# Effects of Molecular Length and Polarity of Chain Extenders on Microphase Separation and on Thermal and Mechanical Properties of Rigid Polyurethane Foam

## TL;DR

This study examines how different chain extenders affect the structure and properties of rigid polyurethane foam.

## Contribution

The novel contribution is identifying how molecular chain length of extenders impacts foam properties more than polarity.

## Key findings

- BDO as a chain extender produced the most uniform pore size and best mechanical properties.
- Hydrogen bonding both promotes microphase separation and hinders it by extending molecular chains.
- Molecular chain length has a greater influence on mechanical properties than polarity.

## Abstract

In this work, rigid polyurethane materials were synthesized via a one-step polymerization method using isocyanate (MDI) and polyether polyol (4110S) as the main raw materials, with 1, 4-butanediol (BDO), 1, 6-hexanediol (HDO), diethylene glycol (DEG), and dipropylene glycol (DPG) as chain extenders. The influence of chain extender structure on the mechanical properties of rigid polyurethane was systematically investigated. The results indicate that when BDO was employed as a chain extender, the polyurethane exhibited the most uniform pore size distribution and the best mechanical properties. It was found that hydrogen bonding plays a dual role: on the one hand, it promotes microphase separation between soft and hard segments; on the other hand, it extends the molecular chains’ length, which hinders segment separation and consequently constrains its mechanical properties. Further analysis reveals that the influence of molecular chain length on mechanical properties outweighs that of polarity.