1. What is Polydispersity Index (PDI)?

Definition: PDI is a measure of the distribution of molecular mass in a given polymer sample, calculated as the ratio of weight average molecular weight (M_w) to number average molecular weight (M_n).

Purpose: It indicates the breadth of the molecular weight distribution and is crucial for quality control in polymer chemistry.

2. How Does the PDI Calculator Work?

The calculator uses the formula:

Where:

• \( PDI \) — Polydispersity Index (unitless)
• \( M_w \) — Weight average molecular weight (g/mol)
• \( M_n \) — Number average molecular weight (g/mol)

Explanation: A PDI of 1 indicates a monodisperse sample where all polymer chains are of equal length. Higher values indicate broader molecular weight distributions.

3. Importance of PDI Calculation

Details: PDI affects polymer properties like viscosity, mechanical strength, and processability. It's critical for material consistency in pharmaceuticals, plastics, and coatings.

4. Using the Calculator

Tips: Enter both molecular weight values in g/mol. Values must be positive numbers with M_w ≥ M_n (PDI ≥ 1).

5. Frequently Asked Questions (FAQ)

Q1: What does a high PDI value indicate?
A: Values significantly greater than 1 indicate a broad molecular weight distribution, which may affect material properties.

Q2: What's a typical PDI range for commercial polymers?
A: Most synthetic polymers have PDI between 1.5-3.0, though controlled polymerization can achieve lower values.

Q3: How are M_w and M_n determined experimentally?
A: Typically measured using techniques like gel permeation chromatography (GPC) or light scattering.

Q4: Can PDI be less than 1?
A: No, by definition PDI ≥ 1 since M_w ≥ M_n for all real polymer samples.

Q5: Why is PDI important in drug delivery systems?
A: It affects drug release kinetics and degradation rates of polymeric carriers.