous medium):
- At low concentrations, the amphiphilic molecules exist separately.
- Above CMC, the hydrophobic tails aggregate together to minimize contact with water, forming a core. The hydrophilic heads orient outwards, interacting with the aqueous medium.
- In non-aqueous media, the orientation is reversed: hydrophilic heads are in the core, and hydrophobic tails project outwards.
Aggregation Number: The number of molecules that aggregate to form a micelle is called the aggregation number, which can range from 60 to 100 or more.

4. Preparation of Colloidal Solutions

The methods used for preparing colloids depend largely on whether they are lyophilic or lyophobic. Lyophilic sols are easy to prepare, while lyophobic sols require special techniques classified into dispersion and condensation methods.

4.1. Condensation Methods (for Lyophobic Colloids)

These methods involve bringing together molecular or ionic species to form particles of colloidal size. They start from true solutions and build up to colloids.

Chemical Methods: Involve chemical reactions that produce insoluble produc