Kinetically Equivalent Functionality and Reactivity of Commonly Used Biocompatible Polyurethane Crosslinking Agents

Area of Science:

• Polymer Chemistry
• Organic Reaction Kinetics
• Materials Science

Background:

• Phenyl isocyanate is a key reagent in polyurethane synthesis.
• Sucrose, sorbitol, and glycerol are common polyol crosslinking agents.
• Understanding the reactivity of hydroxyl groups is crucial for controlling polymer network formation.

Purpose of the Study:

• To investigate and report the reaction kinetics of phenyl isocyanate with sucrose, sorbitol, and glycerol.
• To determine the relative reactivity of different hydroxyl groups within these crosslinking agents.
• To establish the kinetically equivalent functionality of glycerol, sorbitol, and sucrose in crosslinking reactions.

Main Methods:

• Pseudo-first-order kinetics were established by using a high molar excess of crosslinking agents.
• Reaction products were analyzed using High-Performance Liquid Chromatography (HPLC), UV spectroscopy, and Mass Spectrometry (MS).
• Density Functional Theory (DFT) calculations were employed to analyze Atomic Polar Tensor (APT) charges and dipole moments of sorbitol derivatives.

Main Results:

• Primary hydroxyl groups of glycerol were four times more reactive than secondary ones.
• In sorbitol, the reactivity order of hydroxyl groups was determined, with primary OH groups being most reactive.
• Kinetically equivalent functionality (f_k) was found to be 2.26 for glycerol, 2.6 for sorbitol, and 2.96 for sucrose.

Conclusions:

• Experimental and computational results confirm differential hydroxyl group reactivity in polyols.
• The determined kinetically equivalent functionality provides valuable data for designing crosslinked polymer networks.
• This research offers insights into the precise control of reaction pathways in isocyanate-polyol systems.